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12th Grade > Biology

PRINCIPLES OF INHERITANCE AND VARIATION MCQs

Total Questions : 45 | Page 1 of 5 pages
Question 1. From the pedigree chart given below, identify if the trait is sex linked dominant or recessive.
From The Pedigree Chart Given Below, Identify If The Trait I...
  1.    X-linked dominant
  2.    X-linked recessive
  3.    Y- linked
  4.    X and Y- linked
 Discuss Question
Answer: Option A. -> X-linked dominant
:
A
From the pedigree chart, we see that the mother is affected, and father is unaffected. In the first generation 50 percent of the offsprings are affected (one son and one daughter). If the trait was due to a recessive gene on the X-chromosome, only sons would be affected (as they get their X chromosome from the mother) and daughters would be carriers for the trait. But here both sons and daughters are affected indicating that it is an X-linked dominant disorder. In the second generation we see that, in one family the father is affected, so both daughters are affected (daughters get one X-chromosome from the father), indicating that the trait is X-linked dominant. And when the mother is affected (in the second family) 50 percent children are affected and 50 percent unaffected irrespective of the sex. This again proves that it is X-linked dominant disorder.
Question 2. What type of progeny would you expect if genes are completely linked?
  1.    No progeny survive
  2.    Parental types only
  3.    Parental types and recombinants both
  4.    Only recombinanats
 Discuss Question
Answer: Option B. -> Parental types only
:
B
Geneticlinkageis the tendency of alleles that are close together on a chromosome to be inherited together during the meiosis phase of sexual reproduction. Complete linkage is very simply the phenomenon by which a group of genes on a chromosome is inherited as such without any change, from one generation to the next and so onand because there is no change or basically recombination of genes,there should be parental combinations only and no recombinants. Morgan (1919) reported a complete linkage in Drosophila. When ordinary male wild fly with grey body and normal wings was crossed with female having black body and vestigial wings, the F1hybrids were all grey bodied and normal winged (with dominant characters). But theF2ratio deviated significantly from the Mendelian 9:3:3:1. The number of recombinants were considerably lesser, and most of them had the parental phenotypes, grey bodied and normal winged or black bodied and vestigial winged in nearly equal number, thus indicating the complete linkage.
Question 3. Study the following Punnett square and identify the genotypes of male and female parents
Study The Following Punnett Square And Identify The Genotype...
 
  1.    male parent - AaBb and Female parent - aaBB
  2.    Male parent - aaBB and Female parent - AaBb
  3.    Male parent - AaBB and Female parent - AaBb
  4.    Male parent - AABB and Female parent - Aabb
 Discuss Question
Answer: Option A. -> male parent - AaBb and Female parent - aaBB
:
A
The male parent produces 4 types of gametes and hence, its genotype is double heterozygous - AaBb. The female parent produces only one type of gamete. Hence it is double homozygous - aaBB.
Question 4. Regarding assertion and reason, select the right option.
Assertion [A]: Mendel could not come up with physical proof for the existence of his factors, now known as genes or chromosomes.
Reason [R]: Chromosomes were discovered only after 1900 due to advancements in microscopy.
  1.    Both A and R are true and R explains A
  2.    Both A and R are true, but R does not explain A
  3.    A is true and R is false
  4.    Both A and R are false
 Discuss Question
Answer: Option A. -> Both A and R are true and R explains A
:
A
It was only after 1900 that scientists were able to observe cell division which led to the discovery of structures in the nucleus that appeared to double and divide just before each cell division. They came to be known as chromosomes.
Question 5. Colchicine is a __________
  1.    Type of virus that induces mutation in humans
  2.    Physical agent
  3.    Chemical mutagen
  4.    Type of mutation
 Discuss Question
Answer: Option C. -> Chemical mutagen
:
C
A mutagen is any agent that changes the genetic material. They can be either physical mutagens or chemical mutagens. Colchicine is a chemical mutagen that can induce mutation in organisms. It has been used by scientists in research to study the effect of mutation.
Question 6. Blood group AB is called universal donor and blood group O is called universal recipient.
  1.    True
  2.    False
  3.    Dominant over
  4.    Suppressed by
 Discuss Question
Answer: Option B. -> False
:
B
ABO blood groups are controlled by the gene I. The plasma membrane of the red blood cells has sugar polymers that protrude from its surface and the kind of sugar is controlled by the gene. The gene (I) has three alleles IA, IBand i. The alleles IAand IBproduce a slightly different form of the sugar while allele i does not produce any sugar. Blood group AB has both IAand IBalleles, therefore produce both the sugar antigens, while blood group O has both the recessive allele genotype (ii) and does not produce any sugarantigens. GroupABblood contains red blood cells that have both antigens, A and B and thereforedoes not have reactive antibodies in its plasma to these antigens. Therefore an individual with AB blood group can receive blood from any of the other blood groups- Blood group A containing A antigens, blood group B containing B antigens or blood group Ocontaining noantigens because blood group AB have no reactive antibodies against any of these antigens. It is thus the 'universal recipient'. Similarlyblood group O can be donated to any of the other blood groups as it has no antigens, to initiate an antibody reaction. Thusblood group O is the universal donor.
Question 7. Sutton and Boveri explained Mendel’s laws using ___.
  1.    Movement of chromosomes during cell division
  2.    Movement of nuclei during cell division
  3.    Movement of cell organelles during cell division
  4.    Movement of proteins during cell division
 Discuss Question
Answer: Option A. -> Movement of chromosomes during cell division
:
A
Sutton and Boveri noted that the behavior of chromosomes was parallel to the behavior of genes, and used chromosome movement during cell division to explain Mendel’s laws.Sutton and Boveri argued that the pairing and separation of a pair of chromosomes would lead to the segregation of a pair of factors they carried. Sutton united the knowledge of chromosomal segregation with Mendelian principles and called it the chromosomal theory of inheritance.
Question 8. Biston betularia typica and Biston betularia carbonaria, the two types of moth are an example of
  1.    Variation
  2.    Incomplete Inheritance
  3.    Sex linked inheritance
  4.    Linkage
 Discuss Question
Answer: Option A. -> Variation
:
A
Biston betularia typica, (a light coloured peppered moth) and Biston betularaia carbonaria (a dark coloured moth) are two varieties of moth found in England. These two moths belonged to the same species but had a phenotypic variation, one being light in colour and the other being dark. The phenotypic variations affected the population size of both the moths during the time of industrial revolution in England.
Question 9. In diseases that show X-linked inheritance, the females are usually the ______.
  1.    Promoters
  2.    Carriers
  3.    Operators
  4.    None of the above
 Discuss Question
Answer: Option B. -> Carriers
:
B
In females, having a defective allele on the X-chromosome do not express the disorder, when the allele is recessive and the normal allele masks the activity of this allele. Males however having a singleX chromosome, invariably expresses the disease, if they possess the defective allele. Since males get their X chromosome from the mother,the disease pedigree is from the carrier mother to her son.
Question 10. The study of inheritance and variation is termed __.
 Discuss Question

:
Genetics is the branch of biology that deals with the study of inheritance and variation of characters from parents to offspring.

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