Class 10 Science NCERT MCQs-Chapter 8-Heredity

 

NCERT MCQs of Class 10 Science, Chapter 8, Heredity

• 1) What is heredity?
  a) The process of reproduction
  b) Transmission of traits from parents to offspring
  c) Formation of gametes
  d) Evolution of species over time
  Answer: b) Transmission of traits from parents to offspring
  Explanation: Heredity refers to the passing of genetic traits from one generation to the next.

• 2) Who is known as the father of genetics?
  a) Charles Darwin
  b) Gregor Mendel
  c) Robert Hooke
  d) Alfred Wallace
  Answer: b) Gregor Mendel
  Explanation: Gregor Mendel is called the father of genetics for his groundbreaking experiments on inheritance in pea plants.

• 3) What does a dominant trait do?
  a) Remains hidden in the offspring
  b) Masks the expression of a recessive trait
  c) Causes mutations in the offspring
  d) Prevents reproduction
  Answer: b) Masks the expression of a recessive trait
  Explanation: A dominant trait is expressed even if only one allele for the trait is present, masking the effect of a recessive allele.

• 4) What are genes?
  a) The building blocks of proteins
  b) Segments of DNA that code for proteins
  c) Structures within the cytoplasm
  d) Organelles that help in respiration
  Answer: b) Segments of DNA that code for proteins
  Explanation: Genes are specific sequences of DNA that carry instructions for producing proteins and determining traits.

• 5) In Mendel’s experiments, what was the phenotypic ratio in the F2 generation for a monohybrid cross?
  a) 1:2:1
  b) 9:3:3:1
  c) 3:1
  d) 1:1
  Answer: c) 3:1
  Explanation: In a monohybrid cross, Mendel observed a phenotypic ratio of 3 dominant traits to 1 recessive trait in the F2 generation.

• 6) What is the basic unit of heredity?
  a) DNA
  b) Chromosome
  c) Gene
  d) RNA
  Answer: c) Gene
  Explanation: A gene is the fundamental unit of heredity that determines specific traits.

• 7) Which of the following traits in pea plants is dominant?
  a) Wrinkled seeds
  b) White flowers
  c) Round seeds
  d) Short height
  Answer: c) Round seeds
  Explanation: In Mendel’s experiments, round seed shape was observed as a dominant trait.

• 8) How many pairs of chromosomes do humans have?
  a) 22
  b) 23
  c) 46
  d) 44
  Answer: b) 23
  Explanation: Humans have 23 pairs of chromosomes, including one pair of sex chromosomes.

• 9) What does the term "allele" mean?
  a) A type of chromosome
  b) A variant form of a gene
  c) A type of DNA
  d) A reproductive cell
  Answer: b) A variant form of a gene
  Explanation: Alleles are different versions of the same gene, such as those for tall and short height.

• 10) What is the ratio of genotypes in the F2 generation of a monohybrid cross?
  a) 3:1
  b) 1:2:1
  c) 9:3:3:1
  d) 2:1
  Answer: b) 1:2:1
  Explanation: The genotypic ratio in the F2 generation is 1 homozygous dominant: 2 heterozygous: 1 homozygous recessive.

• 11) How is the sex of a child determined in humans?
  a) By the chromosomes in the mother’s egg
  b) By the chromosomes in the father’s sperm
  c) By environmental factors
  d) By the food the mother eats
  Answer: b) By the chromosomes in the father’s sperm
  Explanation: The father’s sperm carries either an X or a Y chromosome, determining whether the child will be female (XX) or male (XY).

• 12) What type of inheritance pattern does blood group follow?
  a) Complete dominance
  b) Incomplete dominance
  c) Co-dominance
  d) Independent assortment
  Answer: c) Co-dominance
  Explanation: In blood groups, both alleles (e.g., A and B) are equally expressed, demonstrating co-dominance.

• 13) What are the sex chromosomes in females?
  a) XX
  b) XY
  c) XO
  d) XXY
  Answer: a) XX
  Explanation: Females have two X chromosomes, whereas males have one X and one Y chromosome.

