Tag: linkage and recombination

Questions Related to linkage and recombination

Genes on same chromosome can be

botany chromosomal basis of inheritance linkage and crossing over linkage and recombination genetics: inheritance

  1. Linked

  2. Homologous

  3. Autosomes

  4. Identical alleles

Show answer
Correct Option: A
Explanation:
  • When two genes are close together on the same chromosome, they do not assort independently and are said to be linked and will segregate together during meiosis, producing only two kinds of gametes. Whereas genes located on different chromosomes assort independently and have a recombination frequency of 50%, linked genes have a recombination frequency that is less than 50%.
  • Hence Genes on the same chromosome can be Linked.
  • So, the correct answer is 'Linked'.

The number of linkage groups in a cell having 10 pairs of chromosomes are

botany chromosomal basis of inheritance linkage and crossing over linkage and recombination genetics: inheritance

  1. 5

  2. 10

  3. 15

  4. 20

Show answer
Correct Option: B
Explanation:

The total number of linkage groups in an organism equals to the number of autosomes in its haploid cell. The cell has ten pairs of chromosomes which means that the number of autosomes in its haploid cell is 10. Hence, total number of linkage groups will be 10 provided all the genes are mapped. Correct answer is B.

Linked gene are separated by

botany chromosomal basis of inheritance linkage and crossing over linkage and recombination genetics: inheritance

  1. Crossing over

  2. Mutation

  3. Both A and B

  4. Mitosis

Show answer
Correct Option: A
Explanation:

Recombination can occur between any two genes on a chromosome, the amount of crossing over is a function of how close the genes are to each other on the chromosome. If two genes are far apart, for example at opposite ends of the chromosome, crossover and non-crossover events will occur in equal frequency. Genes that are closer together undergo fewer crossing over events and non-crossover gametes will exceed than the number of crossover gametes.

Maize has $10$ pairs of chromosomes. How many linkage groups does it have?

botany chromosomal basis of inheritance linkage and crossing over linkage and recombination genetics: inheritance

  1. $20$

  2. $10$

  3. $5$

  4. $40$

Show answer
Correct Option: B
Explanation:
The total number of Linkage groups in an individual is equal to their total number of haploid sets of chromosomes.
Haploid number of chromosome = Linkage groups
In Maize there are 10 linkage groups, since 10 haploid chromosomes.
So, the correct answer is '10'.

A linkage group is defined as

botany chromosomal basis of inheritance linkage and crossing over linkage and recombination genetics: inheritance

  1. All the linked genes of a chromosomal pair

  2. Different groups of genes present on different chromosomes

  3. All the genes located on the same chromosome

  4. None of the above

Show answer
Correct Option: A
Explanation:
Linkage group, in genetics, all of the genes on a single chromosome. They are inherited as a group; that is, during cell division they act and move as a unit rather than independently.
So, the correct answer is 'All the linked genes of a chromosomal pair'.

The blue green algae and bacteria contain.

botany chromosomal basis of inheritance linkage and crossing over linkage and recombination genetics: inheritance

  1. One linkage group

  2. Two linkage groups

  3. Three linkage groups

  4. None of the above

Show answer
Correct Option: A
Explanation:

All the genes which are located on a single chromosome form one linkage group. The total number of linkage groups in an organism corresponds to the haploid number of chromosomes, i.e., to the number of chromosome pairs.

  • Most bacteria have a genome that consists of a single DNA molecule (i.e., one chromosome).
  • The blue-green algae is a cyanobacterium that possesses one chromosome.

So, the correct answer is 'One linkage group'.

Which of the following statements is not true of two genes that show 50% recombination frequency ?

botany chromosomal basis of inheritance linkage and crossing over linkage and recombination genetics: inheritance

  1. The genes may be on different chromosomes

  2. The genes are tightly linked

  3. The genes show independent assortment

  4. If the genes are present on the same chromosome, they undergo more than one crossovers in every meiosis.

Show answer
Correct Option: B
Explanation:

The genes that are not tightly linked to each other do not show 50% of recombination frequency. Genetic linkage is the process in which genes are located close to each other on chromosomes are inherited together. When 2 genes are located far from each other or are located on different chromosomes have 50% of recombination rates.

So, option B is the correct answer.

What is not true of two genes that show $50\%$ recombination frequency?

botany chromosomal basis of inheritance linkage and crossing over linkage and recombination genetics: inheritance

  1. They undergo more than one crossovers in every meiosis

  2. The genes are present on different chromosomes

  3. The genes are tightly linked

  4. The genes show independent assortment

Show answer
Correct Option: C
Explanation:
The tightly linked genes on chromosomes show 100% parental types and 0% recombinants. Two genes that undergo independent assortment indicated by a recombination frequency of 50% are either on non-homologous chromosomes are located far apart on a single chromosome. As the distance between two genes increases, crossover frequency increases. More recombinant gametes, fever parental gametes.

So, the correct answer is 'The genes are tightly linked'.

Which of the following will not result in variations among siblings? 

botany chromosomal basis of inheritance linkage and crossing over linkage and recombination genetics: inheritance

  1. Independent assortment of genes

  2. Crossing over

  3. Linkage

  4. Mutation

Show answer
Correct Option: C
Explanation:

Independent assortment leads to separation of genes and is a violation of genetic linkage. Crossing over leads to exchange of fragments between two homologous chromosomes and results in the formation of chiasmata. The mutation is sudden lethal changes in a chromosome or genetic material that is often lethal. SO, all of these result in variations in genetic material.

Linkage means forming a group of genes together. So, option C is the correct answer.

All genes located on the same chromosome:

botany chromosomal basis of inheritance linkage and crossing over linkage and recombination genetics: inheritance

  1. From different groups depending upon their relative distance.

  2. Form one linkage group.

  3. Will not from any linkage groups.

  4. Form interactive groups that affect the phenotype.

Show answer
Correct Option: B
Explanation:

 Linkage group is a group of a linked gene on the same chromosome and corresponds to the genome of an organism.

So, the correct option is 'Form one linkage group'.