6.3 - Meiosis Flashcards
1
Q
What are alleles?
A
Different versions of the same gene.
Different alleles of a gene will all have the same locus position
2
Q
What are homologous chromosomes?
A
A matching pair of chromosomes in the same loci
3
Q
How many divisions are there in meiosis
A
2
4
Q
What happens in Prophase 1?
A
- Chromosomes condense
- Nuclear envelope disintegrates
- Nucleolus disappears
- Spindle formation begins
(Same as mitosis) - homologous chromosomes pair up to form bivalents
- As they travel through the cytoplasm, the chromatids entangle (crossing over)
5
Q
What happens in Metaphase 1?
A
- Same as in mitosis
- But homologous pairs assemble along the metaphase plate instead of individual chromosomes
- Orientation is random so maternal or paternal can face either pole (independent assortment)
6
Q
What happens in Anaphase 1?
A
- As chromosomes are pulled, the chromatids stay joined together
- Sister entangled chromatids can break off and rejoin. The point at which they break and rejoin are called chiasmata
- This forms recombinant chromatids, allowing more genetic variation as the allele combinations are different.
7
Q
What happens in Telophase 1?
A
- Chromosomes assemble at each pole
- Nuclear membrane reforms
- Chromosomes uncoil
- Cytokinesis occurs
(Same as mitosis)
8
Q
What happens in Prophase 2?
A
(Same as mitosis)
- Chromatids condense + become visible
- Nuclear envelop breaks
- Spindle formation begins
9
Q
What happens in Metaphase 2?
A
- Individual chromosomes line up on the metaphase plate
- Independent assortment because chromatids aren’t identical
10
Q
What happens in Anaphase 2?
A
(Same as mitosis)
- Chromatids get pulled to either pole after division of centromeres
11
Q
What happens in Telophase 2?
A
- Assemble at poles
- Chromosomes uncoil + chromatin formed
- Nuclear envelope reforms + nucleolus is visible
- Cytokinesis produces genetically different 4 daughter cells
