Topic 7.3, 7.4, 7.5: DNA Replication, Transcription, Translation

Question 1

What is the arrangement of nucleotides in a single DNA strand? S = sugar, P = phosphate group, B = organic base

Answer 1

A

Question 2

Which group of three molecules make up one RNA nucleotide?

A. Phosphate, ribose, uracil

B. Phosphorus, ribose, adenine

C. Uracil, deoxyribose, phosphorus

D. Guanosine, deoxyribose, phosphate

Answer 2

A

Question 3

Between which bases are hydrogen bonds formed in DNA?

A. C and U

B. T and G

C. A and T

D. U and A

Answer 3

C

Question 4

What is the function of helicase?

A. It forms bonds between DNA nucleotides.

B. It adds new nucleotides to the DNA helix.

C. It forms the DNA helix.

D. It separates DNA strands.

Answer 4

D

Question 5

Which is the variable part of the DNA nucleotide?

A. The sugar molecule

B. The phosphate molecule

C. The nitrogen base

D. The ribose molecule

Answer 5

C

Question 6

A certain gene codes for a polypeptide that is 120 amino acids long. Approximately how many nucleotides long is the mRNA that codes for this polypeptide likely to be?

A. 30

B. 40

C. 360

D. 480

Answer 6

C

Question 7

The codons CGU and CGC both code for the addition of the amino acid arginine to a growing polypeptide chain. What term is used to describe this property of the genetic code?

A. Universal

B. Degenerate

C. Redundant

D. Complementary

Answer 7

B

Question 8

Draw a diagram showing the molecular structure of a section of the DNA molecule

Answer 8

two polymers shown; arranged in a double helix; sugar shown connected to base; sugar-phosphate backbone shown; If only one nucleotide is drawn, award [2 max] sugar identified as deoxyribose; hydrogen bonding between bases shown; diagram shows complementary base pairing / A bonded to T, C with G; Award previous mark if bases (unlabelled) are shown in the diagram but the complementary base pairing is explained in the annotation. covalent bonding between phosphate and sugar;

Question 9

Outline the process of translation.

Answer 9

mRNA is used as a template / guide; mRNA “read” in base triplets / codon; each codon specifying addition of a particular amino acid to the growing polypeptide; ribosomes bind to mRNA / initiation ribosomes move along mRNA facilitating addition of amino acids / elongation tRNA bring amino acids (to mRNA-ribosome complex); tRNA has a complementary anti-codon; that binds to a specific codon; stop codon causes release of polypeptide / termination;

Question 10

Which labels on the diagram are parts of a nucleotide?

A. I only

B. I and II only

C. II and IV only

D. I, II and III only

Answer 10

D

Question 11

Which enzyme separates the strands of DNA during replication?

A. DNA polymerase

B. RNA polymerase

C. Reverse transcriptase

D. Helicase

Answer 11

D

Question 12

Where do transcription and translation occur in eukaryotic cells?

                   Transcription                      Translation

A. Cytoplasm Cytoplasm

B. Cytoplasm Mitochondria

C. Nucleus Cytoplasm

D. Nucleus Nucleus

Answer 12

C

Question 13

Living organisms use DNA as their genetic material. Explain how DNA is replicated within the cells of living organisms.

Answer 13

helix is unwound; two strands are separated; helicase (is the enzyme that unwinds the helix separating the two strands); by breaking hydrogen bonds between bases; new strands formed on each of the two single strands; nucleotides added to form new strands; complementary base pairing; A to T and G to C; DNA polymerase forms the new complementary strands; replication is semi-conservative; each of the DNA molecules formed has one old and one new strand;

Question 14

Which substance is a base that is found in DNA?

A. Adenosine

B. Cytokinin

C. Guanine

D. Uracil

Answer 14

C

Question 15

Which two processes involve the unwinding (uncoiling) of the DNA double helix and its separation into two strands of nucleotides?

