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Flashcards by Emma Ceolin, updated more than 1 year ago
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Created by Emma Ceolin
about 9 years ago
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| Question | Answer |
| Where can you find DNA? | Stored in the nucleus of a cell |
| Describe Chromosomes | Most of an organism’s DNA is organized into one or more chromosomes, each of which is a string or loop of DNA. A single chromosome can carry many different genes, including the ribosomal RNA genes described above. In prokaryotes, DNA is typically organized into a single circular chromosome (a loop). In eukaryotes, on the other hand, chromosomes are linear structures (strings). Every eukaryotic species has a specific number of chromosomes in the nuclei of its body’s cells. For example, a typical human body cell would have 46 chromosomes, while a comparable fruit fly cell would have eight. (Sex cell, such as sperm and eggs, have just half this number.) |
| Components of prokaryotic cells | A plasma membrane, an outer covering that separates the cell’s interior from its surrounding environment. Cytoplasm, which consists of the jelly-like cytosol inside the cell, plus the cellular structures suspended in it. (In eukaryotes, cytoplasm specifically means the region outside the nucleus but inside the plasma membrane.) DNA, the genetic material of the cell. Ribosomes, molecular machines that synthesize proteins. Despite these similarities, prokaryotes and eukaryotes differ in a number of important ways. A prokaryote is a simple, typically single-celled organism that lacks a nucleus and membrane-bound organelles. (We’ll talk more about the nucleus and organelles in the next article on eukaryotic cells, but the main thing to keep in mind for now is that prokaryotic cells are not divided up on the inside by membrane “walls,” but consist instead of a single open space.) https://www.khanacademy.org/science/biology/structure-of-a-cell/prokaryotic-and-eukaryotic-cells/v/prokaryotic-and-eukaryotic-cells |
| What are the key features of eukaryotic cells? | Unlike prokaryotes, eukaryotic cells have: A membrane-bound nucleus, a central cavity surrounded by membrane that houses the cell’s genetic material. A number of membrane-bound organelles, compartments with specialized functions that float in the cytosol. (Organelle means “little organ,” and this name reflects that the organelles, like the organs of our body, have unique functions as part of a larger system.) Multiple linear chromosomes, as opposed to the single circular chromosome of a prokaryote. Eukaryotic cells are much more complicated than those of prokaryotes. They are packed with a fascinating array of subcellular structures that play important roles in energy balance, metabolism, and gene expression. In the articles and videos that follow, we’ll take a tour through eukaryotic plant and animal cells, exploring the unique structures they contain and the role that each structure plays in the life of the cell. https://www.khanacademy.org/science/biology/structure-of-a-cell/prokaryotic-and-eukaryotic-cells/v/prokaryotic-and-eukaryotic-cells |
| Draw a Eukaryotic Animal Cell | |
| Draw Eukaryotic Plant Cell | |
| Describe a phospholipid bilayer | Like prokaryotes, eukaryotic cells have a plasma membrane, a double layer of specialized lipids that separates the interior of a cell from the surrounding environment. The plasma membrane is made up of two layers of phospholipids, which are lipid molecules with two fatty acid tails (hydrophobic, inward-pointing) and a phosphate-containing head (hydrophilic, outward-pointing). This kind of double-layer structure is found in many biological membranes and is known as a phospholipid bilayer. |
| What is microvillus | The plasma membranes of cells that specialize in absorption are folded into fingerlike projections called microvilli (singular, microvillus). Such cells are typically found lining the small intestine, the organ that absorbs nutrients from digested food. The microvilli help intestinal cells maximize their absorption of nutrients from food by increasing surface area. In celiac disease, people have an immune response to gluten, a protein found in wheat, barley, and rye, and this immune response damages the microvilli. Because of the damage, intestinal cells cannot absorb nutrients normally, leading to malnutrition, cramping, and diarrhea. Fortunately, a gluten-free diet prevents the immune response from taking place, allowing intestinal cells to remain healthy and structurally intact. |
| What is the job of the plasma membrane? | The plasma membrane controls the passage of various molecules, including sugars, amino acids, ions, and water, into and out of the cell. Some small, relatively nonpolar molecules, such as oxygen and carbon dioxide, can pass directly through the phospholipid portion of the membrane. However, larger or more hydrophilic molecules must cross the membrane by way of protein channels, a process that is often regulated by the cell. We’ll examine the plasma membrane, and transport across it, in detail in later articles. |
