They are linked together on the same chromosome. A recombination frequency of 28% between two Drosophila melanogaster genes suggests which of the following regarding their relative chromosomal locations? They are linked together on the same chromosome. They are unlinked from each other on the same chromosome. They are located on two different chromosomes. Recombination frequency does not provide information with respect to chromosome location. Answer: A The recombination frequency is less than 50%, which means that they are linked.

They are linked together on the same chromosome. A recombination frequency of 28% between two Drosophila melanogaster genes suggests which of the following regarding their relative chromosomal locations? They are linked together on the same chromosome. They are unlinked from each other on the same chromosome. They are located on two different chromosomes. Recombination frequency does not provide information with respect to chromosome location. 2

mutations will always occur in non-protein-coding regions A low mutation rate over time can be advantageous to plants and animals because __________. select mutations can allow organisms to adapt to constantly changing environmental conditions mutations will always occur in non-protein-coding regions most mutations cause loss-of-function for the protein encoded by that mutated gene most mutations do not cause loss-of-function for the protein encoded by that mutated gene Answer: A Mutations that are hereditary (as opposed to somatic mutations) give rise to genetic variation within populations of plants and animals. If a particular hereditary mutation confers an advantage to its bearer, then natural selection can favor individuals that share this trait. Thus, mutation is the basis for the evolution of favorable traits. 3

mutations will always occur in non-protein-coding regions A low mutation rate over time can be advantageous to plants and animals because __________. mutations can allow organisms to adapt to constantly changing environmental conditions mutations will always occur in non-protein-coding regions most mutations cause loss-of-function for the protein encoded by that mutated gene most mutations do not cause loss-of-function for the protein encoded by that mutated gene 4

Consider a cross between the parental genotypes RRTT and rrtt in a pea plant. The F1 offspring are doubly heterozygous (dihybrid). The recombinant gametes produced in this F1 generation are __________. RT and rt Tt and Rr Rt and rT RR and TT Answer: C The parental types are RT and rt, therefore Rt and rT must be the recombinant types. 5

Consider a cross between the parental genotypes RRTT and rrtt in a pea plant. The F1 offspring are doubly heterozygous (dihybrid). The recombinant gametes produced in this F1 generation are __________. RT and rt Tt and Rr Rt and rT RR and TT Answer: C The parental types are RT and rt, therefore Rt and rT must be the recombinant types. 6

the genes are nearby on the same chromosome The principle of independent assortment holds true for two given genes only if __________. the genes are nearby on the same chromosome the recombination frequency between the genes is less than 50% the genes are linked the genes are on different chromosomes or very far apart on the same chromosome Answer: D Genes will assort independently if they are on separate chromosomes. If they are located on the same chromosome and are far enough apart from each other (i.e., exhibit a recombination frequency of 50%), then they are effectively not linked and therefore can still assort independently (as if they were on different chromosomes). 7

the genes are nearby on the same chromosome The principle of independent assortment holds true for two given genes only if __________. the genes are nearby on the same chromosome the recombination frequency between the genes is less than 50% the genes are linked the genes are on different chromosomes or very far apart on the same chromosome 8

Recombinant gametes form in meiosis as a result of __________. crossing over between homologous chromosomes alone independent assortment of allele pairs alone both crossing over between homologous chromosomes and the independent assortment of allele pairs tight linkage between genes on the same chromosome Answer: C There are two critical processes that occur in meiosis in order to generate recombinant gametes. Crossing over will occur between unlinked genes on homologous chromosomes. In addition, independent assortment of allele pairs occurs between unlinked genes. 9

Recombinant gametes form in meiosis as a result of __________. crossing over between homologous chromosomes alone independent assortment of allele pairs alone both crossing over between homologous chromosomes and the independent assortment of allele pairs tight linkage between genes on the same chromosome 10

In Mendel’s monohybrid cross between true-breeding round and wrinkled peas, the F2 progeny consisted of the genotypes RR, Rr, and rr (see the figure in the Hint). Which genotype(s) from this F2 generation will breed true if self-crossed? RR Rr rr RR and rr Answer: D Both self-crosses would produce a genotype and phenoytype identical to those in the original parental generation. 11

In Mendel’s monohybrid cross between true-breeding round and wrinkled peas, the F2 progeny consisted of the genotypes RR, Rr, and rr (see the figure in the Hint). Which genotype(s) from this F2 generation will breed true if self-crossed? RR Rr rr RR and rr 12

If you cross a white-eyed female (ww) to a red-eyed male (WY) Drosophila fly, you will see red-eyed females and white-eyed males in the F1 generation. If you cross an F1 red-eyed female to an F1 white-eyed male, what is the approximate percentage of total progeny in the F2 generation that are white-eyed males? 100% 50% 25% 0% Answer: C The F1 cross is Ww  wY, therefore the expected F2 progeny genotypes are: 25% Ww, 25% ww, 25% WY, and 25% wY. Thus, 1/4 of the progeny are expected to be white-eyed males. 13

If you cross a white-eyed female (ww) to a red-eyed male (WY) Drosophila fly, you will see red-eyed females and white-eyed males in the F1 generation. If you cross an F1 red-eyed female to an F1 white-eyed male, what is the approximate percentage of total progeny in the F2 generation that are white-eyed males? 100% 50% 25% 0% 14