Meiosis

Question 1

How does crossing over occur?

Answer 1

Homologous pairs of chromosomes pair up.
The chromatids twist around each other and areas of chromatids swap over.
The chromatids now have the same genes but a difference combination of alleles.
One chromosome from each pair goes into one of the two daughter cells.

Question 2

What is meiosis?

Answer 2

Meiosis usually produces 4 daughter cells, each with half the number of chromosomes of the parent cell.

Meiosis produces haploid cells from diploid cells.
The haploid cells produced are genetically different from one another.

Question 3

Why must meiosis occur?

Answer 3

Because if each gamete had a full set of chromosomes (diploid number) then the cell they produce would have double this number.
This doubling of the number of chromosomes would continue into each generation.
So, in order to maintain a constant number of chromosomes in the adults of a species, the number of chromosomes must be halved at some stage in the life cycle.
This halving occurs as a result of meiosis.

Question 4

Outline the independent segregation of chromosomes.

Answer 4

• Each homologous pair of chromosomes in your cell is made up of a maternal and paternal chromosome.
• When the homologous pairs are separated in meiosis I, it’s random which chronometer from each pair ends up in which daughter cell.
• Meaning the 4 daughter cells produced by meiosis have completely different combinations of these maternal and paternal chromosomes.
• This is called independent segregation of the chromosomes.
• The ‘shuffling’ of chromosomes leads to genetic variation in any potential offspring.

Question 5

How are mitosis and meiosis different?

Answer 5

MITOSIS:

• ONE division (which separates the sister chromatids)
• produces cells with the SAME number of chromosomes as the parent cell
• daughter cells are genetically IDENTICAL to each other and the parent cell
• produces TWO daughter cells

MEIOSIS:

• TWO divisions (which separate the homologous pairs and then the sister chromatids).
• produces cells with HALF the number of chromosomes as the parent cell
• daughter cells are genetically DIFFERENT from one another and the parent cell
• produces FOUR daughter cells