Week 6 - Replication

Question 1

Cytosine makes up about 38% of the nucleotides in a DNA sample of an organism. Provide approximately what percentage of nucleotides is adenine:

a) 12%
b) 24%
c) 38%
d) The percentage of adenine cannot be determined from the information provided.

Answer 1

a) 12%

Question 2

Information-containing element that controls a discrete hereditary characteristic is called:

a) Genome
b) Double helix
c) Gene
d) Base pair

Answer 2

c) Gene

Question 3

One of the two copies of a particular chromosome in a diploid cell, each copy being derived from a different parent, is called:

a) Homologous chromosome (homolog)
b) Chromatin
c) Centromere
d) Histone

Answer 3

a) Homologous chromosome (homolog)

Question 4

A chromosome in which the short arms occur as clumps of chromatin is called a:

a) Metacentric chromosome
b) Submetacentric chromosome
c) Acrocentric chromosome
d) Telocentric chromosome

Answer 4

c) Acrocentric chromosome

Question 5

Long blocks of DNA sequence that differ in the number of times they are present in the genomes of different individuals in a population, is called:

a) Copy number variation (CNV)
b) Single-nucleotide polymorphism (SNP)
c) Homologous
d) Pseudogene

Answer 5

a) Copy number variation (CNV)

Question 6

Okazaki fragments are created:

a) In the process of replication on only one strand of DNA.
b) In the process of replication on both strands of DNA.
c) Only in the process of transcriptional modification of RNA.
d) Only in the process of transcription.

Answer 6

a) In the process of replication on only one strand of DNA.

Question 7

The nucleotide sequence of one DNA strand of a DNA double helix is 5’–GGATTTTTTGCCAAACTCA–3’. What is the sequence of the complementary strand?

a) 5’–CCTAAAAAACGTTTGAGT–3’
b) 3’–CCTAAAAAACGTTTGAGT–5’
c) 5’–CCGTTTTTTGCCAAACTC–5’
d) 5’–GGATTTTTTGCCAAACTCA–3’ 8.

Answer 7

b) 3’–CCTAAAAAACGTTTGAGT–5’

Question 8

DNA repair is:

a) A means of repairing double-strand DNA breaks that links two ends with little regard for sequence homology.
b) Collective term for the enzymatic process that corrects deleterious changes affecting the continuity or sequence of a DNA molecule.
c) A cellular mechanism that repairs damaged DNA by removing small, non-helix-distorting base lesions from the genome.
d) A DNA repair pathway that removes bulky DNA lesions, such as those caused by UV radiation, that distort the double helix.

Answer 8

b) Collective term for the enzymatic process that corrects deleterious changes affecting the continuity or sequence of a DNA molecule.

Question 9

A genetic phenomenon where an individual loses one copy of a gene, resulting in homozygosity. This can occur through various mechanisms, including deletions, gene conversions, and mitotic recombination. This is a definition of:

a) Homologous recombination
b) Loss of heterozygosity (LOH)
c) Strand exchange
d) Crossing-over

Answer 9

b) Loss of heterozygosity (LOH)

Question 10

Phase variation is:
a) A type of transposable element that moves within a genome through a “copy-and-paste” mechanism, similar to retroviruses, but without a retroviral life cycle.
b) A mechanism of genetic variation that involves the reversible switching on and off of gene expression. This allows bacteria to rapidly adapt to changing environments.
c) A type of transposable element that moves within a genome through a “copy-and-paste” mechanism, similar to retroviruses.
d) A DNA sequence that can change its position within a genome, sometimes creating or reversing mutations and altering the cell’s genome size and organization.

Answer 10

b) A mechanism of genetic variation that involves the reversible switching on and off of gene expression. This allows bacteria to rapidly adapt to changing environments.