• 14) Which of the following explains the law of independent assortment?
  a) Genes are always inherited in pairs
  b) Genes for different traits are inherited independently of each other
  c) Dominant traits are always inherited together
  d) Recessive traits are eliminated over generations
  Answer: b) Genes for different traits are inherited independently of each other
  Explanation: Mendel’s law of independent assortment states that the inheritance of one trait does not affect the inheritance of another.

• 15) What is the full form of DNA?
  a) Deoxyribonucleic Acid
  b) Deoxyribose Nucleic Acid
  c) Disaccharide Nucleic Acid
  d) Deoxy Nitrogen Acid
  Answer: a) Deoxyribonucleic Acid
  Explanation: DNA stands for Deoxyribonucleic Acid, the molecule responsible for genetic information.

• 16) What was the key observation in Mendel’s dihybrid cross experiments?
  a) Traits are inherited in pairs
  b) Traits are inherited independently
  c) Only dominant traits are expressed
  d) Traits skip generations
  Answer: b) Traits are inherited independently
  Explanation: Mendel observed that traits like seed shape and color are inherited independently, leading to the 9:3:3:1 ratio.

• 17) What is the term for a pair of chromosomes that are similar in shape and size?
  a) Sex chromosomes
  b) Homologous chromosomes
  c) Heterologous chromosomes
  d) Autosomes
  Answer: b) Homologous chromosomes
  Explanation: Homologous chromosomes carry genes for the same traits at the same loci but may have different alleles.

• 18) What happens during fertilization in sexual reproduction?
  a) DNA is copied identically
  b) Two haploid cells combine to form a diploid zygote
  c) A single parent contributes all the genetic material
  d) Offspring are clones of the parents
  Answer: b) Two haploid cells combine to form a diploid zygote
  Explanation: During fertilization, a sperm and egg cell (haploid) combine, restoring the diploid chromosome number.

• 19) What determines the dominant trait in an organism?
  a) Environmental factors
  b) A single allele
  c) The expression of one allele over another
  d) Equal contribution of both alleles
  Answer: c) The expression of one allele over another
  Explanation: A dominant allele is expressed over a recessive allele, determining the observed trait.

• 20) What is a Punnett square used for?
  a) Studying evolution
  b) Predicting offspring traits in genetic crosses
  c) Determining the lifespan of organisms
  d) Identifying environmental variations
  Answer: b) Predicting offspring traits in genetic crosses
  Explanation: A Punnett square is a tool used to visualize and predict the genetic combinations of offspring.

• 21) What are variations in a species caused by?
  a) DNA copying errors during reproduction
  b) External environmental factors only
  c) Identical inheritance of traits
  d) The absence of genetic material
  Answer: a) DNA copying errors during reproduction
  Explanation: Variations arise due to minor inaccuracies in DNA copying during reproduction, which are essential for evolution.

• 22) What does Mendel’s law of segregation state?
  a) Genes are linked and inherited together
  b) Two alleles for a trait separate during gamete formation
  c) Dominant traits are always expressed
  d) Offspring inherit only one allele from each parent
  Answer: b) Two alleles for a trait separate during gamete formation
  Explanation: The law of segregation states that alleles separate so each gamete carries only one allele for a trait.

• 23) What is the expected phenotypic ratio in the F2 generation of a dihybrid cross?
  a) 3:1
  b) 9:3:3:1
  c) 1:1:1:1
  d) 1:2:1
  Answer: b) 9:3:3:1
  Explanation: A dihybrid cross involves two traits, and Mendel observed a 9:3:3:1 ratio in the F2 generation.

• 24) How does the environment influence traits in organisms?
  a) By altering genetic material permanently
  b) By directly determining inherited traits
  c) By affecting the expression of inherited traits
  d) By eliminating genetic variations
  Answer: c) By affecting the expression of inherited traits
  Explanation: Environmental factors can influence how inherited traits are expressed but do not change the genetic material itself.

