Lab 6

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.

2.) Based on the data table, what can you infer about the relative length of time an onion root tip cell spends in each stage of cell division?

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.

If one parent gives their offspring a purple stem allele while the other parent gives the offspring a non-purple cell allele, their offsprings stem will be purple. If there is two parents who both give their offspring non-purple stem alleles, their offspring will have a non-purple stem. This proves my point completely, because it shows all of the outcomes for an offspring. It also shows if you get two purple genes from your parents, you can only show a purple stem, same for the non-purple gene. And if you get one of each gene from your parents, then you’ll get a purple because purple is a dominant

3. a) A plant can have either tall (T) stems or short (t) stems. Two plants are crossed. One has the genotypeTt and the other has the genotype Tt. Fill in the Punnett square below for this cross. (1

b. Similarly, for the redistillation of Fraction 3, predict how the gas chromatogram for the final fraction would have differed from the gas chromatogram of Fraction 3 from Distillation 1.

For this assignment, I will use the websites, lab and materials from this week and complete an internet search of my own on chromosomes. I will write a two- page essay that explains how conditions caused by extra or missing chromosomes reflect a meiotic error. I will also choose two conditions or diseases to review. Also, distinguish among the modes of inheritance.

Round seeds (R) are dominant to wrinkled seeds (r), and yellow seeds (Y) are dominant

2. How will the alleles for these traits assort into the gametes that each parent might produce? (Hint: For a reminder on how alleles sort independently into gametes, refer to the illustration in Part 2, Question 2, in the Student Guide.)

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.

This lab had 2 exercises. Exercise 9.1 involved observing pictures of 60 F2 offspring and recording the phenotypes for 6 different traits. Exercise 9.2 required us to perform the “chi-square test” to determine whether the data we collected matches the standard Mendelian ratio.

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.

Which of the following is true about “meiosis”? Select all that apply. Answers: Reproductive cells undergo meiosis

In Graph 1, the number of homozygous dominant “BB” genotypes increase while the number of heterozygotes “Bb” and homozygous recessive “b” genotypes decrease over generations. The homozygous dominant genotype starts at six. The heterozygotes start at 13. The homozygous recessive genotype starts at 6. After the first generation, the homozygous dominant genotype changed from six to eight while the heterozygote changed from 13 to 9 and homozygous recessive genotype decreased from 6 to 3. While homozygous dominant increases from 8 to 9, the heterozygote decreases to 8 and the homozygous recessive decreases to 1 during the second generation. From the second generation to the third, the homozygous dominant, heterozygous, and homozygous recessive numbers stay the same so, homozygous dominant genotype is still 9, heterozygous genotype is still 8, and homozygous recessive genotype stays at 1. In the last generation recorded, the homozygous dominant increases to 11 as the heterozygotes decrease to 4. However, the homozygous recessive genotype stays at 1.

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.