Question 11

The bond that connects the nucleotides in a polynucleotide chain is:

a) β-N-glycosidic linkage
b) A phosphodiester bond
c) A peptide bond
d) van der Waals forces

Answer 11

b) A phosphodiester bond

Question 12

The DNA of animals is located in:

a) In the nucleus
b) In the Golgi apparatus
c) In the mitochondria
d) In the endoplasmic reticulum

Answer 12

a) In the nucleus

Question 13

A histone stabilizing the histone octamer (nucleosome) and involved in building a higher-order structure is:

a) Histone H2A
b) Histone H2B
c) Histone H3
d) Histone H1

Answer 13

d) Histone H1

Question 14

Giant chromosome in which the DNA has undergone repeated replication without separation into new chromosomes, is called:

a) Somatic chromosome
b) Lampbrush chromosome
c) Mitotic chromosome
d) Nucleolus

Answer 14

b) Lampbrush chromosome

Question 15

Copy number variation (CNV) is:

a) A copy of a functional gene that has become irreversibly inactivated by multiple mutations.
b) Long blocks of DNA sequence that differ in the number of times they are present in the genomes of different individuals in a population.
c) Evolutionary process that eliminates individuals carrying mutations that interfere with important genetic functions.
d) A gene whose expression stalls at a certain nucleotide position in the genome.

Answer 15

b) Long blocks of DNA sequence that differ in the number of times they are present in the genomes of different individuals in a population.

Question 16

The enzyme responsible for primer attachment during replication is:

a) Primase
b) Topoisomerase
c) Ligase
d) Helicase

Answer 16

a) Primase

Question 17

Sliding clamp is:

a) DNA process that replaces incorrect nucleotides inserted during DNA replication.
b) A protein complex that encircles the DNA double helix and binds to DNA polymerase, keeping it firmly bound to the DNA while it is moving.
c) Enzyme that binds to DNA and reversibly breaks a phosphodiester bond in one or both strands, allowing the DNA to rotate at that point.
d) The newly made strand of DNA found at a replication fork that is made in discontinuous segments, which are later joined covalently.

Answer 17

b) A protein complex that encircles the DNA double helix and binds to DNA polymerase, keeping it firmly bound to the DNA while it is moving.

Question 18

Process by which DNA sequence information can be transferred from one DNA helix (which remains unchanged) to another DNA helix whose sequence is altered, is called:

a) Allele
b) Gene conversion
c) Holliday junction
d) Loss of heterozygosity

Answer 18

b) Gene conversion

Question 19

Reverse transcriptase is:

a) Length of DNA that moves from a donor site to a target site either by cut-and-paste transposition or by replicative transposition.
b) Enzyme that makes a double strand DNA copy from a single strand RNA template molecule.
c) RNA-containing virus that replicates in a cell by first making a double-strand DNA intermediate.
d) Rearrangements of DNA that depends on the breakage and re-joining of two DNA helices at specific sequences on each DNA molecule.

Answer 19

b) Enzyme that makes a double strand DNA copy from a single strand RNA template molecule.

Question 20

It consists of two anti-parallel and complementary polynucleotide chains folded together by hydrogen bonds, and is a major component of the information carried in the DNA of a cell or an organism. It is named:

a) DNA double helix
b) Genome
c) Chromosome
d) Chromatin

Answer 20

a) DNA double helix

Question 21

The totality of the information encoded in the DNA of a cell or an organism is termed:

a) Double helix
b) Genome
c) Base pair
d) Chromosome

Answer 21

b) Genome

Question 22

Complex of DNA, histones, and non-histone proteins found in the nucleus of a eukaryotic cell, is called:

a) Centromere
b) Histone
c) Homologous chromosome
d) Chromatin

Answer 22

d) Chromatin

Question 23

Mitotic chromosome is:

a) Giant chromosome in which the DNA has undergone repeated replication without separation into new chromosomes.
b) Paired chromosomes in meiosis in immature amphibian eggs, in which the chromatin forms large stiff loops from the linear axis of the chromosome.
c) Highly condensed, duplicated chromosome with the two new chromosomes still held together at the centromere by chromatid cohesion.
d) The three-dimensional structure of DNA, in which two DNA chains held together by hydrogen bonds between bases are coiled around one another.

