Chapter 2 Q&A

For cross BB x Bb, what is the expected genotype and phenotype ratio?

genotype ratio will be 1/2 BB and 1/2 Bb. phenotype will be all B.

The dorsal pigment pattern of frogs can be either "leopard" or "mottled." The trait is controlled by an autosomal gene. Males and females are selected from pure-breeding populations and a pair of reciprocal crosses is performed. The cross results are shown: Cross 1: P: male leopard x female mottled F1: all mottled F2: 70 mottled, 22 leopard Cross 2: P male mottled x female leopard F1: all mottled F2: 50 mottled x 18 leopard in the F2 progeny form both crosses, what proportion is expected to be heterozygous?

1/2 of the F2 of both crosses are expected to be homozygous and 1/2 are expected to heterozygous.

True or false? if false correct statement. If a dihybrid cross is performed, the expected genotypic ratio is 9:3:3:1.

False The expected phenotype ratio is 9/16 : 3/16 : 3/16 : 1/16, assuming simple dominance and independent assortment of genetic loci (AaBb x AaBb). The genotype ratio is 1/16 (AABB) : 2/16 (AABb) : 1/16 (AAbb) : 2/16 (AaBB) : 4/16 (AaBb) : 2/16 (Aabb) : 1/16 (aaBB) : 2/16 (aaBb) : 1/16 (aabb)

True or false? if false correct statement. if a dihybrid F1 plant is self-fertilized, 1/2 of the progeny will be heterozygous at one or both loci.

False. Being "heterozygous at one or both loci" excludes only the progeny that are homozygous at both loci. There will be 1/16 AABB, 1/16 AAbb, 1/16 aaBB, and 1/16 aabb. All four genotypes will be true-breeding; therefore 1/4 of the progeny will be homozygous for both loci. Therefore 3/4 will be heterozygous at one or both loci (2/16 AaBB, 2/16 AaBB, 4/16 AaBb, 2/16 AaBB, and 2/16 aaBb).

True or false? if false correct statement. Reciprocal crosses that produce identical results demonstrate that a strain is pure-breeding.

False. Reciprocal crosses that produce identical results indicate that the traits being studied are autosomal.

True or false? if false correct statement. The outcome of a trihybrid cross is predicted by the law of segregation.

False. The law of independent assortment is of primary importance in predicting the outcome of dihybrid and trihybrid crosses. The law of segregation is also necessary but not sufficient.

True or false? if false correct statement. If a woman is heterozygous for albinism, an autosomal recessive condition that results in the absence of skin pigment, the proportion of her gametes carrying the allele that allows pigment expression is expected to be 75%.

False. The law of segregation predicts that she will produce two gamete genotypes with respect to her albinism at equal frequency.

True or false? if false correct statement. if a dihybrid F1 plant is self-fertilized, 1/16 of the progeny will be true-breeding.

False. There will be 1/16 AABB, 1/16 AAbb, 1/16 aaBB, and 1/16 aabb. All four genotypes will be true-breeding; therefore 1/4 of the progeny will be true-breeding.

True or false? if false correct statement. A student uses the product rule to predict that the probability of flipping a coin twice and getting a head and then a tail is 1/4.

True

True or false? if false correct statement. A test cross between a heterozygous parent and a homozygous recessive parent is expected to produce a 1:1 genotypic and phenotypic ratio.

True

True or false? if false correct statement. The progeny of a trihybrid cross are expected to have one of 27 different genotypes.

True.

True or false? if false correct statement. if a dihybrid F1 plant is self-fertilized, 9/16 of the progeny will have the same phenotype as the F1 parent.

True.

A male mouse with brown fur color is mated to two different female mice with black fur. Black female 1 produces a litter of 9 black and 7 brown pups. Black female 2 produces 14 black pups. choose symbols for each allele and identify the genotypes of the brown male and the two black females.

assign the letter B for the black allele and b for the brown allele. the brown male is bb. the first black female is Bb the second black female is BB

A male mouse with brown fur color is mated to two different female mice with black fur. Black female 1 produces a litter of 9 black and 7 brown pups. Black female 2 produces 14 black pups. what is the mode of inheritance of black and brown fur color in mice?

likely a single gene with two alleles controlling fur color and black will be dominant to brown.

The dorsal pigment pattern of frogs can be either "leopard" or "mottled." The trait is controlled by an autosomal gene. Males and females are selected from pure-breeding populations and a pair of reciprocal crosses is performed. The cross results are shown: Cross 1: P: male leopard x female mottled F1: all mottled F2: 70 mottled, 22 leopard Cross 2: P male mottled x female leopard F1: all mottled F2: 50 mottled x 18 leopard which phenotype is dominant?

mottled

The dorsal pigment pattern of frogs can be either "leopard" or "mottled." The trait is controlled by an autosomal gene. Males and females are selected from pure-breeding populations and a pair of reciprocal crosses is performed. The cross results are shown: Cross 1: P: male leopard x female mottled F1: all mottled F2: 70 mottled, 22 leopard Cross 2: P male mottled x female leopard F1: all mottled F2: 50 mottled x 18 leopard propose two different genetic crosses that would allow you to determine the genotype of one mottled frog from the F2 generation.

one would be a test cross: the mottled F2 to a true-breeding leopard. another would be a backcross: the mottled F2 to one of its parents (both are heterozygotes).

The dorsal pigment pattern of frogs can be either "leopard" or "mottled." The trait is controlled by an autosomal gene. Males and females are selected from pure-breeding populations and a pair of reciprocal crosses is performed. The cross results are shown: Cross 1: P: male leopard x female mottled F1: all mottled F2: 70 mottled, 22 leopard Cross 2: P male mottled x female leopard F1: all mottled F2: 50 mottled x 18 leopard compare and contrast the results of the reciprocal crosses in the context of autosomal gene inheritance.

the results are consistent with autosomal gene inheritance.