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Biology 303 Genetics - Study Guide Final - Fall 2004=

Fall 2004 exam

1. = Female Drosophila heterozygous for three recessive traits (mahogany eyes, curled wings, and ebony body) were testcrossed. The phenotypes of the testcross progeny are below. Chi square analys= is of the data suggests that the three genes are linked (analysis not shown).<= o:p>

Draw a genetic map that indicates the order and relative map distances for these three genes.

Wildtype &n= bsp; = ; &n= bsp; 347 &= nbsp; &nbs= p; mahogany, curled, ebony &= nbsp; 368

mahogany= = &nb= sp; 8 = &nb= sp; curled &= nbsp; &nbs= p; &= nbsp; &nbs= p; 78

mahogany= , curled &= nbsp; &nbs= p; 68= &nb= sp; = curled, ebony &n= bsp; = ; &n= bsp; 10

mahogany= , ebony &= nbsp; &nbs= p; 67= &nb= sp; = ebony &= nbsp; &nbs= p; &= nbsp; &nbs= p; 54

2. = Sickle-cell anemia results from a mutation in the gene coding for β-hemoglobin. Individuals homozygous for this mutation (Hb^S Hb^S) have sickle-cell anemia, or “sickle” shaped erythrocytes, which can be fatal. Carriers of t= he sickle-cell trait (Hb^A Hb^S) have a mild form of sickle-cell anemia since many of their blood cells have= the normal phenotype. In one area of Africa = the fitness values for each genotype are as follows:

Genotype &n= bsp; Fitness

Hb^A<= /span> = Hb^A^&=
nbsp;0.88

Hb^A<= /span> = Hb^S^&=
nbsp;1.00

Hb^S<= /span> = Hb^S^&=
nbsp;0.14

a. = If the equilibrium frequency of sickle-cell individuals in this population is 10% in the current generation, what do you expect the equilib= rium frequency of sickle-cell individuals to be in the following generation?

b. = What do you expect will happen to the genotypic and allelic frequencies of this trait over the long term if these fitness values remain the same? Explain your answer.

3. = In tomatoes, cut leaf and potato leaf are alternative characters, w= ith cut (C) dominant to potato (c). Purple stem and green stem are another pair of alternative characters, with purple (P) dominant to green (= p). A true-breeding cut, green tomato plant is crossed with a true-breeding pot= ato, purple plant, and the F1 plants are allowed to interbreed. The 320 F2 plants were phenotypically 189 cut, purple; 67 cut, gr= een; 50 potato, purple; and 14 potato, green. Propose= a hypothesis to explain the data, and use the chi-square to test the hypothes= is.

4. = Eukaryotic mRNA undergoes several posttranscriptional modifications before it can be translated into a polypeptide. Illustrate or describe these modifications and describe why each is necessary.

5. = Avery, Macleod, and McCarty demonstrated that DNA was the transform= ing principle by separating parts of smooth bacteria and then using enzymes to = test each component and confirm that DNA was the component of the preparation wh= ich transformed rough bacteria.

a. = What enzymes did they use and why?

b. = How would their experi= ment have differed if protein were the genetic material?

6. = Below is a partial sequence of a transcribed region of DNA. The sequence corresponds to the non-template strand of DNA. <= /p>

a. = What polypeptide would result from this strand? <= /p>

b. = Assume that a transversion mutation occurs at nucleotide 12 (nucleo= tide 12 is bold, italicized, and underlined). Would this mutation be a missense, nonsense, or silent mutation? Explain your answer.

……&= nbsp; T T T C G A = A C T A T A G C C G A A A= G T G G T …….

7. = Imagine a mutation in a bacterial genome that causes the enzyme primase to work incorrectly. Using your knowledge of = DNA replication, describe how this mutation might affect this process. Describe= how the other enzymes involved in replication will be affected by this single change in the process. (Hint: describe the normal prokaryotic replication process and point out differences based on this mutation.)

8. = Recombinant DNA technology relies on cloning of DNA segments into cloning vectors. Describe several different kinds of cloning vectors and why you might choose to use each of them over some other vector.

9. = If no glucose is present in the environment, use diagrams or words = to describe how the lac opero= n functions in the presence and absence of lactose.

