Announcements. Please don’t interrupt other classes (including other Genetics labs) to check flies in Brooks 204 (see schedule on the door). Bring calculators for next week’s lab. Homework: practice on problems 6,7,8,12 - do not turn in.
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1. In guinea pigs, rough coat (R) is dominant over smooth coat (r). A rough coated guinea pig is bred to a smooth one, giving eight rough and seven smooth progeny in the F1.
What are the genotypes of the parents and their offspring?
If one of the rough F1 animals is mated to its rough parent, what progeny would you expect?
In summer squash, white fruit (W) is dominant over yellow (w), and disk-shaped fruit (D) is dominant over sphere-shaped fruit (d). The following problems give the phenotype of the parents and their offspring. Determine the genotypes of the parents in each case:
White, disk x yellow, sphere gives 1/2 white, disk and 1/2 white, sphere.
White, sphere x white, sphere gives 3/4 white, sphere and 1/4 yellow, sphere.
Yellow, disk x white, sphere gives all white, disk progeny.
2 pts each answer for total of 10 pts
Regulation of the cell cycle - 3 main checkpoints
Meiosis: 2 sequential divisions: one reductional,
one equational. Sources of genetic variation: recombination via crossing over in pachytene of prophase I and independent assortment, metaphase I.
Mendel and his peas - brief intro
Monohybrid cross - Punnett square method
Punnett Square Method
IV. Independent Assortment
Basic Mendelian genetics
Postulate 1. Unit factors in pairs
1.Which traits are dominant?
2. Did the phenotypes of the P1 generation affect the F1 or F2 generations?
Dihybrid Cross: P1 cross
Confirm on your own using a Punnett square!
Mendel’s Fourth Postulate: An Interpretation from the Dihybrid cross
What size of Punnett square needed for analysis?
Genetic ratios are most properly expressed as probabilities:
ex. 3/4 tall: 1/4 dwarf
The probability of each zygote having the genetic potential for becoming tall is 3/4, etc..
Probabilities range from 0 (an event is certain NOT to happen), to 1.0 (an event is certain to happen).
How do we calculate the probability of 2 or more events happening at the same time?
What is the probability (p) of green, wrinkled seeds (ggww) from a dihybrid cross?
Parents: GgWw X GgWw
Possible gametes: GW, Gw, gW, gw so p(gw)= 1/4
One gw must come from each parent (gw and gw), so p(ggww) = p(gw and gw) = 1/4 X 1/4 = 1/16