Genetic Diversity Lab

Chromosome pairs line up across the equator of the spindle at metaphase I (5). In anaphase I the chromosomes separate and travel to opposite ends of the spindle. The chromosomes migrate to the equators of two new spindles for metaphase 2 (7). Next the chromatids are pulled apart in anaphase 2 to form four clusters of chromosomes in telophase 2. The nuclear envelopes reform around four haploid nuclei that will give rise gamete

Exercise 3B is a study of meiosis. You will simulate the stages of meiosis by using chromosome models. You will study the crossing over and

Later on a male and female haploid cell will join to form a diploid cell with the right number of chromosomes.

Mitosis: This is the process by which a cell duplicates the chromosomes in its cell nucleus in order to generate two identical daughter nuclei.

Mitosis and meiosis are similar in several ways and different in others. The similarities include that both processes involve IPMAT. IPMAT is interphase, prophase, metaphase, anaphase and telophase. The parent cells are diploid. They both end with cytokinesis. In Metaphase and Metaphase II, the sister chromatids line up along the center. Then in Anaphase and Anaphase II, these chromatids are split and pulled towards the centrosomes. The differences are that mitosis consists of 1 division while meiosis consists of 2. Four genetically different, haploid sex cells are the products of meiosis and 2 identical, diploid somatic cells from mitosis. Mitosis occurs in all organisms except viruses and meiosis only occurs in plants, animals, and fungi.

The combinations of 4:4, 2:2:2:2, and 2:4:2 can arise through crossing-over (Burpee et al., 2015). A 2:2:2:2 and 2:4:2 combination indicates crossing-over while 4:4 signifies the recombination did not occur. This process occurs during prophase I of meiosis between Wild Type and Tan isolates crossing-over (Burpee et al., 2015). It was initially thought that recombination was random; however, research from the Evolution Canyons shows that S. fimicola is, indeed, affected by the environment (Burpee et al., 2015). This could possibly be from radiation; however, research in this area is sparse. Certain species of fungi have shown increased resistance to radiation (Saleh, Mayo, & Ahearn, 1988), but studies on S. fimicola have not been documented. Based on this information, I hypothesize that when S. fimicola isolates are exposed to X-ray radiation the crossing-over frequency will increase. To test this theory one Tan and one Wild Type sample (with different combinations of x-ray radiation) was placed in a petri dish diagonal from each other. This was repeated to create four quadrants. The S. fimicola isolates were incubated for two weeks to produce perithecia (Burpee et al.,

1 by crossing over in prophase I , 2 , by indpendenent assortment and three by mutations in S phase

Define the term crossing over. (3 points) During meiosis’ prophase the homologous chromatids exchange segments.

A) Meiosis consists of two cell divisions and is broken up into Meiosis I and Meiosis II. At the beginning of the Cell Cycle, in this case there are four chromatids each from the homologous pairs being A, a, B, b. This is the Diploid number (4) meaning it is 2 times the haploid number that will be seen at the end of meiosis II. During the S phase of interphase, the chromatids replicate and reach the end of G2 phase. Now starting meiosis, during the first stage of prophase I the chromosomes condense and pair up through synapsis with their sister chromatids creating AA, aa, BB, bb. After they pair up they go through a process called crossing over, where the homologous chromosomes share a piece of their genetic material with each other. Crossing over allows for the genetic diversity of chromosomes. Now there are four homologous chromosomes Aa, Aa, Bb, Bb, each containing heterozygous alleles because the sister chromatids exchanged genetic information with their homologous pair. During late prophase I, spindle fibers being to form where they will later attach to a homologous chromosomes centromere. The next stage is Metaphase I. During metaphase I, the homologous pairs line up at the metaphase plate, also known to be the center of the cell. The homologous pairs form a tetrad which is considered a group of four homologous chromosomes. These homologous chromosomes orient themselves randomly, which is know as the process of independent

Meiotic errors are alterations of a cell's chromosome number or structure. Chromosomal alterations happen in both mitosis and meiosis. But in other ways meiosis provides more opportunities for errors. Do to the three sources of genetic variation in meiosis that can also be opportunities for errors. Crossing over in prophase I independent assortment and in anaphase I and anaphase II are major sources of genetic variation in the sexually

Apply your understanding of how alleles assort and combine during reproduction to evaluate a scenario involving a monohybrid cross.

with a frequency of 25%, and crossover gametes between genes Y and Z are observed with a

You are also provided with a heterozygous female, and a homozygous recessive male for a genetic cross. In this particular female, all the dominant alleles are on one chromosome, and the recessive counterparts are on the other homologous chromosome. Due to a chromosomal condition, in the female no recombination occurs between the M and N loci. Normal recombination occurs between the L and M loci. Diagram this cross, and show the genotypes and frequencies of all offspring expected from this cross.

Response Feedback: Meiosis occurs only in replicating gametes or reproducing cells. In phase one, the number of chromosomes is reduced by half but the chromatid pairs remain together. In phase two, the chromatids split apart forming four daughter cells. Non-germ cells such as red blood cells or skin cells undergo mitosis.For more information on this topic, consult:Carol Mattson Porth and Glen Matfin, Pathophysiology, 8th Edition,

In meiosis the pairs of chromosomes (that code for possible outcomes of characteristics) temporarily join and exchange information (crossing over) creating different combinations of gene types (alleles). For example; a pair of chromosomes could be a dominant allele (gene type) and a recessive allele which might code for brown hair. After crossing over it might be recessive which could be blond hair.