While carrying out a dihybrid cross [a mating of two organisms heterozygous for two traits], a phenotype ratio of 9:3:3:1 in the offspring is expected when:
 
  •     the genes are linked [located on the same chromosome]
  •     each gene contains two mutations
  •     the gene pairs assort independently during meiosis
  •     the alleles of both genes show either co-dominance or incomplete dominance
A female is a "carrier" for the trait red color blindness [remember this trait is X-linked and colour blindness is sex-linked recessive condition], marries a normal male. What proportion of their female progeny will be affected by the disorder?
 
  •     ¾ 
  •     ½
  •     ¼
  •     0
Sickle cell anaemia is inherited as an autosomal recessive condition. What proportion of progeny will be normal as a result of mating between two individuals who are carriers for the trait but are themselves not affected?
 
  • 25%
  • 100%
  • 50%
  • 75%
The karyotype of a person suffering from Down’s syndrome will show:
  • 44 Autosomes + XXY
  • 44 Autosomes + XO
  • 45 Autosomes [trisomy #21] + XY
  • 43 Autosomes [monosomy #21] + XY
Identify the incorrect statement regarding thalassemia:
 
  • There is reduced synthesis of one of the globin chains
  • It is an autosome-linked dominant blood disease
  • Alpha thalassemia is controlled by two closely linked genes on chromosome 16
  • Beta thalassemia is controlled by a single gene on chromosome 11
Antirrhinum majus with pink flowers was cross pollinated by Antirrhinum majus with white flowers. What proportion of progeny plants are expected to have white flowers?
  • 0
  • ¼
  • ½
  • ¾
When two genes in a dihybrid cross are situated on the same chromosome close to each other, the proportion of parental gene combinations is:
 
  • much higher than the non-parental type
  • much lower than the non-parental type
  • equal to the non-parental type
  • not seen at all
Which of the following is not true regarding phenylketonuria?
 
  • It is inherited as an autosomal recessive condition
  • The affected individual lacks an enzyme phenylalanine hydroxylase
  • The affected individuals lack the capability of converting tyrosine to phenylalanine
  • Clinical features include mental retardation and a reduction in hair and skin pigmentation
Identify the incorrectly matched pair:
1. Pleiotropy Sickle cells anaemia
2. Polygenic inheritance Human skin colour
3. Multiple allelism ABO blood group
4. Gene/point mutation Down’s syndrome

 
  • 1
  • 2
  • 3
  • 4
0:0:1


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Practice Botany Quiz Questions and Answers