Question

CHAPTER 4: Modification of Mendelian Ratios

•  Know the definition of: Wild-type Allele and Null Allele

•  Know the difference between: Gain-of-Function Mutation, Loss-of-Function Mutation, Neutral

  Mutation

•  HAVE to know the difference between: Incomplete Dominance (heterozygote is an intermediate

  phenotype) and Codominance (both alleles are expressed)

•  Know: Multiple alleles can exist for one gene – must observe in populations

•  Know what Lethal Alleles are (homozygous recessive – lethal)

•  Know how to apply the Fork-line Method and Product Rule for finding phenotypic probabilities when

  inheriting two genes with different modes of inheritance

•  Know the definition of: Gene Interaction

Answer 1

Wild type allele is the normal form of an allele.

Null allele is the mutated form of an allele.

Gain of function mutation is a type of mutation which results in the formation of gene responsible for functioning more.

Loss of function mutation is a type of mutation which results in the formation of a gene with less number of functions now.

Neutral mutation is a type of mutation which does not change the function of the gene.

Incomplete dominance is the type of inheritance in which the dominant allele is partially dominant over the recessive allele. It results in the formation of heterozygotes having intermediate phenotype.

Codominance is the type of inheritance in which the two alleles are equally dominant over one another. It results in the formation of heterozygotes having variegated phenotype.

One gene is having multiple alleles, then it is said to be polygenic inheritance. These are the traits which are controlled by more than one genes and therefore many types of alleles are involved. For example, skin colour in human beings.

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