A. Replication and telophase of mitosis

B. Telophase of mitosis and translation

C. Translation and transcription

D. Transcription and replication

Answer 15

D

Question 16

What is a possible consequence of two base substitution mutations occurring in the same gene?

A. Two amino acids coded for by the gene are changed.

B. Amino acids in two polypeptides coded for by the gene are changed.

C. All of the codons between the two mutations are changed.

D. All of the codons from the first mutation onward are changed.

Answer 16

A

Question 17

The diagram below represents a DNA nucleotide. What could the part labelled X represent?

A. Ribose

B. Uracil

C. Guanine

D. Phosphate

Answer 17

C

Question 18

In the structure of DNA what binds with cytosine?

A. Deoxyribose

B. Ribose

C. Thymine

D. Adenine

Answer 18

A

Question 19

What is responsible for the conservation of the base sequence during DNA replication?

A. DNA polymerase working on one strand at the same time.

B. Unpaired bases always attracting their complementary nucleotides.

C. DNA helicase and polymerase are complementary.

D. Both strands are identical to each other.

Answer 19

B

Question 20

Explain the process of translation.

Answer 20

messenger / mRNA attaches to ribosome (small unit); many ribosome/polyribosomes bind to same mRNA; carries codons / triplet of bases each coding for one amino acid; transfer / tRNA each have specific anticodon; triplet of bases for specific amino acid; tRNA carries specific amino acid; tRNA binds to ribosomes; to corresponding triplet base / codon; a second tRNA binds to next codon; two amino acids bind together; in a peptide linkage; first tRNA detaches; ribosome moves along mRNA; another tRNA binds to next codon; continues until polypeptide / protein formed to stop codon; stop codon has no corresponding tRNA/amino acid / causes release of polypeptide;

Question 21

During the process of replication, which bond(s) in the diagram of DNA below is/are broken?

A. 3

B. 4, 5

C. 1, 2, 6, 7

D. 1, 7, 4, 5

Answer 21

B

Question 22

Draw and label a simple diagram to show how DNA is constructed from sugars, phosphates and bases.

Answer 22

Award [1] for each of the following clearly drawn and correctly labelled. labelled phosphate linked to labelled sugar by a single bond; labelled base linked to a labelled sugar by a single bond; correctly linked base, sugar and phosphate labelled as nucleotide; covalent bond(s) labelled between sugar and phosphate/between sugar and base; at least two nucleotides linked by a single sugar-phosphate bond; at least two nucleotides linked by base-base bonds; hydrogen bonds labelled between bases; A-T and/or G-C base pairing; phosphate and base shown linked to correct carbon atoms on sugar;

Question 23

Draw and label a diagram of the molecular structure of DNA.

Answer 23

Award [1] for each of the following clearly drawn and correctly labelled. nucleotide sub-units; composed of sugar-phosphate-base; sugar is deoxyribose; hydrogen bonds between bases; A-T and C-G base pairing; sugar-phosphate backbone; covalent bonds between sugar and phosphate / between sugar and base; helical structure appropriately drawn; (label not required) double-stranded appropriately drawn; (label not required)

Question 24

Compare the structure and composition of DNA with RNA

Answer 24

Direct comparisons must be made to achieve a mark. both are polymers of nucleotides / both are nucleic acids; sugar is deoxyribose in DNA whereas ribose in RNA; DNA is double stranded whereas RNA is single stranded; DNA contains thymine whereas RNA contains uracil; complementary base pairing involved in DNA but not in RNA; both contain four nitrogenous bases;

Question 25

Describe the roles of mRNA, tRNA and ribosomes in translation.

Answer 25

mRNA with genetic code / codons; tRNA with anticodon; tRNA with amino acid attached; ribosome with two sub-units; mRNA held by ribosome; start codon; two tRNA molecules attached with mRNA on ribosome; peptide bond between amino acids on tRNA; polypeptide forms; ribosome moves down mRNA; continues until a stop codon is reached; polypeptide is released;

Question 26

What is true about eukaryotic DNA?

