Definition of Linkage and Linked Genes

Q. Select the incorrect statement(s).
(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 Drosophila is determined by XX-XO chromosomes

1. (a) and (b)
2. (b) and (c)
3. (a), (b) and (d)
4. All of these

Q.

Two heterozygous parents are crossed. If the two loci are linked, what would be the distribution of phenotypic features in $F_1$ generation for a dihybrid cross?

Q. In a cross in Drosphila, the heterozygous animal with grey body $\left(b^{+}\right)$ and long wings $\left(v{g}^{+}\right)$ was crossed with an animal with black body and vestigial wings. The progeny has the animals in the following ratio : Grey vestigial 24; grey long 126; black long26 ; black vestigial 124. What is the frequency of recombinants in the population?

1. 15.8
2. 16.7
3. 17.5
4. 14.5

Q.

What is test cross and its significance?

Q.

What is complete linkage?

Q.

The term ‘linkage’ was coined by

1. Mendel

2. Morgan

3. Bateson & Punnett

4. Sutton

Q. Select the correct statement from the ones given below with respect to dihybrid cross :

1. Tightly linked genes on the same chromosome show higher recombinations
2. Genes far apart on the same chromosome show very few recombinations
3. Genes loosely linked on the same chromosomes show similar recombinations as the tightly linked ones
4. Tightly linked genes on the same chromosome show very few recombination

Q.

What is an example of the mendelian trait in humans ?

Q.

What is an example of linked genes ?

Q.

Which is the most common mechanism of genetic variation in the population of sexually reproducing organisms?

1. Recombination

2. Chromosomal aberrations

3. Genetic drift

4. Transduction

Q.

Linkage was discovered by

1. Blakeslee

2. Sutton

3. Bateson & Punnett

4. Muller

Q.

Who is called as Cinderella of genetics?

Q. Genes which are present near each other on the same chromosome and thus tend to stay together are called genes.

1. recombinant
2. recessive
3. linked
4. associated

Q. A and B genes are linked. What shall be genotype of progeny in a cross between AB/ab and ab/ab:

1. AAbb and aabb
2. AaBb and aabb
3. AABB and aabb
4. None

Q.

Define genetics?

Q. Genetic drift in a new colony is known as

1. Saltation
2. Natural selection
3. Founder effect
4. Branching descent

Q. ‘XX’ is a phase of mitosis, in which the chromatin condenses into discrete chromosomes. During ‘XX’ phase, nuclear envelope breaks down and spindles forms at opposite ends of the cell Identify ‘XX’

1. Interphase
2. Anaphase
3. Telophase
4. Prophase

Q. From the options given below, find out the correct floral formula for a flower having the following characters, namely actinomorphic, bisexual, five united sepals, five united petals, stamens five and epipetalous, bicarpellary, syncarpous with superior ovary–

1. 
2. 
3. 
4. 

Q. A haemophilic man marries a carrier female. Identify the correct representation of the parents and their progeny from the given pedigree charts.

1. 
2. 
3. 
4. 

Q.

What happens at the recombination nodules in the pachytene phase?

Q. There are 10 flowers in one individual plant of Asparagus. Each microsporangium of every stamen contains $25$ microspore mother cells. How many microspore would be produced from this plant?

1. $4000$
2. $6000$
3. $12000$
4. $24000$

Q. Crossing over results in separation of linked genes.

1. completely
2. incompletely
3. adjacent
4. tightly

Q. Select the incorrect statement(s).
(a) Linked genes cause absolute lethality
(b) Persons affected by PKU do not show mental retardation
(c) $F_2$ ratio in codominance and incomplete dominance is same
(d) Sex of Drosophila is determined by XX-XO chromosomes

1. (a) and (b)
2. (b) and (c)
3. (a), (b) and (d)
4. All of these

Q. A cross between two homozygous parents differing from one another by alleles at only one gene locus is

1. backcross
2. monohybrid cross
3. dihybrid cross
4. trihybrid cross

Q. P and Q are linked genes. What shall be the genotype of progeny in cross between PQ/pq and pq/pq?

1. PpQq and ppqq
2. PPQQ and ppqq
3. PPqq and ppqq
4. None of the above

Q.

what is really meant by founder effect?

Q. A scientist performed the gene mapping experiments in maize. He mapped the genes on chromosomes on the basis of % crossing over between different genes. One map unit corresponds to one % crossing over or recombination. The genes showing more than 50% recombination were not supposed to be linked on same chromosome. In crossing over studies on maize, scientist observed the following % crossing over between genes A, B, C, D: between A and D 10%, between A and C 3%, between genes C and D 7%, between genes A and B 5%, and between genes C and B 8%. On the basis of above observation, find out the correct sequence of genes A, B, C and D on chromosomes.

1. BACD
2. DACB
3. BCDA
4. ABCD

Q. Select the incorrect statement(s).
(a) Linked genes cause absolute lethality
(b) Persons affected by PKU do not show mental retardation
(c) $F_2$ ratio in codominance and incomplete dominance is same
(d) Sex of Drosophila is determined by XX-XO chromosomes

1. (a) and (b)
2. (b) and (c)
3. All of these
4. (a), (b) and (d)

Q.

_____ is called the father of genetics.

1. Mendel

2. Hook

3. Virchow

4. Strasburger

Q. Select the incorrect statement(s).
(a) Linked genes cause absolute lethality
(b) Persons affected by PKU do not show mental retardation
(c) $F_2$ ratio in codominance and incomplete dominance is same
(d) Sex of Drosophila is determined by XX-XO chromosomes

1. (a) and (b)
2. (b) and (c)
3. (a), (b) and (d)
4. All of these