• 25) What does a recessive allele require to be expressed?
  a) At least one dominant allele
  b) Two recessive alleles
  c) A mutation in the gene
  d) An external environmental trigger
  Answer: b) Two recessive alleles
  Explanation: A recessive trait is expressed only when both alleles are recessive (homozygous recessive).

• 26) What are autosomes?
  a) Chromosomes that determine sex
  b) Chromosomes involved in somatic traits
  c) Mutated chromosomes
  d) Circular DNA molecules
  Answer: b) Chromosomes involved in somatic traits
  Explanation: Autosomes are non-sex chromosomes that carry genes for all traits except sex determination.

• 27) Which of the following is an example of a co-dominant trait?
  a) Height in pea plants
  b) Blood group AB in humans
  c) Eye color in humans
  d) Flower color in snapdragons
  Answer: b) Blood group AB in humans
  Explanation: In co-dominance, both alleles are equally expressed, as seen in individuals with blood group AB.

• 28) What is the significance of variations in a species?
  a) To maintain uniformity in the population
  b) To ensure survival under changing environmental conditions
  c) To prevent reproduction
  d) To increase the chances of extinction
  Answer: b) To ensure survival under changing environmental conditions
  Explanation: Variations enhance adaptability and survival in different or changing environments.

• 29) Which chromosome combination results in a male child in humans?
  a) XX
  b) XY
  c) YY
  d) XO
  Answer: b) XY
  Explanation: The XY combination (X from the mother and Y from the father) determines a male child.

• 30) What is a homozygous genotype?
  a) One dominant and one recessive allele
  b) Two identical alleles for a trait
  c) Two different traits inherited together
  d) A genotype with no alleles
  Answer: b) Two identical alleles for a trait
  Explanation: Homozygous genotypes consist of identical alleles, such as TT or tt.

• 31) Which of the following traits is inherited independently in Mendel’s experiments?
  a) Flower color and plant height
  b) Seed shape and seed color
  c) Flower position and leaf size
  d) Stem thickness and root length
  Answer: b) Seed shape and seed color
  Explanation: Mendel showed that seed shape and seed color are inherited independently, leading to new combinations.

• 32) What is the function of chromosomes?
  a) Storing nutrients
  b) Controlling metabolic reactions
  c) Carrying genetic information
  d) Synthesizing proteins directly
  Answer: c) Carrying genetic information
  Explanation: Chromosomes carry DNA, which contains the genetic information necessary for inheritance.

• 33) What happens when two heterozygous tall pea plants are crossed?
  a) All offspring will be tall
  b) 50% will be tall, and 50% will be short
  c) 75% will be tall, and 25% will be short
  d) All offspring will be short
  Answer: c) 75% will be tall, and 25% will be short
  Explanation: The phenotypic ratio for a heterozygous cross (Tt × Tt) is 3:1, with 75% tall plants.

• 34) Which type of reproduction introduces maximum genetic variation?
  a) Asexual reproduction
  b) Sexual reproduction
  c) Vegetative propagation
  d) Binary fission
  Answer: b) Sexual reproduction
  Explanation: Sexual reproduction combines genetic material from two parents, leading to greater genetic diversity.

• 35) What does a phenotype represent?
  a) The genetic makeup of an organism
  b) The observable traits of an organism
  c) The number of chromosomes in a cell
  d) The environment’s effect on a gene
  Answer: b) The observable traits of an organism
  Explanation: Phenotype refers to the physical appearance or traits of an organism, such as height or flower color.

• 36) How many chromosomes are present in a human gamete?
  a) 22
  b) 23
  c) 46
  d) 44
  Answer: b) 23
  Explanation: Human gametes (sperms and eggs) are haploid, containing 23 chromosomes each.

• 37) What is the F1 generation in Mendel’s experiments?
  a) The first generation of offspring from the parent plants
  b) The second generation of offspring
  c) The parental generation
  d) A generation with recessive traits only
  Answer: a) The first generation of offspring from the parent plants
  Explanation: The F1 generation refers to the first filial generation resulting from a cross between two parents.