Extra Credit (up to 10 pts)

A newly discovered beetle species, doodlybugs, ha= ve elytra (the hard shell covering the wings) color controlled by three loci. = The C locus has a dominant C allele that causes solid colored elytra; the reces= sive allele results in white spots on a colored background. The B locus black co= lor allele B is dominant to the brown allele b, but these genes are expressed o= nly in the genotype aa. = The A locus has a dominant allele that causes yellow coloration regardless of the= B alleles, so A- individuals are yellow. Six young doodl= ybugs were produced in a mating between a solid yellow male and a solid brown fem= ale. Their phenotypes were 2 solid black, 1 spotted yellow, 1 spotted black, and= 2 solid brown.

a. = What are the genotypes of the parents?

b. = What is the probabilit= y that the next offspring will be spotted brown?

Fall 2003 exam

1. = A four point testcross was conducted to investigate the linkage relationship of four gen= es in the flowering plant Arabidopsis thaliana. The reces= sive allele cnx confers resistance = to chlorate, ga3 results in giberellin-respo= nsive dwarfism, sex1 causes overproduction of starch, and th2 creates a requi= rement for thiamine. A tetrahybrid for all four genetic markers was created by crossing a plant homozygous for= all four traits (= cnx, ga3, sex1, th2) with a wildtype plant. The tetrahybrid F₁ plant was testcrossed with a homozygous mutant plant. When seeds from the testcross were planted they yielded the following phenotypes:

cnx ga3 sex1 th2<= /p>	185=	cnx ga3 sex1 +	29=
cnx ga3 + th2=	205=	cnx ga3 + +	28=
cnx + sex1 th2<= /p>	2	cnx + sex1 +	26=
cnx + + th2=	3	cnx + + +<= /span>	19=
+ ga3 sex1 th2	24<= /o:p>	+ ga3 sex1 +	&nbs= p; 1
+ ga3 + th2=	21<= /o:p>	+ ga3 + +=	&nbs= p; 4
+ + sex1 th2	26<= /o:p>	+ + sex1 +	198=
+ + + th2=	31<= /o:p>	+ + + +=	198=

a) = Are the = ga3 and sex1 genes linked? What do your results suggest about= the location of the ga3 and sex1 genes on the Arabidopsis chromosomes?

b) = Are the cnx and ga3 genes linked? What do your results suggest about= the location of the cnx and ga3 genes on the Arabidopsis chromosomes?

2. = Warfarin is a rat killer that acts by hindering blood co= agulation. Continued use of the poison has re= sulted in the evolution of resistance in most rat populations because of selection favoring a resistance mutation R. The normal sensitive allele, S, confers and overall advantage w= hen warfarin is not present, such that the relative fitnesses of the SS, SR, RR genotypes are 1.00 : 0.77 : 0.46, respectively. In the presence= of warfarin, however, the ratio of = fitnesses is 0.68 : 1.00 : 0.37.

Assuming that the RR genotype accounts for 10% o= f a rat population predict the frequency of the RR genotype in this population after one generation of wa= rfarin exposure and compare that to the frequency of the RR genotype in one generation without warf= arin exposure. What do your results suggest about= the efficiency of warfarin in eliminating this popu= lation of rats?

3.      = In eukaryot= es the structure of chromatin is a major factor in regulation of gene expression.<= span style=3D'mso-spacerun:yes'> Describe the structure of chromati= n and explain how modification of this structure by HATs and HDs can change the regulation of transcript= ion of eukaryotic genes.   =

4.      = Okazaki fragments are generated on the lagging strand o= f the replication fork. Describe th= e two key enzymes and their enzymatic activities that convert the Okazaki fragments into a continuous str= and of DNA.

5.      = Describe or illustrate how the yeast galactose metabolism g= enes are regulated in the absence of galactose.

6.      = Explain how= a missense mutation in the gal80 gene could lead to constitutive production of the galactose metabo= lizing proteins even in the absence of galactose. Be sure to describe missense mutation in this answer!

7.      = Mouse coat = color is controlled by several genes. At the agouti gene the dominant A allele causes the hair shaft to have a band of yellow whereas the recessive aa genotype causes a solid color hair shaft. The brown gene (with dominant allele B, recessive b) has an epi= static relationship with the agouti locus as follows: B- A- is agouti, B- aa is black, bb A- is cinnamon-colored and bb <= span class=3DSpellE>aa is brown.&nbs= p; An agouti female had the following offspring: 3 agouti, 2 ci= nnamon, 1 black and 1 brown. Show the genotypes of the offspring and mother.&nbs= p; What is (are) the possible genotype(s) / phenotype(s) of the male parent?

8.      = Draw a plas= mid that includes a polylinker region, a selectable marker and an origin of replication. Describe how each of these regions contributes when using this plasm= id to construct a DNA library.