894248
Descripción
Fichas por umer.sabir, actualizado hace más de 1 año
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Creado por umer.sabir
hace más de 10 años
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| Pregunta | Respuesta |
| Draw the structure of a DNA nucleotide |
Image:
dna (image/png)
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| What is a gene? | A section of DNA that codes for one or more polypeptides |
| What is a triplet? | Each amino acid is coded for by three bases |
| What is the genetic code? | Different sequences of bases code for different amino acids |
| Why is the genetic code degenerate? | All amino acids apart from methionine have more than one code |
| What happens in transcription? | 1. Gene to be transcribed, unzips and unwinds. H bonds between bases break 2. RNA nucleotides bind to complementary bases 3. RNA polymerase catalyses the reaction 4. mRNA is produced and is released from nucleus via nuclear pores |
| What happens in translation? | 1. mRNA produced by transcription binds to ribosome. 2. Amino acids are carried by tRNA to the ribosome. 3. Ribosome moves along mRNA reading the next codon 4. Peptide bonds form between amino acids 5. Polypeptide chain grows until stop codon is reached. |
| Why is sequence of amino acids in a protein important? | 1. It forms primary structure of protein 2. Primary structure forms tertiary structure 3. Tertiary structure allows the protein to function 4. If tertiary structure is changed, the protein may not be able to function. |
| What is a mutation? | Change in genetic material of a cell |
| What are the types of mutations that can occur? | 1. Substitution- One base is swapped for another 2. Deletion- One or more bases are removed 3. Insertion- One or more bases are added 4. Duplication- One or more bases are repeated 5. Inversion- Sequence of bases are reversed |
| What type of mutations cause a frameshift? | 1. Insertion 2. Deletion |
| Mutation with neutral effects | 1. Mutation may change the triplet but it still codes for same amino acid (silent mutation) 2. Mutation occurs on non-coding region of DNA 3. Mutation changes the triplet but it is similar to the original amino acid so it has no effect |
| Mutations with beneficial effects | 1. Gives organism advantageous feature e.g. increases chances of survival. 2. Mutation will be passed on to offspring |
| Mutations with harmful effects | Gives organism a disadvantageous feature e.g. decreases chances of survival |
| What is a transcription factor? | Protein that binds to DNA and switches genes on or off |
| Lac Operon: Lactose not present in nutrient growth medium | 1. Regulatory gene is expressed and repressor protein is formed. 2. Repressor protein binds to the operator region. 3. This prevents RNA polymerase from binding to the promotor region. 4. Structural genes cannot be transcribed. |
| Lac Operon: Lactose is present in nutrient growth medium | 1. Lactose binds to the repressor protein changing its shape. 2. Repressor moves away from the operator region 3. RNA polymerase can now attach to the promoter 4. Structural genes can be transcribed |
| What genes control the development of a body plan? | Homeotic genes |
| What is apoptosis? | Programmed cell death |
| How does apoptosis work? | 1. Enzymes break down cytoskeleton 2. Cytoplasm becomes dense, organelles tightly packed 3. Cell membrane changes and blebs form 4. Chromatin condenses and nuclear envelope breaks down 5. Cell breaks into vesicles which are taken up by phagocytosis |
| What happens if there is too much apoptosis? | Cell loss and degeneration |
| What happens if there is too little apoptosis? | Leads to formation of tumours |
| What is the function of beta-galactosidase? | Converts lactose into glucose and galactose |
| What is the function of lactose permease? | Allows uptake of lactose from medium |
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