VCE Unit 3 & 4 biology - Home



DNA REPLICATION AND PROTEIN SYNTHESIS

Question 1

In DNA the number of:

a) Phosphate groups equals the number of nitrogen bases

b) Adenine nucleotides equals the number of cytosine nucleotides

c) Phosphate groups equals twice the number of sugar molecules

d) Guanine nucleotides equals the number of uracil nucleotides

Question 2

During DNA replication:

a) Messenger RNA is produced

b) Reverse transcriptase enzymes play an important role

c) Bonds between phosphate and sugar molecules break

d) Each of the DNA strands acts as a template strand

The picture below shows a portion of a cell engaged in protein synthesis.

[pic]

Question 3

It is reasonable to conclude that:

a) Process N is translation

b) Structure P is made of tRNA

c) Compound Q is messenger RNA

d) Structure R is the site of protein synthesis

Use this information to answer the next 2 questions

The following nucleotide sequence forms part of the template strand of a gene coding for protein X

TGGATGAC

Question 4

The complementary base found at the fourth nucleotide in a sequence transcribed from this sequence would be:

a) C

b) G

c) T

d) U

Question 5

In a double stranded molecule formed from this DNA template the number of deoxyribose sugar units you would expect to find is:

a) 4

b) 8

c) 16

d) 32

Question 6

Reverse transcriptase catalyses the production of:

a) DNA from an mRNA template

b) DNA from a protein template

c) mRNA from a DNA template

d) tRNA from a DNA template

Question 7

The last 1-4 below describes events and outcomes of the replication of DNA within a eukaryotic cell.

1. Complementary nucleotides bind to each of the 2 strands

2. Sugar phosphate bonds form between the nucleotides

3. The newly formed DNA molecules are semi conserved

4. Unwinding of the DNA molecule forms two singled strands

The correct order of these events during DNA replication with the earliest event first is:

a) 1,2,3,4

b) 1,4,3,2

c) 4,2,1,3

d) 4,1,2,3

Question 8

The nucleotide found in mRNA but not DNA is:

A. Uracil

B. Adenine

C. Guanine

D. Cytosine

Question 9

DNA was incubated with radioactive nucleotides. After one cycle of replication the distribution of radioactive and non radioactive nucleotides would be:

[pic][pic][pic]

Question 10

Translation of the genetic code occurs in the cytosol of a cell. The following diagram is one representation of translation.

[pic]

In the model presented

a) M represents a ribosome

b) N represent mRNA

c) O represents tRNA

d) P represents an amino acid

Question 11

In eukaryotic organisms genes are:

a) Composed of DNA

b) Alternative forms of an allele

c) Composed of DNA and protein

d) The same length as a chromosome

Question 12

In prokaryotic organisms

a) Translation occurs at the ribosome

b) Transcription occurs in the nucleus

c) Chromosomes are usually linear

d) DNA is only found in plasmids

Question 13

For humans the term nuclear genome refers to all of the genes in:

a) An autosome

b) An X chromosome

c) A y chromosome

d) A set of autosomes plus the sex chromosomes

Question 14

When comparing eukaryotic chromosomes with prokaryotic chromosomes it is true that both:

a) Exist in homologous pairs

b) Are linear chromosomes

c) Are situated within a nucleus

d) Are made of double stranded DNA molecules

Question 15

One section of a polypeptide has the amino acid sequence

Ala – Cys – Lys – Ile – Asn

The codons for these amino acids are:

Ala GCA GCC GCG GCU

Cys UGC UGU

Lys AAA AAG

Ile AUU AUC AUA

Asn AAC AAU

The sequence of DNA coding for this section of the polypeptide could be:

a) CGTACGTTTTATTTG

b) CGTTCGTTTTATTTG

c) CGTACTTTTTACTTG

d) CGAACATTCTATTTT

The following information relates to the next 3 questions. It outlines the production of protein in a cell when DNA is activated.

[pic]

Question 16

At stage I, the DNA molecule involved has the base sequence

a) TACTACGGCCTCCTGCCTGGGGGACTAACT

b) TACTACGGCCTTCTGCCTCCCGGACTAACT

c) TACTACGGCCTTCTGCCTGGGGGACTAACT

d) TACTACGGCCTTCTGTTTGGGGGACTAACT

Question 17

In stage I

a) Step E represents translation.

b) Removal of exons occurs at step F.

c) Product G is the initial mRNA produced.

d) The enzyme RNA polymerase is active.

