Cambridge IGCSE Biology - 0610 - Supplement Paper 4 2021 Winter Zone 3

Enzymes are used in genetic engineering.

(a) Define the term enzyme. [2]

(b) The process of genetic engineering often starts with the steps shown in Fig. 1.1.

(i) State the sequence of bases on the lower strand of the DNA molecule in step 1. [1]

(ii) State the name of enzyme 1 in step 2 of Fig. 1.1. [1]

(iii) Describe the effect of enzyme 1 on the DNA molecule in step 3. [2]

(iv) Explain how enzyme 1 in Fig. 1.1 is specific to the exact sequence of DNA bases. [2]

(c) Another enzyme, enzyme 2, is used later in the process of genetic engineering.

Fig. 1.2 is a diagram showing the action of enzyme 2.

(i) Some organisms naturally contain DNA in the form of a plasmid.

State the name of the type of organism that naturally contains plasmids. [1]

(ii) State the name of enzyme 2 in step 7 of Fig. 1.2. [1]

(iii) State the name of the molecule formed in step 8. [1]

(d) Sketch a graph to describe how the activity of the enzymes used in genetic engineering would change if the reaction occurred at a range of temperatures from very cold to very hot. [3]

Label the axes with appropriate titles.

Do not use units or a numbered scale.

(a) (i) Describe the rate of uptake of nitrate ions along the root. Use the information in Fig. 2.1 and Fig. 2.2 in your answer. [5]

(ii) Explain how nitrate ions move from the soil into roots. [4]

(iii) Explain why the uptake of ions, such as nitrate, is important for the uptake of water in roots. [1]

(iv) Explain why plants need nitrate ions, other than for the uptake of water. [3]

(b) (i) Fig. 2.3 shows some of the events that occur when high concentrations of nitrate ions flow into lakes.

Put the events shown in Fig. 2.3 into the correct sequence. [2]

A researcher investigated genetic variation in fruit flies, Drosophila melanogaster.

The bodies of fruit flies can be black or yellow. A yellow body colour is a recessive feature in fruit flies.

(a) Two heterozygous fruit flies with black bodies were bred together.

Predict the phenotypes of the offspring and the phenotypic ratio for this cross. [1]

(b) In another fruit fly breeding experiment, researchers counted 124 offspring with black bodies and 121 offspring with yellow bodies.

Draw a genetic diagram to explain the results of this cross. Use the letter B to represent the allele for black body colour and the letter b to represent the allele for yellow body colour.

parental phenotypes ................................... \( \times \) ...................................

parental genotypes ................................... \( \times \) ...................................

offspring genotypes ...........................................................................................................................

expected offspring phenotype ratio ................... black : .................... yellow

actual offspring phenotype ratio 124 black : 121 yellow [5]

(c) The crab, Cerberusa caeca, lives in dark caves and has no coloured pigment.

Fig. 3.1 is a photograph of C. caeca.

(i) \( C. \) caeca and \( D. \) melanogaster are both arthropods.

State one feature present in all arthropods but not present in vertebrates. [1]

(ii) \( C. \) caeca is a crustacean and \( D. \) melanogaster is an insect.

State one morphological feature of \( C. \) caeca that distinguishes it as a crustacean and not as an insect. [1]

(d) The ancestors of \( C. \) caeca had pigmented bodies.

The lack of a coloured pigment in \( C. \) caeca is called albinism and was caused by a mutation many thousands of years ago.

(i) Explain the mechanism that has resulted in the allele for albinism becoming common in recent generations in populations of \( C. \) caeca. [3]

(ii) State two factors that can cause mutations. [2]

HIV is a pathogen that can cause AIDS.

 
(a) Describe how HIV is transmitted from one person to another [3]

(b) All viruses contain genetic material. HIV contains genetic material called RNA. State one other feature common to all viruses. [1]

(c)

 (i) Describe the function of lymphocytes [3]

(ii) State how infection with HIV affects the lymphocytes if untreated  [1]

(d) Doctors wanted to determine whether dietary supplements could help people infected with HIV. They randomly put volunteers with HIV into two groups:

• a treatment group, who received HIV medication and additional vitamin and mineral supplements 

• a control group, who received HIV medication but no additional supplements. 

The details of the two groups are outlined in Table 4.1. 

The dietary supplements were given to the treatment group twice a day for three months. The nutrients in the supplements included:

• vitamin C 

• vitamin D 

• calcium 

• iron 

• other minerals and vitamins. 

(i) Explain why vitamin C and iron are important in the human diet.  [4]

(ii) Use the data for the treatment group, shown in Table 4.2, to calculate the percentage decrease in the average number of copies of HIV RNA per cm³ of blood.

Space for working. ................................................................% [2]

(iii) Evaluate the effect of the dietary supplements on the lymphocytes. Use the information in Table 4.2 in your answer.  [2]

Fig. 5.1 shows people fishing on a large scale and a small scale.

All types of fishing can have a negative impact on fish stocks.

(a) Discuss how governments can regulate fishing to maintain fish stocks. Use the word sustainable in your answer. 

(b) Fig. 5.2 shows the location of a chemical factory near a river.

Fig. 5.3 shows the sex ratio of the fish, Catostomus commersonii, in the river at site 1 and site 2. Intersex fish have both female and male reproductive organs.

State and explain what type of chemical the factory could be releasing into the river that would cause the effects shown in Fig. 5.3.

type of chemical ........................................................................................................................................

explanation .................................................................................................................................................

(c) State how sex is inherited in humans.

The heart pumps blood around the body.
(a) Explain why the heart is an organ.
................................................................................................................
................................................................................................................
................................................................................................................ [1]
(b) Complete the sentences:
The ............................................ system includes the heart and blood vessels. Deoxygenated blood from the body is transported to the heart in the ............................................ .
During a heart beat the ventricles contract. The right ventricle pumps deoxygenated blood to the lungs. The right ventricle has a ............................................ muscular wall than the left ventricle.
Gas exchange in the lungs occurs by ............................................ . Oxygenated blood travels back to the heart where it enters the ............................................ of the heart.
The two sides of the heart are separated by the ............................................ . This structure prevents the mixing of oxygenated and deoxygenated blood. Oxygenated blood is then delivered to the rest of the body. Blood is supplied to the muscle of the heart in the ............................................ . [7]
(c) Many people monitor their heart rate by counting their pulse.
State one other method of monitoring heart rate.
................................................................................................................ [1]