Principles of Inheritance and Variation Test

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Principles of Inheritance and Variation Test - 44

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Question 1
1 / -0

The smallest unit of genetic material which upon mutation produce a phenotypic effect is

A
Muton

B
Inducer

C
Regulator

D
None of the above

Solution

A gene carries several cistrons which are defined as a unit of function that exhibits cis-trans test. The smallest unit capable of undergoing recombination is called as recon. A recon consists of one to several mutons, which are the smallest unit of mutation. The inducer is a molecule that binds to the repressor and causes conformational changes in repressor which in turn can no longer bind to the operator. Regulator gene regulates the expression of structural genes by its protein products that are mostly transcription factors. These transcription factors bind to the operator region which is located just upstream the binding site of the RNA polymerase and hence, prevent the binding and transcription.
Thus, the correct answer is option A.
Question 2
1 / -0

Which of the following is a genetic disease?

A
Sickle cell anaemia

B
Tuberculosis

C
Severe Acute Respiratory Syndrome

D
Acquired Immuno Deficiency Syndrome
Question 3
1 / -0

Mutation theory was proposed by

A
Hugo de Vries

B
Gregor Mendel

C
Lamarck

D
Kolreuter
Solution
Correct option - A
Explanation for correct option -
At the starting of the twentieth century, Dutch Botanist and geneticist Hugo de Vries proposed the mutation theory.
According to this theory, living organisms can develop changes to their genes that greatly affect the organisms. These changes are passed down to next generation and result in the formation of new species.
Question 4
1 / -0

The minimum requirement for mutation is a

A
Change of triplet codon

B
Change in single nucleotide

C
Change in whole DNA

D
Change in single strand of DNA

Solution

Mutations are the changes in chemical structure of genes which are manifested in altered protein structure and function. A gene carries several cistrons. A cistron is defined as the unit of function that exhibits cis-trans test. The smallest unit capable of undergoing recombination is called recon. A recon consists of one to several mucons, which are the smallest unit of mutation. A single base pair is recognized as a mucon which is the minimum requirement of a mutation; option B is correct. As we know that DNA is a polymer of deoxyribonucleotides and a set of three nucleotides makes a codon and the 20 standard amino acids are encoded by 61 triplet codons; DNA and codon are not the minimum requirements as they have multiple nucleotides. The correct answer is B.
Question 5
1 / -0

Which of the following undergoes change in mutation?

A
Chromosome

B
Structure of gene

C
Sequence of gene

D
Any of the above

Solution

Mutations are the changes in chemical structure of genes which are manifested in altered protein structure and function. It can alter the sequence of nucleotides in a gene by inversion, deletion, substitution or frameshift changes. DNA replication errors or chemical and physical mutagens disturb the structure of nucleotides and mutate the gene. Structural (inversion, deletion, duplication, translocation) and numerical (aneuploidy, polyploidy) changes in chromosomes are called as chromosomal aberrations which produce the same phenotypic effect as gene mutations. Thus, mutations can change sequence, structure of gene as well as structure of chromosomes.
Question 6
1 / -0

Which of the following is the genotypic ratio of monohybrid cross?

A
1 : 2 : 1

B
9 : 7

C
1 : 2

D
9 : 3 : 3 : 1

Solution

A monohybrid cross is a mating between two individuals with different alleles at one genetic locus of interest.
The expected genotype ratio when two heterozygotes are crossed is 1 (homozygous dominant) : 2 (heterozygous) : 1 (homozygous recessive).
Parents- Tt x Tt
Gametes- T, t T, t
Offspring- TT, Tt, Tt and tt
Phenotype- Tall, Tall, Tall and Dwarf
Genotypic Ratio- 1 : 2 : 1
Phenotypic ratio- 3 : 1
Question 7
1 / -0

When a cross is made between two parents with respect to a single character, it is called as

A
Dihybrid

B
Monohybrid

C
Trihybrid

D
None of these
Solution
A monohybrid cross is a type of cross between two individuals with different alleles at one genetic locus of interest.
The character(s) being studied in a monohybrid cross are governed by two or multiple alleles for a single locus.
A dihybrid cross is a cross between two pure lines (varieties, strains) that differ in two observed traits. In Mendelian sense, between the alleles of both these loci, there is a relationship of complete dominance - recessive.
Trihybrid cross is the mating of two individuals, organisms, or strains that have different gene pairs that determine three specific traits or in which three particular characteristics or gene loci are being followed.
Question 8
1 / -0

Haploids are preferred over diploids for mutation studies because

A
Recessive mutation is expressed in F$$_{1}$$.

