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प्रश्न
Discuss in detail the contributions of Morgan and Sturvant in the area of genetics.
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उत्तर
Experimental verification of the chromosomal theory of inheritance by Thomas Hunt Morgan (Father of experimental genetics) and his colleagues, led to discovering the basis .for the variation that sexual reproduction produced. Morgan worked with the tiny fruit files, Drosophila melanogaster, which were found very suitable for such studies.
- Morgan carried out several dihybrid crosses in Drosophila to study genes that were sex-linked. The crosses were similar to the dihybrid crosses carried out by Mendel in peas. For example, Morgan hybridised yellow-bodied, white-eyed females to brown-bodied, red-eyed males and intercrossed their F, progeny.
- He observed that the two genes did not segregate independently of each other and the F2 ratio deviated very significantly from the. 9 : 3 : 3 : 1 ratio (expected when the two genes are independent). Morgan and his group knew that the genes were located on the X chromosome and saw quickly that when the two genes in a dihybrid cross were situated on the same chromosome, the proportion of parental gene combinations were much higher than the non-parental type.
- Morgan attributed this due to the physical association or linkage of the two genes and coined the term linkage to describe this physical association of genes on a chromosome and the term recombination to describe the generation of non-parental gene combinations.
- His student Alfred Sturtevant used the frequency of recombination between gene pairs on the same chromosome as a measure of the distance between genes and ‘mapped’ their position on the chromosome. Today genetic maps are extensively used as a starting point in the sequencing of whole genomes as was done in the case of the Human Genome Sequencing Project.
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संबंधित प्रश्न
Define the term ‘genome’.
Name the type of cell division involved in the production of sperms by honey bees.
Describe the structure of chromosomes with a suitable diagram.
Give an account of artificial chromosomes in the transfer of genetic material.
A B B C C D E F G H I
From the above figure identify the type of mutation and explain it.
Write the salient features of the Sutton and Boveri concept.
When two different genes came from the same parent they tend to remain together.
Write the observed phenotypic ratio.
If you cross dominant genotype PV/PV male Drosophila with double recessive female and obtain F1 hybrid. Now you cross F1 male with double recessive female.
What is the possible genotype in the F2 generation?
Which of the following is a primary constriction?
From the following identify the INCORRECT statement/s with respect to the chromosomes.
i. Chromosomes are capable of self replication and play vital role in heredity, mutation, variation, and evolutionary development of eukaryotic species.
ii. Chromosomes are visible during cell division.
iii. Chemically eukaryotic chromosomes are made of mRNA, histone and non-histone proteins.
iv. The number of chromosomes varies within the population of a particular species.
Identify the term that represents the degree of repetition of the primary basic number of chromosomes in a cell.
From the following identify the statements that are CORRECT with respect to homologous and non-homologous region of X and Y chromosomes.
i. Non-homologous region of X chromosome is longer and contains more genes than that of non-homologous region of Y chromosome.
ii. X-linked genes are present on nonhomologous region of X-chromosome.
iii. Y-linked genes are present on homologous region of Y-chromosome.
iv. Crossing over occurs only between homologous regions of X and Y chromosomes.
Mendel’s work was rediscovered by three scientists in the year ______.
Experimental verification of ‘chromosomal theory of inheritance’ was done by ______.
Which of the following statements indicates parallelism in genes and chromosomes?
- They occur in pairs.
- They segregate during gamete formation.
- They show linkage.
- Independent pairs segregate independently.
A couple has two daughters. What is the probability that the third child will also be a female?
Which of the following sentences are correct?
1. The offspring exhibit only parental combinations due to incomplete linkage
2. The linked genes exhibit some crossing over in complete linkage
3. The separation of two linked genes are possible in incomplete linkage
4. Crossing over is absent in complete linkage
The Chromosomal Theory of Inheritance is also known by which alternative name?
