Sexual Reproduction and Meiosis

Question 1

what is the role of meiosis

and why is it classified as a reduction division

Answer 1

• produces gametes
• classed as this because the original cell has the full number of chromosomes to start with
• cells that are formed from meiosis have half the number of chromosomes

which are known as Haploid cells

cells formed from meiosis are genetically different

Question 2

prophase I

Answer 2

chromosomes condense

KEY- chromosomes arrange themselves into homologous pairs and crossing over occurs

• centrioles move to opposite ends of the cell
• nuclear envelope breaks down

Question 3

metaphase I

Answer 3

homologous pairs line up along the centre of the cell and attach to spindle fibres by their centromeres

Question 4

Anaphase I

Answer 4

spindles contract separating the homologous pairs( one chromosome goes to each end of the cell)

Question 5

Telophase I

and cytokinesis

Answer 5

nuclear envelope forms around wach group of chromosomes

- cytokinesis occurs and two haploid cells are produced

Question 6

Meiosis II

Answer 6

in anaphase II: pairs of sister chromatids are separated
so each new daughter cell inherits one chromatid from each chromosome

Four haploid cells are produced ( half the number of chromosomes as the original and also genetically different)

so the end result of meiosis is 4 haploid cells

Question 7

what special thing happens in prophase I

Answer 7

• homologous pairs of chromosomes come together and pair up
• chromatids twist around each other
• bits of chromatids swap over

the chromatids have the same genes but now have a different combination of alleles

Question 8

what 2 events lead to genetic variation in meiosis

Answer 8

1) crossing over of chromatids: Each of the 4 daughter cells from meiosis ( chromatids twist around each other and bits of chromatids get swapped over)
2) Independent assortment of chromosomes: is the random separation of chromosomes
the 4 daughter cells have a completely different combination of maternal and paternal

Question 9

what leads to genetic variation in potential offspring

Answer 9

1) different chromatids
2) different combination of alleles
3) increase genetic variation in offspring

• shuffling of chromosomes leads to genetic vatiation in potential offfspring