BSC Chapter 8

BSC Chapter 8 true-breeding strain of tall soybean plants is crossed with a true-breeding strain of short soybean plants. All the offspring are short. Thus, tallness is a _________ trait. - Answer- recessive Genes that confer resistance to antibiotics are usually located on ________ and are transferred between bacterial species via _________. - Answer- plasmids; conjugation People with the _______ blood type are particularly valued as blood donors. - Answer- O The parents of the second filial generation are the ________ generation. - Answer- First filial A population of Drosophila simulans carries three alleles at the white locus: the wild-type allele at 86 percent, w1 at 9 percent, and w2 at 5 percent. What can we say about this locus population? - Answer- The locus must be polymorphic A centimorgan is a unit of - Answer- recombination frequency One true-breeding line of mice is obese and another is lean and light. Dark is dominant to light, but obese and lean exhibit incomplete dominance. What proportion of offspring from a dihybrid cross should be both dark and intermediate between obese and lean? - Answer- 3/8 In bacteria, circular DNA molecules that replicate independently of the main chromosome are known as - Answer- Plasmids Due to the phenomenon of dominance, - Answer- different genotypes can result in the same phenotype In horses, hairs can be black because of allele H1 or white because of allele H2. Horses with both alleles are called blue roans because they have both white and black hairs. What are the expected phenotypic ratios if you crossed blue roan individuals to black individuals? - Answer- Half would be black, and half would be blue roan The most likely explanation for the observation that round is dominant to wrinkled in Mendel's peas is - Answer- The round allele enclosed a functional enzyme, the wrinkled allele encodes a defective enzyme, and the round trait could arise with only one functional allele for the enzyme Suppose the train of bacteria has the genotype EFGhijk and another strain has efgHIJK. After they two strains have been in contact for a while, you find some bacteria that are EFGHIJK. What is the most plausible explanation for this? - Answer- Conjugation One true-breeding line of mice is obese and dark and another is lean and light. Dark is dominant to light, but obese and lean exhibit incomplete dominance. What portion of the offspring from a dihybrid cross should be dark and obese? - Answer- 3/16 In Drosophila, the genes for body coloration and eye size are on different chromosomes. Normal-colored bodies are dominant to ebony-colored (very dark) bodies, and normal-sized eyes are dominant to being eyeless. Line A is true breeding for normal body and normal eye, whereas line B is true breeding for ebony bodies and eyeless. Individuals from lines A and B are crossed. From a dihybrid cross between the F1 generation, 400 flies are scored. How many of these F2 flies are expected to have both normal body color and normal eyes? - Answer- 225 In Drosophila, the genes for body coloration and eye size are on different chromosomes. Normal-colored bodies are dominant to ebony-colored (very dark) bodies, and normal-sized eyes are dominant to being eyeless. Line A is true breeding for normal body and normal eye, whereas line B is true breeding for ebony bodies and eyeless. From a dihybrid cross between lines A and B, 480 flies are scored. How many of these F2 flies are expected to have both normal body color and normal eyes? - Answer- 30 Mendel removed the stamens of the plants in most of his crosses to - Answer- prevent self-fertilization A man has blood type O. From this, we can infer that - Answer- none of his children can be type AB If bacterial conjugation is allowed to take place for more than an hour, two different genes (A and B) are transferred together. Even if conjugation occurs for only a few minutes, both A and B are conjugated or neither of the genes is conjugated. Only when conjugation takes place for only a few seconds are there instances of just one of the genes being transferred. Most likely, genes A and B are - Answer- close together on the bacterial chromosome Consider the progeny of a dihybrid cross. For every double recessive homozygote observed, you can expect _______ double dominant homozygote(s). - Answer- 1 In horses, hairs can be black because of allele H1 or white because of allele H2. Horses with both alleles are called blue roans because they have both white and black hairs. Thus, - Answer- H1 and H2 exhibit codominance Consider crosses between individuals of different heritable phenotypes. The phenotype of the offspring will most likely depend on which parent has a specific phenotype in cases involving - Answer- sex chromosomes