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Exam 11: Genes, Chromosomes, and Human Genetics

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Question 1

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Consider the following genetic study involving two autosomal genes. One of these, eye colour, has the dominant allele (R) for red eye colour and the recessive allele (r) for yellow eye colour. The other has the dominant allele (T) leading to paws with thumbs, while the recessive allele (t) codes for paws without thumbs. Presuming no linkage between the genes, what should be the phenotype ratio of the offspring produced by a testcross (RrTt - rrtt) ?

A) 1 red-eyed with thumbs: 1 yellow-eyed without thumbs
B) 3 red-eyed with thumbs: 1 yellow-eyed without thumbs
C) 1 red-eyed with thumbs: 1 yellow-eyed with thumbs: 1 red-eyed without thumbs: 1 yellow-eyed without thumbs
D) 9 red-eyed with thumbs: 3 yellow-eyed with thumbs: 3 red-eyed without thumbs: 1 yellow-eyed without thumbs

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C

Question 2

Multiple Choice

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How does the age of the mother seem to correlate with the incidence of genetic birth defects?

A) Defect incidence sometimes increases and sometimes decreases with increasing age.
B) Defect incidence decreases with increasing age.
C) Defect incidence increases with increasing age.
D) Defect incidence has no correlation to age.

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Question 3

Multiple Choice

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Suppose two genes a and b are 7.4 map units from each other, and that genes b and c are 5.7 map units from each other. You do a cross to determine the map distance between a and C Which result would indicate that c lies between a and b?

Suppose you are a genetic counsellor, and a man and woman come to you with concerns that if they have a child together, it could have cystic fibrosis. Also suppose that genetic tests reveal that the woman is a carrier for cystic fibrosis but the man is NOT. Which of the following is the best advice you could give them?

Match each of the following genetic conditions with its mode of inheritance. A mode of inheritance may be used once, more than once, or not at all. -Angelman syndrome

Match each of the following genetic conditions with its mode of inheritance. A mode of inheritance may be used once, more than once, or not at all. -achondroplasia

Suppose that you are working in a research lab on the organism Drosophila melanogaster and you have been given the job of determining the relative positions of three linked genes for your undergraduate research project. A graduate student in the lab tells you that gene a is 5.0 centimorgans from gene b, and that gene c is 2.7 centimorgans from gene b. What should you do to finish mapping these three genes? What results are likely to occur, and how would you interpret such results?

Suppose that you have discovered a new mutant in Drosophila melanogaster. What kinds of genetic crosses should you do to determine if the allele causing the mutation is inherited as an autosomal dominant trait, an autosomal recessive trait, or a sex-linked trait?

If two genes on the same chromosome are located 10 map units from each other, what percentage of the offspring should have a recombinant phenotype?

Consider the following genetic study involving two autosomal genes. One of these, eye colour, has the dominant allele (R) for red eye colour and the recessive allele (r) for yellow eye colour. The other has the dominant allele (T) leading to paws with thumbs, while the recessive allele (t) codes for paws without thumbs. If these genes are not linked, what should be the phenotype ratio of the offspring produced by a testcross (RrTt -rrtt) ?

Who developed the concept of mapping genes on chromosomes when he was an undergraduate student?

Suppose that a man and woman have a son with a rare genetic disorder known to be X-linked. There is no occurrence of the disorder on the woman's side of the family, but the man's brother has it, as does her father. What is the probability that the son's defective allele came from the man?

-In the figure, what type of change in the chromosomes is depicted?

Match each of the following genetic conditions with its mode of inheritance. A mode of inheritance may be used once, more than once, or not at all. -phenylketonuria

Which of the following kinds of information can be revealed through a family pedigree analysis?

Under which condition would you expect the SRY gene to be switched on?

About half of all flowering plant species, including many important crop plants, belong to which category of chromosomes?

Prenatal diagnosis techniques such as amniocentesis and chorionic villus sampling involve the removal of cells that were produced by an embryo. What are these cells then used for?

In Drosophila melanogaster the allele for long wings is dominant over the allele for vestigial wings, and the allele for a grey body is dominant over the allele for a black body. A testcross was done to check for genetic linkage between the genes for these traits, with the following results for the offspring: 410 flies with long wings and a black body 105 flies with long wings and a grey body 390 flies with vestigial wings and a grey body 95 flies with vestigial wings and a black body Which of the following best represents the map distance between the genes for these two traits?

Suppose that you are a genetic counsellor, and a couple comes to you with concerns that if they have a child together, it could have hemophilia. Suppose also that neither one of them has hemophilia, but the woman's biological father did have an X-linked recessive form of hemophilia. Which of the following is the best advice you could give them?