• 38) Which process restores the diploid number of chromosomes in organisms?
  a) DNA replication
  b) Fertilization
  c) Meiosis
  d) Independent assortment
  Answer: b) Fertilization
  Explanation: Fertilization combines two haploid gametes to form a diploid zygote, restoring the chromosome number.

• 39) What is a dihybrid cross?
  a) A cross involving two traits
  b) A cross between two identical individuals
  c) A cross involving a single trait
  d) A cross without genetic variation
  Answer: a) A cross involving two traits
  Explanation: A dihybrid cross studies the inheritance of two different traits simultaneously.

• 40) What is the genotype of a pea plant that is heterozygous for tallness?
  a) TT
  b) Tt
  c) tt
  d) TTT
  Answer: b) Tt
  Explanation: A heterozygous genotype has one dominant (T) and one recessive (t) allele.

• 41) What is the purpose of meiosis in reproduction?
  a) To produce identical body cells
  b) To reduce the chromosome number in gametes
  c) To increase the number of chromosomes in offspring
  d) To ensure variation in asexually reproducing organisms
  Answer: b) To reduce the chromosome number in gametes
  Explanation: Meiosis reduces the chromosome number by half in gametes, ensuring that the diploid number is restored during fertilization.

• 42) In Mendel’s experiments, what proportion of F2 plants exhibited both recessive traits in a dihybrid cross?
  a) 1/16
  b) 3/16
  c) 9/16
  d) 4/16
  Answer: a) 1/16
  Explanation: In a dihybrid cross, the recessive-recessive phenotype appears in 1/16 of the offspring as per the 9:3:3:1 ratio.

• 43) Which statement is true about dominant and recessive traits?
  a) Recessive traits are expressed when dominant traits are present.
  b) Dominant traits are expressed even if only one allele is present.
  c) Dominant traits are always inherited from the father.
  d) Recessive traits are always inherited from the mother.
  Answer: b) Dominant traits are expressed even if only one allele is present.
  Explanation: A dominant allele is expressed even in the presence of a recessive allele.

• 44) Which chromosome determines the male sex in humans?
  a) X
  b) Y
  c) Both X and Y equally
  d) Autosomes
  Answer: b) Y
  Explanation: The presence of the Y chromosome determines the male sex in humans.

• 45) What are sex-linked traits?
  a) Traits that are influenced by environmental factors
  b) Traits carried on sex chromosomes
  c) Traits that only males inherit
  d) Traits that only females inherit
  Answer: b) Traits carried on sex chromosomes
  Explanation: Sex-linked traits are determined by genes located on sex chromosomes, such as color blindness.

• 46) What is the phenotypic ratio for a test cross?
  a) 9:3:3:1
  b) 3:1
  c) 1:1
  d) 1:2:1
  Answer: c) 1:1
  Explanation: A test cross is used to determine the genotype of an individual by crossing it with a homozygous recessive individual, resulting in a 1:1 ratio.

• 47) How is sex determined in humans?
  a) By the mother’s contribution of chromosomes
  b) By the father’s contribution of chromosomes
  c) By environmental factors
  d) By random genetic mutations
  Answer: b) By the father’s contribution of chromosomes
  Explanation: The sex of a child is determined by the father’s sperm, which carries either an X or a Y chromosome.

• 48) Which of the following is an example of incomplete dominance?
  a) Red and white flowers producing pink flowers
  b) Blood groups A and B forming AB
  c) Tall and short plants producing only tall plants
  d) Round and wrinkled seeds producing round seeds
  Answer: a) Red and white flowers producing pink flowers
  Explanation: In incomplete dominance, the offspring shows a blend of the parental traits, like pink flowers.

• 49) Which of the following is NOT inherited?
  a) Eye color
  b) Height
  c) Language spoken
  d) Blood group
  Answer: c) Language spoken
  Explanation: Language is a learned trait, not inherited through genetic material.

• 50) What is the relationship between genes and chromosomes?
  a) Genes are made of chromosomes
  b) Chromosomes are made of genes
  c) Genes are independent of chromosomes
  d) Chromosomes only exist in gametes
  Answer: b) Chromosomes are made of genes
  Explanation: Chromosomes are structures made up of DNA, and genes are segments of this DNA.

