CBSE
Multiple Choice QuestionsBarr-body in mammals represents
one of the two X-chromosomes in the cells
all heterochromatin of male and female cells
Y-chromosome of male
all heterochromatin of female cells
Genetic map is one that
shows the stages during the cell division
shows the distribution of various species in a region
establishes sites of the genes on a chromosome
establishes the various stages in gene evolution
If a boy's father has haemophilia and his mother has one gene for haemophilia, what is the chance that the boy will inherit the disease?
100%
50%
0%
75%
Pureline breed refers to
homozygosity
heterozygosity
homozygosity with only dominant genes
heterozygosity and linkage
Discontinuous variations are
essential features
acquired character
non-essential changes
heritable changes
Down's syndrome is caused by an extra copy of chromosome number 21. What percentage of a normal father would be affected by this disorder?
50%
25%
100%
75%
Mendel enunciated
two principles of inheritance
four principles of inheritance
five principles of inheritance
three principles of inheritance
The linkage map of X-chromosome of fruit-fly has 66 units, with yellow body gene (y) at one end and bobbed hair (b) gene at the other end. The recombination frequency between these two genes (y and b) should be
50%
100%
66%
> 50%
Rarely observed phenotype in population is called
wild type
mutant type
variant type
All of these
In Drosophila, the sex is determined by
the ratio of pairs of X-chromosomes to the pairs of autosomes
whether the egg is fertilised or develops parthenogenetically
the ratio of number of X- chromosomes to the set of autosomes
X and Y-chromosomes
