Heredity

1. One way of incorporating desired characters into crop varieties is hyb

One way of incorporating desired characters into crop varieties is hybridization. In this process, there is crossing between genetically dissimilar plants. Which one of the following crossings will not refer to hybridization?

Intervarietal
Interspecific
Intergeneric
Intragenic
This question was previously asked in
UPSC CAPF – 2022
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The correct answer is D) Intragenic.
Hybridization refers to the crossing of genetically dissimilar individuals to produce offspring with a combination of traits from both parents. This can occur between different varieties of the same species (intervarietal), between different species (interspecific), or even between different genera (intergeneric). Intragenic refers to genetic changes or events (like mutation or recombination) occurring within a single gene, not involving the crossing of different individuals or groups.
Hybridization is a key technique in plant and animal breeding to introduce desirable traits from one genetic background into another. Intragenic studies focus on the structure, function, and alterations of individual genes.

2. Father and mother having A and B blood group respectively

Father and mother having A and B blood group respectively

cannot give birth to child with AB blood group
cannot give birth to child with O blood group
can give birth to child with O blood group
cannot give birth to twin child with B blood group
This question was previously asked in
UPSC CAPF – 2011
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A father and mother having A and B blood groups respectively can give birth to a child with O blood group.
Blood group A can have genotypes I^A I^A or I^A i, and blood group B can have genotypes I^B I^B or I^B i. A child with blood group O has the genotype ii. This genotype can only be formed if both parents contribute an ‘i’ allele.
If the father has genotype I^A i (Blood Group A) and the mother has genotype I^B i (Blood Group B), their possible offspring genotypes are I^A I^B (AB), I^A i (A), I^B i (B), and ii (O). Therefore, a child with blood group O is a possible outcome if both parents are heterozygous for their respective blood groups.

3. Different varieties of the same gene are called

Different varieties of the same gene are called

Genotypes
Sib pairs
Alleles
Isomers
This question was previously asked in
UPSC NDA-2 – 2021
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Alleles are different versions or forms of the same gene. They arise through mutations and are located at the same position (locus) on homologous chromosomes.
For example, the gene for flower color might have two alleles: one for purple flowers and one for white flowers. These different alleles determine the variation in traits observed within a population.
Genotype refers to the genetic makeup of an organism, i.e., the combination of alleles it possesses for a particular trait or set of traits. Sib pairs are simply siblings. Isomers are chemical compounds with the same molecular formula but different structural formulas.

4. In pea, a pure tall plant (TT) is crossed with a short plant (tt). Wha

In pea, a pure tall plant (TT) is crossed with a short plant (tt). What will be the ratio of pure tall plants to short plants in the F₂ generation ?

1:1
1:3
3:1
2:1
This question was previously asked in
UPSC CDS-2 – 2021
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The initial cross is between a pure tall plant (TT) and a short plant (tt).
Parental Generation (P): TT x tt
The gametes produced by the TT parent are all T. The gametes produced by the tt parent are all t.
First Filial Generation (F1): When TT is crossed with tt, the offspring (F1) are all heterozygous tall (Tt).
F1 selfing: Tt x Tt
The gametes produced by a Tt plant are T and t, in equal proportions (1:1).
To find the F2 generation, we cross the F1 gametes:
Punnett Square:
| T | t
—|—-|—-
T | TT | Tt
t | Tt | tt
The genotypes in the F2 generation are TT, Tt, and tt in the ratio 1:2:1.
The phenotypes are Tall (TT and Tt) and Short (tt).
The ratio of Tall to Short phenotypes is 3:1.
The question asks for the ratio of **pure tall plants (TT)** to **short plants (tt)** in the F2 generation.
From the genotype ratio (1 TT : 2 Tt : 1 tt), the number of pure tall plants (TT) is 1 unit, and the number of short plants (tt) is 1 unit.
Therefore, the ratio of pure tall plants to short plants in the F2 generation is 1:1.
– Pure tall genotype is TT, short genotype is tt.
– F1 generation from TT x tt is always Tt (heterozygous tall).
– F2 generation from Tt x Tt has genotypes TT, Tt, tt in ratio 1:2:1.
– Pure tall is TT, short is tt.
Mendel’s experiments with pea plants established the principles of dominance and segregation. This question illustrates the segregation of alleles during gamete formation and their re-combination in subsequent generations. The phenotypic ratio is often 3:1 for a monohybrid cross involving a dominant trait, but the question asks for specific genotypes (pure tall and short), not phenotypes.

