Chapter 13 Flashcards
Meiosis
Important for gametes. Produces haploid cells (n), and no 2 gametes are the same. Important for variation.
Involves Interphase, Meiosis I and Meiosis II. Results in 4 daughter cells. Half as many chromosome as parent cell.
Locus
A gene’s specific location along the length of a chromosome. Plural: loci, from Latin, meaning “place.”
Genetics
The study of both heredity and inherited variation.
Gametes
Reproductive cells in plants and animals that are the vehicles that transmit genes from one generation to the next. Haploids in all 3 sex cycles.
Somatic Cells
2n. Any cell of a living organism other than the reproductive cells. Also known as autosomal cells.
Karyotype
1-22 chromosomes. Sex chromosomes are either X X, or X Y.
Homologous Chromosomes (Homologs)
2 chromosomes of a pair have the same length, centromere position, and staining pattern. Both chromosomes of each pair carry genes controlling the same inherited characters. TETRSADS
Same length, centromere position, and staining pattern.
Diploid cells
Diploid number of chromosomes, abbreviated 2n. Differ per species.
Haploid cells
Haploid number of chromosomes, or n. n = 23 in humans, 22 autosomes plus a single sex cell. Gametes are haploid.
Autosomes
Any chromosome that is not a sex chromosomes.
Zygote
Fertilized egg. Is diploid, since it contains 2 haploid sets of chromosomes.
Tetrads
Specifically when there is four chromosomes together. Homologs can refer to the double ones, but tetrads are specifically the 4. Tetra.
Prophase I
When synapsis and crossing over occur.
Metaphase I
No prometaphase, since there is no nuclear envelope. Alignment of homologs at the metaphase plate.
Anaphase I
Separation of homologs. Sister chromatids of each duplicated chromosome remain attached.
Second division
Cells divide twice in meiosis unlike mitosis, where they only divide once. Results in 4 daughter (haploid) cells instead of 2 (diploid) cells.
Meiosis 2 = mitosis without pro-metaphase and prophase.
Synaptonemal complex
A zipper-like protein that forms during crossing over. Attaches one homolog to the other. Once the synaptonemal complex is fully formed; the two homologs are said to be in synapsis.
Synapsis
During synapsis, the DNA breaks, which are precise corresponding points on 2 sister chromatids, are closed up when each broken end is joined to the corresponding segment of the non-sister chromatid, producing crossovers.
Crossing over
How DNA and variation exists. The sharing of precise sections of the homologs. Happens at the chiasma.
2 non sister chromatids.
Chiasma (chiasmata for plural)
Point/points where crossing over has just occurred after the synaptonemal complex dissembles and the homologs move slightly apart from each other.
Mitosis vs. Meiosis.
Mitosis: 2 identical daughter cells.
Meiosis: 4 haploid daughter cells. Has 2 phases of meiosis. No second S phase.
Recombinant chromosmes
Individual chromosomes that carry genes (DNA) from 2 different parents.
