name:______
student ID:______
Genetics L311 exam 3
April 10, 2015
Directions: Please read each question carefully. Answer questions as concisely as possible. Excessively long answers, particularly if they include any inaccuracies, may result in deduction of points. You may use the back of the pages as work sheets, but please write your answer in the space allotted. However, you must show all your work. Clearly define your genetic symbols. We will not make guesses as to what a particular symbol is intended to mean. Also, don’t assume that strains are true-breeding unless this is stated in the question. Finally, show all your work. Good luck.
page 2 ______(20 points possible)
page 3 ______(22 points possible)
page 4 ______(26 points possible)
page 5 ______(17 points possible)
page 6 ______(15 points possible)
total ______(of 100 points possible)
1. Short answers (2 points each, 20 points total)
A. The ability of some bacteriophage to transfer any sufficiently small portion of bacterial chromosome from one strain to another is generalized transduction.
B. A(n) Robertsonian translocation is a special type of rearrangement in which the long arms of two acrocentric chromosomes fuse.
C. In autopolyploidy the duplicate chromosome complement is composed of multiple sets of chromosomes derived from a single species.
D. A genetic element that can exist either free in the cytoplasm or integrated into the chromosome is a(n) episome.
E. The procedure where protein is isolated from cells, separated by SDS-PAGE, transferred to membrane, incubated with a protein-specific antibody and then the antibody detected in some way is called a Western blot.
F. The region of a bacterial cell in which the genome resides, which is not separated from the cytoplasm by a membrane, is called the nucleoid.
G. Deviation from a whole number multiple of the haploid chromosome complement produces aneuploidy.
Please provide concise definitions of the following terms:
H. reverse genetics: Using a cloned gene to generate a mutation in that gene.
I. reporter transgene: Fusing a gene or regulatory regions of a gene to a gene with an easily detected product, such as lacZ, luciferase or gfp.
J. RNAi: Introducing double stranded RNA triggers a pathway that targets the corresponding endogenous gene for degradation, leading to depletion of gene product and a mutant-like phenotype.
2. While exploring an island off the coast of Costa Rica, you discover a dinosaur thought long extinct, called Tejpalasaurus rex, which you take home as a pet. After growing attached, you decide to clone him. Assume you have access to all things you need to do this and that the method discussed in class will work with dinosaurs.
A. Briefly explain how you would go about cloning this animal (6 points).
You would need an egg suitable for Tejpalasaurus development, ideally from Tejpalasaurus. You would remove the nucleus and introduce a nucleus from your pet, probably by fusing one of her somatic cells with the enucleated egg. The egg then needs to be induced to develop and incubated under conditions that permit the resulting embryo to develop (for a mammal this would require implanting in a suitable host).
B. List four reasons why the clones won’t be exactly identical to your original pet dino (6 points).
The clone will be younger
Extranuclear genomes will differ
Random developmental events can’t be duplicated
The environment in which the clone lives will differ
C. You manage to make several clones of Tejpalasaurus rex. Surprisingly a karyotype analysis of your clones found some with unusual chromosome counts. T. rex normally has 39 pairs of chromosomes (i.e. 2n = 78). Fill in the blanks for each of the variants in the table below (10 points):
# chromosomes / ploidy of individual79 / trisomic
117 / triploid
39 / monoploid
156 / tetraploid
77 / monosomic
3A. Your studies of magical talent in British Potter family leads to a remarkable discovery. You find that a single gene, mgc, confers magical abilities. Miraculously you manage to purify the MGC protein and obtain amino acid sequence of a portion of the protein. Name the strategy that you will use and briefly explain how you would go about cloning the mgc gene (8 points)?
You would use nucleic acid hybridization, using degenerate primers. You would prepare DNA (either genomic or cDNA would be fine), cut with appropriate restriction endonuclease, cut vector with enzyme that produced compatible ends, ligate, transform, select transformants, colony lift using degenerate primers as probe (transfer cells to filter, lyse, denature, hybridize with degenerate primers, expose to X-ray film and develop.)
B. After cloning the mgc gene you want to know where it is expressed. You cannot easily address this question in humans so you clone the mouse mgc gene. Explain how you would use the mouse mgc gene to study where it is expressed in mouse. Include the relevant steps and diagram the vector (8 points).
You could fuse either the full length mgc gene or just its promoter to a reporter such as gfp. Put your reporter transgene onto a retroviral vector that includes neoR and transfect ES cells from a black mouse. Select for cells that receive the transgene (verify by PCR). Introduce those cells into an embryo from a while mouse, implant and wait for birth of chimeric mice. Chimeric mice are crossed with white mice. Those that produce all black furred offspring are analyzed for presence of the mgc::gfp transgene by pcr or Southern. Hets are crossed to establish a homozygous line.
4. In the rare dancing lemur of Madagascar, S. reifeisae, you observe two distinct phenotypes: golden fur and brown fur. To study the transmission of this trait you perform crosses that yield the results shown below.
Golden female X Brown male
All Golden
Cross siblings
All Golden
Cross siblings
Golden and Brown
A. Name and describe the type of inheritance determining the fur color in these lemurs (6 points).
This looks like a maternal effect gene controls fur color. In maternal effect, the mother’s genotype determines the offspring’s phenotype through factors deposited in the egg either as RNA or protein.
B. What phenotypic ratio is observed in the F3 generations (4 points)?
3:1
5. You are studying the wild tickling monkey N. kumarae. You want to find out why these creatures are filled with an insatiable desire to tickle others when in large groups. After several bouts of fierce tickling you are able to obtain some hair for genetic testing from several individuals in different troupes. You find that the different troupes have different forms of chromosome 6 present.
A. Determine the order in which the changes occurred and the name of the rearrangement (8 points).
original
duplication
strain III
pericentric inversion
strain II
deletion
strain I
paracentric inversion
strain IV
B. Please diagram synapsis of chromosome 6 in an individual heterozygous for a strain II and a strain III chromosome (3 points).
This is hard to draw on the computer. See your lecture notes, your UTA, the AI or me if you have questions.
6. The production of transgenic crop plants, sometimes referred to as genetically modified plants, is controversial in some places in the world. Please list three potential benefits to engineering such crops and three potential concerns associated with their widespread cultivation (6 points).
Benefits include: better yield, better crop, reduced pesticide use, reduced herbicide use
Drawbacks include: spread of herbicide resistance, spread of pesticide resistance, possible environmental damage, unknown human health risks including the possibility of allergic response in some individuals
7. In two interrupted mating experiments, you obtain the data shown below for the time of entry. All experiments used Hfr strains derived from the same original parent strain.
Hfr1
gal 5 min
arg 8 min
thr 15 min
val 20 min
met 30 min
A. Show the genetic map for each of these genes on the circular chromosome. Indicate the location of each origin and the direction of transfer (5 points).
B. Please describe briefly how you would identify the gal and arg wild-type recombinants that you see in part A of this question (3 points).
After allowing conjugation to occur, cells would be plated on plates that lack gal and include streptomycin and on plates that lack arginine and include streptomycin.
8. Here is the pedigree of a rare genetic disorder. Assume that individuals who marry into the pedigree do not have the mutation that produces the trait.
A. Name and describe the type of inheritance exhibited in this pedigree (4 points).
extranuclear or mitochondrial inheritance
B. What is the probability that the person indicated by the question mark will show the trait (3 points)?
~0
3