Question 18

In stage II

a) Structure K is made of tRNA.

b) The three bases of group H form an anticodon.

c) Bond J represents a hydrogen bond.

d) The mRNA shown will code for a protein containing 10 amino acids.

Question 19

Domestic dogs vary greatly in adult size. All dog breeds have the IGF-1 gene coding for a hormone which promotes growth to adolescence. Scientists have discovered that all small dog breeds have an allele called S, of another gene close to IGF-1. The best hypothesis to explain the size range in dogs is:

a) The gene product of the S allele is a promoter of IGF-1

b) IGF-1 is the only gene controlling growth in dogs

c) When S is translated its product inhibits IGF-1 gene expression

d) Large breeds cannot produce a transcript of the IGF-1 gene

Question 20

In a double stranded DNA molecule 23% of the bases are adenine. What proportion of bases will be guanine?

A. 23%

B. 27%

C. 46%

D. 54%

Question 21

Double stranded DNA is replicated by:

a) A complementary strand being produced which in turn is used as a template for the synthesis of the second strand.

b) A complementary strand being produced for each template strand of DNA

c) 1 template strand being degraded to allow for synthesis of a complementary strand before the damaged strand is repaired.

d) Reverse transcriptase which uses mRNA as the template

e) DNA replicase enzymes which are located on the nuclear membrane

Question 22

Which of the following has the correct base pairing between DNA and mRNA?

[pic][pic][pic]

[pic][pic]

Question 23

Which of the following statements is correct about the synthesis of proteins?

1. Protein synthesis only takes place by ribosomes bound to the endoplasmic reticulum

2. tRNA molecules transport amino acids to ribosomes during protein synthesis

3. A codon can code for more than 1 amino acid

a) 1 only

b) 2 only

c) 3 only

d) 1 and 2 only

e) 2 and 3 only

Question 24

Which of the following mutations to a gene is least likely to affect an organism?

a) A single base change in the initiation codon

b) A single base change near the 5’ end of the reading frame

c) A single base change near the 3’ end of the reading frame

d) A single base deletion near the 5’ end of the reading frame

e) A single base deletion near the 3’ end of the reading frame

Question 25

Which of the following is correct about mutations to a gene of an organism? They always:

a) Result in natural selection and speciation

b) Alert the balance of inorganic chemicals in the body

c) Change the DNA sequence

d) Induce spontaneous adaptations

e) Induce behavioural changes

Question 26

A segment of a template DNA strand is shown below

5’CGCGTAAACAGT3’

The corresponding mRNA strand would be:

a) 5’GCGCAUUUGUCA3’

b) 5’ACUGUUUACGCG3’

c) 5’TGACAAATGCGC3’

d) 5’CGCGTAAACAGT3’

Question 27

In the double helix model of DNA and DNA replication

a) A chromosome is one of the single strands of DNA

b) Each strand of DNA must contain an identical number of adenine bases

c) Each new DNA double helix will contain 1 DNA strand from the original double helix after replication

d) The old DNA strands are completely broken down during replication

Question 28

The diagram below shows a simplified model of a part of a DNA molecule.

[pic]

The parts labelled 1, 2 and 3 are respectively

a) Base, phosphate and sugar

b) Base, sugar and phosphate

c) Phosphate, base and sugar

d) Phosphate, sugar and base

Question 29

Refer to the diagram below:

[pic]

The structures labelled K, L, M and N respectively:

a) Phosphate, sugar, thymine, guanine

b) Thymine, guanine, phosphate, sugar

c) Guanine, thymine, phosphate, sugar

d) Sugar, phosphate, guanine, thymine

Question 30

The following base sequence of DNA represents a segment of the leading strand of DNA. Which of the following represents what the section of double stranded DNA would look like.

GAATTC

[pic][pic][pic][pic]

Question 31

The diagram shows a section of DNA undergoing replication

[pic]

In which 2 strands of DNA would the sequence of bases be the same?

a) 1 and 4

b) 2 and 3

c) 3 and 4

d) 2 and 4

Question 32

The steps involved in DNA replication and protein production are summarised below

[pic]

In which step would a mutation lead to the formation of a new allele?

a) Step A

b) Step B

c) Step C

d) Step D

Question 33

Why is accurate replication of DNA important?

a) It leads to cell differentiation

b) It maintains genetic information

c) It allows for evolution of the species

d) It enables cells to modify their proteins

Question 34

Generally gametes produced by an organism will not be identical. Which of the following does not influence this genetic variability of gamete formation?

a) Mutation

b) Sex linkage

c) Independent assortment of alleles

d) Crossing over in homologous chromosomes

Question 35

The diagram below represents a model of DNA replication. The steps are not in the correct order.

