meiosis

Question 1

1. What does meiosis produce?

Answer 1

One diploid cell produces 4 daughter cells, from 2 nuclear divisions (divisions of the nucleus) that are haploid and genetically different from each other.

Question 2

3. What are homologous chromosomes?

Answer 2

Pairs of chromosomes; With the same genes; At same loci; but maybe different alleles. They could appear with replicated DNA or not.

Question 3

7. Describe the process of crossing over and explain how it increases genetic diversity.

Answer 3

Homologous chromosomes line up, bivalent forms, chiasmata forms and equal lengths of non sister chromatids are exchanged due to tension from chiasmata. This produces recombinant DNA and new combination of alleles

Question 4

8. What are the differences between mitosis and meiosis?

Answer 4

Mitosis maintains the chromosome number, whereas meiosis reduces the chromosome number. In mitosis the homologous chromosomes do not pair, whereas in meiosis the homologous chromosomes associate in pairs. In mitosis there is no crossing-over, whereas in meiosis there is crossing-over. In mitosis there are 2 daughter cells produced, whereas in meiosis 4 daughter cells are produced. In mitosis the cells produced are genetically identical, whereas in meiosis the cells produced are genetically different.

Question 5

9. How can you recognise where mitosis and meiosis occur in a life cycle?

Answer 5

If the chromosome number is reduced (diploid  haploid) it is meiosis. If the chromosome number is maintained (diploid  diploid OR haploid  haploid) it is mitosis.

Question 6

10. What is the formula that can calculate the number of different combinations of chromosomes possible from meiosis?

Answer 6

2n where n is the number of homologous pairs of chromosomes.

Question 7

11. What is the formula to calculate the number of different combinations of chromosomes possible following the random fertilisation of two gametes.

Answer 7

(2n)2 where n is the number of homologous pairs of chromosomes.

Question 8

12. Explain how random fertilisation of haploid gametes further increases genetic variation within a species.

Answer 8

Haploid gametes are genetically unique. When haploid gametes from different parents fuse randomly it produces zygotes with different combinations of chromosomes to both parents and to other offspring.

Question 9

Independent segregation

Answer 9

Homologous chromosomes line up in pairs on the equator, maternal and paternal chromosomes randomly face opposite poles of the cell, homologous chromosomes are pulled to the poles and placed in separate cells that have a random combination of maternal and paternal chromosomes. This produces a new combination of alleles

Question 10

Meiosis process explained

Answer 10

1) independent segregation of homologous chromosomes, crossing over of non sister chromatids within homologous chromosomes. Separation of homologous chromosomes reduces Diploid to a haploid
2) separation of non sister chromatids produces 4 daughter cells that are haploid, generally non identical