IGCSE Biology Paper-3: Specimen Questions with Answers 253 - 254 of 358

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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 253 (1 of 5 Based on Passage)

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Explain the term codominance.

Explanation

In codominance, both the alleles of a gene are equally dominant i.e.. the dominant character is not able to suppress the recessive character & thus both the characters appear side by side in F1 hybrids. F1 generation resembles both the parents.

E. g. , ABO blood group, Roan color in cattle.

Mendel considered that a single factor or gene controls a single character or trait or phenotype, but later it was found that a phenotype of character can be influenced by many genes and a gene can influence many phenotypes or traits.

Question 254 (2 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.

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

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