Monohybrid Cross

Q.

In a certain species of animals, black fur (B) is dominant over brown fur (b). Predict the genotype and phenotype of the offspring when both parents are 'Bb' or have heterozygous black fur.

Q.

Make a Punnett square for finding out the proportion of different genotypes in the progeny of a genetic cross between
(a) A pure tall (TT) pea plant with a pure dwarf (tt) pea plant.
(b) Red flower variety of pea (RR) with white flower variety of pea (rr).

Q. A homozygous plant having round (R) and yellow (Y) seed is crossed with homozygous plant having wrinkled (r) and green (y) seeds: [5 MARKS]
(a) Give the scientific name of the plant on which Mendel conducted his hybridisation experiments.
(b) Give the genotype of the F1 generation.
(c) Give the dihybrid phenotypic ratio and the phenotype of the offspring of the F2 generation when two plants of the F1 generation are crossed.
(d) Name and state the law which explains the dihybrid ratio.
(e) Give the possible combinations of gametes that can be obtained from F1 hybrid.

Q. The phenotypic ratio of Mendel's monohybrid cross for height in pea plants in $F_2$ generation was 3 : 1. The ratio indicates

1. 70% tall and 30% dwarf plants
2. 60% dwarf and 40% tall plants
3. 75% tall and 25% dwarf plants
4. 75% dwarf and 25% tall plants

Q.

In guinea pigs, the allele for short hair(H) is dominant. If all the guinea pigs are born short haired in F1, what are the possible genotypes of the male and female parents?

1. HH and hh

2. HH and HH

3. hh and hh

4. Hh and Hh

Q.

Genotypic ratio of monohybrid cross is _____

1. 3:1

2. 2:1

3. 1:2:1

4. 1:1

Q. A woman heterozygous for B blood group married a man of AB blood group. Their probability of having child of B blood group is

1. 25%
2. 50%
3. 75%
4. 100%

Q. The figure given below shows a family pedigree (family tree) to show the inheritance of cystic fibrosis. [3 MARKS]



(a) Is the allele for cystic fibrosis dominant or recessive?
(b) State with reasons the genotype of individuals 1, 2 and 4.
(c) What are the possible genotypes of individuals 3 and 5?

Q. How do Mendel's experiment show that the (a) trait may be dominant or recessive (b) traits are inherited independently.

Q. What is ratio of f1 and f2 generation ? For experiment of pea plant.

Q.

Recessive gene can express itself only in________.

1. both above conditions

2. none of these conditions

3. homozygous condition

4. heterozygous condition

Q.

Round seeded (RR) plant is crossed with wrinkled seeded plant (rr).What will be the genotypes of the offspring in F2 generation if there are 4 offspring ?

1. RR, Rr, Rr , rr

2. all rr

3. all RR

4. RR , rr, RR, rr

Q.

An organism with two identical alleles is-

1. hybrid

2. dominant

3. homozygous

4. heterozygous

Q.

A black mouse mates with a brown mouse, and all the offsprings are black.

(a) Why are no brown offsprings produced ?

(b) If two of the black offsprings mate with each other what kind of offspring would you expect and in what proportions ? Give reason for your answer.

Q.

A cross in which a single pair of contrasting characters is studied at a time is called a dihybrid cross.

1. False

2. True

Q.

(a) What will you get in the $F_1$ and $F_2$ generations in the following cross ?

Pure tall pea plant $\times$ Pure dwarf pea plant

(b) Is it an example of monohybrid cross or dihybrid cross ?

Q.

In Pea plant, yellow seeds are dominant to green. If a heterozygous plant with yellow seeds is crossed with a plant having green seeds, what ratio of yellow and green seeded plants would you expect in F₁ generation?

1. 9 : 1

2. 1 : 3

3. 3 : 1

4. 50 : 50

Q.

In the $F_2$ generation of a cross, progeny having different traits are produced in the ratio 3 : 1. State whether it is a monohybrid cross or a dihybrid cross ? Give one example of such a cross.

Q.

What will be the genetic make up of plants in F₁ generation when a plant with round and green seeds (RRyy) is crossbred with a plant having wrinkled and yellow seeds (rrYY)?

1. Rryy

2. rryY

3. RRyy

4. RrYy

Q.

If a pure tall plant is crossed with a pure dwarf plant the offsring will be
(a) all tall (b) all dwarf (c) 3 tall 1 dwarf (d) 50% tall 50% dwarf

Q. Genotypic ratio in $F_2$ progeny for monohybrid cross will be________

1. 3 : 1
2. 1 : 2 : 1
3. 9 : 3 : 3 : 1
4. 1 : 3

Q.

The phenotypic ratio of a monohybrid cross is _________

1. 3:1

2. 1:2:1

3. 4:1

4. 1:1

Q.

What is the most dominant eye colour?

Q.

In a certain species of animals, black fur (B) is dominant over brown fur (b). Show the possible ratio of genotypes and phenotypes of the offspring of the pure breeding different coloured parents.

Q.

How many types of gametes will be produced in F2 generation of a monohybrid cross of Mendel?

1. 2

2. 3

3. 8

4. 16

Q. Question 45
In question 44, what are the combinations of character in the F2 progeny? What are their ratios?

Q.

Percentage of homozygous dominant individuals obtained from selfing Rr individuals is

1. 50 percentage

2. 75 percentage

3. 25 percentage

4. 0 percentage

Q.

Question 22
In peas, a pure tall plant (TT) is crossed with a short plant (tt). The ratio of pure tall plants to short plants in F2 is

(a) 1 : 3
(b) 3 : 1
(c) 1 : 1
(d) 2 : 1

Q. Define the following: [5 MARKS]
(a) Genetics
(b) Punnett square
If a pea plant homozygous (pure) for tall is crossed with one homozygous (pure) for dwarf. What will be the appearance of (i) F1 and (ii) F2 progenies?
[The character of tallness (T) is dominant over dwarfness(t)]

Q.

Explain the following term :

1. Monohybrid cross