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| Question | Answer |
| What is genetics? | Genetics is the study of heredity (transfer of characteristics from one generation to the next) |
| Why did Gregor Mendel experiment with garden peas? | - They were easy to grow, produced new generations quickly - They had distinguishable characteristics - He could control their breeding patterns |
| Why was Gregor Mendel's work with garden peas significant? | It showed that characteristics were inherited in a definite pattern. |
| Which 7 pairs of characteristics did Gregor Mendel observe in his study of garden peas? | 1) Flower colour 2) Flower position 3) Seed colour 4) Seed shape 5) Pod colour 6) Pod shape 7) Stem length *He observed dominant & recessive characteristics |
| Before beginning his experiments, Mendel bred out pea plants for each characteristics over several generations. Why did he do this? | To obtain pure bred plants. Pure bred plants: plants which if pollinated by themselves would produce an offspring which was an copy of themselves. |
| How did Mendel conduct his experiment with the pure bred pea plants? | He cross pollinated two different types of pure bred pea plants (i.e. tall x dwarf) = P1, resulting in a hybrid offspring (F1) which all had the dominant gene = tall. He then cross pollinated the F1 generation (tall x self) resulting in offspring (F2) which were tall and dwarf in a ratio of 3:1 (recessive gene appeared) |
| What were Mendel's conclusions on how characteristics are inherited, after his experiment with the pea plants? | - He concluded that each characteristic was controlled by a pair of factors in the parents = passed on in the gamete (sex cell). - When gametes formed: factors separate (containing only 1 factor from pair) - During fertilisation: factors unite at random (predictable ratios) - Dominant factor can mask effect of recessive when both are present - Factors are unchanged from generation to generation, even when effect does not appear. |
| In Mendel's experiment, the experimental ratios were 3:1. Account for this. | The ratios were 3:1 because of the random combination of gametes during fertilisation. |
| What two laws did Mendel develop from his experiments with the garden pea plants? | - The Law of Segregation - The Law of Independent Assortment |
| Explain Mendel's Law of Segregation | - There are two factors (genes) which determines each characteristic in an organism - Genes separate during reproduction (during meiosis) = one factor (gene) appears in each gamete. - Factors recombine during fertilisation |
| Explain Mendel's Law of Independent Assortment | - When pairs of factors separate, they do so independently of other pairs of factors + are distributed into gametes independently of other factors. - When two or more characteristics are inherited, individual heredity factors hereditary factors assort independently during gamete production → giving different traits an equal opportunity of occurring together Note: chromosomes (not genes) separate and are distributed independently Law applies in all cases where genes are situated on same chromosomes |
| Outline reasons why Gregor Mendel was successful, in terms of his experimental techniques. | - Pea plants: easily grown, reproduce rapidly (valid and reliable) - He focused on many characteristics rather than one organism (accurate): chose simple characteristics that had two factors (e.g. tall or dwarf) and had a clear dominant and recessive distinction. He also did them one at a time. - Accuracy: he started with pure bred - Reliable: bred many plants so that random chance provided reliable results. - Isolated experiments from each other - Controlled fertilisation process (accuracy)= used hand pollination and sowed seeds himself. - He collected data + recorded (reliable) - Used mathematical analysis to provide quantitive data = easier to understand. |
| Summarise the 5 reasons why Gregor Mendel was successful in terms of his experimental techniques | 1) studied a large number of characteristics 2) Did several crosses 3) Use pure bred plants 4) Quantitative data = easier to understand 5) He studied simple characteristics that occurred in pairs (purple/white colour) - contrast to previous researchers who used whole organisms/plants. |
| How long did Gregor Mendel collect data for with how many plants and when was Gregor Mendel's work recognised? | - He collected data for over 8 years with 30k pea plants. - His work was published in 1866 but was not recognised until 34 years later. |
| Why was Gregor Mendel's work not recognised until much later, after his publication? | - He presented his data to a small group of scientists. - He was a shy person = lacking emphasis - Paper was written in German, not English or French (more common language) + not many people read Brno Association's Records. - He was an amateur, not a reputable scientist and not sponsored. - His methods were considered unconventional. - Prior to this, mathematics had not been used in biology. - Experiments dealt with a new concept and at the time, people believed: inheritance = blend of characteristics. |
