9.2: Meiosis And Genetic Variation Flashcards
Meiosis
Usually produces four daughter cells each with half the number of chromosomes as the parent cell.
Diploid number
Full set of chromosomes
In humans: 23 pairs/46 individual
Gamete
Sex cell
Haploid number
One chromosome from each pair from each parent.
Half diploid number
Two nuclear divisions in the process of meiosis
Meiosis 1
Meiosis 2
Meiosis 1
Homologous chromosomes pair their chromatids wrap around each other.
Crossing over occurs.
One chromosome from each pair goes into one of the two daughter cells.
Meiosis 2
The chromatids move apart into 4 daughter cells.
Meiosis bring about genetic variation in 2 ways?
- independent segregation of homologous chromosomes
* new combinations of maternal and paternal alleles by crossing over
Crossing over
Equivalent portions of chromatids exchanged.
Gene
Length of DNA that codes for a polypeptide
Locus
The position of a gene on a chromosome or DNA molecule
Allele
One of the different forms of a particular gene.
Homologous chromosomes
A pair of chromosomes, one maternal, one paternal, that have the same gene loci.
Independent segregation
Random which chromosome from each pair ends up in which daughter cell.