Test: Principles of Inheritance & Variation - 1


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QUESTION: 1

The innate tendency of offspring to resemble their parents is called?

Solution:
  • The innate tendency of offspring to resemble their parents is called heredity.
  • The offspring resembles the parents due to same genetic combination inherited from the parents.

Hence, the correct option is B

NCERT Reference: Page no. 60 of chapter 5 of NCERT

QUESTION: 2

Monohybrid ratio is _________.

Solution:
  • Monohybrid ratio is the ratio of different phenotypic traits obtained on hybridizing a single pair of traits. It is 3:1.
  • When tall pea plant is crossed with dwarf, the offspring obtained are in 3/4 tall and 1/4 dwarf.

SOLVED] What will be the ratio of tall and dwarf plants in the - Self Study  365

Fig: Monohybrid cross

Hence, the correct option is B
NCERT Reference: Page no. 71 of topic “5.2 INHERITANCE OF ONE GENE” of chapter 5 of NCERT

QUESTION: 3

Who is regarded as the father of genetics?

Solution:
  • Gregor Mendel is known as the Father of Genetics.
  • He experimented on pea plants and discovered the basic inheritance rules. 

Gregor Mendel - Wikipedia

Hence, the correct option is A
NCERT Reference: Page no. 70 of topic “5.1 MENDEL’S LAWS OF INHERITANCE” of chapter 5 of NCERT

QUESTION: 4

Material used for conducting experiments on genetic traits by Mendel was _________.

Solution:
  • Mendel studied the common garden pea plant, Pisum sativum because it was easy to cultivate and had a relatively short life cycle of 3 months. The plant exhibited discontinuous characteristics such as flower colour and pea texture.
  • Owing to its anatomy, it was easy to control the self-pollination of the plant and cross-fertilization between desired parents could be accomplished artificially.
  • The presence of pure breeding varieties and easily visible contrasting characters and presence of F1 fertile hybrids were the additional advantageous characters for which Mendel choose garden pea as experimental material. 

Hence, the correct option is C

NCERT Reference: Page no. 70 of topic “5.1 MENDEL’S LAWS OF INHERITANCE” of chapter 5 of NCERT

QUESTION: 5

The physical expression or appearance of a character is called as:

Solution:
  • The physical appearance of a character or organism's observable characteristics or traits is called as phenotype.
  • The genetic makeup of an individual is called genotype. Tallness, round, wrinkled, yellow etc. are due to their genetic makeup.

Phenotype Example:
Phenotype - Wikipedia

Hence, the correct option is A
NCERT Reference: Page no. 72 of topic “5.1 MENDEL’S LAWS OF INHERITANCE” of chapter 5 of NCERT

QUESTION: 6

F2 generation is obtained by _________.

Solution:

In monohybrid and dihybrid cross F2 generation is obtained by selfing of F1 hybrids as male and female.
can you please explain the monohybrid cross and dihybrid cross - Biology -  TopperLearning.com | 10190

Fig: Monohybrid cross showing F1 and F2 generation

Hence, the correct option is B

NCERT Reference: Page no. 71 of topic “5.2 INHERITANCE OF ONE GENE” of chapter 5 of NCERT

QUESTION: 7

Dihybrid cross proves the law of _________.

Solution:
  • In a dihybrid cross, two new kinds of plants with new traits are formed. This is possible only when all traits assort independently and recombine to form a new combination.
  • Mendel found that each pair of alleles segregates independently of the other pairs of alleles during gamete formation. 
  • This is known as the Law of independent assortment and hence it can be proved by the dihybrid cross.

Explain the law of independent assortment with a suitable class 12 biology  CBSE

Hence, the correct option is C

NCERT Reference: Page no. 80 of topic “5.3.1 Law of Independent Assortment” of chapter 5 of NCERT

QUESTION: 8

In pea plants, yellow seeds are dominant to green, If a heterozygous yellow seeded plant is crossed with a green seeded plant, what ratio of yellow and green seeded plants would you expect in F1 generation?

