Exercise 45: Principles of Heredity
Actual genetic makeup
Chromosomes determining malesness/femaleness
situation in which an individual has identical alleles for a particular trait
genes not expressed unless they are present in homozygous condition
Expression of a genetic trait
Situation in which an individual has different alleles making up his genotype for a particular trait
genes for the same trait that may have different expressions
chromosomes regulating most body characteristics
The more potent gene allele: masks the expression fo the less potent allele
In humans, farsightedness is inherited by possession of a dominant allele (A). If a man who is homozygous for normal vision (aa) marries a woman who is heterozygous for farsightedness (Aa), what proportion of their children would be expected to be Farsighted? _____%
If the man is aa he can donate a or a to his child. The woman can donate A or a. So the possibilities are: Aa, Aa, aa, aa
So 50% of the time they'll be Aa, 50% aa. Farsightedness is Aa, so 50%
A metabolic disorder call phenylketonuria (PKU) is due to an adnormal recessive gene (p). Only homozygous recessive individuals exhibit this disorder. What percentage of the offspring will be anticipated to have PKU if the parents are Pp and pp? _____%
The possibilities are: Pp, Pp, pp, pp so the answer is: 50%
A man obtained 32 spotted and 10 solid color rabbits from a mating of two spotted rabbits. Which trait is dominant? Recessive? what is the probable genotype of the rabbit parents? _____x_____
Spotted is dominant (there are more of them occuring in the same mating pair)
Recessive is solid.
genotype of parents: Ss X Ss
Assume that that allele controlling brown eyes (B) is dominant over that controlling blue eyes (b) in humans. A blue eyed man marries a brown eyes woman and they have six children, all brown eyed. What is that most likely genotype of the father? of the Mother? If the seventh child had blue eyes what could you conclude about the parents genotype?
The only way to produce a child with blue eyes is bb. This would not be possible then since only the father has a b allele.
Blue eyes child, you can conclude: If the seventh child had blue eyes, the mother must have a b allele as well, so the father would be bb and the mother would have to be Bb.
Tail length on a bobcat is controlled by incomplete dominance. The alleles are (T) for normal tail length and (t) for tail-less
What name could/would you give to the tails of heterozygous (Tt) cats?
How would their tail length compare with that of TT or tt bobcats?
For this one since TT is a normal tail and tt is tail-less, Tt would produce a short tail since its inbetween the two.
Example: Since this is incomplete dominance, there is "blending" for instance if RR was a red flower, and rr was a white flower, Rr would make a pink flower.
If curly-haird individuals are genotypically CC, strait-haired are cc, and wavy haired individuals are heterozygotes (Cc), what percentage of various phenotypes would be anticipated from a cross between a CC woman and a cc man?
curly?_____ % wavy_______? strait_______?
What does it mean when someone says a particular characteristic is sex-linked?
It is carried on the F(X) sex chromosome
You are a male and you have been told that hemophilia "runs in your genes" whose ancestors, your mother's or your father's should you investigate? Why?
Moms because males can only receive the X chromosome from their mothers, the fathers contribution is always Y
An (XC)(Xc) female marries and (Xc)(Y) man:
What is the probability of producing a color blind son?
A color blind daughter?
A daughter who is a carrier for the color-blind allele?
Well the key to this problem is that color blind is recessive, so little c. The mother is a carrier.
So they could have either a daughter who is a carrier (XC)(Xc)
A daughter who has colorblindness (Xc)(Xc)
A son who is color blind (Xc)(Y)
A son who is not (XC)(Y).
Why are marriages between blood relatives prohibited in most cultures?
Because blook relatives have similar gene pools thus the likelihood of receiving a double-dose of recessive genes is increased.
What is the probability of having three daughters in a row?
The empirical probability is approximately 12.5%.
P(girl) = 0.5
Laws of probability dictate event (a) x (b) x (c)
= 0.5 x 0.5 x 0.5