Productive Health Class 12 NEET MCQs

1. Individuals having dissimilar traits (alleles) on homologous chromosomes are called

a) Heterozygous
b) Homozygous
c) Dominant
d) Recessive

Answer:

a) Heterozygous

Explanation:

Heterozygous individuals have two different alleles for a particular trait on their pair of homologous chromosomes.

2. An allele is considered dominant

a) When it expresses in homozygosity
b) When it expresses even in the presence of an alternate allele
c) When it expresses a desirable phenotype
d) Both (b) and (c)

Answer:

b) When it expresses even in the presence of an alternate allele

Explanation:

A dominant allele is one that expresses its phenotype even in the presence of an alternate (recessive) allele.

3. Mendel’s dihybrid ratio is

a) 1:1:1:1
b) 3:1
c) 9:3:3:1
d) 9:1:1:5

Answer:

c) 9:3:3:1

Explanation:

Mendel’s dihybrid ratio is 9:3:3:1, which represents the phenotypic ratio in the offspring when two pairs of contrasting traits are studied together.

4. Mendel studied seven contrasting characters for his breeding experiment with Pisum sativum, which of the following characters did he not use?

a) Pod shape
b) Leaf shape
c) Plant height
d) Pod color

Answer:

b) Leaf shape

Explanation:

Leaf shape was not one of the seven contrasting characters Mendel studied in his experiments with Pisum sativum. He studied pod shape, pod color, plant height, among others.

5. An organism with two identical alleles of a gene in a cell is called

a) Heterozygous
b) Homozygous
c) Hybrid
d) Homozygous

Answer:

b) Homozygous

Explanation:

Homozygous organisms have two identical alleles for a particular trait in their cells.

6. Which principle of inheritance was not given by Mendel

a) Independent assortment
b) Dominance
c) Purity of gametes
d) Linkage

Answer:

d) Linkage

Explanation:

The principle of linkage was not described by Mendel. It was discovered later and refers to the tendency of genes located close together on a chromosome to be inherited together.

7. When dominant BB and recessive bb is crossed, the percentage of progeny showing the parental genotype is

a) 0%
b) 25%
c) 50%
d) 75%

Answer:

a) 0%

Explanation:

When a homozygous dominant BB is crossed with a homozygous recessive bb, all the resulting F1 progeny will be heterozygous Bb, which does not resemble either of the parental genotypes. Therefore, the percentage of progeny showing the parental genotype is 0%.

8. The year 1900AD is highly significant for genetics due to

a) Chromosome theory of heredity
b) Discovery of genes
c) Rediscovery of Mendelism
d) Principle of linkage

Answer:

c) Rediscovery of Mendelism

Explanation:

The year 1900AD is significant for the rediscovery of Mendel’s work on genetics. Three scientists, Hugo de Vries, Carl Correns, and Erich von Tschermak independently rediscovered Mendel’s work which laid the foundation of modern genetics.

9. The process by which the segregation of Mendelian factors takes place is

a) Hybridisation
b) Mitosis
c) Meiosis
d) Fertilisation

Answer:

c) Meiosis

Explanation:

Meiosis is the process by which Mendelian factors or alleles segregate independently into separate gametes, following Mendel’s law of segregation.

10. Which would most probably be the genetic makeup of the parents of a color blind daughter?

a) Carrier mother and normal father
b) Carrier mother and color blind father
c) Color blind mother and normal father
d) Normal mother and normal father

Answer:

b) Carrier mother and color blind father

Explanation:

Color blindness is an X-linked recessive trait. A color-blind daughter would inherit an affected X chromosome from both parents. The most probable genetic makeup of the parents would be a carrier mother (X^NX^c) and a color-blind father (X^cY).

11. If a heterozygous tall plant is crossed with a homozygous dwarf plant the proportion of dwarf progeny will be

a) 25%
b) 50%
c) 75%
d) 100%

Answer:

b) 50%

Explanation:

In this cross (Tt x tt), half of the progeny will inherit the recessive allele from both parents and will be dwarf (tt).

12. When two tall plants are crossed 45 tall plants and 14 dwarf plants are obtained. The genotype of parent plants is

a) TT x TT
b) TT x tt
c) Tt x Tt
d) TT x Tt

Answer:

c) Tt x Tt

Explanation:

The ratio of tall to dwarf plants is close to 3:1, which is typical for a monohybrid cross between two heterozygous individuals (Tt x Tt).