Solution:
  • Since the yellow seeds are dominant to green, the allele for yellow seeds should be represented with upper case letter while the one for green seeds should be written in lower case letter.
  • Let's suppose that the allele for yellow seed is Y and that for green seeds is y. Hence the genotype of the heterozygous yellow seeded plant will be "Yy" and that for green seeded plant will be "yy" (as the recessive allele is expressed only in homozygous conditions).
  • The cross between heterozygous yellow seeded plant and green seeded plant will produce 50% yellow seeded plants and 50% green seeded plants.

Hence, the correct option is C

NCERT Reference: Topic “5.2 INHERITANCE OF ONE GENE” for basic understanding of this cross from chapter 5

QUESTION: 9

In a cross between a pure tall plant with green pod and a pure short plant with yellow pod. How many short plants are produced in F2 generation out of 16?  

Solution:
  • Genotype of pure tall plant with green pod = TTGG
  • Genotype of pure dwarf plant with yellow pod = ttgg
  • P generation:  TTGG    X  ttgg
  • F1 generation: TtGg (tall plant, green pod)

Selfing: TtGg X  TtGg

As can be seen from the table, a total 4 short plants with genotypes ttGG, ttGg, ttGg and ttgg are produced.

Hence, the correct option is B

NCERT Reference: Topic “5.3 INHERITANCE OF TWO GENES” from Chapter 5 of NCERT for understanding this question.

QUESTION: 10

The test cross is used to determine the  ________.

Solution:

In a test cross:

  • The organism with the dominant trait is always crossed with an organism with the recessive trait. 
  • If any offspring show the recessive trait, the unknown genotype is heterozygous
  • If all the offspring have the dominant trait, the unknown genotype is homozygous dominant.

Fig: The test cross

Hence, the correct option is A

NCERT Reference: Page no. 74 of topic “5.2 INHERITANCE OF ONE GENE” of chapter 5 of NCERT.

QUESTION: 11

The genotypes of a husband and wife are IIB and IAi. Among the blood types of their children how many different genotypes and phenotypes are possible?

Solution:

A cross between two individuals, one with AB blood group and the other with A blood group will produce four genotypes and three phenotypes.

The genotypes of a husband and wife are IAIB and IAi.
Four different possible genotypes of their children are: IAIB, IAi, IBi, IAIA

The possible number of phenotypes of their children are:

  • Blood group A (IAIA, IAi)
  • Blood group B (IBi)
  • Blood group AB (IAIB)

Fig: Cross between blood groups AB and A 
Hence, the correct option is B.
NCERT Reference: Refer topic “5.2.2.2 Co-dominance” of chapter 5 for understanding this question.

QUESTION: 12

Inheritance of skin colour in human beings is an example of _______.

Solution:
  • Polygenic/Quantitative inheritance: Controlling a character by two or more genes is called Multi factor inheritance.
    Example: Inheritance of skin colour of human beings.
  • Mendelian Inheritance: The transfer of traits from one generation into another into the next generation in the form of a particulate structure is called Mendelian Inheritance.
    Example: Cross based on height or colour and shape of seeds.
  • Monogenic inheritance: It is also called the Monohybrid cross. Cross between a homozygous dominant parent and a homozygous recessive parent on the basis of a single character.
    Example: Cross based on the height of the pea plants.
  • Complementary genes: Two independent pairs of genes, which interact to produce a trait together, but each dominant gene alone does not show its effect, are called complementary genes.
    Example: Cross based on the colour of flowers in Sweet potato.

Hence, the correct option is B.

NCERT Reference: Page no. 85 of topic “5.4 POLYGENIC INHERITANCE” of chapter 5.

QUESTION: 13

Which of the following is an example of co-dominance?

Solution:
  • Co-dominance is the phenomenon that deviates from Mendel’s law of inheritance.
  • Both the alleles appear in offspring instead of one as in Mendel’s experiment.
  • ABO blood grouping in human beings is an example of co-dominance in which both IA and IB appear simultaneously to form AB blood type.

Hence, the correct option is D.

NCERT Reference: Page no. 77 of topic “5.2.2.2 Co-dominance” of chapter 5.