| What is cytoplasm? | In eukaryotes, the cytoplasm refers to everything in the region of the cell between the plasma membrane and the nuclear envelope. (In prokaryotes, which lack a nucleus, cytoplasm simply means everything found inside the plasma membrane.) One major component of the cytoplasm is the gel-like cytosol, a water-based solution that contains ions, small molecules, and macromolecules. Also part of the cytoplasm are the cell’s membrane-bound organelles, which float suspended in the cytosol. The cytoskeleton, a network of fibers that supports the cell and gives it shape, is another part of the cytoplasm and helps to organize its various components. Even though the cytoplasm consists of 70 to 80 percent water, it has a semi-solid (Jello-like) consistency, thanks to the proteins and other macromolecules floating in it. The cytoplasm contains a rich broth of macromolecules and smaller organic molecules, including glucose and other simple sugars, polysaccharides, amino acids, nucleic acids, and fatty acids. Ions of sodium, potassium, calcium, and other elements are also found in the cytoplasm. |
| Nucleus | The nucleus (plural, nuclei) houses the cell’s genetic material, or DNA, and is also the site of synthesis for ribosomes, the cellular machines that assemble proteins. Inside the nucleus, chromatin (DNA wrapped around proteins) is stored in a gel-like substance called the nucleoplasm. Around the boundary of the nucleus lies the nuclear envelope, which consists of two phospholipid bilayers: an outer membrane and an inner membrane. There’s a thin space between these two layers of the nuclear envelope, and this space is directly connected to the interior of another membranous organelle, the endoplasmic reticulum (which we’ll examine in more detail shortly). Nuclear pores, small holes that span the nuclear envelope, allow substances to enter and exit the nucleus. Each pore is lined by a set of proteins called the nuclear pore complex, which control what can go in or out. The interior of the nuclear envelope is criss-crossed by a network of proteins called the nuclear lamina, which supports and gives shape to the nuclear envelope. |
| Chromosomes | Now that we have a sense of the structure of the nucleus, let’s have a closer look at the genetic information stored inside it: the DNA. Most of an organism’s DNA is organized into one or more chromosomes, each of which is a string or loop of DNA. A single chromosome can carry many different genes, including the ribosomal RNA genes described above. In prokaryotes, DNA is typically organized into a single circular chromosome (a loop). In eukaryotes, on the other hand, chromosomes are linear structures (strings). Every eukaryotic species has a specific number of chromosomes in the nuclei of its body’s cells. For example, a typical human body cell would have 46 chromosomes, while a comparable fruit fly cell would have eight. (Sex cell, such as sperm and eggs, have just half this number.) |
| Chromatin | Chromosomes are only visible as distinct structures when the cell is getting ready to divide. When the cell is in the growth and maintenance phases of its life cycle, the chromosomes instead resemble an unwound, jumbled bunch of threads. In this form, the DNA is accessible to the enyzmes that transcribe it into RNA, allowing the genetic information to be put to use (expressed). In both their loose and compact forms, the DNA strands of chromosomes are bound to structural proteins, including a family of proteins called histones (see picture below). These DNA-associated proteins organize the DNA and help it fit into the nucleus, and they also play a role in determining which genes are active or inactive. The complex formed by DNA and its supporting structural proteins is known as chromatin. |
| Ribosomes | As mentioned above, ribosomes are the molecular machines responsible for protein synthesis. A ribosome is made out of RNA and proteins, and each ribosome consists of two separate RNA-protein complexes, known as the small and large subunits. The large subunit sits on top of the small subunit, with an RNA template sandwiched between the two. (An assembled ribosome looks a little like a hamburger with a puffy bun on top, with an RNA “patty” threading through it.) |
