Biology 210

Answers to Sample Final Exam Questions (Molecular Biology)

1.

Step 1: Map the gene involved to a chromosomal position by linkage mapping

Step 2: Obtain a clone that maps to that chromosomal position.

Step 3: When you find the gene and determine its base pair sequence, you can determine the amino acid sequence of the protein. From this you can learn about the function of the protein.

2. Much of the human genome is composed of intergenic regions, which do not contain any genes. Many of the recombinant DNA molecules in your human genomic library will have only intergenic sequences as inserts, and contain no genes.

3. There are two good ways you could do this:

First way – Isolate chimp genomic DNA, digest it with restriction enzymes, run it on a gel, and Southern blot the gel. Hybridize the Southern blot with the labeled mouse brainy gene as a probe. Do autoradiography, and if you see bands, you have determined that chimps have a homologue of the mouse brainy gene.

Second way – Isolate chimp genomic DNA, and use it as Template DNA to do a PCR reaction with a pair of primers designed based on the sequence of the mouse brainy gene. run the PCR products on a gel. If you see a band, it respresents the chimp homolog of the mouse brainy gene.

4.
a) A recombinant DNA molecule is a DNA molecule that consists of a fragment of DNA from one species, combined with a fragment of DNA from a different species. One of the fragments of DNA in a recombinant DNA molecule is called a vector.

b)

plasmid

cosmid

bacteriphage lambda genome

or,

yeast artificial chromosome (YAC)

bacterial artifical chromosome (BAC)

5.
autosome – a chromosome that is not a sex chromosome (example: human chromosomes #1-22)

transcription factor – a protein that binds to regulatory sequences of a specific target gene, and regulates the transcription of that target gene

transversion – a change from a purine to a pyrimidine, or from a pyrimidine to a purine, in a DNA molecule.

histone – a protein around which DNA is wrapped in order to package DNA in a chromosome.

6. A mutant allele that is dominant due to haplo-insufficiency codes for too little or no protein, or for a non-functional protein, or a protein with greatly reduced function. This allele is dominant because, in the heterozygous cell, the one wild-type allele of the gene cannot code for enough functional protein to get the necessary cellular function accomplished. The phenotype is thus abnormal.

A mutant allele that is dominant due to dominant gain-of-function codes for too much protein, or a protein with a new, abnormal function, or a protein with excessive function. This mutant protein is “toxic” to the heterozygous cell, even in the presence of the normal protein being coded for by the wild-type allele of the gene.