| How was Mendel's work recognised? | Three other botanists independently came to the same conclusion which lead to the rediscovery of Mendel's work = verified = recognition = gave rise to new branch of science: "genetics" |
| What are monohybrid crosses used for? Monohybrid crosses: involves looking at one characteristic only. | - Parents: use to determine the possibility of an abnormal child (if the parents are carrying disease) - In animals: used to breed suitable parents to produce offspring with certain desirable characteristics. |
| What is genotype? | Genotype: genetic material - Genetic information which produces the trait in an organism (gene) - Gene: pair of alleles |
| What is a phenotype? | The outward appearance - Genetic information which controls the outward appearance (i.e. dominant) - What comes about from the gene and genotype - Don't need to mention recessive (only what can be seen) |
| In a phenotype, for each characteristics, at the least--what is the number of factors which control it? | 2 factors |
| When gametes form, a pair of factors (genes) segregate. What does this mean for the factors that will be in the gamete? | - This means that there is only ONE factor from each parent in a gamete. |
| The gene that is passed on is randomly selected during meiosis and is randomly united with one of its _____ during fertilisation to form a ______. | The gene that is passed on is randomly selected during meiosis and is randomly united with one of its ALLELES during fertilisation to form a ZYGOTE. |
| What is a zygote? | A fertilised ovum. |
| In alleles, one allele is ______ over the other which is _______. | One allele is DOMINANT over the other which is RECESSIVE. |
| If both alleles are the same, they form what type of a genotype? | - Homozygous genotype (TT, tt) |
| If both alleles are different, what genotype do they form? | - Heterozygous (Tt) |
| Hence, how does genotype affect phenotype? | - The recessive gene in a heterozygous offspring is makes by the dominant gene. In this case, it then affects the phenotype as the offspring will have a tall appearance. |
| What are genes? | A section of DNA coding for proteins that expresses itself as a phenotype for that trait. |
| Genes occur in ____ | pairs. |
| Where are genes situated? | - in homologous chromosome because they code for the same factor |
| How is each gene expressed in a diagram of a chromosome? | In a diagram of a chromosome, each gene can be expressed as a band |
| How are genes passed on and what do they determine? | Genes are passed on from parent to offspring and they determine the inherited characteristics of an individual. |
| In a sexually reproducing organism, where does the offspring's genes come from? | In the offspring of a sexually reproducing organism, half its genes come from one parent and the other half comes from the other. 23 from mother, 23 from father. |
| In humans, how many chromosomes are there? | - 23 pairs homologous chromosomes, except the 23rd pair XY is not completely homologous. The X has more genes. |
| Two genes code for each factor on every pair of homologous chromosomes EXCEPT for? | Except for genes that ONLY exist on X chromosome. |
| Some genes have several alleles. Why is this? | This is because each inherited characteristic is controlled by AT LEAST two genes = and each gene has a PAIR of alleles, therefore if a characteristic is controlled by more than two genes, it will have several alleles. |
| What is an allele? | Alleles are different varieties of a gene. They are an alternative for a particular inheritable characteristic. |
| Some factors only have 2 genes and 2 varieties (alleles) however, others may have many different varieties = many different genes BUT only 2 can be inherited- one on each homologous chromosome. | :) |
| Where do alleles occur? | on the same place as genes ---on homologous chromosomes. |
| Alleles make us ___ | individual. |
| Provide an example of an allele and a gene/ | Eye colour = gene. Alleles for eye colour = brown eyes, blue eyes. - Brown (B) dominant: blue (b) recessive. |
| Provide another example of a gene and an allele. | Blood type = gene. It is controlled by 4 different alleles but only 2 are inherited in one person. Alleles: - AO: code for blood group A, as do alleles AA - BO: blood group B, as do BB - AB: blood group AB OO = blood group O |
| What are the 3 alleles of the gene of blood type. | A, B, O |
| Explain the genes and alleles in Mendel's experiment. | - Pea experiment - Flower colour: gene - Alleles: purple or white. |
| > explain the relationship between dominant and recessive alleles and phenotype using examples. | :P |
| For every characteristic, there are two alleles present in pairs in body cells. One of the alleles are dominant, the other is recessive. | :D |
| What is phenotype? | - the visible outward appearance of a genetic factor (genotype) of an organism. - What the offspring will look like, chemical/behavioural characteristcis. |
| The dominant and recessive nature of alleles control---> | the phenotype of an organism. |
| Dominant alleles are expressed as _____ | phenotype. |
| Provide an example of a dominant allele expressed as a phenotype. | - Mendel's experiment: Tallness (T) is dominant and shortness (t) is recessive, an organism with TT or Tt = tall phenotype. |
