Genetics_Long2

The table below shows the blood stock of the South African National Blood Service (SANBS) at a certain date for the different blood types. Study the table and answer the questions that follow. The Day’s Stock indicates how many days of stock the blood bank has left or each blood group.

State THREE disadvantages of genetic engineering. (3)

DISADVANTAGES:

Expensive /research money could be used for other needs.

May be hard for poor people to access/compete.

Interfere with nature /immoral/ we cannot play God.

Domination of the world food products by only a few companies.

Loss of flora and fauna biodiversity by inbreeding /entire species to be wiped out if exposed to disease against it has no resistance /such as allergens.

Potential health impacts.

Violation of natural organism's intrinsic value /right to independent existence by changing the genetic make up of an organism.

Unsure of long term effects.

Genes from transgenic organisms could escape and be transferred to wild organisms.

State THREE advantages of genetic engineering. (3)

ADVANTAGES:

Production of medication/resources cheaply.

Control pests with specific genes inserted into the crop.

Selecting the best genes to produce better resistant crops.

Using specific genes to increase crop yields / food security.

Selecting genes to increase shelf life of plant products.

Selecting genes that delay ripening of fruits to meet the demand.

Using specific genes to improve nutritional value of food for better health.

Using specific genes to introduce new traits in crops to suit specific needs of a population (e.g. to increase vitamin A in food).

DNA and proteins of transgenic organisms unlikely to cause problems since it is digested in human gut.

Transgenic organisms do not survive easily in wild.

Use a genetic cross to show the possible genotypes and phenotypes of the children. (6)

Answer

What are the chances of the parents having a haemophiliac son? (2)

25% chance / 1 out of 4

Explain why the father is not a carrier of haemophilia. (2)

The male has only one X chromosome Y chromosome does not have the allele for this trait /can only be affected or unaffected/if he had 'h' he would be a sufferer, therefore he must have had 'H'.

Set 2

Set 2

Choose

Question 1

- Multiple Alleles and Sex-linked Alleles -

Question 2

Haemophilia is a sex-linked disease caused by the presence of a recessive allele (Xh). A normal father and heterozygous mother have children.

Question 3

Which blood type has the lowest number of day's stock? (1)

Type O

State ONE possible reason why the stock of this blood type is lower than other blood types. (1)

It has insufficient donors/used most by patients, etc.

SANBS needs an eight-day supply of blood at all times. Suggest ONE reason why there is a shortage of donated blood in South Africa. (2)

There are high numbers of people with blood-borne diseases/HIV/AIDS/hepatitis. OR

Certain beliefs may make people hesitant to donate blood.

Sarah has a child who is blood group B. There are two men who are claiming paternity of the child. Paul is blood group O and James is blood group AB. Sarah is heterozygous for blood group A. Use a genetic cross to show why James is the father of the child. (6)

Answer

With regard to the above question, what is the genotype of the child's blood? (1)

Question 4

Mrs Mkhize and Mrs Sithole both gave birth to baby boys on the same day. Somehow, the babies were mixed up in the nursery. It was decided to determine the blood types of the babies in order to give each pair of parents the correct baby. One baby was found to be blood type O and the other, blood type B. Mr Mkhize is blood type AB, while Mr Sithole is blood type A. Both mothers are blood type O. Can you match each pair of parents with their correct baby? Show ALL working. (16)

Answer

Study the genotypes and phenotypes below that show how the alleles for colour-blindness are inherited. X and Y represent sex chromosomes. A carrier does not suffer from colour-blindness but can pass the allele for colour-blindness to their children.

Question 5

State why colour-blindness is referred to as a sex-linked disorder. (2)

The genes for colour-blindness is carried on the sex chromosomes.

Is colour-blindness caused by a dominant or a recessive allele? Give a reason your answer. (3)

Recessive. The trait only shows up if it is in the homozygous recessive/not in the heterozygous state.

Explain why Thabani is colour-blind. (2)

Thabani has only one X chromosome with a recessive allele for colour-blindness, the Y chromosome does not carry an allele for the characteristic.

Sarah and Paul marry and have two children, a son and a daughter. Represent this genetic cross by using the information in the table above to determine the genotypes and phenotypes of the son and the daughter. (6)

Answer

The table below shows the percentage distribution of blood groups in a province in South Africa.

Question 6

How many genes control the blood groups shown above? (1)

One gene, that has 3 alleles.

Explain how it is genetically possible to have four blood groups in a population. (2)

Blood groups are controlled by three alleles/ IA , IB , i which when in combination provide four phenotypes/A, AB, B, O.

Draw a pie chart using the information in the table above. Show ALL calculations. (8)

Set 5

Questions source: DBE (Authorisation 11798)

- Greg Gopaul -