| Eukaryotic Ribosomes | In eukaryotes, ribosomes receive their orders for protein synthesis from the nucleus, where portions of DNA (genes) are transcribed into messenger RNA (mRNA). The mRNA travels to the ribosomes, which use the information it contains to build a protein with a specific amino acid sequence. (In prokaryotes, there is no nucleus, so mRNAs are transcribed in the cytoplasm and can associate with ribosomes without a transport step.) Eukaryotic ribosomes may be either free, meaning that they are floating around in the cytoplasm, or bound, meaning that they are attached to the endoplasmic reticulum or the outside of the nuclear envelope. (In the first diagram in this article, the red dots represent bound ribosomes.) Free ribosomes typically make proteins that will be used in the cytoplasm, while bound ribosomes make proteins that need to enter the endoplasmic reticulum (for example, so they can be inserted into the plasma membrane or exported from the cell by secretion). A ribosome may switch back and forth between free and bound states, depending on what kind of protein it’s making at a giv |
| Endoplasmic reticulum and Golgi bodies | https://www.khanacademy.org/science/biology/structure-of-a-cell/tour-of-organelles/v/endoplasmic-reticulum-and-golgi-bodies |
| Endomembrane system in Eukaryotic Cells | https://www.khanacademy.org/science/biology/structure-of-a-cell/tour-of-organelles/v/endomembrane-system |
| Define a Gene | A section of DNA that has an identifiable function |
| Define an Allele | An allele is a variant form of a gene. Some genes have a variety of different forms, which are located at the same position, or genetic locus, on a chromosome. Humans are called diploid organisms because they have two alleles at each genetic locus, with one allele inherited from each parent. |
| What is a Loci? | A locus (plural loci) is the specific location or position of a gene, DNA sequence, on a chromosome, in the field of genetics. Each chromosome carries many genes; humans' estimated 'haploid' protein coding genes are 20,000-25,000, on the 23 different chromosomes. |
| What is a genotype? | A genotype is an individual's collection of genes. |
| What is a phenotype? | The composite of an organism's observable characteristics or traits. |
| Define Genomics | Genomics is a discipline in genetics that applies recombinant DNA, DNA sequencing methods, and bioinformatics to sequence, assemble, and analyze the function and structure of genomes |
| Why is the deletion of p53 genes damaging to an organism? | The p53 protein pauses the cell cycle for repairs when necessary. |
| If the coding strand of DNA has the sequence 5'-CGAGACTTCTGA-3', what will the sequence of the transcribed RNA be? | 5'-CGAGACUUCUGA-3' |
| How do homeotic genres contribute to the pattern formation in the early embryo? | Homeotic gene products are necessary for proper morphogenesis of an embryo |
| What is the chromosomal theory of inheritance? | The "heritable factors" of Mendel, which are genes or alleles, are located on the chromosomes. |
| A couples first son is colourblind, though neither parents is. Colourblindness is an X-linked recessive trait. What is the probability that the couple's second son will be colourblind? Explain why. | 50% Because the first son is colourblind, one parent has passed on the X-linked recessive trait. As the offspring are both male male, the Y chromosome must come from the father and X from the mother. Because the mother is not colourblind, she must only carry 1 colourblind gene. |
| You have successfully cloned DNA from HindIII-digested bacteriophage λ by ligating it into the plasmid pBluescript and transforming the plasmid into Escherichia coli cells. You grew the bacteria on an agar plate containing ampicillin and X-gal. Many colonies of E.coli grew - both blue and whit. So far, no satellite colonies have grown. Which colonies (blue and/or white) contain: - The multiple cloning site? - A gene for ampicillin resistance? - A λ DNA Insert? | TBA |
| Unicellular organisms reproduce by? | Binary Fission |
| _____________ is the process by which eukaryotic organisms generate two genetically identical daughter cells. _____________ is the process in by which eukaryotic organisms generate gametes for sexual reproduction. | Mitosis is the process by which eukaryotic organisms generate two genetically identical daughter cells Meiosis is the process in by which eukaryotic organisms generate gametes for sexual reproduction. |
| Which os the following statements is not correct in regard to cell division? a) Chromatine uncoils to form the chromosomes b) Chromatin is found within the nucleus c) chromatin is made up of the DNA double helix and associated proteins d) Chromosomes can be seen just as the cell divine is about to occur | NOT TRUE a) Chromatine uncoils to form the chromosomes - TRUE b) Chromatin is found within the nucleus TRUE c) chromatin is made up of the DNA double helix and associated proteins TRUE d) Chromosomes can be seen just as the cell divine is about to occur |
| Why must a cell duplicate its genetic information before splitting in half? | To ensure each daughter cell has a full set of identical DNA |
| Why do some bacteria form endospores? | Bacterial Endospores allow the bacterium to produce a dormant and highly resistant cell to preserve the cell's genetic material in times of extreme stress. |
| Each duplicated chromosome prior to divines will be held together at a region called the _______________? | Centromere |