[pic]

Which of the following is the correct order?

a) 1,2,3,4

b) 2,3,4,1

c) 2,4,3,1

d) 4,3,2,1

SHORT ANSWER QUESTIONS

Question 1

The template strand for a section of a gene is shown below:

AAAGTACTGCGC

What is the complementary sequence for the other strand of DNA?

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What does the A represent in this sequence?

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The first step in the process of gene transcription. What is produced during transcription?

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The compound produced during transcription attaches to an organelle in the cell. What is the name of this organelle?

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What is the name of the step in gene expression which follows transcription and occurs at this organelle?

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Question 2

Below is the DNA sequence from the beginning of a gene coding for an enzyme involved in photosynthesis. The upper line of bases represents the template strand.

[pic]

Write the mRNA sequence that would be transcribed from this DNA sequence

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Use the genetic code table below to help answer the following questions

[pic]

The 6th base on the template strand is substituted by C. What type of mutation is this?

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Explain the effect this mutation will have on the amino acid sequence produced

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The 11th base pair of the sequence is deleted. Explain the effect that this mutation will have on the amino acid sequence of the protein produced.

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Question 2

A US company has recently released what is believed to be the first designer transgenic pet. The Glofish is derived from the zebra fish, which is normally silver with black stripes. The zebra fish has been genetically modified by adding a gene found in a sea coral into zebra fish eggs. The offspring resulting from these genetically modified eggs are reddish in colour and glow or fluoresce under UV light.

[pic]

Although the added gene is from a different species it is expressed in the same way in both the sea coral and transgenic zebra fish. What feature of the genetic code makes it possible for a gene to be transferred from one species to another and to be expressed in the second species?

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What steps are required within zebra fish cells for the sea coral to be expressed?

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Question 3

During their work in establishing the structure of DNA, Watson and Crick were interested in the proportion of nucleotides in skin cells from a particular organism. They considered the results from 3 different laboratories. The results were as follows:

[pic]

Watson and Crick used the results of laboratories 2 and 3. What difference would it have made to the model they constructed of DNA had they used the results of laboratory 1 only?

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Question 4

Use the table below to answer the following questions

[pic]

What sequence of nucleotides in DNA code for the amino acid histidine (His)?

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Which of the following DNA sequences could lead to the production of an uninterrupted chain of amino acids?

[pic]

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Question 5

The following diagram outlines events associated with the production of a polypeptide chain in a eukaryotic cell.

[pic]

What is the name of the process at step 1?

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Name the product of step 1

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Outline what occurs at step 2

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Name the event that occurs at structure 3

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Name the structure at 4

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Outline the function of structure 4

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Question 6

Organisms can regulate the expression of their genes in a number of ways. Suggest why an organism regulates the expression of its genes.

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One example in bacteria is the regulation of the expression of a gene which produces an enzyme (enzyme X) involved in the metabolism of the amino acid tryptophan.

Enzyme X is only produced when tryptophan is in high concentration. This gene regulation involves several genes. Two of the genes include a gene for the production of enzyme X and an operator gene.

If a protein called a repressor protein, binds to the operator gene, transcription of the gene for enzyme X is stopped.

If no repressor protein is bound to the operator, transcription of the gene for enzyme X occurs. A summary of this regulation is shown below:

[pic]

The gene coding for enzyme X is not transcribed when the repressor protein binds to the operator gene. What enzyme is prevented from functioning during this biding?

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When tryptophan binds to the repressor protein, the repressor protein can no longer bind to the operator gene as shown below.

[pic]

When tryptophan binds to the repressor protein, what will happen to the production of enzyme X?

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Suggest how tryptophan prevents repressor protein function

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Question 7

Bacteria require amino acids to produce proteins. For example bacteria in a human intestine may absorb amino acids from digested food but at times there may be a deficiency of a particular amino acid. If this is the case the bacteria will produce the necessary amino acid themselves. The diagram below is a regulation system in a bacterial cell involving the production of the amino acid tryptophan. Note that there are 2 pathways (X and Y). Tryptophan is the regulatory compound in these 2 pathways and acts as a repressor in both.

[pic]

Describe the immediate outcome when tryptophan activates pathway X.

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Describe the immediate outcome when tryptophan activates pathway Y.

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Suggest how the action of tryptophan as a repressor in this system could be of selective advantage to a bacterial cell in the digestive tract.

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