Genetics Exam

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You may write all over this exam, but only your #2 pencil answers on the blue opscan sheets will be graded. Bubble-in only one answer for each question; there are no purposely tricky questions. If you think you have found a trick question or a question is not clear, ASK when leaving the exam room. You may leave when you are done.

1. Chromosomes, colored bodies, are composed of proteins and DNA; so are chromatids. At metaphase I there are 46 chromosomes aligned in pairs along the human cells equatorial plate. At this stage there are______chromatids. a. 23 b. 46 c. 92 d. 8 e.16

2..After pairing at metaphase I chromosomes disjoin
a. without centromeric fission. b. with chromatids together. c. into opposite daughter cells. d. a,b & c are all true.

3. If a pair of chromosomes at metaphase I contain the alleles A & A in one chromosome and a & a in the other chromosome the first daughter cells will contain a. either a & a or A & A b. either A & a or a & A c. A & a and A & a

d. AB, Ab, aB & ab e. a

4. One reason that parents in many cultures have for centuries asked that their children marry their "own kind" was the belief that the material basis of inheritance was fluid (BLENDING THEORY). Marriage outside their own kind would adulterate the purity of the blood lines. Mendel's experiments refuted this fluid based theory of inheritance.(Not all parents know this.) The critical observation in Mendel's work which led to the rejection of BLENDING THEORY was a. chromosome condensation b. reappearrance of the recessive phenotype in the F2 c. anaphase I pairing d. mitosis e. enteleky

5. The gametic ratio for a heterozygote is roughly 1:1, 1/2 : 1/2 or whatever expression you like for equivalence. This results from a. anaphase I disjunction b. mitotic crossingover c. Chi-square degrees of freedom d. telomeric sequences

e. all of the above

6. Mendel's Law of Independent Assortment basically states that the alleles of two or more genes segregate independently within and between loci; the chromosomal explanation of this observation is a. alignment of nonhomologous chromosomes at metaphase I b. alignment of nonhomologous chromosomes at metaphase II c. alignment of mitochondria at anaphase

d. misalignment of tetrads during mitosis
e. very much like transformation

7. Knowing that the segregation ratios for a set of loci are all 1/2 : 1/2, we can predict the frequencies of all possible gametic types by multiplying, if the loci are on different chromosomes and independent. For an AaBbCcDd four locus heterozygote there are ______ possible gametes of equal frequency. a. 2 b. 4 c. 8 d. 16 e. 32

8. Ten years after the Avery et al experiment was reported (50 ago) Watson and Crick used model building and the data of other workers to propose a double helical model for DNA. In their model a. phosphodiester linkages between sugars are covalent b. purine content = pyrimidine c. the two chains are held by hydrogen bonds d. the DNA molecule is a double helix and bases face each other in the molecules interior e. a,b,c,& d are true

9. The DNA structure proposed by Watson and Crick suggested a replication model which was tested by Meselson and Stahl. They used nitrogen isotopes to label replicating DNA which was then separated into bands on a density gradient. The three possible models of replication predicted different numbers of bands after one and then two DNA replications. For the conservative model of DNA replication two bands were expected after the first round of replication. The semiconservative model predicted the presence of...
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