Assertion: XX-XY type of sex determination mechanism is an example of female heterogamety and is found in Drosophila.

Reason: Male heterogamety is seen in moths where males produce two different types of gamete.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

If both parents are carriers for thalassaemia, which is an autosomal recessive disorder, what are the chances of pregnancy resulting in an affected child?

• 25%

• 100%

• No chance

• 50%

In rabbits, the gene for grey fur (G) is dominant over that for black fur (g). In a litter, if 50% rabbits are grey, then the possible parental cross combination is

• GG x Gg

• gg X gg

• GG x GG

• Gg x gg

Barr body is missing in the female suffering from

• Huntington's disease

• Tay-sach's disease

• Klinefelter's syndrome

• Turner's syndrome.

Which is genetically not possible

• Haemophilic father transfers the haemophilic gene to his son.

• Haemophilic father transfers the haemophilic gene to his daughter.

• Carrier mother transfers the haemophilic gene to her son.

• Carrier mother transfers the haemophilic gene to her daughter

If 'A' represents the dominant gene and 'a' represents its recessive allele, which of the following would be the most likely result in the first generation offspring when Aa is crossed with aa ?

• All will exhibit dominant phenotype

• All will exhibit recessive phenotype

• Dominant and recessive phenotypes will be 50% each

• Dominant phenotype will be 75%

Assertion : Foetal disorders can be diagnosed by chorionic villi sampling.

Reason : Karyotyping can be done for mitotically dividing cells of chorionic villi.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false

Assertion : Curdling is required in the manufacture of cheese.

Reason : Lactic acid bacteria are used for the purpose.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false

139.

Assertion :  Number of chromosomes in one genome is equal to number of linkage groups.

Reason : Linkage groups give important information about the location of genes in the chromosomes.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false

• If both assertion and reason are false

Which of the following occurs due to monosomy of sex chromosome

• Down's syndrome

• Turner's syndrome

• Haemophilia

• Sickle cell anaemia