1.
What process produces male and female reproductive cells in plants?
Correct Answer
B. Meiosis
Explanation
Meiosis is the process that produces male and female reproductive cells in plants. During meiosis, the number of chromosomes is halved, resulting in the formation of haploid cells called gametes. These gametes, which are the reproductive cells, contain half the genetic material of the parent plant. This reduction in chromosome number is important for sexual reproduction, as it allows for the fusion of gametes during fertilization to restore the full complement of chromosomes in the offspring.
2.
In humans the trait of having freckles (F) is dominant to not having freckles (f).
Which genotype and phenotype are correctly paired?
Correct Answer
C. Ff—freckles
Explanation
The trait of having freckles (F) is dominant, meaning that if an individual has at least one copy of the F allele, they will have freckles. The genotype Ff represents an individual who has one copy of the F allele and one copy of the f allele. Since the F allele is dominant, even having one copy of it will result in the phenotype of having freckles. Therefore, the genotype Ff is correctly paired with the phenotype of freckles.
3.
The allele for tasting PTC (T) is dominant to the allele for nontasting PTC (t). Which of these sets of parents can produce offspring who cannot taste PTC?
Correct Answer
C. a heterozygous male who can taste PTC and a heterozygous female who can taste PTC
Explanation
Two heterozygous parents carry the recessive allele, so there is a 25% chance that they would have offspring that would show the recessive trait.
4.
A couple has several children. All of the children have attached earlobes because their parents' genotypes can only produce children with attached earlobes. The allele for unattached earlobes (E) is dominant, and the allele for attached earlobes (e) is recessive. Which of these are most likely the genotypes of the two parents?
Correct Answer
D. Ee and ee
Explanation
The only way the parents can produce 100% homozygous recessive offspring is if they also are homozygous recessive.
5.
A pair of laboratory mice are crossed to obtain offspring. Three alleles found in the female gamete are ABC. Three alleles found in the male gamete are Abc.
Which of these is a possible combination of alleles for the offspring produced by these mice?
Correct Answer
D. AABbCc
Explanation
In fertilization, each gamete contributes its alleles to the zygote.
6.
One parent is homozygous dominant for brown hair (BB). The other parent is heterozygous for brown hair (Bb).
What is the probability that the offspring will have brown hair?
Correct Answer
A. 100%
Explanation
The only possible combinations are homozygous dominant and heterozygous. In both cases, the offspring have brown hair.
7.
The allele for attached earlobes (e) is recessive to the allele for unattached earlobes (E). A woman with the genotype (Ee) and a man with the genotype (ee) have a child.
What is the probability that the child is heterozygous for this trait?
Correct Answer
C. 50%
Explanation
Do a Punnet Square and you will see that the heterozygous (Ee) outcome is possible 50% of the time.
8.
In guinea pigs, the allele for black fur (B) is dominant. The allele for brown fur (b) is recessive. Two guinea pigs were crossed as shown in the Punnett square below. Numbers 1, 2, 3, and 4 represent the types of offspring produced from the cross.
What is the probability that an offspring from this cross would have brown fur?
Correct Answer
A. 0%
Explanation
All the offspring will be either homozygous dominant or heterozygous. In both cases, the phenotype is black, not brown.
9.
In guinea pigs, the allele for black fur (B) is dominant. A homozygous guinea pig (BB) is crossed with a heterozygous guinea pig (Bb). What are the phenotypes of the parents?
Correct Answer
A. Both parents have black fur.
Explanation
When the allele for black fur (B) is dominant, a homozygous guinea pig (BB) will always express the black fur phenotype. In this case, one parent is homozygous for the dominant allele (BB), so it will have black fur. The other parent is heterozygous (Bb), meaning it carries both the dominant black fur allele (B) and the recessive brown fur allele (b). However, because the dominant allele is expressed over the recessive allele, this parent will also have black fur. Therefore, both parents have black fur.
10.
