Protein synthesis

Figure 9 shows an aphid.

An aphid inserts its mouthpart into plant tissue to feed on plant sap.

(Source: http://www.biology-resources.com/drawing-aphid-wingless.html)

Figure 9

Aphids can transfer plant viruses from one plant to another.

Which term describes the role of the aphid in the transmission of plant viruses?

Describe the physical barriers of a leaf that the virus gets through when an aphid feeds.

The genetic material from the virus is transcribed by the plant cell.

Describe how mRNA is produced during transcription.

Name the stage of protein synthesis after transcription.

Biological control can be used on aphid populations feeding on crops.

Explain the advantages of using biological control on aphid populations.

Plant growth can be affected by the environment, by pathogens, or both.

A farmer found lesions on crop plants growing in one of their fields.

Figure 11 shows lesions on leaves.

*(i) Discuss how the cause of the lesions and their spread through the crops could be investigated.

You should refer to distribution analysis in your answer.

The farmer decides to dig up the affected crop plants.

Give one precaution the farmer should take when digging up the affected crop plants.

The genetic material of some plant viruses is single-stranded RNA.

The RNA is copied by the infected host cell and acts as a mRNA molecule.

Describe how protein synthesis makes viral proteins from this mRNA.

DNA molecules contain base pairs.

Describe how the base pairs are bonded together in a DNA molecule.

Figure 1 shows part of a DNA molecule.

Write the code for the complementary DNA strand in Figure 1.

Three bases code for each amino acid.

Which is the maximum number of amino acids coded for by this strand of DNA?

What is the shape of a DNA molecule?

A student wanted to extract the DNA from fresh peas.

The student crushed the peas and added washing up liquid and water.

The enzyme protease was then added to this mixture.

Explain why the enzyme protease was added to the mixture.

The mixture was then heated and filtered.

Finally, the student poured the filtrate into a test tube and ice cold ethanol was poured down the side of the test tube into the filtrate.

State why ice cold ethanol was poured into the filtrate.

10 (a) One gene can have several different alleles. Explain why these alleles can produce proteins with different structures.

(b) Monoclonal antibodies are proteins. Figure 16 shows the process of monoclonal antibody production.

mouse hybridoma

Figure 16

(i) Which type of cell is added to the B lymphocytes to produce the hybridoma?

(ii) A person with blood group A has the A antigen on the surface of their red blood cells. Monoclonal antibodies can be used to detect the A antigen on red blood cells to determine the blood group of a person. Explain why monoclonal antibodies, used to detect blood group A, would not react with the blood of a person with blood group B.

(c) The allele for blood group A and the allele for blood group B are codominant. Gregor Mendel investigated the inheritance of alleles using flowering plants. He showed that the allele for red flowers (I) is codominant with the allele for He showed that the allele for red flowers (I^R) is codominant with the allele for white flowers (I^W). A heterozygous plant produces pink flowers.

(i) Give the genotype for a plant producing white flowers.

(ii) Explain the outcome if two plants that produce pink flowers are crossed. You should complete the Punnett square as part of your answer.

(TOTAL FOR PAPER = 100 MARKS)

The UK driving test requires a person to be able to read a number plate at a distance of 20.5 metres.

Some people are short-sighted so cannot read the number plate at this distance.

Explain how a diverging lens corrects short-sightedness.

You may draw a diagram to help with your answer.

Colour blindness affects approximately 1 in 12 men.

In a city of 2 million people, 51% are men.

What is the number of men who are colour blind in the city?

Colour blindness is a sex-linked genetic disorder caused by a recessive allele.

Colour blindness only affects 1 in 200 women.

Explain why more men than women are colour blind.

A female without the allele for colour blindness has a baby boy.

The father is colour blind.

Explain the probability of the baby boy being colour blind.

One cause of colour blindness is a change in the DNA sequence of a gene.

This results in the production of a different protein in cone cells in the retina of the eye.

Explain how a change in the DNA sequence of a gene can result in the production of a different protein.

Transcription and translation are stages in the synthesis of proteins.

Which enzyme is involved in the process of transcription?

Describe how a mutation in the non-coding region of the DNA can prevent a gene being transcribed.

A gene coding for a protein has two alleles.

Figure 14 shows the first 5 codons of an mRNA strand for these alleles.

Allele 1 – AUG CCA CAG GAG UUC

Allele 2 – AUG CCA GAG GAG UUC

Figure 14

Allele 2 has a mutation.

Figure 15 shows the key needed to predict the translated amino acid sequence of the protein.

Explain how the mutation in allele 2 could affect the functioning of this protein.

*(c) The inheritance of different alleles affects the phenotype of an individual.

A child is blood group O.

The child’s mother is blood group A and the child’s father is blood group B.

Explain how this child is blood group O.

Use the Punnett square and probability in your answer.

A scientist was planning to compare the effectiveness of the antibiotic myxopyronin on two different species of bacteria.

Figure 18 shows the equipment the scientist can use.

agar plates
two species filter discs of
spreader
incubator of bacteria myxopyronin

Figure 18

Describe how the scientist could determine the effectiveness of myxopyronin on the two species of bacteria.

Myxopyronin inhibits bacterial RNA polymerase.

Explain why the antibiotic myxopyronin can be used to treat bacterial infections in humans.

*(b) Infections can also be caused by viruses.

Describe the lytic pathway of a virus and how this causes the spread of infection through a population.

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