Zoology 101 - Meiosis

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What is the purpose of meiosis?: Transmit genes in an orderly fashion by creation of gametes
Go from diploid to haploid (seperate homologous pairs)
Shuffle genes for variation
What is a karyotype?: Visual picture of condensed chromosomes
What is a homolog?: A pair of chromosomes that contain the same genes at the same loci (alleles for the genes may be different)
What is a gene?: Inheritable unit of genetic information (DNA) that codes for a specific protein or trait
What is an allele?: A different version of a gene

i.e. gene for pea flowers has white allele and purple allele
Diploid vs. Haploid: Diploid/2N = having full complement (2 sets) of chromosomes; one from each parent
Haploid/N = having only 1/2 complement ( 1 set) of chromosomes
What is synapsis?: During prohpase I, homologs find each other and pair up
What is "crossing over"?: When homologs pair up, they get so close that they stick to each other; they often swap pieces of their chromatids; one way to get genetic variation
What is the difference between DNA replication for Mitosis (mt) and Meiosis (me)?: mt = S of interphase
me = S of interphase
Number of divisions?: mt = 1
me = 2
Synapsis of homologous chromosomes?: mt = no
me = yes; prophase I
Number of daughter cells and genetic composition?: mt = 2; genetically identical to each other and parent cell; all diploid

me = 4; genetically different to each other, all haploid
Role in the animal body?: mt = growth/repair
me = create gametes for reproduction
What is the differences between Meiosis I and II in interphase?: Meiosis 1 = G1/S/G2

Meiosis 2 = n/a
Prophase?: Meiosis 1 = DNA condensed as chromosomes nuclear membrane breaks down centrosomes migrate spindle fibers form
synapsis/crossing over of homologs

Meiosis 2 = DNA condensed centrosomes migrate spindle fibers form
Metaphase I and II?: Meiosis 1 = homologous pairs line up on plate (independent assortment)
spindles attach to each kinetochore

Meiosis 2 = chromosomes line up individually with centromeres on plate spindle fibers attach to each kinetochore
Anaphase I and II?: Meiosis 1 = homologous pairs pulled apart/to opposite poles (law of segragation)

Meiosis 2 = sister chromatids pulled apart/to opposite poles (now called chromosomes)
Telophase/Cytokinesis I and II?: Meiosis 1 = same events of mitosis, but now the two cells are haploid, non-identical

Meiosis 2 = same events of mitosis; each cell from meiosis I has gone through M-II, so now there are 4 non-identical haploid cells
How is meiosis II similar to mitosis?: In both mitosis and meiosis II, sister chromatids are being seperated, so chromosomes line up in the same fashion on the metaphase plate, and sister chromatids are pulled apart during anaphase
If 2n=14, how many chromosomes will be present in somatic cells?: 14
How many chromosomes will be found in the gametes?: 7
If n=14, how many chromosomes will be found in diploid somatic cells?: 28
For the human. 2n=___ & n=___: 46;23

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