Answer 23

c) Highly condensed, duplicated chromosome with the two new chromosomes still held together at the centromere by chromatid cohesion.

Question 24

Pseudogene is:

a) A copy of a functional gene that has become irreversibly inactivated by multiple mutations.
b) Long blocks of DNA sequence that differ in the number of times they are present in the genomes of different individuals in a population.
c) Evolutionary process that eliminates individuals carrying mutations that interfere with important genetic functions.
d) Variation between individuals at a certain nucleotide position in the genome.

Answer 24

a) A copy of a functional gene that has become irreversibly inactivated by multiple mutations.

Question 25

The active region for DNA replication is called: a) The replication fork b) Leading strand c) Lagging strand d) Ori

Answer 25

a) The replication fork

Question 26

The nucleotide sequence of one DNA strand of a DNA double helix is 5'–GGATTTTTTGCCAACTCA–3'. What is the sequence of the complementary strand? a) 5'–CCTAAAAAACGTTGAGT–3' b) 3'–CCTAAAAAACGTTGAGT–5' c) 3'–CCGTTTTTTGCCAACTCT–5' d) 5'–GGATTTTTTGCCAACTCA–3'

Answer 26

b) 3'–CCTAAAAAACGTTGAGT–5'

Question 27

End-directed mismatch repair is: a) DNA process that replaces incorrect nucleotides inserted during DNA replication. b) A protein complex that encircles the DNA double helix and binds to DNA polymerase, keeping it firmly bound to the DNA while it is moving. c) Enzyme that binds to DNA and reversibly breaks a phosphodiester bond in one or both strands, allowing the DNA to rotate at that point. d) The newly made strand of DNA found at a replication fork that is made in discontinuous segments, which are later joined covalently.

Answer 27

a) DNA process that replaces incorrect nucleotides inserted during DNA replication.

Question 28

A set of alternative forms of a gene. In a diploid cell, each gene will have two of these located on homologous chromosomes. It is called: a) Allele b) Holliday junction c) Hybridization d) Chromatin

Answer 28

a) Allele

Question 29

Guanine makes up about 38% of the nucleotides in a DNA sample of a human organism. Provide approximately what percentage of nucleotides is thymine: a) 12% b) 24% c) 38% d) 39%

Answer 29

a) 12%

Question 30

Epigenetic inheritance is: a) Difference in gene expression that depends on the location of the gene on the chromosome. b) Form of transmission of information from cell to cell, or parent to progeny that is not encoded in DNA. c) Less encoded region of an interphase chromosome that stains diffusely d) A complex of nuclear DNA with histone proteins and chromosomal non histone protein.

Answer 30

b) Form of transmission of information from cell to cell, or parent to progeny that is not encoded in DNA.

Question 31

Constricted region of a mitotic chromosome that holds sister chromatids together is called: a) Kinetochore b) Centromere c) Chromosome d) Chromatin

Answer 31

b) Centromere

Question 32

Light G bands in cytogenetics: a) Represent regions with high AT base pair content, late replicating DNA, and few active genes b) Represent regions with a high GC base pair content, early replicating DNA, and few active genes c) Represent regions of early replicating and transcriptionally active euchromatin d) Represent regions of early replicating and transcriptionally inactive euchromatin

Answer 32

c) Represent regions of early replicating and transcriptionally active euchromatin

Question 33

Any cell of an organism other than a germ cell or germ-line precursor is: a) Germ cell b) Replication c) Somatic cell d) Mutation

Answer 33

c) Somatic cell

Question 34

Mismatch repair is: a) A means of repairing double strand DNA breaks that link 2 ends with little regard for sequence homology b) A DNA repair system that corrects errors that occur during dna replication. It recognizes mismatched base pairs and removes the incorrect nucleotide replacing it with the correct one c) A cellular mechanism that repairs damaged dna by removing small, non helix distorting base lesions from the genome d) A DNA repair pathway that removes bulky DNA lesions such as those caused by UV radiation that distort the double helix

