meiosis + genetic variation Flashcards
Describe the process of meiosis
DNA replicates
Each chromosome lines up on opposite sides of the equator with its homologous pair
cell divides into two haploid data cells as the homologous pairs split
Cells divide again in sister chromatids separate to form four haploid genetically different daughter cells each with different combinations of alleles
What is the point of meiosis?
to create genetic variation by creating genetically unique daughter cells with different combinations of alleles
What is a chromatid?
An arm/strand of a chromosome
What does homologous mean?
Containing the same genes
what does diploid mean?
There are two copies of each chromosome in the cell
What does haploid mean?
There is one copy of each chromosome in the cell
what is the ploidy
The number of copies of each chromosome in a cell
what are the similarities between mitosis and meiosis?
In both
DNA Replicates
Sister chromatids separate
What are the differences between mitosis and meiosis?
In mitosis there is one round of cell division, in meiosis there is two
mitosis produces 2 daughter cells, meiosis produced 4
in mitosis daughter cells are genetically identical, in meiosis daughter cells are genetically unique
in mitosis daughter cells are diploid, in meiosis daughter cells are haploid
In mitosis homologous chromosomes do not separate, in meiosis homologous chromosomes do separate
What are the four ways of genetic variation is created through meiosis?
mutation- create new alleles
Independent assortment- new combinations of existing alleles
Crossing over of homologous chromosomes
Random fertilisation
What happens during independent assortment?
homologous chromosomes arrange themselves randomly along the equator. each different arrangement lead to different combinations of alleles in gametes
what is the equation to calculate number of combinations of alleles in gametes
2 to the power of n
what is crossing over?
Occurs between homologous chromosomes and early meiosis to create new combinations of alleles
What is the process of crossing over?
Homologous pairs physically attach inform bivalent the chiasma snaps off two parts of the chromosome so the alias on each chromosome swap and are arranged differently. New combinations of all are created in doubles the number of possible gametes, increasing genetic variety
how does meiosis increase genetic variety?
New combinations of alleles are created and doubles the number of possible gametes
What is the bivalent?
where homologous pairs physically attach
What is a nondisjunction mutation?
homologous pairs of chromosomes Don’t separate
so gametes have the incorrect number of chromosomes
This can occur in meiosis one or two as there will be a change in the number of chromosomes or chromatids
Leading to down syndrome
