Exam 3: Mendelian Genetics

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

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?

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?

Provide simple definitions that distinguish segregation and independent assortment.

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

Under what conditions does one expect a 9:3:3:1 ratio?

Assuming a typical monohybrid cross in which one allele is completely dominant to the other,what ratio is expected if the F₁s are crossed?

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: $\quad$ 30 = tall $\quad$ 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?

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?

The phenotype of vestigial (short)wings (vg)in Drosophila melanogaster is caused by a recessive mutant gene that independently assorts with a recessive gene for hairy (h)body.Assume that a cross is made between a fly with normal wings and a hairy body and a fly with vestigial wings and normal body hair.The wild-type F₁ flies were crossed among each other to produce 1024 offspring.Which phenotypes would you expect among the 1024 offspring,and how many of each phenotype would you expect?

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?

Assume that a black guinea pig crossed with an albino guinea pig produced 5 black offspring.When the albino was crossed with a second black guinea pig,4 black and 3 albino offspring were produced.What genetic explanation would apply to these data?

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

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 (both heterozygous),would you expect all the children to be deaf? Explain your answer.

Assume that you have a garden and some pea plants have solid leaves and others have striped leaves.You conduct a series of crosses [(a)through (e)] and obtain the results given in the table. Cross solid striped (a) solid X striped 55 60 (b) solid X solid 36 0 (c) striped X striped 0 65 (d) solid X solid 92 30 (e) solid X striped 44 0 Define gene symbols and give the possible genotypes of the parents of each cross.

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

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

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

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 X aaBBccDDEE parents? (d)Would you change your answers to part (a)and/or part (b)if the initial cross occurred between AABBCCDDEE X aabbccddEE parents?

In a Chi-square test,as the value of the χ² increases,the likelihood of rejecting the null hypothesis ________.