dominance in Mirabilis jalapa.
a. 2 : 1 : 1 b. 1 : 2 : 1
c. 3 : 1 d. 2 : 2
2. In dihybrid cross, F2
generation offsprings
show four different phenotypes while the
genotypes are ................
a. six b. nine
c. eight d. sixteen
3. A cross between an individual with
unknown genotype for a trait with
recessive plant for that trait is ..............
a. back cross b. reciprocal cross
c. monohybrid cross d. test cross
4. When phenotypic and genotypic ratios
are the same, then it is an example of
............
a. incomplete dominance
b. complete dominance
c. Multiple alleles
d. cytoplasmic inheritance
5. If the centromere is situated near the end
of the chromosome, the chromosome is
called ................
a. Metacentric b. Acrocentric
c. Sub-Metacentric d. Telocentric
6. Chromosomal theory of inheritance was
proposed by ................
a. Sutton and Boveri
b. Watson and Crick
c. Miller and Urey
d. Oparin and Halden
7. If the genes are located in a chromosome
as p-q-r-s-t, which of the following gene
pairs will have least probability of being
inherited together?
a. p and q b. r and s
c. s and t d. p and s
8. Find the mis match pair :-
a. Down’s syndrome = 44 + XY
b. Turner’s syndrome = 44 + XO
c. Klinefelter syndrome = 44 + XXY
d. Super female = 44 + XXX
9. A colourblind man marries a woman,
who is homozygous for normal colour
vision ,the probability of their son being
colourblind is –
a. 0% b. 25%
c. 50% d. 100%
Answers
Answer:
Incomplete dominance is the condition when none of factors of a gene is dominant, the phenotype of heterozygous dominant individual is blend of dominant and recessive traits. For example flower colour in Mirabilis jalapa shows incomplete dominance and the monohybrid cross between two pure varieties gives 1 : 2 : 1 phenotypic ratio in F
2
generation which is 3 : 1 in otherwise dominant traits. This is because the heterozygous genotypes do not show the dominant trait but they are blend of dominant and recessive phenotype. A cross between two pure breeding genotypes that differ in two pairs of trait (dihybrid cross) followed by selfing of F
1
hybrid gives 9 : 3 : 3 : 1 phenotypic ratio and 1 : 2 : 1 : 4 : 1 : 1 : 2 : 1 : 2 : 1 genotypic ratio. Option B and C show both dihybrid (9 : 6), a dihybrid cross gives total 16 types which make these two options wrong.
Explanation: