[Maximum number: 4]

Fig. 2.1 shows a dwarf sunflower and a tall sunflower, Helianthus annuus. The height of the dwarf sunflower is 0.45 m and the height of the tall sunflower is 4.5 m .

not to scale

Dwarf plants like the one in Fig. 2.1 have mutant alleles.

(a)

Define the term allele.

[ 1 ]

(b)

Shoot growth in plants is controlled by auxins. An enzyme in shoot tips converts molecules of an amino acid into auxins as shown in Fig. 2.2.

Fig. 2.2

Explain how a mutation in DNA results in an abnormal enzyme which does not catalyse the reaction shown in Fig. 2.2.

[ 3 ]

[Maximum number: 6]

Many researchers are studying the structure and function of genes.

(a)

Define the term gene.

[ 2 ]

(b)

Every living cell is able to make proteins.

The process begins in the nucleus.
Describe how proteins are made in a cell.

[ 4 ]

[Maximum number: 8]

Fig. 2.1 is a diagram of part of a DNA molecule.

Fig. 2.1

(a)

(i)

State the name given to a length of DNA that codes for a protein.

[ 1 ]

(ii)

Explain how proteins are made by a cell.

[ 5 ]

(iii)

DNA controls cell function by controlling the production of proteins.

State two types of cell membrane proteins.
1

2

[ 2 ]

[Maximum number: 4]

Quinoa, Chenopodium quinoa, is a dicotyledonous plant that produces seeds that resemble those of cereals, such as rice.

(a)

During seed development, amino acids are converted into storage proteins and proteases.

Protease molecules become active when the seed absorbs water at the start of germination.
Fig. 2.1 shows the formation of a storage protein and a protease in developing quinoa seeds and the action of protease on the storage protein during germination.

Fig. 2.1

[ 2 ]

(i)

During seed development in quinoa some genes are 'switched on'.

Define the term gene.

[ 2 ]

(b)

State the roles of mRNA and ribosomes in protein synthesis.
mRNA
ribosome

[ 2 ]

[Maximum number: 3]

The Indian muntjac deer, Muntiacus muntjak, is recorded as the mammal with the lowest number of chromosomes.

Fig. 2.1 is an image of the chromosomes in the nucleus of a diploid cell of a female muntjac deer.

Fig. 2.1

(a)

State the diploid number of chromosomes for the female muntjac deer.

[ 1 ]

(b)

Fig. 2.2 is an image of the chromosomes in the nucleus of a diploid cell of a male muntjac deer.

Fig. 2.2

Describe how the sex chromosomes of the male muntjac deer shown in Fig. 2.2 differ from those of the female shown in Fig. 2.1.

[ 2 ]

[Maximum number: 3]

Fig. 2.1 is a diagram showing a small region of DNA.

Fig. 2.1

Fig. 2.2 shows part of the DNA enlarged to show the sequence of bases.

Fig. 2.2

(a)

Fig. 2.3 shows how DNA is involved in protein synthesis.

Fig. 2.3 not to scale

Explain how mRNA is involved in protein synthesis.

[ 3 ]

(a)

A gene is responsible for the production of lycopene in fruits. Geneticists have recently produced genetically modified pink pineapples using the gene associated with the production of lycopene.

[ 1 ]

(i)

Genes are found at specific locations on an important biological molecule.

State the name of this biological molecule.

[ 1 ]

[Maximum number: 7]

Red blood cells contain the protein haemoglobin.

(a)

Fig. 2.1 shows a photomicrograph of some red blood cells from a person with sickle cell anaemia.

Abnormal red blood cells occur because of a mutation in the gene for haemoglobin.

Fig. 2.1

Suggest how the shape of the abnormal red blood cell shown in Fig. 2.1 will affect blood flow.

[ 2 ]

(b)

Fig. 2.2 and Fig. 2.3 are maps showing some of the different regions in a country. Scientists studied the distribution of the $\mathbf{H b}^{\mathbf{S}}$ allele in the country.

Fig. 2.2 shows the estimated frequency of the allele within the population.

Fig. 2.3 shows the estimated number of babies born with sickle cell anaemia in each region.

Fig. 2.3

The scientists made a statement:
'There is a relationship between the frequency of the $\mathbf{H b}^{\mathbf{S}}$ allele and the number of babies born with sickle cell anaemia in regions A, B and C.'

[ 1 ]

(i)

Suggest how the scientists would identify the presence of the $\mathbf{H b}^{\mathbf{S}}$ allele in tissue samples.

[ 1 ]

(c)

Mutations are always inherited in single-celled organisms that reproduce asexually but are not always inherited in organisms that reproduce sexually.

Explain why.

[ 4 ]

[Maximum number: 2]

The genes for antibodies are only active in lymphocytes.

(a)

Define the term gene.

[ 2 ]

[Maximum number: 4]

Insulin is a protein made by cells in the pancreas.
Fig. 2.1 shows how insulin is made in a pancreatic cell.

Fig. 2.1

(a)

(i)

State the name of molecule A in Fig. 2.1.

[ 1 ]

(ii)

Explain the role of molecule A in protein synthesis, as shown in Fig. 2.1.

[ 3 ]