| Recessive alleles are expressed as ___ | phenotypes when the organism is homozygous. |
| Provide an example of a recessive allele in phenotype. | Genotype: tt = expressed as a short plant phenotype. |
| > Perform an investigation to construct pedigrees or family trees, trace the inheritance of selected characteristics and discuss their current use | :D |
| Define a pedigree. | Pedigree is a record of the features of family members, shown as a diagram (or a family tree) and it assists in examining or explaining the inheritance of the feature. |
| How is pedigree used in families? | - Scientifically analyse inheritance of genetic traits within families = study heredity patterns in humans and other animals. |
| How is pedigree used for tracing? | - Trace the occurrence of inherited traits in parents and offspring through generations. |
| How do pedigrees assist humans in medical terms? | - pedigrees can be analysed to identify and trace the occurrence of genetic disorders/disease over generations. |
| How are pedigrees useful in animals? | -useful for selecting individuals with desirable traits for breeding |
| How do pedigrees assist families for the future? | - Determine probability that future parents are carriers of a particular defective allele. - Predict likelihood of a family member inheriting a trait or developing a disorder. |
| What is the limitation of pedigrees in animals? | - Only useful when studying animals which do not produce too many offspring (mammals). |
| What is the limitation of pedigrees in humans? | - Usefulness relies on accurate and reliable record kept within families. - If the family is too small or too few members are affected = uncertain conclusions. |
| How are females and males symbolised in pedigrees? | -Female: circle - Male: square. |
| What is Hybridisation? | A process in which two genetically different strains of an organism are crossed to produce an offspring with more desirable characteristics than the parents. |
| What is this offpsring called? | Hybrid |
| Define hybrid: | offspring of two species of the same genus OR two varieties of the same species. |
| Provide an example of organism of the same genus which are bred into a hybrid offspring. | E.g. horse and donkey = mule. - Desirable characteristics: steadier, smarter, but are infertile. E.g. labrador + poodle = labradoodle. - Hybrid does not shed hair (good for people with asthma or allergies) - No body odour (doesn't need constant bathing) - Easily trained. |
| Describe how farmers attempted this method with crops. | - Hybrid plants that are heterozygous for particular alleles are stronger, healthier and more disease resistant than inbred strains of the same species = heterosis or hybrid vigour = used by agriculturalists to improve crop (corn, tomatoes, potatoes). |
| Explain how corn was bred in a hybrid form: | - Method: crossing inbred strains of corns with other, genetically different inbred strains. |
| As a result, the corn now is: | - <1% USA-grown corn was hybrid before but now = all of it is. - Corn is = in greater quantity with less labour due to increased plant size + hardiness. |
| What happens with the hybrid plants produced from these crosses? | - Crossed with others to produce seed for planting. |
| What is a disadvantage of 'hybrid vigour' ? | - Hybrid vigour occurs after F1 generation, therefore, F1 seeds need to be constantly produced to guarantee the quality of the crop. |
| What is a disease related disadvantage of 'hybrid vigour' | - the favourable qualities that plant breeders select (height, seed production, stem length etc) have not always included resistance to particular diseases or other features which may aid its survival. |
| What are examples of 'hybrid vigour' leading to death of plants due to disease? | - 1970: 15% of US corn destroyed by leaf blight (fungal disease) - Irish Potato Famine (1846): a lot of potato crop wiped out by fungal attach |
| Samples of original plants should be crossed with modern hybrids--why? | - to maintain genetic diversity within these particular species. - E.g. strains of wild tomatoes x modern hybrids = plants are more resistant to Fusarium moul + viral diseases |
| Explain the issue with Australian produced wheat. | - late 1800s, flour produced from Australian grown wheats = too poor for baking bread. - Flour imported from Canada. -Wheat in Australia = old English varieties = ripened too late to survive hot summers = affected by fungal disease. |
| How did this change? | - William Farrer = pioneered Australian wheat research - Hybridisation = used varieties of bread - Prevented self pollination = carried out artificial crosses of wheat varieties. |
| How was William Farrer successful? | - Features = narrow leaves (reduce water loss) = suited to Australian dry conditions. - earlier ripening = suit shorter growing season in Australia - improved baking quality - improved yield (grains per head) - resistance to fungal disease = bunt. |
| What did William Farrer fail to do? | Breed a whet variety which is resistant to another fungal disease called rust. |
| The end | :) |
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