Genetics Exam 2 (Recitation Problems)

How many different gametes can P#1 (AABbCcddEeFf) produce?

P#1 can produce 16 gametes (2 options each for B, C, E, F).

How many different gametes can P#2 (AabbCcDDEeFf) produce?

P#2 can produce 16 gametes (2 options each for a, C, E, F).

How many entries in the Punnett Square for P#1 x P#2 cross?

16 x 16 = 256 entries.

How many different phenotypes and genotypes can result from the cross?

Many combinations: phenotypes depend on dominant/recessive expression; exact number requires accounting for all loci but >30 phenotypes possible.

What fraction of progeny are phenotypically identical to P#1?

1/32, since all loci must match phenotype expression of P#1.

What fraction of progeny are genotypically identical to P#2?

1/256, since all 6 loci must match genotype of P#2 exactly.

What fraction of progeny will be homozygous at all six loci?

1/64 (since 1/4 chance per locus x 6 loci).

What fraction will be heterozygous at exactly five of the six loci?

Very rare: (6 choose 5)(1/2^5)(1/4) = 6/128 = 0.0469.

What is the probability that all 5 children are male?

(1/2)^5 = 1/32.

What is the probability that 3 are males and 2 are females?

10/32 = 5/16, using binomial coefficient.

What is the probability that 2 are males and 3 are females?

10/32 = 5/16.

What is the probability that all 5 are the same sex?

2 x (1/32) = 1/16.

What is the null hypothesis for Mendel’s pod and flower crosses?

Observed ratios fit expected 3:1 Mendelian ratios.

What was the χ² result for full vs constricted pods (882:299)?

x² = 0.47, p > 0.5, deviation due to chance.

What was the χ² result for violet vs white flowers (705:224)?

x² = 0.16, p > 0.5, deviation due to chance.

Which cross showed greater deviation?

The pod shape cross, but both are non-significant.

What inheritance pattern causes Chromedomeitis?

X-linked recessive.

Genotypes of parents e and f (in pedigree)?

e = X+Xcd, f = X+Y.

Probability child of e × f is daughter with trait?

0 (daughters need Xcd from both parents, father only has X+).

Probability their child is normal?

3/4 (sons 1/2 normal, daughters all normal).

Probability 2 of 4 children normal and 2 with trait?

Using binomial: 6 x (3/4)^2 x (1/4)^2 = 0.21 (21%).

What ratio results from Pp × Pp in foxes?

1/4 PP (lethal), 1/2 Pp (platinum), 1/4 pp (silver). Ratio among living: 2 platinum : 1 silver.

Is P allele dominant or recessive for lethality and platinum coat?

Dominant for platinum coat, recessive for lethality.

In mice, short-tailed × normal cross gave ~1:1 short:long. What does this suggest?

Trait is dominant with heterozygotes showing short tails.

When two short-tailed crossed, 6 short:3 long observed. What does this suggest?

Cross is heterozygote x heterozygote — 2/3 short, 1/3 long; homozygous short is lethal.

If male parent is blood type B with mother O, what is his genotype?

IBi.

If female parent is blood type A with father B, what is her genotype?

IAi.

What offspring blood types are possible from IBi × IAi?

A (1/4), B (1/4), AB (1/4), O (1/4).

Child is type O, mother is type A. Which paternal blood type excludes fatherhood?

Type AB (cannot produce an i allele).

Do other blood types prove paternity?

No, they only show possibility, not certainty.

How many genes control cat eye color (gray, blue, green, brown)?

Two genes with epistatic interaction.

What are the gene interactions in cats?

Green dominant over gray and brown; blue appears in double recessive combination.

In cross C (gray × brown, F2 9:3:3:1 ratio with blue), what does this show?

Two-gene inheritance with complementary action.

If gray-eyed crossed with unknown gave cross C ratio, what is unknown’s genotype?

Brown-eyed cat with genotype bbdd; F1 heterozygotes produced 9:3:3:1 ratio.