Biology Answers

QUESTION ELEVEN: GENETICSThe kiwifruit species need both female and male plants to be closeto each other for it to reproduce. The kiwifruit has 58 chromosomesin a body cell.(a) Using the information above describe how meiosis in kiwifruitoccurs.(b) Explain how meiosis causes a random assortment of genesfrom the parent plant.(c) An orchard is infected with the disease BSA which attackskiwifruit vines. Discuss why some infected plants will survive.ANSWER ELEVEN: GENETICSa) The egg cell (ovule) in the female plant would divide to produce 4 cellswith 29 chromosomes each. The sperm cell (pollen) in the male plantwould also contain 4 cells with 29 chromosomes each. All of the cellsdiffer from the parent cells.b) Discusses how meiosis gives rise to new genes.During meiosis crossing over (overlapping) of the homologous chromosomes /chromosome pairs (or DNA) occurs. Pieces of DNA are swapped and this givesrise to new sequence of DNA/genes.During meiosis homologous chromosomes are independently assorted into theresulting gametes. This independent assortment results in millions of possiblecombinations of alleles in the gametes produced.When the egg and sperm cells of 2 different plants of the same species combinethis also produces genes which are different from the original plants. There israndom mixing of the gametes.c) Discusses how genetic variation enables different plants to survive thedisease because of their differing genesThere should be variation (genetic diversity) in kiwifruit plants across thecountry as each plant is different from the parent plants due to meiosis. So as adisease which affects one plant should not affect all the plants because of thedifferent combination of genes. Some plants are more resistant than others dueto differences in genetic material and can therefore survive the BSA disease.For Achievement your answer should have TWO correct statements. E.g.a) 29 chromosomes would be in each gameteb) Recognises that meiosis produces new combinations of genesc) Describes how variation may occur (due to new combinations ofgenes)For Merit your answer should have TWO correct explanations. E.g.d) The egg cell (ovule) in the female plant would divide to produce 4 cellswith 29 chromosomes each. The sperm cell (pollen) in the male plantwould also contain 4 cells with 29 chromosomes each. All of the cellsdiffer from the parent cells.Explains the process of crossing over (or how the new genes areproduced) during meiosis.e) Explains that because of variation not all the plants should be affectedFor Excellence your answer should have TWO correct discussions for band c.