2.Meiosis forms variable gametes Flashcards
In Diploid cells, how do chromosomes typically appear as?
Homologous Chromosomes
How are homologous chromosomes the same?
- Same size
- Same sequence of genes at same loci (locus is the position of genes on chromosomes)
- Same position of centromere
How are homologous chromosomes different?
They have different alleles
What are linked genes?
Genes found on the same chromosomes
Why is it important that there is genetic variation within a population?
Allows a species to adapt and survive in a changing environment and enables long term evolutionary changes
What are chiasmata?
Points of contact between the non-sister chromatids of homologus chromosomes, crossing over may occur here.
What is crossing over?
Section of DNA are exchanged between non-sister chromatids of homologous pair.
How does crossing-over, help to maintain genetic variation within the population in the production of new phenotypes?
It separates linked genes and produce genetically different recombined chromosomes.
What is independent assortment?
The orientation of the pairs of homologous chromosomes at the equator is random. Each pair of homologous chromosomes is positioned independently of the other pairs, irrespective of their maternal and paternal origin.
What does meiosis result in?
The formation of haploid gametes from diploid gametocyte.
Briefly, what happens during meiosis one?
The homologous, chromosomes separate
Briefly, what happens during meiosis, two?
The chromatids separate.
How does increased variation rise during meiosis?
Independent assortment of homologous, chromosomes, and crossing over between nonsister chromatids of homologous chromosomes.
What happens during meiosis one in detail?
Start with a diploid gametocyte. Chromosomes replicate to form to genetically identical chromatid attached at centromeres. Nuclear membrane disintegrate, spindle form.
Chromosomes condense at homologous, chromosomes pair up. Chiasmatic form where nonsister chromatids touch.Random crossing over, may occur at chiasmatic, resulting in sections of DNA are arranged between nonsister chromatids of homologous chromosomes. This produces genetically different recombinant recombinant chromosomes. Spindle fibres attach to the homologous pairs and lined them at the equator of the spindle. Independent assortment occurs. The orientation of the pairs of homologous chromosomes at the equator is random. Each pair of homologous chromosomes is positioned independently of the other peers, irrespective of their maternal and paternal origin homologous chromosomes are separated by spindle fibres. New nuclear membrane are formed around. Each set of chromosomes cytokinesis occurs two daughter cells form. Each has with one set of chromosomes.
What happens during meiosis two in detail?
Two new spindles form one and each cell. Chromosomes lineup singly on equator and sister chromatids of each chromosome separate. New nuclear membrane are formed and cytokinesis occurs. Four haploid gametes are formed all genetically different from each other and gametocyte.