5. In human beings, the chromosomes that determine birth of a normal fema

In human beings, the chromosomes that determine birth of a normal female child are

one X chromosome from mother and one X chromosome from father
one X chromosome from mother and one Y chromosome from father
two X chromosomes from mother and one X chromosome from father
one X chromosome and one Y chromosome from father and one X chromosome from mother
This question was previously asked in
UPSC CDS-2 – 2020
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In humans, sex is determined by the sex chromosomes. Females have two X chromosomes (XX), and males have one X and one Y chromosome (XY). A female child inherits one X chromosome from her mother (who can only contribute an X) and one X chromosome from her father (who can contribute either an X or a Y).
The mother’s gametes (ova) always carry an X chromosome. The father’s gametes (sperm) carry either an X or a Y chromosome. Fertilization with an X-carrying sperm results in an XX zygote (female), while fertilization with a Y-carrying sperm results in an XY zygote (male).
The father determines the sex of the child based on whether the sperm contributing to fertilization carries an X or a Y chromosome.

6. Human insulin molecule is composed of one α-chain having 21 amino acid

Human insulin molecule is composed of one α-chain having 21 amino acids and one β-chain having 30 amino acids. How many functional insulin genes occur in adult humans?

One
Two
Three
Four
This question was previously asked in
UPSC CDS-2 – 2017
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There are two functional insulin genes in adult humans.
The gene encoding human insulin, INS, is located on chromosome 11. Humans are diploid organisms, meaning they have two sets of chromosomes (except for sex chromosomes in males). Therefore, a healthy individual has two copies of the INS gene, one on each of the homologous chromosome 11 pair. Both copies are typically functional, encoding the proinsulin precursor that is cleaved to form mature insulin.
Mutations in the INS gene can lead to various forms of diabetes, such as Maturity Onset Diabetes of the Young type 1 (MODY1). The structure of the insulin molecule, composed of alpha and beta chains linked by disulfide bonds, is derived from a single proinsulin polypeptide chain.

7. Photo 51 refers to an image of

Photo 51 refers to an image of

a crater on the Moon
DNA molecules
the virus responsible for COVID-19
the virus responsible for common cold
This question was previously asked in
UPSC CDS-1 – 2024
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Photo 51 refers to a famous X-ray diffraction image of DNA molecules.
Photo 51 was an X-ray diffraction pattern of DNA, obtained by Rosalind Franklin and Raymond Gosling in 1952 at King’s College London. This image was crucial in determining the double helix structure of DNA by James Watson and Francis Crick.
The clarity of Photo 51 provided key information, including the helical nature of DNA, its diameter, and the spacing between the base pairs, which were essential clues for building the correct molecular model.

8. A child receives a tall beautiful plant as a birthday gift from his fa

A child receives a tall beautiful plant as a birthday gift from his father with a quiz. The father asked her how she would verify whether this tall plant was the progeny of both the tall parents or one tall and one short parent plant. She could verify this through

cross-pollination
self-pollination
tissue culture
negative propagation
This question was previously asked in
UPSC CDS-1 – 2021
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She could verify this through cross-pollination.
To determine the genotype of a plant showing a dominant phenotype (tall), the standard method is a test cross. A test cross involves cross-pollinating the plant with a homozygous recessive plant (short). If the progeny includes any short plants, the tall parent must be heterozygous (Tt). If all progeny are tall, the tall parent is likely homozygous dominant (TT). This method allows differentiation between potential parental genotypes (Tall x Tall vs. Tall x Short leading to different progeny genotypes).
Self-pollination could also provide clues (a heterozygous plant would produce some recessive offspring upon selfing), but a test cross is more definitive for confirming homozygosity vs. heterozygosity. Tissue culture is a propagation technique, and ‘negative propagation’ is not a standard biological term in this context.

9. The process of copying genetic information from one strand of DNA into

The process of copying genetic information from one strand of DNA into RNA is termed as

translation
transcription
replication
mutation
This question was previously asked in
UPSC CDS-1 – 2017
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The process of copying genetic information from a DNA template to synthesize an RNA molecule is called transcription. This process is carried out by enzymes called RNA polymerases.
Knowing the central dogma of molecular biology (DNA -> RNA -> Protein) and the processes involved (replication, transcription, translation) is essential.
Replication is the process of duplicating DNA. Translation is the process of synthesizing protein from an mRNA template. Mutation is a permanent alteration in the DNA sequence.
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