October 05 - Homologous chromosomes are chromosome pairs of...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Homologous chromosomes are chromosome pairs of approximately the same length, centromere position, and staining pattern, with genes for the same characteristics at corresponding loci. One homologous chromosome is inherited from the organism's mother; the other from the organism's father. They are usually not identical. Homologous chromosomes pair during meiosis - the cell division that occurs as part of the creation of gametes . Sections of the DNA can sometimes cross over between homologous pairs. Each chromosome in the pair contains genes for the same biological features, such as eye color, at the same locations (loci) on the chromosome. However, each can contain either the same allele (e.g., both alleles for blue eyes) or different alleles (e.g., one allele for blue eyes and one allele for brown eyes) for each feature. Homologous chromosomes are similar in length, except for sex chromosomes in several taxa, where the X chromosome is considerably larger than the Y chromosome. These sex chromosomes share only small regions of homology. Humans have 22 pairs of homologous non-sex chromosomes (called autosomes ), and one pair of sex chromosomes, making a total of 46 chromosomes in a genetically normal human. Each member of a pair is inherited from one of the two parents. Polyploidy Important to plants and some animals (5%) - 40% of flowers and plants are polyploidy, salmon, some birds and frogs are polyploidy, some reptiles. If 40% of plants are polyploidy, does that mean that each one is a product of hybridization and Chromosome doubling: going from 2 to 4 (polyploidy). If 40% of all plants, all species polyploidy, does that mean that the ancestors of each of the polyploidy was a diploid and the diploid hybridized and gave rise to each of these species? No, because polyploidy, once they evolve, may undergo gradual allopatric speciation— Allopatric speciation is speciation (Speciation is the evolutionary process by which new biological species arise) that occurs when biological populations of the same species become isolated due to geographical changes such as mountain building or social changes such as emigration.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 4

October 05 - Homologous chromosomes are chromosome pairs of...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online