Meiosis Flashcards
1
Q
What causes genetic variation?
A
The crossing over of chromosomes
2
Q
How many chromosomes should a human zygote have?
A
46
3
Q
What are the chromosomes that pair up called?
A
Homologous
4
Q
What represents chromosome number during fertilisation?
A
n+n=2n
5
Q
What is meiosis?
A
Cell division in reproductive structures of an organism
6
Q
What happens during Interphase?
A
- Before meiosis I occurs
- DNA for each chromosome are copied; now consists of two sister chromatids
7
Q
What happens during Prophase I?
A
- Before meiosis I occurs
- Chromosomes shorten
- Centrioles move to opposite ends of cell
- fibres of spindle develop
8
Q
What happens during Late Prophase I?
A
- The start of meiosis I
- nuclear envelope breaks down
- Chromosome move together to form pairs (homologous)
- Chiasma occurs, chromatids cross over
9
Q
What happens in Metaphase I?
A
- Nuclear membrane gone
- Chromosome pairs line up in centre of spindle, attached at the centromere
10
Q
What happens during Anaphase I?
A
- Spindle fibres shorten, chromosomes are pulled towards poles
- each poor has complete set of haploid chromosomes
11
Q
What happens during Telophase I?
A
- Two groups of chromosomes form at pole, start to uncoil
- Two nuclei start to form
- Nuclear membrane appears
12
Q
What happens during Prophase II?
A
- Start of Meiosis II
- Centrioles move to opposite ends of cell
- Spindle fibres develop
- Nuclear envelope breaks down
13
Q
What happens during Metaphase II?
A
- Chromosomes line up randomly on the centre of the spindle
14
Q
What happens during Anaphase II?
A
- Centromeres split, separating sister chromatids and pulling to each end of the cell
15
Q
What happens during Telophase II?
A
- Nuclear envelope surrounds each haploid set of chromatids
- Chromatids uncoil, spindles disappear
- Four cells are produced with half the number of chromosomes as the parents
