Meiosis Flashcards
What is a gene?
A section of DNA which codes for a specific protein.
What is a locus?
The location of the allele on the chromosome
What is an allele?
A different version of a gene
What are homologous chromosomes?
A pair of nearly identical chromosomes, one maternal & one paternal
What are diploid cells?
They have homologous pairs of chromosomes (A cell with pairs of chromosomes) = ‘2n’
What are haploid cells?
They do not have homologous pairs of chromosomes (they have a single one of each type of chromosome) = ‘n’
eg: gametes
What kinds of cells does meiosis produce?
Gametes
How many divisions happen in meiosis?
2
How many gametes are produced?
4
How many chromosomes do gametes have?
Half the no. compared to body cells
Are gametes haploid or diploid?
Haploid
When is a gamete’s diploid state restored?
During fertilisation
What happens during the first division (meiosis 1)?
- Homologous chromosomes pair up (synapsis) & their chromotids wrap around each other
- Alleles can be swapped (crossing over)
- At end of division, the homologous pairs have separated, with one chromosome from each pair going in 1 of the 2 daughter cells
what happens during meiosis 2?
- The chromatids move apart
- At the end, 4 cells have usually been formed
- Each of the cells contain 23 chromosomes
What happens during independent segregation?
- During meiosis 1, each chromosome lines up alongside it’s homologous partner at the equator of the cell
- Since the homologous chromosomes pairs are lined up at random, the combination of chromosomes of maternal or paternal origin that goes into the daughter cell at meiosis 1 is also a matter of chance.