13. Which of the following is not a dominant character selected by Mendel in Pisum?

a) Yellow pod color
b) Violet flower color
c) Axillary flowers
d) Yellow seed color

Answer:

a) Yellow pod color

Explanation:

Mendel chose green pod color as a dominant trait, so yellow pod color is not a dominant character selected by Mendel in Pisum sativum.

14. How many types of gametes are produced by a trihybrid?

a) 3
b) 4
c) 8
d) 16

Answer:

c) 8

Explanation:

A trihybrid individual has three pairs of contrasting traits. According to Mendel’s law of independent assortment, each pair of alleles segregates independently. Therefore, the number of different types of gametes produced by a trihybrid is 2^3 = 8.

15. A cross by changing the source of ovum is

a) Back cross
b) Test cross
c) Monohybrid
d) Reciprocal cross

Answer:

d) Reciprocal cross

Explanation:

A reciprocal cross is a breeding experiment designed to test the role of parental sex on a given inheritance pattern by reversing the sexes of the parents and comparing the outcomes.

16. When the phenotypic and genotypic ratios resemble in the F2 generation it is an example of

a) Independent assortment
b) Qualitative inheritance
c) Segregation
d) Incomplete dominance

Answer:

d) Incomplete dominance

Explanation:

Incomplete dominance results in a third phenotype where the observed physical characteristics are a blend of the dominant and recessive phenotypes. The genotypic and phenotypic ratios are identical in such cases (1:2:1).

17. In what situation, the phenotype of a dihybrid cross would exhibit parental combination of characters in more than the expected value and recombination in less than the expected value?

a) When genes are in mitochondria
b) When duplicate genes are present
c) When genes are linked
d) When supplementary genes are present

Answer:

c) When genes are linked

Explanation:

Linkage results in a higher frequency of parental combinations and a lower frequency of recombinations as the genes are located close together on the same chromosome and tend to be inherited together.

18. When the dihybrid Tt rr plants are self-fertilized, what percentage of descendants would be heterozygous for one character and homozygous for another?

a) 25%
b) 50%
c) 75%
d) 100%

Answer:

a) 25%

Explanation:

When the dihybrid Tt rr plants are self-fertilized, the genotype for the seed color trait is fixed to rr (homozygous recessive). For the height trait, the Punnett Square for Tt x Tt gives a 1/4 chance of obtaining Tt (heterozygous). Since the seed color trait is fixed, the overall probability of obtaining Tt rr genotype in the offspring is 1/4 or 25%.

19. Back cross with recessive parent is called

a) Monohybrid cross
b) Multiple cross
c) Single cross
d) Test cross

Answer:

d) Test cross

Explanation:

A test cross is a way to explore the genotypic ratio of a particular organism. It’s performed by mating the organism in question with an individual that is homozygous recessive for the trait in question.

20. If a gene has multiple effects, it is called

a) Multiple allelism
b) Pleiotropism
c) Polygeny
d) Epistasis

Answer:

b) Pleiotropism

Explanation:

Pleiotropy occurs when one gene influences two or more seemingly unrelated phenotypic traits. An example of pleiotropy is the human disease phenylketonuria (PKU).

21. Maize has 10 pairs of chromosomes. How many linkage groups should it possess

a) 5
b) 10
c) 20
d) 40

Answer:

b) 10

Explanation:

A linkage group corresponds to the number of chromosomes, as each chromosome corresponds to a linkage group. Since maize has 10 pairs of chromosomes, it should possess 10 linkage groups.

22. Linked genes may be separated by

a) Gene mutation
b) Polyploidy
c) Segregation
d) Crossing over

Answer:

d) Crossing over

Explanation:

Crossing over during meiosis can separate linked genes. This process involves the exchange of genetic material between non-sister chromatids of homologous chromosomes.

23. Crossing over ißn diploid organism is responsible for

a) Recombination of linked gene
b) Segregation of alleles
c) Dominance of genes
d) Linkage between genes

Answer:

a) Recombination of linked gene

Explanation:

Crossing over is a mechanism that allows the recombination of linked genes, providing genetic variation.

24. Crossing over takes place between

a) Sister chromatids of homologous chromosomes
b) Non-sister chromatids of homologous chromosomes
c) Sisters of non-homologous chromosomes
d) DNA and RNA

Answer:

b) Non-sister chromatids of homologous chromosomes

Explanation:

Crossing over occurs between non-sister chromatids of homologous chromosomes, allowing for the exchange of genetic material.

25. If the distance between genes on a chromosome is more, the linkage strength is

a) More
b) Less
c) Unaffected
d) More in somatic cells

Answer:

b) Less

Explanation:

The further apart two genes are on a chromosome, the higher the chance that crossing over will occur between them, which results in less linkage strength.