Answer 34

b) A DNA repair system that corrects errors that occur during dna replication. It recognizes mismatched base pairs and removes the incorrect nucleotide replacing it with the correct one

Question 35

A critical step in Homologous recombination where a single stranded DNA invades a double stranded DNA molecule, leading to the exchange of genetic material between the two molecules. a) Loss of heterozygosity (LOH) b) Strand exchange c) Hybridization d) Gene conversion

Answer 35

b) Strand exchange

Question 36

Transposition is: a) A mechanism of genetic variation that involves the reversible switching on and off of gene expression, period. This allows bacteria to rapidly adapt to changing environments b) A type of transposable element that moves within a genome through a copy and paste mechanism, similar to retroviruses. It involves reversible transcription of RNA into DNA, which is then integrated into a new genomic location. c) A DNA sequence that can change its position within a genome, sometimes creating or reversing mutations and altering the cell's genome size and organization. d) A process by which a transposable element moves from one position in the genome to another.

Answer 36

d) A process by which a transposable element moves from one position in the genome to another.

Question 37

What is NOT a characteristic of the DNA molecule? a) Double-stranded structure with hydrogen bonds according to the rule of complementarity b) Sugar-phosphate backbone forms the centre of the double helix c) Sequence of pyrimidines is located inside the double helix d) Sequence of purines is located inside the helix

Answer 37

b) Sugar-phosphate backbone forms the center of the double helix

Question 38

Homolog is defined as: a) Derived from the copies of a particular chromosome in a diploid cell, each copy being derived from a different parent b) Double structure in eukaryotic chromatin, composed of a short length of DNA wrapped around a core of histone proteins c) Centromeric region of a mitotic chromosome that holds sister chromatids together d) Repeated sequence of events by which a cell duplicates its contents and divides into two

Answer 38

a) Derived from the copies of a particular chromosome in a diploid cell, each copy being derived from a different parent

Question 39

Highly condensed, duplicated chromosomes with the two new chromosomes still held together at the centromere as sister chromatids, is called: a) Polytene chromosome b) Lampbrush chromosome c) Mitotic chromosome d) Nucleolus

Answer 39

c) Mitotic chromosome

Question 40

Evolutionary process that eliminates individuals carrying mutations that interfere with important genetic functions is called: a) Copy number variation (CNV) b) Single-nucleotide polymorphism (SNP) c) Purifying selection d) Pseudogene

Answer 40

c) Purifying selection

Question 41

Enzyme that joins two adjacent DNA strands together is called: a) DNA helicase b) DNA ligase c) RNA primer d) Single-strand DNA binding (SSB) protein

Answer 41

b) DNA ligase

Question 42

Loss of heterozygosity (LOH) is: a) A type of genetic recombination that occurs during meiosis, where homologous chromosomes exchange genetic material. It contributes to genetic diversity and is essential for proper chromosome segregation. b) A critical step in homologous recombination where a single-stranded DNA invades a double-stranded DNA molecule, leading to the exchange of genetic material between the two molecules. c) A genetic phenomenon where an individual loses one copy of a gene, resulting in homozygosity. This can occur through various mechanisms, including deletions, gene conversions, and mitotic recombination. d) A DNA repair pathway that uses a homologous DNA sequence as a template to accurately repair double-strand breaks. It's also a crucial mechanism for genetic diversity during meiosis.

Answer 42

c) A genetic phenomenon where an individual loses one copy of a gene, resulting in homozygosity. This can occur through various mechanisms, including deletions, gene conversions, and mitotic recombination.

Question 43

A mechanism of genetic variation that involves the reversible switching on and off of gene expression. This allows bacteria to rapidly adapt to changing environments: a) Reverse transcriptase b) Retrovirus c) Conservative site-specific recombination d) Phase variation

Answer 43

d) Phase variation

Question 44

The enzyme that prevents telomere shortening is: a) Ligase b) RNA polymerase I c) DNA polymerase delta d) Telomerase

Answer 44

d) Telomerase

Question 45

Eukaryotic Okazaki fragments: a) Correspond to the replication of a DNA fragment spanning a single nucleosome b) Do not occur c) Are 1,000 to 2,000 nucleotides in length d) Are up to 1000 nucleotides long.