| Two main phases of the cell cycle are? | Interphase Mitotic Phase |
| True or false: the cell is metabolically active during mitosis? | False |
| What are the 2 things that happen during S Phase? | 1. DNA Replication occurs 2. Chromosome number double so that by the end of the phase each chromosome consists of two identical sister chromatids |
| During which phase of the cell cycle are gene mutations most likely to occur? | S Phase |
| During which phase does the cell check DNA copies? What happens to mitosis if they are not? | G2 They won't copy |
| What are the 2 sub phases of the mitotic phase? | Mitosis and Cytokinesis |
| Explain what happens during each phase: Prophase, Prometaphase, Metaphase, Anaphase, Telophase | Prophase: Chromosomes become visible as paired chromatids and the nuclear envelope disappears Prometaphase: Chromosomes attache to the mitotic spindle and the nuclear membrane disappears Metaphase: Chromosomes become attached to the spindle fibres. Anaphase: Chromosomes move away from one another to opposite poles of the spindle Telophase: Chromatids or chromosomes move to opposite ends of the cell and two nuclei are formed |
| What is cytokinesis? How does it differ in plant cells and animal cells? | Cytokinesis is the the cytoplasmic division of a cell at the end of mitosis or meiosis, bringing about the separation into two daughter cells. In plant cells, a cell plate forms between two nuclei: in animal cells, a cleavage furrow informs and the cytoplasm i pinched in half. |
| When is mitochondrial DNA duplicated? | After Mitosis. |
| Sum up the Central Dogma of protein synthesis | DNA > Transcription > RNA > Translation |
| The site where RNA polymerase attached to the DNA molecule to start the formation of RNA is called? | Prometer |
| If the DNA coding strand ACAGTCGAT, what is the template stand for the same sequence? | TGTCAGCTA Think: AT Gold Coast |
| If the DNA coding strand is ACAGTCGAT, what is the mRNA strand? | UGUCAGCUA Think: AT Gold Coast and sub U |
| What process moves carbon from living things to the atmosphere? | Cellular Respiration |
| What are the 4 main role of proteins in the body? | 1. Sending and receiving signals 2. Defending against pathogens 3. Transporting nutrients across membranes 4. Structural Support |
| Which of the following does a catalyst change during a chemical reaction? | Activation energy |
| What processes occur in the body due to mitochondria? | Citric acid cycle and oxidative phosphorylation |
| Describe the law of independent assortment? | Mendel's law of independent assortment states that allele pairs separate independently during the formation of gametes. |
| 1. What are the common features of a tree and a dog? How does the existence of these features support the ideas of both evolution and a universal common ancestor? | Common Ancestor: Numerous common features is evidence that both these organisms have evolved from a common ancestor. It is unlikely they have evolved separately. Multicellular organisms made of eukaryotic cells Nucleus, Cytoplasma, Mitochondria Very similar DNA with the same nucleotides (ATCG) Homologous genes. Evolution: There are some small differences such as the cell wall and the presence of chloroplasts in plant cells. This suggests that they have evolved differences in accordance with their environmental requirements. |
| 2. During his voyage to the Galapagos Islands, Darwin noticed that several closely related species of finches had slightly different beak structures, which favoured the use of different food sources. Based on this one observation, could you prove or disprove Darwin’s or Lamarck’s theory of evolution? Explain why or why not. | Both Darwin and Lamarck’s theory could be proved based on this observation at this point Darwin’s theory of evolution through natural selection states that these Finches were born with the characteristics through mutation. These characteristics favoured the bird’s changes of survival and reproduction so they were passed on to the next generation. Lamark’s theory of evolution explains that the differences in the beak shape arose because the finch’s perused different foods during their lifetime, then passed these acquired characteristics on to their offspring. |
| 3. Explain the different ways glucose monomers can be linked together into polysaccharides? Explain how this affects the structure and possible uses of these compounds in cells. Use the following terms in your explanation: Glycosidic bonds; Starch; Glycogen; Cellulose | Glucose monomers are linked by glycosidic bonds and into polysaccharides Plants store glucose through starch, which is polysaccharide of glucose. It has little branching within the polysaccharide. Because of linkage configuration, they are easily broken and starch is easily digested by plants. Animals store glucose through glycogen, which is also a polysaccharide of glucose. It has more branching. Because of the configuration of the linkages, they are easily broken and glycogen is easily digested by animals. Glycogen is a more energy dense compound because it allows for more branching. Cellulose is the major component of the tough walls inside plant cells. It is a structural polysaccharide. Because of the beta configuration of the linkages, this cannot be digested. But is useful for building a strong structure. |