A. It contains the complementary base pair adenine-uracil.

B. It is naked.

C. The majority consists of repetitive sequences.

D. The majority codes for genes.

Answer 26

C

Question 27

What is removed to form mature eukaryotic mRNA?

A. RNA primers

B. Exons

C. RNA polymerases

D. Introns

Answer 27

D

Question 28

Which enzymes are needed to produce recombinant plasmids that are used in gene transfer?

A. DNA polymerase and ligase

B. DNA polymerase and restriction enzymes

C. Restriction enzymes and ligase

D. Helicase and restriction enzymes

Answer 28

C

Question 29

Which molecule is involved in the process of transcription?

A. DNA polymerase

B. Helicase

C. DNA ligase

D. mRNA

Answer 29

D

Question 30

What is the composition of the backbone of DNA?

A. Alternating sugar and phosphate molecules

B. Complementary base pairs

C. Alternating sugar and base molecules

D. A polysaccharide

Answer 30

A

Question 31

A strand of mRNA codes for a polypeptide and has the sequence: AUGGCAACCGGU

what is the complementary strand of DNA?

A. ATGGCAACCGGT

B. UACCGUUGGCCA

C. TACCGTTGGCCA

D. TUCCGUUGGCCA

Answer 31

C

Question 32

Which of the following are connected by a hydrogen bond?

A. The hydrogen and oxygen atoms of a water molecule

B. A base pair of a DNA molecule

C. Two amino acid molecules of a dipeptide

D. Two glucose molecules in a disaccharide

Answer 32

B

Question 33

Which molecule represents ribose?

Answer 33

D

Question 34

What fact is supported by this evidence?

A. The bases in an organism are in equal proportions

B. The sequence of bases in a molecule of DNA are constant

C. The ratio of adenine to guanine is the same as the ratio of adenine to thymine

D. The ratio of adenine to thymine is the same as the ratio of guanine to cytosine

Answer 34

D

Question 35

State a role for each of four different named enzymes in DNA replication.

Answer 35

Award [1] for any two of the following up to [2 max]. helicase; DNA polymerase / DNA polymerase III; RNA primase; DNA polymerase I; (DNA) ligase; [2 max] Award [1] for one function for each of the named enzymes. helicase: splits / breaks hydrogen bonds / uncoils DNA / unwinds DNA; (DNA) polymerase III: adds nucleotides (in 5’ to 3’ direction) / proof reads DNA; (RNA) primase: synthesizes a short RNA primer (which is later removed) on DNA; (DNA) polymerase I: replaces RNA primer with DNA; (DNA) ligase: joins Okazaki fragments / fragments on lagging strand / makes sugar-phosphate bonds between fragments;

Question 36

The structure of the DNA double helix was described by Watson and Crick in 1953. Explain the structure of the DNA double helix, including its subunits and the way in which they are bonded together.

Answer 36

subunits are nucleotides; one base, one deoxyribose and one phosphate in each nucleotide; description / diagram showing base linked to deoxyribose 1 C and phosphate to 5 C ; four different bases – adenine, cytosine, guanine and thymine; nucleotides linked up with sugar-phosphate bonds; covalent / phosphodiester bonds; two strands (of nucleotides) linked together; base to base; A to T and G to C; hydrogen bonds between bases; antiparallel strands; double helix drawn or described; [8 max] Accept any of the points above if clearly explained in a diagram.

Question 37

Compare DNA transcription with translation.

Answer 37

both in 5’ to 3’ direction; both require ATP; DNA is transcribed and mRNA is translated; transcription produces RNA and translation produces polypeptides/protein; RNA polymerase for transcription and ribosomes for translation / ribosomes in translation only; transcription in the nucleus (of eukaryotes) and translation in the cytoplasm/at ER; tRNA needed for translation but not transcription;

Question 38

The process of translation involves the use of transfer RNA (tRNA) and amino acids. Outline the structure of tRNA.

