Gen MCQ & sample

Question 1

A human cell containing 22 autosomes and a Y chromosome is
A a liver cell
B a brain cell
C an ovum
D a sperm cell
E a muscle cell

Answer 1

D

Question 2

Crossing over most commonly occurs during
A prophase I
B anaphase I
C interphase
D prophase II
E telophase

Answer 2

A - occurs during prophase I of meiosis

Question 3

Homologous chromosomes segregate towards opposite poles of a dividing cell during:
A mitosis
B meiosis I
C meiosis II
D fertilization
E crossing-over

Answer 3

B

Question 4

In tomatoes, red fruit (R) is dominant to yellow fruit (r) and tallness (T) is dominant to shortness (t). If a plant with an RrTt genotype is crossed with a plant that is rrtt:
A all the offspring will be tall with red fruit
B 75% will be tall with red fruit
C 50% will be tall with red fruit
D 25% will be tall with red fruit
E 10% will be tall with red fruit

Answer 4

D

Question 5

Two organisms, heterozygous for a particular trait, mate. One thousand offspring are produced. The number of heterozygous offspring should be about
A two hundred and fifty
B seven hundred and fifty
C three hundred
D one thousand
E five hundred

Answer 5

E (50%)

Question 6

In humans pointed eyebrows (P) are dominant to smooth
eyebrows (p). Mary’s father has pointed eyebrows but she and her mother have smooth. What is the genotype of her father?
A PP
B Pp
C pp
D any one of these
E none of these

Answer 6

B

Question 7

In Drosophila, a mating between red-eyed females (homozygous for the red-eye trait) and white-eyed males reveals a ratio in the next generation of
A 100% red-eyed
B 75% red-eyed, 25% white-eyed
C 50% red-eyed, 50% white-eyed
D 25% red-eyed, 75% white-eyed
E 100% white-eyed

Answer 7

B - eye colour determined by sex-linked genes in Drosophila

Question 8

The ratio of __________ is 1:1 in DNA
A guanine to adenine
B adenine to thymine
C cytosine to adenine
D uracil to cytosine
E none of the above

Answer 8

B
adenine to thymine
guanine to cytosine

Question 9

A biochemist isolated and purified components needed for DNA replication. When DNA was added, replication occurred but the DNA molecules formed were defective. Each consisted of a normal DNA strand paired with numerous segments of DNA a few hundred nucleotides long. What had the biochemist probably left out of the mixture?
A DNA polymerase
B DNA ligase
C nucleotides
D primers
E helicase

Answer 9

B

Question 10

With regard to the elongation of the leading strand during DNA synthesis, which of the following statements is true:
A it progresses away from the replication fork
B it occurs in the 3’ to 5’ direction
C it produces Okazaki fragments
D it depends on the action of DNA polymerase
E it does not require a template strand

Answer 10

D - leading strand is synthesised continuously in the 5’ to 3’ prime direction towards the replication fork

Question 11

Synthesis of the new DNA strand usually begins with
A. telomerase
B. a DNA primer
C. DNA primase
D. an RNA primer
E. an Okazaki fragment

Answer 11

D - begins with the addition of a short RNA primer synthesised by the enzyme primase

Question 12

The complementary sequence of RNA made from the DNA sequence of bases, ATCGTC, when read left to right, is
A CTGCTA
B CUGCUA
C TAGCAG
D UAGCAG
E GAGAGA

Answer 12

D - note thymine replaced by uracil

Question 13

RNA polymerase binds to a sequence called a/an __________ before initiating (beginning) transcription
A promoter
B operator
C structural gene
D replication origin
E repressor

Answer 13

A

Question 14

In eukaryotic cells, genes specify (code for) proteins in the following steps:
A transcription, RNA processing, translation
B transcription, translation, RNA processing
C RNA processing, transcription, translation
D translation, RNA processing, transcription
E translation, transcription, termination

Answer 14

A

Question 15

Which of the following mutations is most likely to be harmful?
A a single base substitution
B a single base deletion near the middle of an intron
C a deletion of three consecutive bases near the middle of a gene
D a single base insertion near the start of a coding sequence
E a single base deletion close to the end of a coding sequence

Answer 15

D - causes a frameshift mutation, which alters the reading frame of the genetic code, meaning all codons downstream of the mutation are read incorrectly

Question 16

asexual reproduction occurs during which of the following
A mitosis
B fertilisation
C meiosis

