WorksheetsMeiosis and Sources of Genetic Variation (Unit 5 A)
Total questions: 10
Worksheet time: 14mins
Table 1 shows the stage and number of cells and chromosomes per cell at the end of the stage in a 2n=24 organism. Which of the following statements correctly describes the chromosomes in each daughter cell at the end of meiosis I ?
Each daughter cell contains 12 chromatids. Each chromatid is one of two from a single chromosome with the other one of the pair found in the other daughter cell.
Each daughter cell contains 12 chromosomes, each composed of two chromatids. Since the chromosomes were randomly divided, one daughter cell may contain both of a pair of homologous chromosomes, while the other cell contains both of another pair of homologous chromosomes.
Each daughter cell contains 12 chromosomes, each composed of two chromatids. Each chromosome is one of a pair of homologous chromosomes from the parent cell, with the other homologue found in the other daughter cell.
Each daughter cell contains 24 separate chromatids. Since every two chromatids were originally joined, forming one homologous chromosome, the number of chromatids is divided by two to determine the number of chromosomes.
Both mitosis and meiosis begin with a parent cell that is diploid. Which of the following best describes how mitosis and meiosis result in daughter cells with different numbers of chromosomes?
In mitosis, the chromosomes consist of a single chromatid, which is passed to two haploid daughter cells. In meiosis, the chromosomes consist of two chromatids during the first round of division and one chromatid during the second round of division, resulting in two haploid daughter cells.
In mitosis, synapsis of homologous chromosomes results in four haploid daughter cells after one division. In meiosis, synapsis of homologous chromosomes occurs during the second division and results in four diploid daughter cells.
Mitosis produces one identical daughter cell after one round of division. Meiosis has two rounds of division and doubles the number of chromosomes in the second round of division, producing four diploid cells.
Mitosis produces two identical diploid daughter cells after one round of division. Meiosis produces four haploid daughter cells after two rounds of division.
Saccharomyces cerevisiae is a diploid yeast species that can reproduce either sexually or asexually. An experiment was performed to induce mitotically dividing S. cerevisiae cells in G2 to undergo meiosis. Which of the following best describes the steps these cells will follow to form gametes?
The first division will result in crossing over between homologous chromosomes, and the second division will reduce the original number of chromosomes by half in the daughter cells.
The first division will reduce the number of chromosomes by half for each daughter cell, and the second division will result in each daughter cell having one-fourth of the original number of chromosomes.
The first division will move single chromatids to each daughter cell, and the second division will double the number of chromosomes in each daughter cell.
The first division will reduce the number of chromosomes by half for each daughter cell, and the second division will move single chromatids to each daughter cell.
Scientists have found that DNA methylation suppresses crossing-over in the fungus Ascobolus immersus. Which of the following questions is most appropriately raised by this specific observation?
Is the level of genetic variation in the gametes related to the amount of DNA methylation observed?
Without crossing-over, will gametes be viable and be able to produce zygotes?
Does DNA methylation result in shorter chromosomes?
Is this species of fungus a diploid organism?
During prophase I replicated homologous chromosomes pair up and undergo synapsis. What testable question is generated regarding synapsis and genetic variability by Figure 1 ?
Is the distance between two gene loci related to crossover rate?
Does crossing over occur more often in some chromosomes than in others?
Is crossing over inhibited by methylation?
Is crossing over promoted by methylation?
A model showing two possible arrangements of chromosomes during meiosis is shown in Figure 1. Which of the following questions about genetic diversity could most appropriately be answered by analysis of the model in Figure 1 ?
Does crossing-over generate more genetic diversity than the fusion of gametes does?
Does DNA methylation prevent independent assortment during metaphase II ?
How does the independent assortment of the two sets of homologous chromosomes increase genetic diversity?
Do daughter cells that are not genetically identical to parent cells produce viable zygotes?
Nondisjunction during meiosis can negatively affect gamete formation. A model showing a possible nondisjunction event and its impact on gamete formation is shown in Figure 1. Which of the following best describes the most likely impact on an individual produced from fertilization between one of the daughter cells shown and a normal gamete?
Because nondisjunction occurred in anaphase I , all gametes will be normal and the resulting individual will be phenotypically normal.
Because nondisjunction occurred in anaphase I , all gametes will have an abnormal chromosome number and the individual will likely exhibit phenotypic evidence of the nondisjunction event.
Because nondisjunction occurred in anaphase II , all gametes will be normal and the resulting individual will be phenotypically normal.
Because nondisjunction occurred in anaphase II , all gametes will have an abnormal chromosome number and the individual will likely exhibit phenotypic evidence of the nondisjunction event.
Which of the following is NOT a source of genetic variation that causes siblings to look different from one another?
Independent assortment
Random fertilization
Crossing Over
Meiosis
All of these are sources of genetic variation
Figure 1 illustrates the X and Y chromosomes during meiosis I and meiosis II of normal spermatogenesis in a mammal species. If the normal spermatogenesis is disrupted, the gametes can have different chromosomes than expected. Which of the following is the most likely cause of one of the four gametes having two X chromosomes and one having neither an X nor a Y chromosome?
Nondisjunction of the chromosomes during meiosis I
Nondisjunction of both the X and Y chromosomes during meiosis II
Nondisjunction of the Y chromosome during meiosis II
Nondisjunction of the X chromosome during meiosis II
Trisomy 21 is a condition in which a child is born with an extra chromosome in pair 21. Researchers assessed the frequency of children born with trisomy 21 by age of the mothers at birth (maternal age) and primary cause of the error leading to trisomy 21. The findings are presented in Figure 1. Based on the data in Figure 1, which of the following is most likely the primary cause of the pattern of frequency of trisomy 21 births in the selected maternal age-groups?
At older maternal ages, there is an increase in the number of errors during mitosis, which leads to an increase in nondisjunction during egg production.
The incidence of nondisjunction errors in meiosis during sperm production is positively correlated with increasing maternal age.
At older maternal ages, the incidence of errors in meiosis during egg production increases, which leads to an increase in nondisjunction.
Errors in meiosis leading to nondisjunction are more likely to occur during meiosis I than during meiosis II