• 51) Which of the following organisms reproduces through binary fission?
  a) Hydra
  b) Amoeba
  c) Frog
  d) Yeast
  Answer: b) Amoeba
  Explanation: Amoeba reproduces asexually through binary fission, where the cell splits into two identical offspring.

• 52) How does independent assortment create genetic variation?
  a) By linking genes together
  b) By randomly combining maternal and paternal chromosomes during gamete formation
  c) By ensuring identical offspring
  d) By mutating the DNA
  Answer: b) By randomly combining maternal and paternal chromosomes during gamete formation
  Explanation: Independent assortment ensures that each gamete gets a random combination of chromosomes, creating variation.

• 53) What is the scientific term for the observable characteristics of an organism?
  a) Genotype
  b) Phenotype
  c) Allele
  d) Chromosome
  Answer: b) Phenotype
  Explanation: The phenotype represents the physical traits or characteristics that can be observed.

• 54) In which organisms is temperature known to influence the determination of sex?
  a) Snakes
  b) Humans
  c) Turtles
  d) Frogs
  Answer: c) Turtles
  Explanation: In some reptiles, like turtles, the temperature at which eggs are incubated determines the sex of the offspring.

• 55) What are germ cells?
  a) Cells involved in digestion
  b) Cells involved in reproduction
  c) Cells that carry oxygen
  d) Cells that protect the body
  Answer: b) Cells involved in reproduction
  Explanation: Germ cells are reproductive cells (sperm and eggs) that carry genetic information to offspring.

• 56) Which term describes an organism with two different alleles for a trait?
  a) Homozygous
  b) Heterozygous
  c) Diploid
  d) Haploid
  Answer: b) Heterozygous
  Explanation: A heterozygous organism has two different alleles for a particular trait, such as Tt.

• 57) What does Mendel’s law of dominance state?
  a) Recessive traits are always expressed
  b) Dominant traits are expressed over recessive traits
  c) All traits are inherited equally
  d) Traits are inherited randomly
  Answer: b) Dominant traits are expressed over recessive traits
  Explanation: Mendel’s law of dominance states that the dominant allele masks the expression of the recessive allele.

• 58) Which chromosome combination results in a female child in humans?
  a) XX
  b) XY
  c) XO
  d) YY
  Answer: a) XX
  Explanation: An XX combination, with one X chromosome from each parent, results in a female child.

• 59) What are traits?
  a) External environmental factors
  b) Inherited characteristics
  c) Mutations in DNA
  d) Uncontrolled changes in body cells
  Answer: b) Inherited characteristics
  Explanation: Traits are inherited characteristics passed down from parents to offspring.

• 60) What is the importance of Mendel’s work?
  a) It explained evolution in detail
  b) It formed the basis of modern genetics
  c) It eliminated the need for genetic research
  d) It prevented the study of variation
  Answer: b) It formed the basis of modern genetics
  Explanation: Mendel’s experiments on pea plants laid the foundation for understanding genetic inheritance.

MCQ from the exercise part of the chapter.

1) A Mendelian experiment consisted of breeding tall pea plants bearing violet flowers with short pea plants bearing white flowers. The progeny all bore violet flowers, but almost half of them were short. This suggests that the genetic make-up of the tall parent can be depicted as:
a) TTWW
b) TTww
c) TtWW
d) TtWw

Answer: c) TtWW

Explanation:

• Progeny all bore violet flowers:

• This indicates that the violet flower trait (W) is dominant over white flowers (w).

  Since all progeny have violet flowers, the tall parent must carry two dominant alleles for flower color (WW).

• Almost half of the progeny were short:

• This means the short trait (t) is recessive, and the tall parent must be heterozygous for height (Tt), allowing the short allele (t) to appear in the offspring.

• Genotype of the tall parent:

• To explain the results, the tall parent’s genotype must be TtWW (heterozygous for height and homozygous for flower color).