Answer 45

a) Correspond to the replication of a DNA fragment spanning a single nucleosome

Question 46

The enzyme responsible for primer attachment during replication is: a) Helicase b) Primase c) Type II topoisomerase d) Ligase

Answer 46

b) Primase

Question 47

Initiation of replication in Eukaryotes takes place in: a) In many random places on the DNA strand b) One well-defined spot on the DNA strand c) In one random place on the DNA strand d) Strictly defined places on the DNA strands.

Answer 47

d) Strictly defined places on the DNA strands.

Question 48

What is NOT characteristic of the DNA molecule? a) DNA strands running in parallel b) Opposite bases connecting through hydrogen bonds according to the rule complementarity. c) Sugar component in the centre of the double helix. d) Presence of pyrimidine bases.

Answer 48

a) DNA strands running in parallel

Question 49

Homolog is: a) One of the two copies of a particular chromosome in a diploid cell, each copy being derived from a different percent. b) Beadlike structure in eukaryotic chromatin, composed of a short length of DNA wrapped around a core of histone proteins. c) Constructed region of a mitotic chromosome that holds sister chromatids together. d) The orderly sequence of ... by which a cell duplication its contents and divides into two.

Answer 49

a) One of the two copies of a particular chromosome in a diploid cell, each copy being derived from a different percent.

Question 50

Indicate the human karyotype: a) 46 chromosomes, with 22 pairs of autosomes and one pair of sex chromosomes. b) 48 chromosomes, with 23 pairs of autosomes and one pair of sex chromosomes. c) 78 chromosomes, with 38 pairs of autosomes and one pair of sex chromosomes. d) 8 chromosomes, with 3 pairs of autosomes and one pair of sex chromosomes.

Answer 50

a) 46 chromosomes, with 22 pairs of autosomes and one pair of sex chromosomes.

Question 51

Linker DNA is: a) A section of DNA that connects chromatosomes into a nucleofilament. b) A section of DNA that connects chromosomes into a nucleofilament. c) A section of DNA that connects nucleosomes into a nucleofilament. d) A section of DNA that connects nucleosomes into a solenoid.

Answer 51

a) A section of DNA that connects chromatosomes into a nucleofilament.

Question 52

Short length of RNA synthesized on the lagging strand during DNA replication and subsequently removed, is called: a) DNA helicase b) DNA ligase c) RNA d) Single-strand DNA binding (SSB) protein

Answer 52

c) RNA

Question 53

A DNA repair system that occur during DNA replication. It recognizes mismatched base pairs and removes the incorrect nucleotide, replacing it with the correct one, is called: a) Nonhomologous end joining (NHEJ) b) Base excision repair c) Nucleotide excision repair d) Mismatch repair

Answer 53

d) Mismatch repair

Question 54

Crossing over: a) A type of genetic recombination that occurs during meiosis, where homologous chromosomes exchange genetic material. It contributes to genetic diversity and is essential for proper chromosome segregation. b) A critical step in homologous recombination where a single-stranded DNA invades a double-stranded DNA molecule, leading to the exchange of genetic material between the two molecules. c) A DNA repair pathway that uses a homologous DNA sequence as a template to accurately repair double-stranded breaks. It's also a crucial mechanism for genetic diversity during meiosis. d) Experimental process in which two complementary nucleic acid strands form a double helix, a powerful technique for detecting specific nucleotide sequences.

Answer 54

a) A type of genetic recombination that occurs during meiosis, where homologous chromosomes exchange genetic material. It contributes to genetic diversity and is essential for proper chromosome segregation.

Question 55

A DNA sequence that can change its position within a genome, sometimes creating or reversing mutations and altering the cell's genome size and organization. (Another term for transposable element) a) Retrovirus b) Conservative site-specific recombination c) Transposition d) Transposon

Answer 55

d) Transposon