1. During which meiotic phase are sister chromatids separated?
Prophase I
Metaphase I
Metaphase II
Anaphase I
Anaphase II
2. One cell that undergoes meiosis will yield how many independent cells?
1
2
3
4
5
3. In which generation of a monohybrid cross do all the individuals look the same?
Parental
F1
F2
F3
F4
4. In a monohybrid cross, the two parental genotypes are AA and aa. The genotype of all F1 plants is Aa. If the F1 plants are crossed to get an F1 generation, what percentage of the F2 generation will have the dominant phenotype?
0%
25%
50%
75%
100%
5. You are performing a dihybrid cross with two traits encoded by two different genes. These genes are on two different chromosomes and follow the law of independent assortment. The two parental genotypes are AABB and aabb. The genotype of all F1 plants is AaBb. What phenotype ratio will you observe in the F2 generation?
8:4:2:1
1:1:1:1
4:2:2:1
1:2:2:1
9:3:3:1
6. A scientist is studying the inheritance of two traits: stem height and stem color. Tall is dominant over short; brown is dominant over green. The scientist wants to do a test cross to determine the genotype of a tall, brown F1 hybrid individual. What will be the height and color of the other plant he uses in this test cross?
Tall and brown
Tall and green
Short and brown
Short and green
It doesn’t matter; any of the above will work.
7. You are studying the inheritance of stem height and stem color. For height, the tall phenotype is dominant over short; for color, the brown phenotype is dominant over green. You mate a purebred tall, brown plant to a purebred short, green plant and all of the F1 offspring are tall and brown. You then mate two of these F1 hybrid offspring together, and you count the following phenotypes in their F2 offspring: 61 tall and brown, 1 tall and green, 2 short and brown, and 18 short and green. Which of the following is probably true?
The two genes controlling these traits are sex linked.
The two genes controlling these traits might be on different chromosomes.
The two genes controlling these traits are linked with no crossing over.
The two genes controlling these traits are nearby on the same chromosome.
The two genes controlling these traits are far apart on the same chromosome.
8. Which of the following is usually NOT true of an autosomal recessive disease?
Most people with the disease have parents who do not have the disease.
An equal number of males and females get the disease.
If both parents have the disease, 50% of their offspring will have the disease.
If both parents are heterozygous, 75% of their children will not get the disease.
The genes for the disease are not located on the sex chromosomes.
9. A woman who is a heterozygous carrier of the hemophilia allele marries a man who has hemophilia. What percentage of their female children would you expect to have hemophilia?
0%
25%
50%
75%
100%
10. A boy with red-green color blindness has a color-blind father and a mother who is not color blind. From which parent did the boy inherit his color blindness?
No way to know—it could have been either one.
His father
His mother
It had to come partly from both his mother and father.
It had nothing to do with either his mother or father.
Explanations1. E
In meiosis, sister chromatids separate during anaphase II. During prophase I, sister chromatids are linked at their centromeres. At metaphase I, each pair of sister chromatids lines up in the middle of the cell together with its homologous pair of sister chromatids, and only homologous chromosomes separate during anaphase I. During metaphase II, each pair of sister chromatids again lines up along the metaphase plate, but they do not separate until anaphase II.
2. D
Meiosis divides a single diploid cell into four haploid cells. In the case of oogenesis, only one of those daughter cells goes on to become a fully developed egg cell, leaving three “polar bodies” to disintegrate; the original product, however, is still four cells.
3. B
The first generation of offspring from a hybrid cross will all look the same. A hybrid cross involves the mating of a homozygous dominant individual with a homozygous recessive individual, so the parents do not look the same. In the F1 generation, all offspring will have genotype Rr and will all show the dominant trait. Other generations will contain some individuals with the dominant phenotype and some with the recessive phenotype and so will not all look the same.
4. D
Approximately 75% of the F2 generation will exhibit the dominant phenotype. Genotypically, there will be three types of offspring: 25% homozygous dominant, 50% heterozygous dominant, and 25% homozygous recessive. Only the homozygous recessive will show the recessive phenotype—therefore, a total of 75% will have the dominant phenotype.
5. E
Because these genes are on separate chromosomes and therefore act independently, we can use a Punnett square to work out the results of this dihybrid cross.
10. C
Although the father is color blind, the gene for this condition is located on the X chromosome. The father could not have given his son the condition, because he only contributes a Y chromosome to his son; therefore, the gene that causes the disease must have been inherited from the mother.