In a species of fly, the allele for red eyes (R) is dominant to the allele for brown eyes (r). Red eye color in the flies is not sex-linked. Students crossed male and female flies that had red eyes and recorded the eye color of their offspring. Their data are shown below.
Fly Offspring
Eye Color
Number of Offspring
Red
77
Brown
27
What are the most likely genotypes of the parent flies?
Correct Answer
B. Rr and Rr
Explanation
The most likely genotypes of the parent flies are Rr and Rr because red eye color is dominant and the offspring includes both red-eyed and brown-eyed flies. This suggests that both parents must have at least one copy of the red eye allele (R) and one copy of the brown eye allele (r), resulting in a genotype of Rr.
11.
A sperm cell of a fruit fly has 4 chromosomes. How many chromosomes are in the cells of a fruit fly’s leg?
Correct Answer
C. 8
Explanation
Sperm cells are haploid. Therefore the number of chromosomes is 1/2 that of the leg cell. To find the leg cell, we must multiply 4 by 2.
12.
Sex cells are produced during
Correct Answer
B. Meiosis
Explanation
Meiosis is the process by which sex cells, such as sperm and eggs, are produced. During meiosis, the number of chromosomes in the parent cells is halved, resulting in cells with half the genetic material. This is important for sexual reproduction as it ensures that when the sperm and egg combine during fertilization, the resulting offspring will have the correct number of chromosomes. Mitosis is the process of cell division that occurs in somatic cells, not sex cells. Fertilization is the process of the sperm and egg combining, not the production of sex cells. Binary fission is a form of asexual reproduction in which a single cell divides into two identical daughter cells.
13.
Which of these represents the number of chromosomes in cells before and after the process of meiosis?
Correct Answer
C. 2n -> n
Explanation
The correct answer is 2n -> n. This represents the number of chromosomes in cells before and after the process of meiosis. In meiosis, the number of chromosomes is reduced by half, so the cell goes from having 2n (diploid) chromosomes to n (haploid) chromosomes.
14.
How many chromosomes are in a normal human skin cell?
Correct Answer
B. 46
Explanation
A normal human skin cell contains 46 chromosomes. Chromosomes are thread-like structures that contain DNA and carry genetic information. In humans, chromosomes come in pairs, with 23 pairs in total, making a total of 46 chromosomes. This is known as the diploid number, and it is the standard number of chromosomes in most cells of the human body.
15.
Which processes of cell division creates genetic diversity?
Correct Answer
B. Meiosis
Explanation
Meiosis is the process of cell division that creates genetic diversity. During meiosis, the genetic material is shuffled and recombined, leading to the formation of genetically unique cells. This is achieved through the crossing over of genetic material between homologous chromosomes and the random assortment of chromosomes during the formation of gametes. In contrast, mitosis is a process of cell division that produces genetically identical cells, as it involves the replication and division of the genetic material without any shuffling or recombination.
16.
During prophase I, sections of homologous chromosomes switch places.
What is this process called?
Correct Answer
C. Crossing over
Explanation
During prophase I of meiosis, homologous chromosomes pair up and exchange genetic material through a process called crossing over. This process involves sections of the chromosomes breaking and rejoining with their homologous partner, resulting in the exchange of genetic information. This genetic recombination leads to genetic diversity among offspring and is an essential step in sexual reproduction.
17.
What results in the separation of chromosomes randomly and independently during the production of sperm and egg cells (meiosis)?
Correct Answer
C. Independent assortment
Explanation
During meiosis, the process of independent assortment occurs, which results in the random and independent separation of chromosomes during the production of sperm and egg cells. This means that each pair of chromosomes aligns randomly during meiosis I, leading to a random distribution of maternal and paternal chromosomes in the resulting gametes. This process contributes to genetic diversity as it allows for different combinations of genes to be passed on to offspring. Binary fission is a type of cell division in prokaryotes, crossing over occurs during meiosis but is not the main cause of the random separation of chromosomes, and mitosis is a different process of cell division that does not involve the production of sperm and egg cells.