The Difference Between Haploid and Diploid Cells

1. Describe the difference between haploid and diploid cells. Can each type of cell go through meiosis?  Why or why not? (2 points)

Haploid cells have one complete pair of chromosomes while diploid cells have two pairs of chromosomes. Only diploid cells go through meiosis. During the process, four haploid cells are produced.  However, haploid cells cannot go through meiosis because they lack enough chromosomes for meiosis. That said, there would not be enough genetic material in daughter cells if a haploid cell went through meiosis.

2. Chromosomes can be viewed as “collections of genes.”  Diploid organisms have homologous pairs of chromosomes; one member of each pair was received from each parent, and so these ”collections” are not completely identical.  Recalling the cell division processes that give rise to different kinds of cells, consider how the ”collections of genes” that occur in the somatic cells (general body cells) of an individual compare with the ”collections of genes” that occur in the gametes produced by the same (human) individual. Explain the difference in terms of both the types of combinations that can occur and the quantity of genetic information in the cell. (2points)

The collection of genes occurring in somatic cells of an individual is the same. The reason behind this is that are diploid and divide through mitosis. On the other hand, gametes produced by the same individual have different genetic material since the parent cell’s genetic material is shuffled before division takes place. As such, the types of combinations that occur are virtually limitless.

3. Crossing over between homologous chromosomes occurs during meiosis.  What is the significance of two genes occurring physically close to each other (that is, at nearby loci) on the same chromosome - what effect does this have on how often crossing over will occur between them? Conversely, what is the impact of there being a large distance between two genes on the same chromosome on the probability and frequency of crossing over between them? Is there a limit to this effect? (2 points)

When two genes on the same chromosome occur physically close to each other, the frequency of crossing over decreases. On the other hand, crossing over occurs more often when there is a large distance between two genes on the same chromosome. This phenomenon facilitates genetic variation.

4. The diagram below shows chromosomes in a nucleus that has already been through an S-phase and is on the way to a segregation of chromosomes.  Based on what you see in the diagram, answer the following questions:

a. What is the haploid chromosome number in this cell? (1 point)

The cell’s haploid chromosome number is 3.

b. Is this nucleus undergoing mitosis or meiosis?  Identify the features of the diagram that helped you to make this decision. (1 point)

The nucleus is undergoing meiosis. The reason behind this is that the chromosomes have crossed over; a phenomenon that only occurs during meiosis.

c. Which phase of cell division is this cell experiencing? Describe what the next phase will be and what the chromosome numbers will be for the daughter cells resulting from this process (at the very end). (2 points)

The cell is experiencing metaphase of meiosis I. The next phase, therefore, will be anaphase. The chromosome numbers for the daughter cells at the very end of the process is 3.