26. A trisomic individual has a chromosomal number of

a) 2n -1
b) 2n +2
c) 2n + 1
d) 2n + 3

Answer:

c) 2n + 1

Explanation:

In trisomy, an individual has an extra chromosome, making the chromosomal number 2n + 1.

27. Among the following which one is the best chemical for inducing the polyploidy?

a) Ethylene
b) Colchicine
c) Acridines
d) Mustard gas

Answer:

b) Colchicine

Explanation:

Colchicine is a chemical used to induce polyploidy by preventing the formation of the spindle fibers necessary for chromosome separation during cell division.

28. Down’s syndrome is an example of

a) Monosomy
b) Trisomy
c) Triploidy
d) Eupolyploidy

Answer:

b) Trisomy

Explanation:

Down’s syndrome is caused by trisomy of chromosome 21, where an individual has three copies of chromosome 21 instead of the usual two.

29. Which of the following is 6x (hexaploid) wheat?

a) Triticum durum
b) T. monococcum
c) T.aestivum
d) Triticale

Answer:

c) T.aestivum

Explanation:

Triticum aestivum is a hexaploid wheat species with six sets of chromosomes.

30. The holandric genes are located on

a) Mitochondria
b) X- chromosome
c) Y-chromosome
d) Polytene chromosome

Answer:

c) Y-chromosome

Explanation:

Holandric genes are genes located on the Y-chromosome and are passed from father to son.

31. If the haploid number of chromosomes in a plant is 12, then the number of chromosomes in monosomic is

a) 22
b) 23
c) 25
d) 26

Answer:

b) 23

Explanation:

In monosomy, an individual is missing one chromosome. So, if the haploid number is 12, the total chromosome number in a monosomic individual would be 2n – 1 = 24 – 1 = 23.

32. Alleles are paired in

a) In zygote
b) In diploid organism
c) Dihybrid
d) All of these

Answer:

b) In diploid organism

Explanation:

Alleles are paired in diploid organisms where each cell contains two alleles for each trait, one from each parent.

33. Haemophilia most likely originated as a result of

a) The separation of two homologous chromosomes
b) A non disjunction of chromosome number 21
c) The crossing over to two sex chromosomes
d) A gene mutation in the X- chromosome

Answer:

d) A gene mutation in the X- chromosome

Explanation:

Haemophilia is a genetic disorder caused by a mutation in the genes on the X chromosome that codes for blood clotting factors.

34. Chromosome complement with 2n-1 is called as

a) Monosomy
b) Trisomy
c) Nullisomy
d) Tetrasomy

Answer:

a) Monosomy

Explanation:

Monosomy refers to the condition where an individual has one less chromosome than the normal diploid number, represented as 2n-1.

35. The most striking example of point mutation is found in a disease called

a) Night blindness
b) Turner’s syndrome
c) D0own’s syndrome
d) Sickle cell anemia

Answer:

d) Sickle cell anemia

Explanation:

Sickle cell anemia is caused by a point mutation in the gene that codes for beta-globin, a subunit of hemoglobin, resulting in abnormal sickle-shaped red blood cells.

36. In which of the following, females are heterogametic

a) Humans
b) Grasshopper
c) Drosophila
d) Fowl

Answer:

d) Fowl

Explanation:

In birds (fowl), females have heterogametic sex chromosomes (ZW), whereas males have homogametic sex chromosomes (ZZ).

37. Gynaecomastia is a common feature seen in:

a) Down’s syndrome
b) Turner’s syndrome
c) Cystic fibrosis
d) Klinefelter’s syndrome

Answer:

d) Klinefelter’s syndrome

Explanation:

Gynaecomastia, the enlargement of breast tissue in males, is a common feature of Klinefelter’s syndrome, a condition where males have an extra X chromosome (XXY).

38. XO type of sex determination is seen in:

a) Man
b) Grasshopper
c) Drosophila
d) Birds

Answer:

b) Grasshopper

Explanation:

In grasshoppers, the XO system of sex determination is used. Males have a single sex chromosome (XO), while females have two (XX).

39. Which of the following is not a Mendelian disorder?

a) Haemophilia
b) Cystic fibrosis
c) Thalassemia
d) Turner’s syndrome

Answer:

d) Turner’s syndrome

Explanation:

Turner’s syndrome is a chromosomal disorder caused by the absence or partial absence of an X chromosome, whereas the others are genetic disorders inherited in a Mendelian manner.

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