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.
What happens during crossing over?
When homologous chromosomes come together in meiosis I, parts of the chromatids swap over. The chromatids all have the same genes but different alleles.
What is recombination?
When the broken off portions of chromatids recombine with another chromatid.
What is excytosis?
When vesicles bind to membranes to release its contents.
