Question

"The orange locus in cats is located on the X chromosome. In females, XoXo results in orange cats and X+X+ results in black cats When a female is heterozygous XoX+, they express both colors in patches due to a phenomenon called X-inactivation in which one X in every cell is inactivated. These females are called calico or tortoiseshell, depending on the presence of white spots. Male cats are either orange (XoY) or black (X+Y). A cross between a black female and an orange male results in a male tortoiseshell kitten. How is this possible?"

		He is XXY due to non-disjunction at meiosis II in the father
		He is XXX due to non-disjunction at meiosis I in the mother.
		He is XXY due to non-disjunction at meiosis II in the mother.
		He is XXY due to non-disjunction at meiosis I in the father.

"Xeroderma pigmentosum is a rare, recessive genetic disease that affects the ability of the individual to repair DNA damage caused by exposure to the sun. Individuals so afflicted soon develop multiple skin cancers, and usually die before age 12. It occurs in about one in 20,000 births. Among the progeny of brother-sister crosses, at what frequency would you expect to find a person affected by xeroderma? "

		0.00181
		0.0161
		0.000283
		0.00333
		0.00209

"In Drosophila, scarlet eyes (st), curled wings (c), and stubbloid bristles (sbd) are all recessive and all found on chromosome 3. Scarlet and curled are separated by 6 map units, while curled and stubbloid are separated by 10 map units. The order of the genes is scarlet, curled and stubbloid. A female expressing scarlet and curled is crossed to a male expressing stubbloid. The resulting F1 female is testcrossed to a male expressing all three traits. The coefficient of coincidence is 0.8. How frequently would you observe a fly expressing curled wings only?"

		0.4224
		0.0552
		0.0048
		0.0276
		0.0952
		0.0476
		0.0024

"Notch wing (N) is a dominant, sex-linked mutant of D. melanogaster on the X-chromosome. Ebony (e) body is a recessive, autosomal mutant on chromosome III. Brown (bw) eyes is an autosomal recessive on chromosome II. A homozygous notched wing female is crossed to an ebony and brown male. All of the F1 males and females were phenotypically notched wing. The F1 males and females were crossed to produce an F2. At what frequency is a notch, ebony, but not brown female expected in the F2?"

		1/16
		3/64
		3/32
		1/32
		0

"In Drosophila, the locus for maroon-like eyes is found on the X chromosome and the recessive mutation leads to altered pigment in the eye. The locus for white eyes is also on the X chromosome and the recessive mutation leads to an absence of pigment in the eye due to an affect on the pigment transporter. This function means that the white locus is epistatic to the maroon-like locus. Maroon and white are separated by 22 map units.The locus for vestigial wings is autosomal and the mutant in recessive. A female that is recessive for both white and maroon-like is crossed to a male that is recessive for vestigial. The F1 flies are inbred. What proportion of the F2 will be flies of either sex expressing white eyes only?"

		0.14625
		0.1875
		0.04875
		0.0625
		0.375
		0.125

"A 26 base pair long sequence of DNA is known to bind only at the human locus for catalase-A (an enzyme used in metabolism). When labeled with a fluorescent dye, this sequence is used as one primer for PCR amplification. A second, unlabelled primer of the sequence ACGG is used, and the PCR is cycled 20 times. When the resulting amplified DNA is run on a gel, individual A has two different bands, one at 370 BP and one at 220 BP, while individual B has only one band at 220 BP. How does one explain the difference between these two individuals?"

		Individual B is normal, but individual A has a translocation that duplicates the locus.
		A duplication of the locus has occurred, and 150 bases have been added in individual A .
		Individual A is heterozygous, while individual B is homozygous for the catalase-A locus.
		The DNA sample from individual A got contaminated with a gorilla's DNA.

"The Vulcan salute, marked by the ability to form a V between your middle and ring fingers, is possibly inherited in a dominant fashion. Two individuals who are heterozygous for the trait are planning to have 3 children. What is the probability that 2 of the 3 children are unable to do the Vulcan salute? (RIP Spock)"

		0.25
		0.422
		0.0156
		0.375
		0.141

"The ability to taste phenylthiocarbamide (PTC) is dominant to non-tasting. The locus is not sex linked. If a tasting woman with a non-tasting father marries a tasting man and they have a non-tasting daughter for their first child, what is the probability their second child will be a tasting daughter?"

		1/8
		1/4
		1/2
		2/3
		1/3
		3/8

"The ability to taste phenylthiocarbamide (PTC) is dominant to non-tasting. The locus is not sex linked. If a tasting woman with a non-tasting father marries a tasting man and they have a non-tasting daughter for their first child, what is the probability their second child will be a tasting daughter?"

		1/8
		1/4
		1/2
		2/3
		1/3
		3/8

Answer 1

The male tortoiseshell kitten will be XXY (XoX+Y) because of the disjunction at meiosis II in the mother.

A tortoiseshell kitten has both black and orange patches on his fur which is only possible by the activation of only one X chromosome in every shell. But a male only has one X chromosome, which means that for a male kitten to be tortoiseshell, he must have two X chromosomes along with the Y chromosome. And this condition is possible when the XX chromosomes fail to separate during the meiosis II phase in females, resulting in an XXY male kitten.