Cellular Replication and Variation

Question 1

What is the role of homologous chromosomes in meiosis 1 and 2?

Answer 1

Homologous chromosomes line up and allow for recombination resulting in gametes with unique combination of alleles on each chromosome. Thus, creating genetic diversity.

Question 2

Describe the processes of crossing over and recombination and how they contribute to genetic variation.

Answer 2

Crossing over is the exchange of genetic material between non-sister chromatids of homologous chromosomes occurring in prophase 1 of meiosis 1. Matching regions of homologous chromosomes can break and reattach to the other homologous chromosome, effectively exchanging sections of genetic information which, as result of this exchange of genetic information recombination has occurred as new gene combinations are created. Crossing over and recombination increases genetic variability by altering the genetic combination of information on a chromosome.

Question 3

Compare the process of spermatogenesis and oogenesis.

Answer 3

Differences:
-Spermatocytes are diploid and produce 4 haploid spermatids while oocytes are also diploid however they divide into 1 haploid oocyte.
-Spermatogenesis produces large quanities of spermatids daily while only 1 oocyte is produced every 28 days.
-Spermatogenesis occurs throught the reproductive life of men while oogenesis can be irregular and will stop at menopause.

Similarities
-Both originate as haploid cells and produce diploid cells
-Horemones play a crucial role in initiating and controlling the processes

Question 4

How do independent assortment and random fertilisation cause genetic variation?

Answer 4

Random fertilisation means that the sperm cell that fertilises the egg is random and so will have randomised pool of genes and genetic variation. Independent assortment states that chromosomes are seperated randomly meaning each gamete will have a unique combination of chromosomes.