Tag: linkage and crossing over
Questions Related to linkage and crossing over
Genes on same chromosome can be
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Linked
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Homologous
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Autosomes
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Identical alleles
- 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
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5
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10
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15
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20
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
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Crossing over
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Mutation
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Both A and B
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Mitosis
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?
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$20$
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$10$
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$5$
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$40$
A linkage group is defined as
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All the linked genes of a chromosomal pair
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Different groups of genes present on different chromosomes
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All the genes located on the same chromosome
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None of the above
The blue green algae and bacteria contain.
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One linkage group
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Two linkage groups
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Three linkage groups
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None of the above
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.
Which of the following statements is not true of two genes that show 50% recombination frequency ?
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The genes may be on different chromosomes
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The genes are tightly linked
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The genes show independent assortment
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If the genes are present on the same chromosome, they undergo more than one crossovers in every meiosis.
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.
What is not true of two genes that show $50\%$ recombination frequency?
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They undergo more than one crossovers in every meiosis
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The genes are present on different chromosomes
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The genes are tightly linked
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The genes show independent assortment
Which of the following will not result in variations among siblings?
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Independent assortment of genes
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Crossing over
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Linkage
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Mutation
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.
All genes located on the same chromosome:
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From different groups depending upon their relative distance.
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Form one linkage group.
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Will not from any linkage groups.
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Form interactive groups that affect the phenotype.
Linkage group is a group of a linked gene on the same chromosome and corresponds to the genome of an organism.