MOCK EXAM 3
1. In a test cross between a homozygous recessive white flower and an unknown purple flower,
the cross results in ½ white flowers and ½ purple flowers. What is the genotype of the unknown
purple flower?
a. Homozygous dominant
b. Heterozygous
c. Homozygous recessive
d. None of the above
test crosses helps us identify if an organisms genotype is heterozygous or homozygous dominant
2. A cross between two heterozygous purple flowers results in a ________ genotype and a _______
phenotype.
a. 1:2:1, 3:4
b. 2:3, 1:4
c. 1:2:1, 3:1
d. 2:1:2, 1:4
for a cross between 2 heterozygotes these is always the expected mendelian inheritance
patterns
3. A true breeding parental crosses result in _________ F1 offspring.
a. Heterozygous
b. Homozygous Dominant
c. Homozygous recessive
d. None of the above
True breeding is when you cross a homozygous dominant genotype with a homozygous
recessive genotype which always results in heterozygous offspring
4. A di-hybrid cross between 2 yellow round pea plants heterozygous for both seed shape and
seed color result in a ________ phenotypic ratio?
a. 9:3:4
b. 3:1
c. 9:3:3:1
d. 1:2:1
When crossing 2 things both heterozygous for both traits in a dihybrid cross this will always be
your expected Mendelian ratio
5. A botanist breeds a red flower with a white flower and observes that their offspring are white,
red, and pink. What sort of dominance does this plant display?
a. Complete dominance
b. Codominance
c. Incomplete Dominance
d. Blending Hypothesis
In an incomplete dominance situation there is a blending of phenotypes in the heterozygous
offspring. The homozygous genotypes express their phenotype as they normally would in
classic Mendelian inheritance
6. Two Black Labs with the genotype BbEe are mated together. What is the chance that they
have a puppy that has a yellow coat?
a. 9/16
b. 3/16
c. 1/4
d. Not a possible coat color
Remember that in epistatic inheritance the ratio of the offspring of 2 organisms that are both
heterozygous for both traits will result in a 9:3:4 ratio. In this example the “E” gene determines
if pigment will be sent to the hair follicles. If the E genes are both homozygous recessive this will
result in yellow or lighter coats.
7. Sickle Cell Anemia and Cystic Fibrosis are both examples of _____________ and _____________
inherited diseases.
a. homozygous advantage/ dominantly
b. heterozygous advantage/ recessively
c. homozygous advantage/ recessively
d. heterozygous advantage/ dominantly
being heterozygous for sickle cell prevents you from getting malaria… being heterozygous for
cystic fibrosis prevents you from getting cholera..
8. pH’s effect on the color of Hydrangeas is an example of how inheritance can be _________.
a. recessive
b. multifactorial
c. dominant
d. Sex-Linked
9. Type AB+ blood possesses _________ surface antigens and can receive ________ blood.
a. AB/ All blood types
b. A only/ type O
c. B only/ All blood types
d. No/ Only A and B
10. Epistasis can result in a 9:3:4 and __________ phenotypic ratio and is controlled by _________.
a. 1:2:1/ the same gene at different loci
b. 9:7/ the same gene at different loci
c. 3:1/ 2 different genes at the same loci
d.9:7/ 2 different genes at 2 different loci
11. Early in a pregnancy, a physician suspects that a mother’s child may have a severe genetic
disorder. Which test is the doctor most likely to perform?
a. Amniocentesis
b. Chorionic Villus Sampling
c. Cesarean Section
d. None of these procedures would be useful
CVS is done in the 8th 10th week.. more risky
Amniocentesis done 14th 16th week… less risky
12. John and Katy each have a sibling with Thalassemia (an autosomal recessive disease), but
neither John nor Katy nor any of their parents have the disease. Calculate the probability that if
this couple has a child, the child will have Thalassemia.
a. 1/8
b. 1/4
c. 1/9
d. 2/3
2/3 chance each of them are carriers… times the probability ¼ that the bay has cystic fibrosis.
2/3 x 2/3 x ¼
13. Using the previous question’s information, what would the probability be if a test revealed
that John is a carrier and Katy is not?
a. 1/4
b. 0
c. 2/3
d. 1/9
they both have to be carriers in order for their child to have Thalassemia because it is
recessively inherited… so the child would need 2 recessive alleles to have the disease.
14. If a plant is heterozygous for 3 traits (complete dominance) is allowed to self fertilize, what
proportion of its offspring do you expect to be homozygous recessive for all 3 traits?
a. 1/9
b. 1/32
c. 1/64
d. 1/8
¼ x ¼ x 1/4
15. Newly discovered recessively inherited disease is expressed only in individuals with type O
blood, although the disease and blood groups are independently inherited. A normal man with
type A blood and a normal woman with type B blood have already had a child with the disease.
The woman is now pregnant for a second time. What is the probability that the second child will
also have the disease? Assume that both parents are heterozygous for the gene causing the
disease.
a. 1/8
b. 1/4
c. 1/32
d.1/16
Ai x Bi = ¼… x1/4 from the both heterozygous part = 1/16
16. If a male that has Agammaglobulinmia (X-linked) mates with a female that is not a carrier for
the same disease, what percentage of their offspring will potentially be carriers?
a. 25%
b. 50%
c. 75%
d. 100%
17. If a female carrier mates with a color-blind male what is the percentage that each child born
to them will be color-blind?
a. 25%
b. 50%
c. 75%
d. 100%
18. A mitochondrial disease will be passed on to __________.
a. only males
b. only females
c. males and females equally
d. not heritable
Remember the mitochondrion is inherited from the mother… this does not matter if you are a
girl or boy; it is inherited by all from the mother.