| 4. Why do all cells need membranes, and why is it important that membranes are made out of phospholipids? Incorporate the following terms into your answer: hydrophobic; hydrophilic; semi-permeable. | Cells need membranes for a well-controlled environment, to allow the reactions for life to occur. It is important that membranes are made out of phospholipids because they contain a hydrophilic head and hydrophobic tails. Hydrophobic tails attract to each other and make a layer of the membrane that is very hydrophobic. This stops a lot of things from passing through the membrane giving it its semi-permeable nature. Small lipid soluble substances can penetrate the membrane but water cannot. |
| 5. Why is it important that each base pair in DNA contains a purine and a pyrimidine base rather than having two purines or two pyrimidines forming a pair? What would happen to the DNA structure if purines bonded to purines and pyrimidines bonded to pyrimidines? | If two purines were to pair, it would make the helix stretch out. If two purines were to bond afterwards this wouldn’t allow them to connect and they wouldn’t be able to base pair. The pairing of pyrimidines with purines allow for uniform spacing between the two strand of DNA, which allows the double helix to form. If the spacing is not uniform the base pairing could be disrupted and the formation of the helix could be disrupted. |
| 6. Mitochondria and chloroplasts contain small DNA molecules that encode some of the proteins needed in these organelles. Explain why this is the case and why other membrane-bound organelles (Golgi apparatus, endoplasmic reticulum) do not contain their own DNA. What other common feature of mitochondria and chloroplasts can be explained in the same way? Use terms such as: endosymbiont, bacteria, uptake, remaining DNA. | Endosymbiont theory explains that mitochondria and chloroplasts were originally bacteria that experienced uptake by a eukaryotic cell. Together they formed a mutually beneficial relationship. Therefore mitochondria and chloroplasts contain remaining DNA that is more similar to bacteria than the eukaryotic cells. The other membrane bound organelles, such as golgi apparatus and endoplasmic reticulum, derive from the membrane of the eukaryote cell, thus contain no DNA. Mitochondria and chloroplasts both contain a double membrane. The outer membrane resembles Eukaryote cell membrane while the inner membrane resembles that of bacteria. |
| 7. Why do endergonic reactions need to have an activation energy barrier? | An endergonic reaction is used to create more ordered structures from disordered reactants. This requires the input of energy from the environment. Endergonic reactions also need to overcome the activation energy barrier. Once the organised structure is made, you don’t want it to spontaneously fall apart. |
| 8. Could cells function in the absence of catalysts? Why? Explain by using the following terms: metabolism, catalyst; substrate; activation energy. | Cells could not function in the absence of catalysts because metabolism (the chemical reactions necessary for life) would not occur fast enough with out them. Catalysts speed up chemical reactions involving substrates, often by lowering he activation energy. This means the substrate can be broken down faster because less energy has to be put into the reaction. |
| 9. How would the process of DNA replication change if DNA polymerases could start DNA synthesis ‘from scratch’ (without having to add nucleotides onto an existing nucleotide chain)? Use terms such as: primase, RNA primer, telomere shortening. | DNA polymerases must start from the end of an RNA primer, which is established by the enzyme primase. DNA polymerases continues to copy the DNA until is reaches the next RNA primer and then falls off. DNA replication must always start with an RNA primer and go in the 5' to 3' direction. But there is no way to replace the furthest 5' RNA primer. This creates a mismatch between the two strands of DNA at the telomere, which is then chopped off resulting in telomere shortening. If you didn’t need an RNA primer, you wouldn’t need this extra information at the Telomere because it wouldn’t get shorted over time. |
| 1. A particular mutation in E. coli changes the lac operator so that the active repressor cannot bind. How would this affect the bacterial cells production of the lac gene products? | When there is no lactose the repressor protein binds to the operator, which blocks the transcription of these lac genes. If a mutation happened so that the repressor cannot bind, the RNA polymerase will produce mRNA transcripts of the lac genes. The lac genes will be expressed and the protein product from them will be produced. |
