Exam 6: Genetic Linkage and Mapping in Eukaryotes

You notice that in most biology and genetics textbooks, the authors show that Gregor Mendel used flower color as one of his pairs of traits. The purple flower phenotype is dominant to the white flower phenotype. However, if you go back to Mendel's experiments, you see that he actually studied seed coat color. The purple seed coat phenotype was dominant to the white seed coat phenotype. Mendel did note that plants with purple seed coats had purple flowers and plants with white seed coats had white flowers. Is the gene for seed coat color pleiotropic because it also affects flower color, or are the seed coat color gene and the flower color gene very closely linked? To find out the answer to this question, you assume that the genes for flower color and seed coat color are different genes, and your null hypothesis is that they assort independently. You designate the flower color gene wf and the seed coat color gene sw. Plants that are WF__, SW___ have purple flowers and purple seed coats. Plants that are wf wf, ws ws have white flowers and white seed coats. You do the testcross WF wf, SW sw X wf wf, sw sw and collect 15,206 offspring. What result would tell you that the wf and sw loci are probably the same, pleiotropic locus?

The process of recombination may rarely occur during mitosis.

If you want to determine how the alleles of different loci interact in their various combinations, it is best to have a system where you do not have to worry about dominance and recessiveness. Which of the following would represent a system where you do not have to worry about dominance and recessiveness?

Two genes that are located on the same chromosome are said to be _______.

The number of linkage groups in an organism with sex chromosomes equals:

The genotype hsp+ HSP- is something that you could easily expect to find in the fungus Neurospora crassa.

While mapping two genes in Drosophila, you observe 30 recombinants among 200 total offspring. What is the distance between these genes?

Which of the following procedures may be used to map genes in a fungi with an unordered tetrad ascus?

In a chi-square test to determine if two genes are linked or assorting independently, what is the default (null) hypothesis that is tested?

An organism that contains patches of tissue that vary for a specific characteristic such as a pigment, can be an example of which of the following?

An ascus that contains two parental spores and two nonparental spores is called a tetratype.

Map distances above 50 are considered unreliable due to the occurrence of double-crossovers between the genes.

Crossing over is more likely to occur between genes that are ______ on a chromosome.

Twin spotting provides evidence of what genetic event?

Mitotic recombination occurs between homologous chromosomes. In which of the following would you not expect to encounter mitotic recombination?

The diploid garden pea plant has 14 chromosomes. The haploid fungus Neurospora crassa has 7 chromosomes. Neither organism has separate male and female individuals. Therefore, the number of linkage groups in these two organisms is:

In fungi like Neurospora crassa, the diploid structures are called spores.

The rearrangement of alleles by the process of crossing over is called genetic linkage.

The visual proof that chromosomes exchange pieces of information during crossing over was provided by __________.

You have calculated the interference value for a given mapping experiment to be 30%. What does this mean?