B
Recessive mutation is expressed in F$$_{2}$$.

C
Dominant phenotype is expressed.

D
Dominant phenotype is suppressed.

Solution

Dominant mutations are the one that expresses themselves in heterozygotes as well as in homozygous dominant genotypes; thus a cross between two pure breeding genotypes produces the dominant phenotype in F$$_1$$ hybrid. This means that dominant mutations are expressed in successive generations of diploids; options C and D are incorrect in respect to the question. Recessive mutations are suppressed by the presence of wild-type dominant alleles in diploids and are expressed only in recessive homozygotes; their detections need development of hybrid line by the cross between two pure varieties followed by selfing of hybrid to obtain recessive homozygotes in F$$_2$$ generation. Since haploids carry a single copy of allele for a gene, they express both dominant and recessive mutations in successive generations which makes option B incorrect and option A correct. The correct answer is A.
Question 9
1 / -0

Pleiotropic effect is found in

A
Scurvy

B
Night blindness

C
Haemophilia

D
Sickle cell anaemia

Solution

Human skin colour is a polygenic trait governed by more than one gene where dominant allele of each gene express only a part of trait and the full trait is expressed only in the presence of dominant alleles of all multiple genes. It controls skin pigmentation only, no other phenotypic trait is affected by these genes.
Night blindness is impaired ability to see in dim light; it is an autosomal disorder. Haemophilia is an inherited bleeding disorder characterized by lacking or low levels of clotting factors resulting in the inability or impaired ability of blood clotting.
When a single gene mutation affects more than one phenotypic traits, it is called as pleiotropy. Sickle cell anaemia is caused by a mutation in Hb$$^b$$ gene, that codes the $$\beta$$-chain, causes replacement of A by T at the 17th nucleotide of the Hbb gene changes the codon GAG (glutamic acid) to GTG (which encodes valine). The mutated allele Hb$$^s$$ encodes the abnormal haemoglobin molecules which stick to one another and cause stiffness and sickle shape of red blood cells which in turn has two major phenotypic effects. The sickled cells are destroyed by the liver, causing anemia which is manifested as physical weakness, slow development, and hypertrophy of the bone marrow and the “tower skull”. The sickled cells interfere with capillary blood flow, stick together and damage every major organ which in turn causes pain, heart failure, rheumatism, and other ill effects. Thus, sickle cell anemia shows pleiotropy; the correct answer is D.
Question 10
1 / -0

Which one is a dominant trait out of the characters chosen by Mendel?

A
Pod Colour - Yellow

B
Seed Colour - White

C
Flower Position - Axile

D
Plant height - Dwarf

Solution

Mendel studied inheritance of seven pairs of contrasting characters in pea plant. The green pod colour was dominant over yellow pod colour. The grey seed coat colour was dominant over white. Axile flower position was dominant over terminal. Tall plants were dominant over dwarf ones. To confirm the dominance, two pure breeding plants showing contrasting traits were crossed. According to law of dominance, only dominant trait was expressed in progeny. Correct answer is C.

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Principles of Inheritance and Variation Test - 44

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Principles of Inheritance and Variation Test - 44

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SHARING IS CARING

Question 1

Muton

Inducer

Regulator

None of the above

Solution

Question 2

Sickle cell anaemia

Tuberculosis

Severe Acute Respiratory Syndrome

Acquired Immuno Deficiency Syndrome

Question 3

Hugo de Vries

Gregor Mendel

Lamarck

Kolreuter

Solution

Question 4

Change of triplet codon

Change in single nucleotide

Change in whole DNA

Change in single strand of DNA

Solution

Question 5

Chromosome

Structure of gene

Sequence of gene

Any of the above

Solution

Question 6

1 : 2 : 1

9 : 7

1 : 2

9 : 3 : 3 : 1

Solution

Question 7

Dihybrid

Monohybrid

Trihybrid

None of these

Solution

Question 8

Recessive mutation is expressed in F$$_{1}$$.

Recessive mutation is expressed in F$$_{2}$$.

Dominant phenotype is expressed.

Dominant phenotype is suppressed.

Solution

Question 9

Scurvy

Night blindness

Haemophilia

Sickle cell anaemia

Solution

Question 10

Pod Colour - Yellow

Seed Colour - White

Flower Position - Axile

Plant height - Dwarf

Solution

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