Exam 3: Mendelian Genetics

In a Chi -square analysis, what condition causes one to reject (fail to accept) the null hypothesis?

Two organisms, AABBCCDDEE and aabbccddee, are mated to produce an F1 that is self -fertilized. If the capital letters represent dominant, independently assorting alleles: a() How many different genotypes will occur in the F2? b() What proportion of the F2 genotypes will be recessive for all five loci? c() Would you change your answers to part (a) and/or part (b) if the initial cross occurred between AAbbCCddee × aaBBccDDEE parents? d() Would you change your answers to part (a) and/or part (b) if the initial cross occurred between AABBCCDDEE × aabbccddEE parents?

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. 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)].

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?

Polydactyly is expressed when an individual has extra fingers and/or toes. Assume that a man with six fingers on each hand and six toes on each foot marries a woman with a normal number of digits. Having extra digits is caused by a dominant allele. The couple has a son with normal hands and feet, but the couple's second child has extra digits. What is the probability that their next child will have polydactyly?

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 a cross is made between a heterozygous tall pea plant and a homozygous short pea plant. Fifty offspring are produced in the following frequency: 30 = tall 20 = short a() What frequency of tall and short plants is expected? b() To test the goodness of fit between the observed and expected values, provide the needed statement of the null hypothesis. c() Compute a Chi -square value associated with the appropriate test of significance. d() How many degrees of freedom are associated with this test of significance?

Mendel's discoveries were well received and understood by his contemporaries.

The Chi -square test involves a statistical comparison between measured (observed) and predicted (expected) values. One generally determines degrees of freedom as _.

How many kinds of gametes will be expected from an individual with the genotype PpCcTTRr?

How many different types of gametes can be produced by an individual with the genotype AABbCCddEeFf?

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.

Assuming complete dominance, a 3:1 phenotypic ratio is expected from a monohybrid sib or self -cross.

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?

Mendel's postulate of independent assortment is supported by a 1:1:1:1 testcross ratio.

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?

A 1:1 phenotypic ratio is expected from a monohybrid cross involving a heterozygote with a homozygous recessive organism.

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

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 child will be albino?

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.