Download Practice Exam II

G E N E T I C S 310
PRACTICE EXAM II-1
I. Assume that the absence of each of the enzymes in the pathways for pea flower color below is
inherited as a simple recessive (one gene) trait and that the genes are independent.
A)
white1
white2
red.
B)
white
pink
red.
C)
white1
red
white2.
1. How many genes are required for each pathway?
A ¨2
B 2
C 2
(each arrow is an enzyme & one gene per enzyme)
2. A pea that is heterozygous each gene in each pathway is self-pollinated.
a) What color is the heterozygous parent in pathway:
A)
red
B
red
C
red
b) Give the phenotypic ratio expected in the progeny of each selfed heterozygote:
A)
B)
C
9 red:7 white
9 red: 3 pink: 4 white
15 red: 1 white
(red :6 pink :1 white accepted also)
II. Both a man and his wife are heterozygous for α-thalassemia and for sickle cell anemia.
What fraction of their children will be normal?
Since normal is dominant for each trait, 9/16 of the progeny will normal
III. a) What purines (abbreviate!) are found in RNA?
A& G
b) What RNA base pairs with A? U
with T? A
c) What sugar is part of DNA nucleotides?
deoxyribose
d) Which base pair has the most H-bonds?
G:C
DNA A & G
How many
3
IV. Single stranded RNA viruses can be either + stranded, meaning they act directly as a
message or - stranded, meaning they are complementary to the message.
Following is the sequence of part of a - stranded virus:
3'-UACGUAUGUAUGACU-5'
A) Write the sequence of the + strand.
5'- AUGCAUACAUACUGA-3'
B) Show a picture of translation when the last codon in still in position; label all components
including the amino acid sequence of the peptide produced.
peptide bond
"P" site
"A" site
peptidyl synthase
growing amino acid chain
large ribosomal subunit with rRNA
F-MET)•HIS•THR•Tyr
Release factor
tRNA
anticodon
mRNA
UAG
5'AUGCAUACAUACUGA
small ribosomal subunit
stop codon
V. A mutation changes the middle base in a codon near the beginning of a gene from A to G:
T The change could occur spontaneously in the DNA via tautomerization.
T The change is an example of a point mutation.
F The change is an example of a transversion.
T The change would always create a missense mutation.
F The change would affect all subsequent amino acids inserted in translation.
T The change could replace 3 different amino acids with Arg.
T
The mutant organism might have a temperature sensitive phenotype.
T The mutation could be induced by a base analog or an alkylating agent.
F The mutation could be reverted by treatment with ICR 170 or ethidium bromide.
VI. In class we saw many similarities between prokaryotes and eukaryotes but also some
significant differences. Using E for eukaryote only, P for prokaryote only, B for both and N
for neither, fill in the blanks below:
E
chromosomes contained in a nucleus.
B
B
UV light causes T-T dimers
P
Streptomycin prevents translation.
E
Introns disrupt coding sequences of genes.
B
multiple copies of rRNA genes
P
messages may encode multiple proteins
B
promoters have TATA box
E
Messages have poly-A tails
Translation starts during transcription
E
3 different RNA polymerases
N
only 4 of 6 Ser codons are used
P
F-met inserted to start translation
E
mitosis precedes cell division
N
The first base in all mRNAs is the A from a start codon.
P
UGA is a stop codon.
VII. Match the descriptions on the left with the agents on the right by placing the letter(s) in the
blank.
A) Mutagens:
B
mutagen also used as a food additive
A. caffeine
J
artificial sweetener that increased tumors in male rats
B. nitrite (NA)
C. dioxin
G
the first proven mutagen
E
the first proven chemical mutagen
D. acridine orange
C
toxic compound not mutagenic in the Ames test
E. mustard gas
F. UV light
I
pregnancy drug that increased cancer years later
D
causes frameshift mutations
G. X-rays
H. 2-aminopurine
F
problem for xeroderma pigmentosum patients
A(&H) a non-mutagenic base analog
I. DES
J. saccharin
H
mutagen used in chemotherapy
B) Recombinant DNA Technology
F
permits blue/white screening
D
required for plasmid replication
G
cuts DNA at specific sequences
H
makes DNA from RNA
B
captures poly-A tailed mRNA
A
fastens DNA fragments together
E
selectable marker in plasmid vector
C
may be used to target specific tissues
A. DNA ligase
B. oligo-dT
C. virus vector
D. ori
E. ampicillin resistance
F. lac-Z gene
G. restriction endonuclease
H. reverse transcriptase
VIII Define the term nonsense mutation.
A change in the DNA of a structural gene that results in changing a sense codon to a stop codon.
IX. Gene Regulation: A series of strains of E. coli with one or copies f the lac operon were
grown on two carbon sources, lactose and glucose. Mutations in the various genes are shown
with a superscript minus sign (ex I-) unless they are frameshifts where the superscript is an F
(ex ZF). A) Tell whether β-galactosidase and permease would be present in very low levels
(L), at high induced levels (H) or completely absent (A).
Strain
grown on glucose
β gal'ase
permease
1) p I p O Z Y A
L
L
H
H
H
A
H
A
A
A
A
A
A
H
A
H
L
L
H
H
H
A
H
A
H
H
H
H
-
F
2) p I p O Z Y A
-
-
3) p I p O Z Y A
-
-
-
4) p I p O Z Y A
grown on lactose
β gal'ase
permease
(the rest are partial diploids)
-
5) p I p O Z Y A
-
p I p O ZYA
-
F
6) p I p O Z Y A
-
-
pI pO ZY A
7) p I p O Z Y A
-
p I p O Z YA
B) What do the following symbols in the lac operon stand for?
p promoter; site of attachment of RNA polymerase to make mRNA
O operator; switch sequence recognized by normal repressor protein
Z the gene that encode β−galactosidase