QUESTION: 14

A human male produces sperms with the genotypes AB, Ab, aB, ab pertaining to two diallelic characters in equal proportions. What is the corresponding genotype of this person?

Solution:
  • If the genotype is AaBb the alleles that are produced will be AB, Ab, aB, ab, since there are two diallelic characters in the genotypes the person must be heterozygous for both genes. AABB is homozygous. So, the correct answer is "AaBb".

Fig: Diallelic characters in the genotype

Hence, the correct option is B.

NCERT Reference: Topic “5.3 INHERITANCE OF TWO GENES” of chapter 5 for better understanding of this question.

QUESTION: 15

In Mirabilis jalapa, when two F1 pink flowered plants were crossed with each other, the F2 generation produced 40 red, 80 pink and 40 white flowering plants. This a case of:

Solution:
  • F1 pink flowered plants are heterozygous. When selfing is done the genotype and phenotype develops as 1:2:1 as 40 red, 80 pink and 40 white flowering plants.  It is called Incomplete dominance.
  • The appearance of a new phenotype in the progeny but not either of the parents is called Incomplete dominance.

Fig: Cross showing incomplete dominance in Mirabilis jalapa

Hence, the correct option is C.
NCERT Reference: Page no. 76 of topic “5.2.2.1 Incomplete Dominance” of chapter 5.

QUESTION: 16

Assertion: The cross between red and white flower-bearing snapdragon plants results in pink coloured flower.
Reason: Incomplete dominance of red and white flower results in pink coloured flowers.

Solution:
  • In Snapdragon flower, cross between true-breeding white and red coloured flower produce pink coloured flower in the F1 generation.
  • This happens due to the incomplete dominance of alleles over the other.

Hence, the correct option is A.
NCERT Reference: Page no. 76 of topic “5.2.2.1 Incomplete Dominance” of chapter 5.

QUESTION: 17

People suffering from colour blindness fail to distinguish which of the two colours?

Solution:
  • People who are colour blind fail to distinguish between red and green colours.
  • Colour blindness is a sex-linked recessive trait in which the normal gene and its recessive allele are carried by X-chromosome.

Hence, the correct option is A.

NCERT Reference: Page no. 89 of topic “5.8.2 Mendelian Disorders” of chapter 5.

QUESTION: 18

Plotting of specific genes on the chromosome is known as _________.

Solution:
  • Plotting of specific genes on the chromosome is known as chromosomes map or linkage map or genetic map.
  • It shows the position of genes on chromosome in respect to others.

Fig: Chromosome Map

Hence, the correct option is D.
NCERT Reference: Page no. 83 of topic “5.3.3 Linkage and Recombination” of chapter 5.

QUESTION: 19

When two genes are situated very close to one another on a chromosome _________.

Solution:
  • When two genes are situated very close to one another on the chromosome, hardly any cross-over is produced.
  • Such genes are called linkage and do not separate from each other during gamete formation.

Hence, the correct option is A.

NCERT Reference: Page no. 83 of topic “5.3.3 Linkage and Recombination” of chapter 5.

QUESTION: 20

XY chromosome that determine the sex in human beings are:

Solution:

Sex chromosomes of human beings are heteromorphic as they are of different size. Y chromosome is smaller than X chromosome in size.

Hence, the correct option is D.
NCERT Reference: Page no. 85 of topic “5.6 SEX DETERMINATION” of chapter 5.

QUESTION: 21

Statement I: The bridge between one generation and the next is sperm and ovum.
Statement II: Both sperm and ovum contribute equally to heredity.
Statement III: Somatic diploid cells possess two chromosomes as well as two mendelian factors of each type.

Solution:
  • Bridge between one generation and the next is through sperm and ovum.
  • The sperm provides only the nuclear part to the zygote. As such hereditary characters must be carried by nuclear materials.
  • There is fusion of the sperm and egg nuclei during fertilization.
  • Both the sperm and egg contribute equally in the heredity of the offspring. 

Hence , the correct answer is option B.

NCERT Reference: This question is based on basic understanding of inheritance.