Answer 16

A

Question 17

Which of the following statements is true of a species that has a chromosome number of 2n = 16?
A a gamete from this species has four chromosomes
B the species is diploid and has 32 chromosomes per cell
C each diploid cell has 8 homologous pairs of chromosomes
D the species has 16 sets of chromosomes per cell

Answer 17

C

Question 18

A particular organism has 46 chromosomes in its karyotype. Which of the following statements is correct regarding this organism?
A It must be an animal
B It reproduces asexually
C It produces gametes with 23 chromosomes
D It must be human

Answer 18

C

Question 19

Which of the following statements best describes homologous chromosomes?
A They carry the same alleles
B They align on the metaphase plate in meiosis II
C They carry information for the same traits
D They were inherited from the same parent

Answer 19

C

Question 20

Which of the following statements describes the chromosomal makeup of each daughter cell after telophase of meiosis I?
A The cells are diploid, and the chromosomes are each composed of two chromatids
B The cells are haploid, and the chromosomes are each composed of a single chromatid
C The cells are haploid, and the chromosomes are each composed of two chromatids
D The cells are diploid, and the chromosomes are each composed of a single chromatid

Answer 20

C

Question 21

How do cells at the completion of meiosis compare with cells that are in prophase of meiosis I?
A The cells have half the number of chromosomes and one-fourth the amount of DNA
B The cells have half the amount of cytoplasm and twice the amount of DNA
C The cells have half the number of chromosomes and half the amount of DNA
D The cells have the same number of chromosomes and half the amount of DNA

Answer 21

A

Question 22

During which of the following processes do sister chromatids separate from each other?
A during both mitosis and meiosis I
B during meiosis II only
C during meiosis I only
D during both mitosis and meiosis II

Answer 22

D

Question 23

Which of the following statements correctly describes the terms monohybrid cross and dihybrid cross?
A a dihybrid cross involves organisms that are heterozygous for two characters that are being studied, and a monohybrid cross involves organisms that are heterozygous for only one character being studied
B a monohybrid cross results in a 9:3:3:1 ratio, whereas a dihybrid cross gives a 3:1 ratio
C a monohybrid cross is performed for one generation, whereas a dihybrid cross is performed for two generations
D a monohybrid cross involves a single parent, whereas a dihybrid cross involves two parents

Answer 23

A

Question 24

Which of the following sentences state a significant conclusion that Gregor Mendel drew from his experiments with pea plants?
A There is considerable genetic variation in garden peas
B Recessive genes occur more frequently in the F1 generation than do dominant ones
C Traits are inherited in discrete units and are not the result of “blending.”
D Genes are composed of DNA

Answer 24

C

Question 25

Which of the following statements about the law of independent assortment is correct? A It describes the inheritance of different genes relative to one another B It is the consequence of having two copies of each chromosome in somatic cells and one copy in gametes C It describes the inheritance of different alleles relative to one another D It is the reason that dominant alleles are visible in the organism's phenotype

Answer 25

A

Question 26

Having polydactyly (extra digits on hands and feet) is a dominant trait. A man has polydactyly. His wife and oldest daughter do not have polydactyly. The couple's second child has polydactyly. What is the probability that their next (third) child will have extra digits? A 1/16 B 1/8 C 3/4 D 1/2

Answer 26

D

Question 27

In some parts of Africa, the frequency of individuals who are heterozygous for the sickle-cell anemia allele is higher than the frequency in North America, presumably because this reduces the frequency of malaria. Such a relationship is related to which of the following? A Mendel's law of segregation B Mendel's law of independent assortment C Darwin's theory of natural selection D Punnett square's modelling inheritance

Answer 27

C

Question 28

The SRY gene is best described as ________ A an autosomal gene whose product is required for the expression of genes on the Y chromosome B a gene present on the Y chromosome whose product regulates male development C a gene present on the X chromosome whose product regulates female development D an autosomal gene that whose product is required for the expression of genes on the X chromosome

Answer 28

B

Question 29

Which of the following phrases correctly defines one genetic map unit? A the physical distance between two genes that results in a 1% frequency of recombination B the recombination frequency between two independently assorting genes C the physical distance between any two linked genes D one nanometer of distance between two genes

