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Genetics - Basis of Inheritence

Description: This topic includes 25 mcq and is an important topic for various MBBS/BDS ENTERANCE exam.
Number of Questions: 25
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Tags: GENETICS Heredity and Variation Principles of Inheritance and Variation Mendelian Inheritance Mendel-s Law of Inheritance Post Mendelian Discoveries Inheritance Pattern of Haemophilia and Blood Groups in Human Beings Haemophilia Genetics
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Who is the father of modern genetics?

  1. Gregor John Mendel

  2. Bateson

  3. T.H Morgan

  4. Louis Pasteur

  5. None of the above


Correct Option: B
Explanation:

He is father of modern genetics.

The term allele was given by whom?

  1. Johnsann

  2. Mendel

  3. Correns

  4. Bateson

  5. Morgan


Correct Option: D
Explanation:

He gave term allele, homozygous and heterozygous.

What will be the total number of phenotype and genotype of a monohybrid cross?

  1. 13

  2. 5

  3. 8

  4. 11

  5. 6


Correct Option: B
Explanation:

In a monohybrid cross phenotype obtained is tall and dwarf, genotype obtained is TT, Tt and tt. Thus if you count total is 5.

The phrase "like begets like" is best analysed in the context of which of the following?

  1. Forward genetics

  2. Classical genetics

  3. Reverse genetics

  4. Cytogenetics

  5. Both forward and classical genetics


Correct Option: E
Explanation:

They deals with phenomenon of like begets like, e.g.,  human babies are like human beings in over all characteristics. As forward genetics is study on the basis of phenotype, study of DNA sequences comprising the gene for this phenotype and classical genetics is also known as transmission genetics, e.g.,: Mendelian genetics, Non-mendelian genetics.

The cross of F1 hybrid with a dominant parent is known as

  1. test cross

  2. out cross

  3. back cross

  4. both test and back cross

  5. none of these


Correct Option: B
Explanation:

It is a cross of F1 hybrid with dominant parent.

What is ratio of parental and non-parental recombinant in a phenotypic ratio of dihybrid cross?

  1. 5:3

  2. 3:5

  3. 9:1

  4. 1:1

  5. None of the above


Correct Option: A
Explanation:

Phenotypic ratio in a dihybrid cross is 9:3:3:1 this means 9 and 1 are parental, 3 and 3 are non-parental recombinant, so total parental is 10 and total recombinant is 6 thus ratio is 10/6 i.e 5:3.

Which principle of Mendel is known as law of purity of gametes?

  1. Principle of Paired factor

  2. Principle of Dominance

  3. Principle of Segregation

  4. Principle of Independent assortment

  5. None of the above


Correct Option: C
Explanation:

It states that the two factors of a character segregate at the time of gamete formation and then reunite at the time of fertilisation. it is also known as law of purity of gamete.

The genes which occur in more than two allelic forms are known as______.

  1. pleiotropic gene

  2. polygene

  3. complementary gene

  4. multiple alleles

  5. duplicating gene


Correct Option: D
Explanation:

More than two alternative forms of gene, present on same locus are called multiple alleles.

What will be the number of gametes produced by individual AaBBCc and AABBCC?

  1. 4 and 1

  2. 4 and 0

  3. 8 and 8

  4. 2 and 4

  5. 8 and 0


Correct Option: A
Explanation:

Number of gametes  = 2n where n is the number of heterozygous condition. In AaBBCc, number of gametes is 4 and in AABBCC, since number of heterozygous condition is zero, so anything raised to the power zero is one.

Which of the following is an example of incomplete dominance?

  1. Mirabilis jalapa

  2. Antirrhinum majus

  3. Pod colour in Andalusian fowl

  4. All of these

  5. None of the above


Correct Option: D
Explanation:

In all of the above, the gene of allelomorphic pair are neither regarded as dominant nor recessive, but both of them express themselves partially in hybrid. Genotypic and Phenotypic ratio is the same.

As per detailed investigation by S.Blixt on pea plant, on which of the chromosomes were the seven selected characters of Mendel were located?

  1. Chromosome number - 1, 3, 5 and 7

  2. Chromosome number - 1, 4, 5 and 7

  3. Chromosome number - 3, 4, 5 and 7

  4. Chromosome number - 1, 4, 5 and 11

  5. Chromosome number - 1, 3, 5 and 11


Correct Option: B
Explanation:

As per detailed investigation by S.Blixt on pea plant ,  7 selected characters were located on following chromosome -   stem height on chromosome number 4, flower colour on chromosome number 1, flower position on  chromosome number 4, pod shape on chromosome number 4, pod colour on chromosome number 5, seed shape on chromosome number 7 and seed colour on chromosome number 1.

Who discovered the fourth blood group AB?

  1. Landsteiner

  2. A. S. Wiener and Landsteiner

  3. De Castello and Steini

  4. Bernstein

  5. None of these


Correct Option: C
Explanation:

De Castello and Steini discovered the fourth blood group AB.

Albinism in maize, is an example of ____________.

