Download GENETICS 310

NAME
GENETICS 310
EXAM 3
April 28, 2015 I. a) Place the letter of the Gene Class and the number(s) of one or more examples in the
blank preceding the definition:
Normal role of the gene
Gene Class
Example gene
B 2
functions to turn on cell division
C, 1
remove thymine dimers from DNA
A, 3,4
functions to turn off cell division
A tumor suppressor 1 xeroderma
B oncogene
2 Src (sarcoma)
C DNA repair
3 RB
4 p53
b) Which of the 3 gene classes (A, B or C in part a) is most likely to cause a problem
when over-expressed and what is the problem?
Class B
Problem
cancer
c) Which gene class is sometimes found in a retrovirus?
B
II. Given the legends:
R_ red eye
E_ gray body
rr white
ee ebony
A test cross is made involving a red-eyed, gray body parent; 15 % of the progeny have
red eyes and ebony bodies.
a) Are the genes linked?
yes
If so, what is the map distance
b) Show the genotypes of the two parents
Red eye, gray body
R E/r e
30 map units
testcross parent r e/r e
c) Show the gametes, with frequencies from each parent:
Red eye, gray body
35% RE
testcross parent: all re
15% Re
15% rE
35% re
III. Check the following that contribute to the “C value paradox”.
Eukaryotic chromosomes have both DNA and histone proteins
X
Some organisms have millions of copies of short DNA repeat sequences
Humans have more DNA than Neurospora, a fungus
Mitochondrial DNA is Circular
X
One algal species has 100 times as much DNA as another
The DNA in eukaryotic chromosomes is coiled and supercoiled
Organelles add a large amount of DNA to eukaryotic cells.
IV. Below are 7 family pedigrees labeled A to G where individuals with a genetic trait are filled in squares or circles. List the pedigrees could potentially result from a trait inherited through each of the mechanisms listed. Pedigree Mechanism A. Sex Linked Recessive A, E, F B. Sex Linked Dominant A, B, C, D C. Cytoplasmic Inheritance C D Holandric Inheritance F E. Sex Limited Inheritance B, F F Sex Influenced trait A, B, C, D, E, F G. V. Give the, visible sex, # of chromosomes, effective treatment if any, loss of IQ (large, small or none) and sex chromosomes present for an individual with the following : Syndrome Sex chrom# Treatment IQ loss Sex chromosomes Turner F 45 Estrogen& HGH small XO Jacob M 47 none small XYY Klinefelter M 47 testosterone small XXY Triplo X F 47 none small XXX Tfm (androgen insensitivity) F 46 remove testes none XtfmY VI. Are the following statements concerning chromosomal aberrations true or false: F Seedless watermelons are haploid. T The bananas we eat are triploid. T Trisomics arise as a result of nondisjunction for a single chromosome. T Bread wheat is an example of an allohexaploid. T Bread wheat is an example of an amphidiploid. F Autotetraploids are common in animals T Some trisomy 21 cases arise when a parent has a translocation F Plants homozygous for a reciprocal translocation are typically semi-­‐sterile VII. Two highly inbred mouse colonies were each homozygous for the following chromosome 1 & 2 arrangements (Letters and numbers indicate specific genes). Colony 1 Colony 2 Chr 1. A B • C D E F A B • C 6 5 4 7 Chr 2. 1 2 • 3 4 5 6 7 1 2 • 3 D E F A) What aberrations separate the two colonies? Paracentric inversion and reciprocal translocation B A purebred female from colony 1 is crossed to a homozygous male from colony 2 and the F1 progeny are viable. Show how F1 chromosomes will appear at synapsis in meiosis1. C) What is the expected frequency of viable gametes for the F1 animals? 25% (lose half of expected per aberration) VII. In sampling from a field of flowers where R”R” are red, R”R are pink and RR are white, it was determined that 64% were red, 32% pink and 4% white. A) What are the allele frequencies for the R” 0.8 and R alleles 0.2 B) Do you think these flowers are open (random) pollinated or self pollinated? random C) What is the basis for your answer to part B? The expected genotypic array matches HW equilibrium under Random mating model VIII. Recall that Rh+ is a dominant single gene trait and rh negative (rh-­‐/rh-­‐) is recessive. Sampling a large population shows that 84% are Rh+ and 16% are rh-­‐. A) Calculate the frequencies of the Rh+ and rh-­‐ alleles (f) rh-­ = 0.4: (f) Rh+ = 0.6 B. Predict the genotypic frequencies in the population 36 % Rh+/Rh+ : 48% Rh+ /rh-­‐: 16% rh-­‐/rh-­‐ C. What assumption(s) are you making in part B? Random mating D. Suppose that it was found that there were many more heterozygous Rh+/rh-­‐ individuals than you predicted. What force or forces are likely to be involved? Selection favoring the heterozygotes (other forces OK, but needed this too) VIII. a) List 3 ways fetal DNA samples can be obtained for prenatal diagnostics. amniocentesis Chorionic villus sampling (or biopsy) Fetal Cell sorting from mother’s blood Cell free fetal DNA in mothers blood b) Very briefly, why can’t fetal blood be tested for the presence of b-­‐globin? b-­‐globin is part of adult HB, and the gene is not expressed in early embryology