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GENETICS 310
EXAM II
March 20, 2014
I. The eyes of wild type fruit flies are ‘brick red’ because they contain a mix of
red and brown pigments, each made from colorless precursors. Abbreviated
paths for each pigment are shown below;
E1
E2
Colorless1
tan
brown
Colorless2
peach
red
E3
E4
Using the gene symbols A, for E1, B for E2, C for E3 and D for E4:
a) Truebreeding red eyed females are mated to true breeding brown eyed males.
Each parent has a single gene defect. If the F1 have wild type brick red eyes,
give genotypes for the parents, the F1 and the predicted phenotypic ratio in the
F2.
Red parent aa, BB, CC, DD brown parent AA, BB, cc, DD F1 Aa, BB, Cc, DD
F2 phenotypic ratio expected 9A_, BB, C_, DD brick red
3 A_, BB, cc, DD brown
3 aa, BB, C_, DD red
1 aa, BB, cc, DD colorless
B1. Propose phenotypes for the following genotypes:
aa, BB, CC, dd
peach
AA, bb, cc, DD
b2) predict the genotype Aa, Bb, Cc, Dd
a cross between these two flies.
and phenotype
tan
brick red
of
C1 A tan eyed fly crossed to a brown eyed fly gave all brown.
Give genotypes for the tan AA, bb, cc brown AA, BB, cc and F1
Predict the F2 phenotypic ratio:
3 brown : 1 tan
AA, Bb, cc
II. a) A single strand of DNA has 21% T. That means (true or false)
F
The other strand would also have to have 21% T.
T
The other strand could have 21% T.
T
The other strand would have 21% A.
F
58% (100% – 42%) of the base pairs in the double helix must be G:C.
b) According to ‘wobble’, a G in a tRNA anticodon at the third codon/tRNA
pairing position can pair with either C or U, a U with either A or G, and an I
can pair with A, C or U. An A in that tRNA position can only pair with U and a
C pairs only with G.
1) Check the following propert(y)ies of the genetic code that this addresses:
X
universality
ambiguity
degeneracy
stop codons
commalless
nonoverlapping
2) What is the fewest number of tRNAs required to translate all 6 serine codons
and what are their anticodons ? #
3
anticodons AGG/I, AGU, UCG
3) which of the following codons could be translated using a unique tRNA?
X
CGG X
AGG
ACA X
ACU
c) Check the appropriate Eukaryote and Prokaryote boxes in the table if the
feature is a property of that group of organisms.
Feature
Eu
Introns are present in most genes
x
x
One message is translated to multiple different proteins
Nuclear membrane disintegrates during mitosis
Pro
x
x
Translation begins during transcription
x
x
One mRNA can be translated many times
x
x
A TATA box is present in promoters of mRNA encoding genes
x
x
mRNAs have a poly-A tail
x
More than one copy of the genes encoding rRNA
UGA, UAG and UAA all function to stop transcription
AUG codons only occur at the 5’ (beginning) of mRNAs
An F-met is inserted to start translation, but later removed
x
More than one ribosome can ‘read’ a mRNA at the same time
x
x
GTP provides the energy for translation.
x
x
III. A
segment
of a
mRNA
has
the following
sequence:
IV. a) Tell how β-galactosidase and lactose permease will be made in the
following strains of E. coli. Use R for regulated, C for constitutive and N for not
made. (a minus superscript means that component is inactive) A – superscript
indicates that component is non functional and an F indicates the gene has a
frameshift mutation.
STRAIN GENOTYPE
P I P O ZF Y A
-
-
P IP O Z Y A
-
P I P O
-
P I P
-
P I
-
P I
A
O Z Y A
P O Z Y A
-
P O ZF Y A/ P I P O Z Y
-
P I P O
-
-
Z Y
-
Z
-
P I P O Z
Permease
β-galactosidase
-
Y A/ P I
-
A
-
P O Z Y
-
Y A/ P I P O Z Y
A
A
N
N
C
C
C
N
N
N
C
C
R
N
R
C
C
C
b) How would you test to see if enzyme synthesis is regulated?
c) Give an example of a chemical mutagen that could cause the frameshift
mutations.
V. a) The mutation that causes sickle cell anemia (SCA) results from a glu to
val change in β-globin. Check the terms that apply to this mutation:
nonsense
X
recessive
X
missense
dominant
transition
X
point X
frameshift
transversion
b) In one β-globin mutation, an A added to the gene in codon 4 led to chain
termination at codon 52. This is an example of a:
(OK) nonsense
missense
transition X
frameshift
X
recessive
And would cause
dominant
X
α-thalassemia
point
X
transversion
β-thalassemia
SCA
c) Nitrite at low pH, such as in the stomach, is a mutagen, yet we allow nitrite
to be added to some foods. Why? prevents growth of Clostridium botulinum
and thus botulism poinsoning
d) Which of the following would increase the frequency of his+ colonies in the
Ames test?
Caffeine
X UV-light
Dioxin
X mustard gas
X radon
X acridine
dyes
phenylalanine
MSG
d) Which of the following base sequences could be targets for a restriction
endonuclease which is at least a ‘4 cutter’? (all are written 5’ to 3’)
X
AAAAAA
X ATATAT
ACCGGA
X GCGATCGC
CTGGTC
X ATCGAT
e) Check the following that are properties or advantages of pUC plasmid vectors
for use in cloning over virus vectors.
Larger inserts
marker
X blue-white screening
X Ori allows multiple copies
X selectable
easier to target cell types
f) What does “PCR” stand for and what enzyme is used?
Stands for: Polymerase Chain Reaction
Enzyme used: TAQ (or other heat stable) polymerase
What does cDNA stand for and what enzymes are used to make cDNA?
Stands for: copy or complimentary (to mRNA) DNA
Enzymes: Reverse transcriptase, RNAse H, Ligase