Answer 38

tRNA is composed of one chain of (RNA) nucleotides; tRNA has a position/end/site attaching an amino acid; (Reject tRNA contains an amino acid.) at the 3’ terminal / consisting of CCA / ACC; tRNA has an anticodon; anticodon of three bases which are not base paired / single stranded / forming part of a loop; tRNA has double stranded sections formed by base pairing; double stranded sections can be helical; tRNA has (three) loops (sometimes with an extra small loop); tRNA has a distinctive three dimensional / clover leaf shape; [5 max] Accept any of the points above if clearly explained using a suitably labelled diagram

Question 39

Which enzyme is used to produce complementary DNA (cDNA) from mRNA?

A. Restriction endonuclease

B. Reverse transcriptase

C. DNA ligase

D. RNA primase

Answer 39

B

Question 40

Outline the structure of DNA

Answer 40

double helix; two chains of nucleotides / composed of nucleotides; nucleotides consist of base, deoxyribose (sugar)and phosphate; bases are adenine, cytosine, guanine and thymine; anti-parallel / strands; 3 -5′ ′ links between nucleotides; hydrogen bonds between base pairs / purine and pyrimidine on opposite chains; only A-T and G-C / complementary base pairs are A-T and G-C ; two bonds between A-T and 3 between G-C; [5 max] Credit can be given for any of these points shown on a correctly drawn and labelled diagram.

Question 41

Explain the process of transcription in eukaryotes.

Answer 41

RNA polymerase controls transcription / is the enzyme used in transcription; DNA is unwound by RNA polymerase; DNA is split into two strands; mRNA is made by transcription; promoter region (by start of gene) causes RNA polymerase to bind; anti-sense/template strand of DNA is transcribed; direction of transcription is 5 -3′ ′ ; free nucleotide triphosphates used; complementary base pairing between template strand and RNA nucleotides/bases; Accept this marking point if illustrated using a diagram RNA contains uracil instead of thymine; terminator (sequence) stops RNA polymerase / transcription; mRNA is released / RNA polymerase released;

Question 42

Outline the structure of part of a double stranded DNA molecule, using a simplified diagram.

Answer 42

two strands of DNA; anti-parallel; 3 to 5 ′ ′ linkages; purine / pyrimidine; A-T / G-C base pairing; hydrogen bonds; sugar-phosphate backbone; [5 max] Award [3 max] if answer does not include a diagram.

Question 43

Which events take place in DNA replication?

I. Formation of messenger RNA II. Unwinding of DNA double helix III. Formation of complementary strands by DNA polymerase

A. I and II only

B. I and III only

C. II and III only

D. I, II and III

Answer 43

C

Question 44

If a polypeptide consists of 240 amino acids, what is the minimum number of nucleotides needed on the sense strand of a gene to code for it?

A. 80

B. 240

C. 720

D. 1440

Answer 44

C

Question 45

Draw and label a simple diagram showing how DNA nucleotides are linked together in a single strand.

Answer 45

Award [1] for each of the following clearly drawn and correctly labelled. nucleotides – labelled with at least two shown; sugar, phosphate and base – labelled correctly and positioned in relation to one another; ⎧ ⎨ ⎩ Accept absence of C5 or A/T/C/G in absence of word “base”. sugar attached to base – clearly shown linked to C1; ⎧ ⎨ ⎩ C1 does not need to be labelled. deoxyribose – drawn as a pentagon; covalent bond in S-P backbone/between sugar and base;

Question 46

Explain the process of DNA replication

Answer 46

helicase uncoils/splits DNA double helix; RNA primase; (creates a primer for) DNA polymerase III to bind/begin replication; deoxyribonucleoside triphosphates (free in cell); two phosphates removed to release energy; DNA polymerase III adds nucleotides in 5′ to 3′ direction; A paired with T / C paired with G; discontinuous copying / Okazaki fragments / short lengths of DNA formed (between RNA primers) on lagging strand; continuous on leading strand; DNA polymerase I removes RNA primers/replaces them with DNA; DNA ligase joins the fragments; initiated at many points in the (eukaryotic) chromosomes;