Crossing Over Research Paper

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

Meiosis consists of one DNA replication and two nuclear divisions resulting in 4 daughter cells. The process which provides for genetic variation is crossing over. Crossing over occurs in the early stages when homologous chromosomes move together so that their chromatids form a tetrad. This is called synapsis and allows for the exchange of chromosome sections.

These bivalents line up along the equator during metaphase I, the arrangement of the bivalent is completely random and relative to the orientation of the other bivalents, this is known as the independent assortment of chromosomes. This is followed by anaphase I where the homologous chromosomes separate and move to the opposite poles of the cell. At telophase I the cell divides into two, each cell contains one chromosome from each homologous pair. The second stage of meiosis is similar to mitosis.

parent carried the b allele. The F1 offspring of such a cross would be Bb, and

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

For one of the monohybrid crosses you performed in this Investigation, describe how to use the phenotype ratios to determine

Suppose the feather color of a bird is controlled by two alleles, D and d. The D allele results in dark feathers, while the d allele results in lighter feathers.

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

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

Now you have determined some facts about the grounded allele and the trait that it causes. Given what you know, do you expect the mutant F1 flies to be homozygous or heterozygous for the allele that causes the grounded trait? According to your reasoning, if you mated two mutant F1 flies, what percentage of flies would you expect to be wild type versus mutant in the F2 progeny? Draw a Punnett square of this cross to justify your answer.

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.

The distances between the centromeres and genes were determined. Refer to results section for exact distances for each gene. The distance or location is a significant because it can affect the frequency of crossing over and thus recombination. The results of this crossing further determine if recombination occurred in Sordaria. Recombination is important because it is an indication of the genes joining together to form new combinations; increasing genetic variation/diversity. The results encountered (according to percentage error) indicate that recombination did not occur in high quantities. The data collected experimentally (my own group) resulted with a 60% recombinant rate concerning the wildtype and tan crossing. The wildtype and grey crossing resulted with a 52% recombinant rate. The arrangement most encountered was a 2+: 2t: 2+: 2t, meaning a crossover between the gene and centromere did occur in the second division of meiosis II (recombinant chromatids). Another common arrangement encountered were the asci having a pattern of 6:2 and one 5:3 arrangement due to the genes undergoing gene conversion.

Introduction: The gene that codes for red-green color blindness, the most common form of color blindness in humans, is found on the X chromosome. One in 12 males is color blind. In females, however, color blindness affects only about 1 in 200. Why is

In order to select the chromosome with a maximum fitness value to have a better chance to be selected, roulette wheel selection mechanism was adopted. Two chromosomes are selected as parents as follows.

The pairs of alternative traits examined segregated among the progeny of a particular cross, some individuals exhibiting one traits, some the other