Meiosis Flashcards
1
Q
What does meiosis produce?
A
4 new genetically different gametes with haploid number of chromosomes
2
Q
Where does meiosis occur?
A
Reproductive organs
3
Q
What are the reproductive organs of animals?
A
- Ovaries
- Testes
4
Q
What are the reproductive organs of plants?
A
- Ovaries
- Anthers
5
Q
What does meiosis maintain?
A
Genetic variation
6
Q
Describe the process of meiosis.
A
- DNA replicates so there are 2 identical copies of each chromosome (chromatids)
- DNA condenses to form double armed chrosomes (made from 2 sister chromatids)
- Chromosomes arrange themselves into homologous pairs
- In the first division homologous pair is seperated, halves the chromosome number
- In the second division, the sister chromatids are seperated
7
Q
What are the two ways genetic variation is ensured in meiosis?
A
- Independent assortment
- Crossing over
8
Q
What is independent assortment? 2
A
- Different combinations of maternal and paternal chromosomes go into each cell
- Each chromosome of the homologous pair separates independently and ends up in a different gamete
9
Q
What is crossing over?
A
- Before 1st meiotic division
- Homologous pairs of chromosomes come together and pair up
- Two of the chromatids in each pair twist around each other
- Crossed over parts break off their original chromatid at the chiasmata
- These parts rejoin onto the other chromatids exchanging corresponding sections of DNA
- Chromatids have same genes but different combination of alleles
