Unit 2: AoS 1 Flashcards
1
Q
What is meiosis
A
The reduction division of a diploid gonad cell into 4 genetically different haploid gametes
2
Q
What happens in the first division of meiosis
A
Separates pairs of homologous chromosomes to halve the number of chromosomes- diploid to haploid
3
Q
What happens in the second division of meiosis
A
Separates sister chromatids that were created by the replication of DNA in interphase
4
Q
Prophase 1
A
- Chromosomes condense
- Nuclear membrane dissolves
- Homologous chromosomes cross over and exchange segments of DNA at the same gene loci
5
Q
Metaphase 1
A
- Spindle fibres from opposing centrosomes connect to bivalents
- Align the chromosomes in the centre of the cell
6
Q
Anaphase 1
A
- Spindle fibres contract and split the bivalent
- Homologous chromosomes pulled to opposite poles of the cell
7
Q
Telophase 1
A
- Chromosomes decondense
- Nucleur membrane reforms
- Cytokenisis occurs to form 2 haploid daughter cells
8
Q
Prophase 2
A
- Chromosomes condense
- Nucleur membrane dissolves
- Centrosomes move to opposite poles
9
Q
Metaphase 2
A
- Spindle fibres from opposing centrosomes attatch to chromosomes at the centromere
- Align chromosomes along the cell equator
10
Q
Anaphase 2
A
- Spindle fibres contract and separate the sister chromatids
- Chromatids move to opposite poles
11
Q
Telophase 2
A
- Chromosomes decondense
- Nuclear membrane reforms
- Cytokenisis occurs to form four haploid daughter cells
12
Q
Crossing over
A
- Exchange of segments of DNA between homologous chromosomes during Prophase 1
- Occurs between non-sister chromatids at points called chiasmata
- Outcome: Recombinant chromosomes that contain a combination of DNA from both homologous chromosomes
- Greater genetic diversity- not the same gene combination as either parent
13
Q
Indepandant assortment
A
- Random order of chromosomes lining up at the equator in Metaphase 1
- Occurs independantly of each other
- Means a random conmbination of maternal/ paternal chromosomes can be inherited
