Exam 2: Extensions to Mendels Laws

What is the major cause of Down syndrome?

Haemophilia is caused by an X-linked recessive mutation in humans.If a woman whose paternal uncle (father's brother)was a haemophiliac marries a man whose brother is also a haemophiliac,what is the probability of their first child having haemophilia? Assume that there are no other cases of haemophilia in the pedigree and no hidden carriers.

Which of the following can arrest the cell cycle?

Bridges crossed white-eyed female and red-eyed male fruit flies and recovered rare exceptional white-eyed females and red-eyed males in addition to the usual red-eyed females and white-eyed males.How did Bridges' observations lend support to the chromosome theory of inheritance?

A chromosome with two arms of equal length is referred to as

The stage of mitosis when sister chromatids separate from each other and migrate to opposite poles of a cell is called

In the following pedigree,the indicated trait is caused by which type of allele? Assume the trait is fully penetrant and that the trait is rare in the population,so that alleles for the trait are not carried by anyone who is not the progeny of a mating shown in the pedigree.

In fruit flies,an X-linked dominant mutation (N)causes Notch wings in heterozygous females but is lethal in hemizygous or homozygous condition.What ratio of offspring would be observed in a cross of a Notch female with a normal male?

Explain the reasoning Sutton used when proposing the chromosome theory of inheritance in 1903.

In crosses of white-eyed Drosophila females with red-eyed males,Bridges recovered white-eyed daughters and red-eyed sons at a rate of around one per 2,000 offspring.(Most of the offspring were white-eyed males and red-eyed females. )He hypothesized that these exceptional progeny resulted from nondisjunction of the X chromosomes in meiosis in the female.Why did he suspect that nondisjunction was occurring in the female parent? What types of progeny would result from nondisjunction in the male parent?

In Drosophila,white eyes (w)and yellow body (y)are both recessive X-linked mutations.The wild type alleles,w⁺ and y⁺,control red eyes and dark body colour,respectively.If a homozygous yellow body,red-eyed female is crossed with a dark body,white-eyed male,and F₁ progeny are interbred,what will the phenotypes and ratios of the F₁ and F₂ be?

Here is a list of meiotic events in no particular order. A: Segregation of homologous chromosomes to opposite poles. B: Segregation of sister chromatids to opposite poles. C: Alignment of homologous pairs on the midplate of the cell. D: Pairing and synapsis of homologous chromosomes. E: Condensation of chromosomes in a diploid nucleus. What is the correct order of events?

In Drosophila,vestigial wings (vg)is a recessive autosomal mutant allele,and yellow body (y)is a recessive X-linked mutant allele.The wild-type alleles,vg⁺ and y⁺ control normal wings and dark-brown body colour respectively.If a homozygous yellow,vestigial female is crossed to a normal male and the F₁ offspring are interbred,what will be the phenotypes and ratios of the F₁ and F₂?

If you are a male,your X chromosome contains genes derived from

A chromatin-laden nucleus is quiescent.

Humans have 22 pairs of autosomes plus one sex chromosome pair.How many autosomes are present in a normal human primary spermatocyte?

In the following pedigree,the indicated trait is caused by what type of allele? Assume the trait is fully penetrant and that the trait is rare in the population,so that alleles for the trait are not carried by anyone who is not the progeny of a mating shown in the pedigree.

What is meant by the term "checkpoint" with respect to regulation of the cell cycle?

A ________________________ is an animal cell with two or more nuclei.

Which of the following did not directly observe chromosomes to study their role in heredity?