AP Biology Chapter 14

What are three events that occur in meiosis, but not mitosis?

1) In prophase 1, crossing over and synapsis occur. 2) In metaphase 1, tetrads (homologous pairs) line up at the metaphase plate. 3) In anaphase 1, homologous pairs separate and the sister chromatids stay together.

What is the difference between asexual and sexual reproduction?

Asexual reproduction comes from a single individual, while sexual reproduction comes from two parents. There is no fusion of gametes in asexual reproduction. Also, the offspring are clones (identical copies) vs the genetically unique offspring that results from sexual reproduction. Asexual reproduction utilizes mitosis while sexual reproduction needs meiosis. Finally, sexual reproduction results in genetic variation from parents to offspring. The only way to have variation in asexual organisms is through DNA mutations.

What is the importance of crossing over, independent assortment, and random fertilization to increase genetic diversity?

Crossing over causes homologous chromosomes to exchange genetic material. This leads to recombinant chromosomes. Independent assortment of chromosomes means that chromosomes are randomly aligned along the metaphase plate so it is completely random which chromosomes end up in each cell. Random fertilization means any sperm can fertilize any egg. This creates genetic diversity because the sperm is less likely to be similar to the egg. The possibilities are limitless for the DNA each offspring will acquire.

What is crossing over and how does it increase genetic diversity?

Crossing over in Prophase 1 occurs when nonsister chromatids exchange segments. This results in recombinant chromosomes.

What is the difference between haploid and diploid?

Diploid cells have pairs of chromosomes (a full set), one from each parent, and are represented by 2n. Haploid cells have a single set of chromosomes, represented by n.

How does fertilization increase genetic diversity?

During sexual reproduction, any gamete from one parent can combine with any gamete from another parent, resulting in genetically different offspring. This increases the genetic diversity within a population.

What is the importance of homologous chromosomes in meiosis?

Homologous chromosomes carry the same information. You have one from dad and one from mom. They are important because they lead to genetic variation in offspring since the offspring now has DNA from both parents. In addition, homologous chromosomes are needed for crossing over to add even more genetic variation. The random orientation of chromosomes ensures that the 4 haploid cells are genetically unique.

What happens in the series of steps that make up meiosis?

Meiosis involves two rounds of cell division. In meiosis 1, pairs of chromosomes separate, resulting in two haploid cells containing only one of the double chromosomes from each pair. In meiosis 2, double chromosomes separate, resulting in 4 haploid cells, each with single chromosomes.

What is the role of meiosis and fertilization in passing traits to offspring?

Meiosis is needed to create four haploid daughter cells called gametes. These are necessary for fertilization to occur. Once fertilization occurs, the offspring will have traits from both parent's chromosomes.

What are the similarities and differences between mitosis and meiosis?

Mitosis and meiosis are similar in the overall process (PMAT) of how genetic information is passed onto daughter cells. However, mitosis produces two genetically identical cells, while meiosis produces 4 haploid, genetically varied cells.

When does random assortment of chromosomes in meiosis increase genetic diversity?

Random assortment of chromosomes in metaphase 1 can result in different combinations of chromosomes in gametes.

What is the purpose of meiosis?

The purpose of meiosis is to produce haploid gametes.

How is the chromosome number reduced from diploid to haploid?

When a chromosome goes through meiosis to form gametes for sexual reproduction, 4 haploid cells result. Haploid cells have half the number of chromosomes as the diploid cell.