19. If a female carrier of Duchenne’s muscular dystrophy (X-linked) mates with an unaffected
male what are the chances they will have a male with Duchenne’s?
a. 25%
b. 50%
c. 75%
d. 100%
½ chance of being a male x ½ chance of being affected
20. The inactivation of an X chromosome is called ______________.
a. epistasis
b. Polygenics
c. Lyonization
d. Single X hypothesis
21 A male with _________ could be confused with a woman if a scientist looked at a tissue sample.
a. Turner’s Syndrome
b. Triple X
c. XYY
d. Kleinfelter’s Syndrome
XXY so they would have a bar body or inactivated X chromosome like a woman
22. In a cross between a yellow round pea plant with the genome YyRr and a green wrinkled pea
plant with the genome yyrr, what phenotypes represent the recombinants of the cross?
a. Yellow round
b. green round
c. green wrinkled
d. Yellow wrinkled
e. Both B and D
Recombinants are any new combination of traits that were not seen in the parent generation of
the cross..
23. The physical basis for crossing over occurs during ___________.
a. lyonization
b. outbreeding
c. meiosis 2
d. meiosis 1
24. Nondisjunction during meiosis 2 results in ____________.
a. 2 triploid cells and 2 monosomic cells gametes
b. 2 monosomic cells and 2 diploid cells gametes
c. one triploid one monosomic and 2 diploid gametes
d. the shutdown of meiosis
25. Is non-disjunction in Meiosis 1 or 2 more dangerous (per say)?
a. Meiosis 1
b. Meiosis 2
c. Mathematically they are equally as dangerous as each other
d. Not enough is known about nondisjunction
M1 results in 2 triploid cells and 2 monosomic cells…. M2 results in 2 normal cells and the other
half is screwed up
26. In which genomic sequence is an inversion present : ABCDE
a. ACDEB
b. ACDE
c. AABCDE
d. ADCBE
27. A translocation error occurs between ____________.
a. homologous chromosomes
b. non-homologous chromosomes
c. Alternatively spliced RNA
d. Both A and B
28. A woman with Turner’s syndrome has how many pairs of homologous chromosomes?
a. 23
b. 21
c. 22
d. 24
Doesn’t have a second X… a pair consists of 2 things Turners syndrome is X0
29. There are three genes in question: S, A, and T. According to recent experiments it has been
determined that T and A share a 12% recombination frequency, S and A share a 6%
recombination frequency, and S and T share a 18% recombination frequency. What order are
there genes located in in a chromosome?
a. AST
b. STA
c. TAS
d. not enough information to determine
30. By convention, each map unit corresponds to 1% recombination frequency. T or F
31. What is the percentage of Thymine in a DNA backbone if you know: Adenine = 30.3%,
Guanine = 19.5%, and Cytosine = 19.5%.
a. 19.5%
b. 10.0%
c. 30.3%
d. 19.3 %
32. DNA replication is a _____________ process.
a. conservative
b. dispersive
c. semiconservative
d. non-conservative
33. The Hershey chase experiment proved that DNA was the genetic material found in living
organisms because radiolabeled 35-S was found inside the bacterial cells. T or F
32P is found in DNA…. 35S is found in proteins
34. Trisomy 21 is normally caused by a ___________________.
a. Nondisjunction M2
b. Nondisjunction M4
c. Nondisjunction M3
d. Nondisjunction M1
M1 nondisjunction results in 50% triploid
35. A color-blind man marries a woman with normal vision whose father is color-blind. What is
the probability that they will have a colorblind daughter? What is the probability that their first
son will be color-blind?
a. 1/4, 1/4
b. 1/2, 1/4
c. 1/4, 1/2
d. 1/3 , 1/4
36. A white-eyed female Drosophila is mater with a red-eyed wild type male. What phenotypes
and genotypes do you predict for the offspring?
a. all white eyed females, all red eyed males
b. all red eyed heterozygous females, all white eyed males
c. none of the above
d. both A and B
37. Which of the following is NOT true of a codon?
a. It consists of 3 nucleotides
b. It may code for the same amino acid as another codon
c. It never codes for more than one amino acid
d. It extends from one end of a tRNA molecule
ANTICODON.
38. Which of the following mutations would be most likely to have a harmful effect on an
organism?
a. a base pair substitution
b. A single nucleotide insertion downstream of and close to the start of the coding sequence.
c. a deletion of 3 nucleotides near the middle of a gene
d. a single nucleotide deletion in the middle of an intron
39. Which component is not directly involved in translation?
a. mRNA
b. DNA
c. tRNA
d. ribosomes
e. GTP
40. The anticodon of a particular tRNA molecule is
a. complementary to the corresponding mRNA codon
b. complementary to the corresponding triplet in rRNA
c. The part of the tRNA that bonds to the specific amino acid
d. catalytic making the tRNA a ribozyme
41. In a nucleosome, the DNA is wrapped around
a. polymerase molecules
b. ribosomes
c. histones
d. thymine dimer
e. satellite DNA
42. What molecules are recruited in the process of repairing DNA strands?
a. Nuclease
b. DNA Polymerase
c. Ligase
d. All of the above
cut… replase… puts back together
43. The trp operon is an example of a _______ operon.
a. inducible
b. Repressible
c. Human
d. Bacterial
e. Both B and D
44. In the lac operon, bacteria make their repressors in the __________ form
a. inactive
b. unprocessed
c. active
d. depends on if lactose is present
45. In the lac operon, __________ binds to CAP. CAP then binds to ___________.
a. cAMP, lactose
b. lactose, cAMP
c. lactose, the promoter region
d. cAMP, the promoter region