| 2. Cyclins are proteins that control the cell cycle through binding to Cdks (cyclin-dependent kinases) to form Maturation Promoting Factor (MPF). Draw a diagram showing the changes of cyclin concentrations, Cdk concentrations and MPF concentrations during the different phases of the cell cycle. Speculate on possible reasons why the formation of MPF does not fully coincide with the production of cyclin. Use the following terms in your explanation: ‘concentration-dependent binding’, free cyclin, Cdk-cyclin complex, free Cdk concentrations and MPF concentrations. | *illustration in book (Week 5, Lec 2) CDK and cyclin don’t bind very well to form the CDK cyclin complex, they exhibit concentration dependent binding where the concentration of free cyclin has to be very high where they can bind together to create MPF. Free CDK concentrations remain constant throughout the cell cycle. MPF concentration increase prior to mitosis |
| 3. Why is it beneficial for the genetic material of a cell to condense into chromosomes when the cell undergoes cell division? Also speculate on why DNA is not always in this state. | By condensing DNA into chromosomes, cells can align each chromosome on the spindle to prepare for separation. This avoids one cell getting two copies of the same gene and having the other cell be deficient in that gene. DNA is usually not condensed into chromosomes because when it is in the condensed chromosome form you cannot receive the transcription. |
| 4. Mitosis gives rise to two daughter cells that are genetically identical to the parent cell. Yet you, the product of many mitotic divisions, are not composed of identical cells. Why? | All cells are genetically identical after mitosis. The reason they don’t appear to be genetically identical cells is because of the differential transcriptional control (not all genes are turned on in all cells). |
| 5. Eukaryote transcriptional regulation elements are often orientation-independent and can function in a variety of locations. Explain the meaning of this statement with a brief explanation of how this occurs. | Transcription in eukaryotic cells is controlled by proteins that bind to specific regulatory sequences and modulate the activity of RNA polymerase. Reflation elements, such as enhancers, can function in a variety of orientations – sense, antisense, locations, far away to the gene, close to the gene, or after the gene. What allows this is DNA bending. Bending proteins allow DNA to be bent so that the regulatory elects come closer to the promoter. This allows them to affect transcription of the gene. |
| 6. RNA viruses encode a viral RNA polymerase in their genomes that function in the virus replication cycle. Compare this with a cellular RNA polymerase in terms of template and overall function. | Cellular RNA polymerase in found in both Eukaryotes and Prokaryotes and uses DNA as a temple to produce RNA. RNA polymerases in viruses use RNA templates to produce more RNA. It can either produce more anti sense or sense RNA. |
| 7. Describe the natural function of restriction enzymes. | Restriction enzymes are enzyme that cut DNA at or near specific recognition nucleotide sequences. Their main natural function is to identify foreign DNA e.g. viruses and cut their DNA so it is no longer functional. This is one of the ways we can prevent viruses from replicating. |
| 8. The template strand of a gene contains the sequence 3’- TTCAGTCGT – 5’. Draw the non template sequence and mRNA sequence, indicating the 5’ and 3’ ends. Compare the two sequences. | Non Template Sequence: 5’- AAGTCAGCA – 3’ mRNA Sequence: 5’- AAGUCAGCA – 3’. The non template sequence is complimentary and goes in the opposite direction. The mRNA sequence is the same for non template sequence except U is substituted for T. |
| 9. There are fewer than 21000 human genes. How, then, can human cells make 75000-100000 different proteins? | Due to alternative splicing of exons, each gene can result in multiple different mRNAs and can thus direct synthesis of multiple different proteins. |
| 1. A mutant yeast strain is found with a mutation affecting a tRNA Ser. The wild type normally produces a tRNA that recognizes the codon UCA, and is charged with the amino acid Serine (Ser) – tRNA Ser. The mutant’s tRNA is still charged with Ser, but the anticodon is mutated and now recognises the codon UGA. What effect will this have on translation in these yeast cells? How will the proteins produced be different? | The tRNA being 'charged' means it has the amino acid (Ser) already attached, so although the anticodon recognises the UGA codon, instead of a STOP codon being inserted, a Serine will be placed instead and translation will continue past the UGA codon until it finds the next STOP codon. |
