Multiple Choice QuestionsThe trisomy for 21st chromosome is called
Down's syndrome
Turner's syndrome
Sickle cell anaemia
Klinfelter's syndrome
If root of a flowering plant has 24 chromosomes, then its gamete has how many chromosomes?
24
12
4
8
Balbiani rings are the structural features of
allosomes
polytene chromosomes
autosomes
Lampbrush chromosomes
X- linked recessive gene is
always expressed in male
always expressed in femlae
lethal
sub- lethal
1 : 2 : 1 phenotypic and genotypic ratio is found in
complementary genes
blending inheritance
multiple alleles
pseudo alleles
A man and a woman, who do not show any apparent signs of a certain inherited disease, have seven children (2 daughters and 5 sons). Three of the sons suffer from the given disease but none of the daughters are affected. Which of the following mode of inheritance do you suggest for this disease?
Autosomal dominant
Sex-linked dominant
Sex-limited recessive
Sex-linked recessive
D.
Sex-linked recessive
Sex linked characteristic is determined by the genes located on the sex chromosome ie X or Y. Sex limited characteristic is the condition where expression of sex linked genes is limited to one sex.
In the given problem, neither man nor woman are deceased by the disease. Therefore, women must be the carrier of the disease causing gene. Also, none of the daughters are suffereing from the disease except the sons, ie, daughters are also carrier.
Suppose, XY = genotype of man
XdX = genotype of woman (d refers to disease causing gene)
The probability for each combination is 25%. Therefore, among seven children, 2 are normal daughter, 3 diseased sons and 2 normal sons are possible.
A haemophilic woman marries a normal man then
all the children will be normal
all the sons will be haemophilic
all the girls will be haemophilic
half girls will be haemophilic
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