  1. dominant epistasis

  2. recessive epistasis

  3. dominant-recessive epistasis

  4. dominant lethality

  5. recessive lethality


Correct Option: E
Explanation:

It causes death of organism in homozygous recessive state.

Sickle cell anemia is an example of _______.

  1. dominant epistasis

  2. absolute lethality

  3. delayed lethality

  4. sub-lethality

  5. recessive epistasis


Correct Option: D
Explanation:

It means that death of organism occurs before reproductive maturity.

What is the phenotypic ratio for dominant epistasis?

  1. 9 : 7

  2. 12 : 3 : 4

  3. 9 : 3 : 4

  4. 15 : 1

  5. 13 : 1


Correct Option: B
Explanation:

It is the phenotypic ratio for dominant epistasis, for eg. fruit color in summer squash.

If lethality is existing in a population, then it is because of _________.

  1. heterosis

  2. heterozygosity

  3. both homozygosity and heterozygosity

  4. homozygous dominant

  5. homozygous recessive


Correct Option: B
Explanation:

Heterozygosity is always inherited because of recessive gene.

What is the total phenotype and genotype for recessive epistasis?

  1. 12

  2. 11

  3. 3

  4. 9

  5. None of the above


Correct Option: A
Explanation:

In recessive epistasis phenotypic ratio is 9 : 3 : 4 and genotypic ratio is 1 : 2 : 1 : 2 : 4 : 2 : 1 : 2 : 1. So if we count, the total is 12.

Who studied the polygenic inheritance in case of cob length in maize?

  1. Nilsson-Ehle

  2. Kolreuter

  3. Devenport

  4. Emerson and East

  5. Galton


Correct Option: D
Explanation:

Emerson and East studied polygenic inheritance in case of cob length in maize.

Which one of the following will not suffer from malaria?

  1. HbAHbS

  2. HbAHbA

  3. HbSHbS

  4. Both HbAHbS and HbAHbA

  5. Both HbAHbS and HbSHbS


Correct Option: A
Explanation:

It represents carrier and does not suffer from malaria because RBC being sickle shaped, malarial parasite plasmodium vivax cannot penetrate into RBC.

In pedigree analysis, a cross or shade (of any type) in the symbol, signifies which of the following?

  1. Male

  2. Female

  3. The carrier of recessive allele

  4. Parents

  5. None of the above


Correct Option: C
Explanation:

A cross or shade (of any type) in the symbol signifies the carrier or recessive allel.

What will be the number of phenotypes in polygenic inheritance in case of human skin color?

  1. 7

  2. 11

  3. 3

  4. 5

  5. None of the above


Correct Option: A
Explanation:

Number of phenotypes in polygenic inheritance is calculated by = ( 2 x n ) + 1, where n is number of pairs of polygene. As human skin color is controlled by 3 pairs of polygenes, thus number of phenotypes = ( 2 x 3 ) + 1 = 7. Also, phenotypic ratio for human skin color is 1 : 6 : 15 : 20 : 15 : 6 : 1. So, if counted, the answer is 7.

Which of the following is the correct answer for the person, whose case history start in pedigree analysis is female?

  1. Propositus

  2. Proposita

  3. Proband

  4. Propita

  5. None of the above


Correct Option: B
Explanation:

Female case history start.

In capsicum, genotype aabbcc produces 200 gm capsicum and genotype AABBCC produces 260 gm. What will be the contribution of each gene, and what will be the weight of capsicum in progeny, if AAbbcc x aaBBcc?

  1. 20 and 240

  2. 10 and 220

  3. 20 and 280

  4. 10 and 180

  5. None of the above


Correct Option: B
Explanation:

Contribution of each gene = (maximum wt - minimum wt ) / number of polygene: (260 - 200 ) / 6 = 10, weight of progeny = ( number of dominant gene x contribution of each gene ) + minimum value. Thus, number of dominant gene in progeny = 2 (AaBbcc), weight of progeny = ( 2 x 10) + 200 = 220.

If frequency of dominant allele is 0.6 and frequency of recessive allele is 0.4, then find out frequency of heterozygous carrier.

  1. 0.48

  2. 0.36

  3. 0.16

  4. 0.24

  5. None of the above


Correct Option: A
Explanation:

According to hardy - weinberg equation, p refers to frequency of dominant allele and q refers to frequency of recessive allele. p = 0.6 and q = 0.4 Thus, frequency of heterozygous carrier = 2pq = 2 x 0.6 x 0.4 = 2 x 0.24 =0.48.

If frequency of dominant phenotype is 75%, find out frequency of recessive allele.

  1. 50%

  2. 25%

  3. 100%

  4. 75%

  5. 5%


Correct Option: A
Explanation:

As p2+2pq refers to frequency of dominant phenotype therefore   p2 + 2 pq = 75 % (given) p2 + 2 pq + q2 = 1 then 0.75 + q2 = 1 so q2 = 0.25 thus q = 0.5.Therefore frequency of recessive allele is 50 %.

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