Practice free Hereditary and Variation (Botany) NEET multiple-choice questions online with instant answers and detailed explanations. No login required.
Which of the following is an example of a physical mutagen mentioned in the context?
The context provides: 'UV radiations can cause mutations in organisms – it is a mutagen.' This identifies UV radiation as a physical mutagen.
Mutation leads to changes in which of the following aspects of an organism?
The NCERT text defines mutation as: 'a phenomenon which results in alteration of DNA sequences and consequently results in changes in the genotype and the phenotype of an organism.'
The loss or gain of a segment of DNA leads to an alteration in chromosomes. These chromosomal alterations are also known as:
The text states: 'Therefore loss (deletions) or gain (insertion/duplication) of a segment of DNA, result in alteration in chromosomes. Since genes are known to be located on chromosomes, alteration in chromosomes results in abnormalities or aberrations. Chromosomal aberrations are commonly observed in cancer cells.'
Which of the following describes the inheritance pattern observed in the flower color of the dog flower (snapdragon)?
The text states: 'The inheritance of flower colour in the dog flower (snapdragon or Antirrhinum sp.) is a good example to understand incomplete dominance.' In incomplete dominance, the F1 phenotype is intermediate between the two parental phenotypes.
In a cross between true-breeding red-flowered (RR) and true-breeding white-flowered (rr) dog flowers, what proportion of the F2 generation would be pink?
The F1 generation will be Rr (pink). When F1 is self-pollinated, the F2 generation will have a genotypic ratio of 1 RR (red): 2 Rr (pink): 1 rr (white). Therefore, 2/4 or 1/2 of the F2 generation will be pink.
If starch grain size in pea seeds is considered as the phenotype, what type of inheritance pattern is observed?
The text explicitly states: 'Heterozygotes produce round seeds, and so B seems to be the dominant allele. But, the starch grains produced are of intermediate size in Bb seeds. So if starch grain size is considered as the phenotype, then from this angle, the alleles show incomplete dominance.'
In incomplete dominance, the phenotypic ratio of the F2 generation typically deviates from the standard Mendelian monohybrid cross ratio of:
The text mentions: 'Here the genotype ratios were exactly as we would expect in any mendelian monohybrid cross, but the phenotype ratios had changed from the 3:1 dominant : recessive ratio.' In incomplete dominance, the F2 phenotypic ratio becomes 1:2:1 (e.g., Red:Pink:White in snapdragons).
Which of the following statements is true regarding the explanation of dominance provided in the text?
The text states: 'Therefore, dominance is not an autonomous feature of a gene or the product that it has information for. It depends as much on the gene product and the production of a particular phenotype from this product as it does on the particular phenotype that we choose to examine, in case more than one phenotype is influenced by the same gene.'
Why is the F1 generation in incomplete dominance sometimes distinguishable from both homozygous parents?
The text states: 'What happened was that R was not completely dominant over r and this made it possible to distinguish Rr as pink from RR (red) and rr (white).'
Consider a gene that produces an enzyme. If a modified allele leads to a less efficient enzyme, what could be a possible outcome in a heterozygote if the normal allele produces a normal enzyme?
The text mentions that a modified allele could be responsible for the production of a 'normal/less efficient enzyme'. If the enzyme is less efficient, and only one normal allele is present in a heterozygote, the overall enzyme activity might be reduced compared to a homozygote with two normal alleles, leading to an intermediate phenotype, a characteristic of incomplete dominance.
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