Exam 3: Mendelian Genetics

The nonfunctional form of a gene is called a wild-type allele.

Mendel's Law of Segregation is supported by a 1:1 testcross ratio.

Albinism,lack of pigmentation in humans,results from an autosomal recessive gene (a).Two parents with normal pigmentation have an albino child.What is the probability that their next three children will be albino?

A certain type of congenital deafness in humans is caused by a rare autosomal recessive gene.In a mating involving a deaf man and a deaf woman,could some of the children have normal hearing? Explain your answer.

A certain type of congenital deafness in humans is caused by a rare autosomal dominant gene.In a mating involving a deaf man and a deaf woman,could all the children have normal hearing? Explain your answer.

Assuming independent assortment,what proportion of the offspring of the cross will have the aabbccdd $A a B b C c D d \times A a b b C C d d$ genotype?

For the purposes of this question,assume that being Rh⁺ is a consequence of D and that Rh⁻ individuals are dd.The ability to taste phenylthiocarbamide (PTC)is determined by the gene symbolized T (tt are nontasters).A female whose mother was Rh⁻ has the MN blood group,is Rh⁺ and a nontaster of PTC,and is married to a man who is MM,Rh⁻,and a nontaster.List the possible genotypes of the children.Assume that all the loci discussed in this problem are autosomal and independently assorting.

To test Mendel's Law of Segregation,the experimenter needs a minimum of two contrasting forms of a gene.

Among dogs,short hair is dominant to long hair and dark coat color is dominant to white (albino)coat color.Assume that these two coat traits are caused by independently segregating gene pairs.For each of the crosses given below,write the most probable genotype (or genotypes if more than one answer is possible)for the parents.It is important that you select a realistic symbol set and define each symbol below. $\text { Parental Phenotypes }$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$ $\text { Phenotypes of Offspring }$ Short Long Short Long Dark Dark Albino Albino (a) dark, short \times dark, long 26 24 0 0 (b) albino, short \times albino, short 0 0 102 33 (c) dark, short \times albino, short 16 0 16 0 (d) dark, short \times dark, short 175 67 61 21 Assume that for cross (d),you were interested in determining whether fur color follows a 3:1 ratio.Set up (but do not complete the calculations)a Chi-square test for these data [fur color in cross (d)].

If one is testing a goodness of fit to a 9:3:3:1 ratio,how many degrees of freedom would be associated with the Chi-square analysis?

Tightly curled hair is caused by a dominant autosomal gene in humans.If a heterozygous curly-haired person marries a person with straight hair,what phenotypes (and in what proportions)are expected in the offspring?

Assume that in a series of experiments,plants with round seeds were crossed with plants with wrinkled seeds and the following offspring were obtained: 220 round and 180 wrinkled. a) What is the most probable genotype of each parent? b) What genotypic and phenotypic ratios are expected? c) Based on the information provided in part (b),what are the expected (theoretical)numbers of progeny (400 total)of each phenotypic class?

A 1:1 phenotypic ratio is expected from a monohybrid testcross with complete dominance.

Under what conditions does one expect a 1:1:1:1 ratio?

Assume that a Chi-square test was conducted to test the goodness of fit to a 9:3:3:1 ratio and a Chi-square value of 10.62 was obtained.Should the null hypothesis be accepted?

A certain type of congenital deafness in humans is caused by a rare autosomal (not X-linked)dominant gene. a) In a mating involving a deaf man and a deaf woman (both heterozygous),would you expect all the children to be deaf? Explain your answer. b) In a mating involving a deaf man and a deaf woman (both heterozygous),could all the children have normal hearing? Explain your answer. c) Another form of deafness is caused by a rare autosomal recessive gene.In a mating involving a deaf man and a deaf woman,could some of the children have normal hearing? Explain your answer.

Assume that a Chi-square test was conducted to test the goodness of fit to a 3:1 ratio and that a Chi-square value of 2.62 was obtained.Should the null hypothesis be accepted? How many degrees of freedom would be associated with this test of significance?

What is the probability of flipping a penny and a nickel and obtaining one head and one tail?

Which types of phenotypic ratios are likely to occur in crosses when dealing with three gene pairs for which all the genotypic combinations are of equal viability?

A recessive allele in tigers causes the white tiger.If two normally pigmented tigers are mated and produce a white offspring,what percentage of their remaining offspring would be expected to have normal pigmentation?