Tag: botany

When the genes are present on the same chromosomes they are said to be linked. When gene remains together for two or more generation they are said to have complete or perfect linkage. Thus the bond between them becomes strong. Thus, the correct answer is option A.

Thomas Hunt Morgan was an American evolutionary biologist, geneticist, embryologist, and science author who won the Nobel Prize in Physiology or Medicine in 1933 for discoveries elucidating the role that the chromosome plays in heredity.
Following the rediscovery of Mendelian inheritance in 1900, Morgan's research moved to the study of mutation in the fruit fly Drosophila melanogaster. Morgan demonstrated that genes are carried on chromosomes and are the mechanical basis of heredity. These discoveries formed the basis of the modern science of genetics. As a result of his work, Drosophila became a major model organism in contemporary genetics.

Linkage is the tendency of alleles present close to each other to be inherited together during meiosis and hence they show parental combinations. But since complete linkage occurs rarely, sometimes the linked genes separate during meiosis and new combinations are formed. Hence, option B is correct.

Linkage is the tendency of genes present close on the chromosomes to be inherited together and not to assort independently in the offspring. It gives only parental combinations in the offspring. Since, complete linkage is a rare phenomenon, the linked genes sometimes show tendency of independent assortment and results in production of new combinations in offspring in lower percentage. Hence, production of parental characters combinations in the offsprings of a dihybrid in excess to non-parental combinations is due to "linkage". Option "C" is correct.

Sudden inheritable changes in genetic material are called as mutations. Translation is the process of synthesis of polypeptides by polymerization of amino acids on ribosomes using the mRNA triplets as template. Transcription is the process of synthesis of RNA by RNA polymerase using DNA template strand. Thus mutation, translation and transcription are independent of distance between the genes on chromosomes which makes options A, C, and D wrong. Linkage is the tendency of closely placed genes on a chromosome to stay together during inheritance; it produces more parental combination and less/no new combinations of gene. Genes present together on a chromosome show linkage and do not follow independent assortment resulting in more parental types and less recombinants in progeny. Correct answer is B.

The frequent occurrence of the phenomenon leading to the trait 'deafness' in
cats being associated with cats with 'white coat color' is possible only in the case when the alleles for these traits are so close together on a chromosome that they are inherited together during the meiosis phase. This tendency of the alleles to be inherited together is known as genetic linkage or gene linkage. Thus, the correct answer is option A.

Tendency of genes located on the same chromosome, to stay together in hereditary transmission, is known as linkage. The genes located on the same chromosome are called as linked genes.

Mendel's law of independent assortment is not applicable for the genes which reside on the same chromosome. He was able to interpret the results and give out the laws because the 7 pair of contrasting characters which he chose in pea were residing on different chromosomes. 

The number of linkage groups equals the number of chromosomes in the basic set. The number of linkage groups in an organism is equal to the haploid number of its chromosomes. Example - In Drosophila, the haploid number is n = 4, so linkage group is 4. But the number of linkage group is prokaryotes (bacteria, like E. coli) is one. This is because bacteria being prokaryotes have only a single circular chromosome.

DNA Ligase is the enzyme which helps in joining the fragments of DNA, basically, it acts as a glue. In the given options endonuclease helps in cutting the DNA into fragments it cleaves the polynucleotide chain by acting on the nucleotides by breaking the hydrogen bonds between them, whereas DNA polymerases synthesize the DNA molecule from deoxyribonucleotides. So, the correct answer is "DNA ligase".