Answer 29

A

Question 30

A phenotypically normal couple seeks genetic counseling because the man's karyotype showed that his chromosomes had a reciprocal translocation between chromosomes 4 and 12. Because the translocation is reciprocal there was no genetic information lost and he is healthy; however, he and his wife want to know the probability that his sperm cells will be abnormal. Which fraction of his sperm cells is predicted to carry at least one chromosome with a translocation? A None will carry the translocation B One-half will have the father's translocation and 1/2 will carry normal chromosomes 4 and 12 C All will carry the same translocation as the father D Three-fourth will have at least one chromosome with a translocation; the other 1/4 will carry normal chromosomes 4 and 12

Answer 30

D - Instead of forming regular homologous pairs, the translocated chromosomes form a quadrivalent structure (a four-part pairing) during meiosis

Question 31

Frederick Griffith heat-killed a culture of pathogenic bacteria. He split the sample and injected half of it into mice. The mice lived. He then mixed the other half of the sample with a living, nonpathogenic bacteria strain and injected the mixture into mice. The mice died. Which of the following describes a treatment that would help clarify interpretation of these data? A Heat killing the mixed sample and injecting it into mice B Culturing bacteria from blood isolated from the living mice (injected with heat-killed pathogenic bacteria) C Injecting another population of mice with the original, heat-killed pathogenic bacteria D Examining tissue from the dead mice (injected with mixed sample) for the presence of pathogenic bacteria

Answer 31

D - want to determine what killed the mice

Question 32

Which of the following investigators was (were) responsible for determining that DNA contains equal amounts of adenine and thymine, and equal amounts of guanine and cytosine? A Erwin Chargaff B Oswald Avery, Maclyn McCarty, and Colin MacLeod C Alfred Hershey and Martha Chase D Matthew Meselson and Franklin Stahl

Answer 32

A

Question 33

Rosalind Franklin's X-ray crystallography data suggested DNA is double stranded and has a uniform diameter. These observations can be used to rule out base pairing between two of the same nucleotide because ________ A thymine dimers are removed by excision repair B an A-A pair is wider than a C-C pair C identical nucleotides would not have the appropriate number of hydrogen bonding sites to pair D the antiparallel orientation of strands would result in one of the pair being upside down

Answer 33

B

Question 34

Two students decided to repeat the Hershey and Chase experiment, with modifications. Like Hershey and Chase they used radioactive sulfur but they substituted radioactive nitrogen for radioactive phosphate. They reasoned that each nucleotide has only one phosphate and two to five nitrogen atoms. Thus, labeling the nitrogen atoms would provide a stronger signal than labeling the phosphates. Which of the following is the biggest shortcoming in their experimental design? A The signal from the nucleotide would be so strong that it would overwhelm the signal from sulfur B There is no radioactive isotope of nitrogen C Radioactive nitrogen has a half-life of 100,000 years, therefore, the material would be too dangerous for too long D The radioactivity would not distinguish between DNA and proteins because proteins contain nitrogen

Answer 34

D

Question 35

In E. coli, a mutation in a gene called dnaB prevents the helicase from binding at the origin of replication. Which of the following events would you expect to occur as a result of this mutation? A Replication will occur via RNA polymerase alone B No replication fork will be formed C Additional proofreading will occur D Replication will require a DNA template from another source

Answer 35

B

Question 36

Which of the following is a reason that the low error rate of DNA replication is important to evolution? A Rare errors are the source of variation B Replication with a high error rate is likely to kill the cell C Most mutations have no effect on phenotype D Fixing replication errors provides a cellular role for mismatch repair enzymes

Answer 36

A

Question 37

Which of the following statements correctly describes the difference between the leading and the lagging strands of DNA in DNA replication? A The leading strand is synthesized at twice the rate of the lagging strand B The lagging strand is synthesized continuously, whereas the leading strand is synthesized in short fragments that are ultimately stitched together C The leading strand is synthesized by adding nucleotides to the 3' end of the growing strand, and the lagging strand is synthesized by adding nucleotides to the 5' end D The leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction

Answer 37

D

Question 38

What is the role of DNA ligase in the elongation of the lagging strand during DNA replication? A It joins Okazaki fragments together B It stabilizes the unwound parental DNA C It unwinds the parental double helix D It synthesizes RNA nucleotides to make a primer

Answer 38

A

Question 39

Transcription in eukaryotes requires which of the following molecules in addition to RNA polymerase? A Ribosomes and tRNA B Transcription factors C Anticodons D Aminoacyl-tRNA synthetase

Answer 39

B