IGCSE Biology Paper-3: Specimen Questions with Answers 256 - 258 of 358

Passage

Coat color in cattle is inherited in a very similar way to blood groups in humans. The gene for coat color has two codominant alleles:

CB which is the allele for brown coat

CW which is the allele for white coat.

Table shows the genotypes and phenotypes of different coat colors seen in a herd of cattle.

The Genotypes and Phenotypes of Different Coat Colors Seen in a Herd of Cattle
genotypephenotype
CBCBbrown
CWCWwhite
CBCWroan

Question 256 (4 of 5 Based on Passage)

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A farmer has a herd of cows that produce milk. The farmer wants to improve the milk yield of the herd by using artificial selection (selective breeding) . The farmer buys semen (fluid containing sperm) to inseminate the cows artificially.

Suggest one useful feature, other than milk yield and coat color, which a farmer might wish to develop in a herd of cows.

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Explanation

  • increase in meat quantity
  • milk quality
  • resistance to disease
  • fast growth & development
  • good temperament
  • meat quality

Question 257 (5 of 5 Based on Passage)

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Milk yield can also be increased by injecting cows with the hormone bovine somatotropin (BST) .

Explain why there may be concerns about the use of this hormone to increase milk yield.

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Explanation

Concerns About the Misuse of Hormone to Increase Milk Yield

  • already an overproduction of milk in the market
  • consumer is concerned about hormones in the milk
  • may cause allergy in humans
  • long term use ongoing cost to farmers
  • not suitable to animal welfare
  • side effects for both humans as well as cattle

Question 258

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Describe and explain what could happen when blood of different groups is mixed.

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Explanation

Our immune system will produce antibodies against any blood antigens that we don՚t have in our own blood. That means people with type A blood create antibodies against B antigens. A person with type A blood receiving a transfusion of type B or AB blood would have an ABO incompatibility reaction. In an ABO incompatibility reaction, our immune system attacks the new blood cells and destroys them. In many cases this incorrect transfusion is fatal.

Others symptoms may include:

  • fever and chills
  • breathing difficulties
  • muscle aches
  • nausea
  • chest, abdominal, or back pain
  • blood in your urine
  • jaundice