| 2. What is more likely to have a detrimental effect on the phenotype: a single base pair deletion from the middle of the coding sequence of a gene, or a 9 base pair deletion from the same region of the gene? Why? Would the outcome be different if the deletions happened within the gene’s intron? Why? | A single base pair is more detrimental to the phenotype because it can cause a frameshift mutation where all animo acids after that deletion can be different. This could even add a stop code on creating a very short protein. With a 9 base pair deletion, this will delete 3 amino acids from the protein, but the ones after will still be the same. |
| 4. Describe how antibiotic resistance can spread through different species of bacteria. Hint: there are 3 common mechanisms. | Conjugation - F+ Cell create sex pills/mating bridge to the F- Cell and bases on it’s F plasmid. If the F plasmid has the gene for antibiotic resistance, it will pass this on. Transformation - Bacteria takes us naked DNA from the environment. If this DNA had the genes for antibiotics resistance, this would be incorporated into Bacterial Chromosome and the bacteria would express the antibiotic resistance. Transduction - Virus pick up DNA from a bacteria with antibiotic resistance, it can then spend these genes to other bacteria that infects them. |
| 5. If the two chromosomes in a cell have the same two alleles for every gene, will crossing over in meiosis I lead to genetic variation? | No. Crossing over may lead to swapping alleles, but this will not lead to genetic variation as alleles are still the same. Because they have the same allele for every gene, no matter how they are sorted or crossed over there would be no phenotypic or genotypic variation as there is only one version of the gene available. |
| 6. Define and compare a bacteriophage lytic cycle and lysogenic cycle. Include in your answer an explanation of how the two cycles are related/connected. | Lytic - Virus infects bacteria and injects DNA, then uses bacteria cell machinery to make copies of itself (DNA and proteins), then resembles the virus inside the bacteria, then break free and destroy cell (lyse). Lysogentic - Bacteriophage integrate into the host DNA. When host DNA replicate the prophage is also copied and is present in each of the daughter cells. Lysogens can remain in the lysogenic cycle for many generations but can switch to the lytic cycle at any time via a process known as induction. The key difference between the lytic cycle and the lysogenic cycle is that the lysogenic cycle does not lyse the host cell. |
| 7. Describe the difference between a gene,, allele, loci, genotype, phenotype, genomics. Is it possible for two individuals to have the same phenotype and different genotypes? Explain your answer. | Gene: A unit of heredity which is transferred from a parent to offspring and is held to determine some characteristics of offspring. Allele: A variant form of a gene Loci: Specific location of a gene/DNA sequence on a chromosome Genotype - An individuals collection of alleles . Phenotype - Observable characteristics or trait Genomics: Recombinant SNA, DNA sequencing and bioinformatics to sequence, assemble and analyse the functions and structure of genomics Yes it is possible for individuals to have the same genotype but difference phenotypes. This would mean that the individual is heterozygote and the other individual is homozygote dominant, but share the same phenotype. |
| 8. How would you demonstrate that two loci are independently assorting? Describe your experimental design and your specific predictions. Locus A has two possible alleles, A1 and A2, and Locus B has two possible alleles, B1and B2. Hint: Use a Punnett square to compose your answer. | Dihybrid cross of 2 true breeding individuals. one is homozygote dominant and one is homozygote recessive. Phenotype Ratio: 9:3:3:1 |
| 9. A woman is pregnant and the foetus is male. The woman’s father was colour blind. The baby’s father has normal vision. a) What is the probability that the baby will be colour blind? Explain your reasoning. b) A few years later, the same couple is expecting and this time the foetus is female. What is the chance that the baby will be colour blind? Explain your reasoning. | Allele for colour blindness only occurs on the X chromosome and is also recessive. This means that if a female possesses only one copy of the allele, she won't be colour blind - the dominant allele on her normal X chromosome will be preferentially expressed (although she will still "carry" the gene). In order to be colour blind, she would need to inherit two copies of the colour blindness allele, one on each chromosome. Meanwhile, males only possess one X chromosome, which means that a male only needs to inherit one colour-blindness allele to express colour blindness. If a male is colour blind, he will always pass on his colour blindness allele to his daughters. |
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