Select incorrect statement
$(A)$ Linked genes cause absolute lethality
$(B)$ Persons affected by $PKU$ do not show mental disorder
$(C)$ $F_{2}$ ratio in codominance and incomplete dominance are same
$(D)$ Sex of male Drosophila is dependent on $Y-$chromosome
$(A) \;\& \;(B)$
$(B) \;\&\; (C)$
$(A), (B) \;\&\; (D)$
All of these
How many sentence are correct ?
$(i)$ Every gene contains the information to express a particular trait.
$(ii)$ Gene responsible for $\beta$ - thalassemia is present on $21^{st}$ pair of autosomal chromosome.
$(iii)$ Mendel's approach of using mathematics to explain biological phenomena was totally new and unacceptable to many of the biologists of his time.
Pick out the correct statements.
$(1)$ Haemophilia is a sexlinked recessive disease.
$(2)$ Down’s syndrome is due to aneuploidy.
$(3)$ Phenylketonuria is an autosomal recessive gene disorder.
$(4)$ Sickle cell anaemia is an $X$-linked recessive gene disorder.
Match the terms in column $I$ with their description in column $II$ and choose the correct option.
Column $-I$ | Column $-II$ |
$(A)$ Dominance | $(i)$ Many genesgovern a single character |
$(B)$ Codominance | $(ii)$ In a heterozygousorganism only one allele expresses itself |
$(C)$ Pleiotropy | $(iii)$ In a heterozygousorganism both alleles express themselves fully |
$(D)$ Polygenic | $(iv)$ A single gene inheritanceinfluences many characters |
Choose correct answer :
$(i)$ Queen Elizabeth shows a number of haemophilic descendents.
$(ii)$ Variation in blood group prevalences due to incomplete dominance.
$(iii)$ Drosophila has three pairs of autosomal chromosomes.
$(iv)$ In birds, female is heterozygous.
Marriages between close relatives and cousins is not advisable because