Variation of Chromosome Number in Human
In this article we will discuss about the chromosomal aberrations and variation of chromosome number in human.
Any anomaly in the normal structure of chromosome or any variation in the normal karyotype of human causes an abnormal development of human or resulting in zygotic loss, still births or infant death. The degree of the abnormalities in the human structure will ultimately depend upon the types of anomalies in the human normal karyotype.
Q. 1. Name the process by which the traits
(characters) are passed on from parent to progeny.
Ans. Inheritance.
Q. 2. Define variation.
Ans. It is the degree by which progeny differs from their parents.
Q.3. Give one example to state that humans knew as
early as 8000-1.000 BC the causes of variation and exploited it.
Ans. Sahiwal cows in Punjab.
Q. 4. What is a true-breeding line?
Ans. A true-breeding line is that, which has undergone continuous self
pollination (e.g. pea plant) i.e. it is pure and does not have any cross
pollination/contamination.
Q. 5. What is the phenotypic ratio of monohybrid
cross in F2?
Ans. 3:1.
Q. 6. What is the removal of anthers from a flower
called?
Ans. Emasculation.
Q. 7. Where do you think that information required
to be expressed for a particular trait is
stored?
Ans. Genes.
Q. 8. Distinguish between— genotype and phenotype.
Ans. The genetic representation (e.g. TT) for a trait is called genotype
and descriptive terms (e.g. Tall) for a trait is called phenotype.
Q. 9. Which type of cross is termed as monohybrid
cross?
Ans. A cross between plants/parents alleles where one trait is studied
is called monohybrid cross.
Q. 10. Under which condition you will recommend a
test cross?
Ans. To determine the unknown genotype of a dominant phenotype.
Q. 11. State the 1st law of inheritance.
Ans. The law of dominance states that the expression of only one of the
parental characters in the F, and expression of both in F2, (in case of monohybrid cross) in a
ratio of 3:1 in F2.
Q. 12. A monohybrid cross produced similar ratios
of phenotype and genotype in F2. The genotype ratio is similar to
monohybrid Mendelian cross. Name the phenomenon.
Ans. Incomplete dominance.
Q. 13. Give an example of multiple alleles in
human.
Ans. ABO blood grouping.
Q. 14. Name the scientists who used chromosome
movement to explain Mendel’s Laws.
Ans. Walter Sutton and Theodour Bovesi.
Q. 15. Who had proposed the chromosomal theory of
the inheritance?
Ans. Walter Sutton.
Q. 16. Briefly mention the contribution of T.H.
Morgan in genetics.
Ans. Experimental verification of chromosomal theory of inheritance was
done by T.H. Morgan which led to discovery of the basis of the variation due to
sexual reproduction.
Q. 17. Which type of sex determination is present
in grasshopper? Mention the chromosomes of male and female grasshopper.
Ans. XO type sex determination. Male grasshopper has XO and female
grasshopper has XX.
Q. 18. Name a phenomenon that results in alternation
of DNA sequences.
Ans. Mutation (or also recombination).
Q. 19. What is point mutation? Give one example.
Ans. The change in a single base pair of DNA is called point mutation
e.g. Sickle cell anemia.
Q. 20. Mention the significance of pedigree study
in human genetics.
Ans. It provides a strong tool, which is utilized to trace the
inheritance of a specific trait, disease or abnormality of an individual.
Q. 21. A diploid organism is heterozygous for 4
loci, how many types of gametes can be produced?
Ans. 4 types of gametes.
Q. 22. When a cross is made between tall plant with
yellow seeds (Tt Yy) and tall plant with green seed (Tt yy), what proportions
of phenotype in the offspring could be expected to be—
(a) tall and green
(b) dwarf and green
Ans.
(a) 50%
(b) 25 %
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