QUESTION: 22

Sex determination in human beings is _________.

Solution:
  • In humans, the males are heterogametic as they have XY sex chromosomes, so they make 50% sperms with X chromosome and 50% sperms with Y chromosome. Females are homogametic. All gametes made by them have X chromosomes. So, humans show XX-XY type of sex determination.

Hence, the correct option is A.
NCERT Reference: Page no. 87 of topic “5.6 SEX DETERMINATION” of chapter 5.

QUESTION: 23

XO type of sex determination is found in _________.

Solution:
  • In grasshopper, sex determination is of XO type, in which the males have only one X-chromosome besides the autosomes whereas females have a pair of X-chromosomes.

Hence, the correct option is A.
NCERT Reference: Page no. 86 of topic “5.6 SEX DETERMINATION” of chapter 5.

QUESTION: 24

In human beings, if ovum fertilizes with a sperm carrying X-chromosome, the zygote develops into _________.

Solution:
  • Females have the genetic composition XX, while males have the genetic makeup XY.
  • The female ovum has an X chromosome, whereas male sperm might have either an X or a Y chromosome.
  • When X chromosome-carrying sperm fertilises an egg with an X chromosome, the zygote grows into a female.

Hence, the correct option is B.

NCERT Reference: NCERT Reference: Page no. 87 of topic “5.6 SEX DETERMINATION” of chapter 5.

QUESTION: 25

Henking X-body present in 50% of sperms are now known as:

Solution:
  • Henking traces a specific structure in 50% of sperms. He gave the name x-body to this structure but he was not able to explain the significance of this structure.
  • Further, investigation revealed that the x-body was a chromosome, called X-chromosome.

Hence, the correct option is D.

NCERT Reference: Page no. 85 of topic “5.6 SEX DETERMINATION” of chapter 5.

QUESTION: 26

How can a female be haemophilic?

Solution:
  • A female can only be haemophilic if her mother is at least a carrier of this disease and her father is haemophilic.
  • But the possibility of a female becoming haemophilic is extremely rare because being haemophilic for the parents at the later stage of life is unviable.

Hence, the correct option is C.

NCERT Reference: Page no. 90 of topic “Haemophilia” of chapter 5.

QUESTION: 27

A colour blind girl is rare because she will be born only when 

Solution:
  • The father of a colour blind female must be colour blind.
  • The mother has to be at least a carrier. This is possible if the maternal grandfather was colour blind [remember criss-cross].

Hence, the correct option is B.

NCERT Reference: Page no. 89 of topic “Colour Blindness” of chapter 5.

QUESTION: 28

Which of the following is a recessive trait for a character chosen by Mendel in garden pea?

Solution:
  • Yellow pod colour of the pea plant is a recessive trait.
  • Mendel studied seven contrasting traits in pea (Pisum sativum), which are as follows:


Hence, the correct option is B.

NCERT Reference: Page no. 70 of topic “5.1 MENDEL’S LAWS OF INHERITANCE” of chapter 5.

QUESTION: 29

Identify the incorrect statement:

Solution:
  • Both tall and dwarf plants produce gametes by mitosis.
  • Plants use meiosis only to produce spores that develop into multicellular haploid gametophytes which produce gametes by mitosis.

Therefore, gamete formation in both tall and dwarf plants is by mitosis.

Hence, the correct option is A.
Note: This question is based on basic understanding of inheritance of genes.

QUESTION: 30

The ultimate source of allelic variation is:

Solution:
  • Gene is a segment of DNA and new alleles arise by mutation - a sudden inheritable change in DNA. Mutations can alter single nucleotides or entire chromosomes.
  • The ultimate source of genetic variation is random mutation i.e. changes in nucleotide sequences of DNA. They may involve only a single base pair or many as in chromosomal mutations.
  • Change in the allele frequency and introduction of new alleles are the basis of genetic variation occurring in any population.

Fig: Showing Mutation 

Hence, the correct option is C.
NCERT Reference: Page no. 88 of topic “5.7 MUTATION” of chapter 5.

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