Zoo 317 Heredity, Evolution and Society

Lecture 4 Cummings 2: pp 33-45

I. Meiosis

II. Recombination

III. Gametogenesis



Page 39, Fig. 2.22, under mitosis, anaphase is missing a light blue chromosome.
Page 40, definition of recombination: Recombination of genes occurs either by independent assortment of chromosomes if the genes are on different chromosomes or by crossing over if they are on the same chromosome.

I. Meiosis is the form of cell division that underlies sexual reproduction. It occurs only in germ cells.

II. Meiosis produces new combinations of genes by recombination of parental gametic combinations. E.g. In a cross AABB × aabb, there is one possible gamete from each parent: AB and ab. The offspring would be AaBb (or AB/ab, if we wish to distinguish the parental gametic combinations). Nonrecombinant gametes from this individual are AB and ab; recombinant gametes are Ab and aB. [Refer to Fig. 2.25.]

III. Gametogenesis refers to formation of mature ova and sperm.

meiosis asexual reproduction sexual reproduction meiosis I
meiosis II synapsis crossing over disjunction
independent assortment recombination nonrecombinant recombinant
gonial cell spermatogonia oögonia oöcyte
primary oöcyte secondary oöcyte oögenesis ovarian follicle
ovum polar body spermatogenesis spermiogenesis
stem cell spermatocyte spermatid spermatozoa
gamete fertilization    

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last revision: 13 August 1999
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