1. Mendel’s experiments on pea plants primarily involved studying the
inheritance of:
- A) Color of leaves
- B) Shape of seeds
- C) Plant height
- D) Color of flowers
Answer: B
Explanation: Mendel's experiments primarily involved studying
the inheritance of traits like seed shape, color, and plant height in pea
plants.
2. The law of independent assortment states that:
- A) Alleles for different traits segregate independently during gamete formation
- B) Alleles for a single trait segregate independently during gamete formation
- C) Recessive traits are never expressed
- D) Dominant traits are always expressed
Answer: A
Explanation: The law of independent assortment states that
alleles for different traits segregate independently during gamete formation, as
shown by Mendel's dihybrid cross.
3. Which of the following is NOT a characteristic of Mendel's
experiments?
- A) Use of true-breeding plants
- B) Cross-fertilization between plants
- C) Selection of traits with multiple alleles
- D) Study of seven pairs of contrasting traits
Answer: C
Explanation: Mendel focused on traits with two contrasting
forms, not traits with multiple alleles.
4. The term "genotype" refers to:
- A) Physical appearance of an organism
- B) Genetic makeup of an organism
- C) The way an organism reacts to its environment
- D) All observable traits of an organism
Answer: B
Explanation: Genotype refers to the genetic makeup of an
organism, while phenotype refers to its observable traits.
5. A dihybrid cross involves the inheritance of:
- A) One pair of alleles
- B) Two pairs of alleles
- C) Three pairs of alleles
- D) Multiple pairs of alleles
Answer: B
Explanation: A dihybrid cross involves the inheritance of two
traits, each determined by a pair of alleles.
6. The phenotype of an organism is determined by:
- A) Genotype alone
- B) Environment alone
- C) Genotype and environment
- D) None of the above
Answer: C
Explanation: The phenotype is the result of both the genotype
and environmental factors.
7. Which of the following best describes a test cross?
- A) Crossing two individuals with similar phenotypes
- B) Crossing a dominant phenotype with a recessive homozygote
- C) Crossing two homozygous recessive individuals
- D) Crossing two heterozygous individuals
Answer: B
Explanation: A test cross involves crossing an individual with
a dominant phenotype with a recessive homozygote to determine its genotype.
8. The principle of segregation states that:
- A) Two alleles of a gene separate during gamete formation
- B) Alleles for different traits assort independently
- C) Dominant alleles mask the expression of recessive alleles
- D) Two alleles of a gene always segregate together
Answer: A
Explanation: The principle of segregation states that two
alleles for a gene separate during gamete formation, ensuring that each gamete
gets only one allele from each gene pair.
9. In a monohybrid cross between two heterozygous individuals (Aa x Aa),
the phenotypic ratio of the offspring will be:
- A) 1:1
- B) 3:1
- C) 1:2:1
- D) 9:3:3:1
Answer: B
Explanation: The phenotypic ratio for a monohybrid cross
between two heterozygous individuals is 3:1 (dominant to recessive traits).
10. In incomplete dominance, the F1 generation exhibits:
- A) The dominant trait
- B) A mixture of the two parental traits
- C) Only the recessive trait
- D) A new trait
Answer: B
Explanation: In incomplete dominance, the F1 generation
exhibits a phenotype that is a mixture of both parental traits (e.g., red and
white flowers producing pink flowers).
11. A human with the genotype X^N X^n will:
- A) Be colorblind
- B) Have normal vision
- C) Be a male
- D) Be a female carrier of colorblindness
Answer: D
Explanation: X^N X^n represents a female carrier of
colorblindness, as colorblindness is an X-linked recessive trait.
12. The term "allele" refers to:
- A) A gene that codes for a protein
- B) A variant form of a gene
- C) A mutation in the DNA sequence
- D) A pair of chromosomes
Answer: B
Explanation: An allele is a variant form of a gene, which can
exist in multiple forms, leading to different traits.
13. Which of the following is an example of co-dominance?
- A) Pink flowers in snapdragons
- B) AB blood type in humans
- C) White and red flowers producing pink flowers
- D) Flower color in pea plants
Answer: B
Explanation: Co-dominance occurs when both alleles of a gene
are equally expressed, as seen in AB blood type, where both A and B alleles are
expressed equally.
14. The gene responsible for sickle cell anemia is an example of:
- A) Codominance
- B) Incomplete dominance
- C) Multiple alleles
- D) Mendelian inheritance
Answer: A
Explanation: Sickle cell anemia is an example of codominance,
where both normal and sickle-shaped hemoglobin are expressed in heterozygous
individuals.
15. Which of the following refers to a situation where one gene
influences the expression of multiple traits?
- A) Pleiotropy
- B) Epistasis
- C) Dominance
- D) Independent assortment
Answer: A
Explanation: Pleiotropy occurs when a single gene influences
multiple traits or phenotypic features.
16. The inheritance of blood groups in humans is an example of:
- A) Codominance
- B) Incomplete dominance
- C) Multiple alleles
- D) Dominant-recessive inheritance
Answer: C
Explanation: The inheritance of human blood groups is an
example of multiple alleles, where the A, B, and O alleles exist for this trait.
17. Which of the following is a sex-linked genetic disorder?
- A) Hemophilia
- B) Cystic fibrosis
- C) Phenylketonuria
- D) Sickle cell anemia
Answer: A
Explanation: Hemophilia is a sex-linked recessive disorder
carried on the X chromosome.
18. The phenomenon of "carrier" in genetics refers to:
- A) An individual who has both alleles for a trait
- B) An individual with only one allele of a recessive disorder
- C) An individual with a dominant disorder
- D) An individual with multiple alleles
Answer: B
Explanation: A carrier is an individual who carries one allele
for a recessive disorder but does not show the symptoms because the other allele
is dominant.
19. Which of the following statements is true about Mendel's Law of
Dominance?
- A) A dominant allele completely masks the expression of a recessive allele
- B) A recessive allele is always expressed in a heterozygote
- C) Both alleles in a heterozygote are equally expressed
- D) Only recessive alleles are expressed in homozygotes
Answer: A
Explanation: According to Mendel's Law of Dominance, the
dominant allele completely masks the expression of the recessive allele in a
heterozygote.
20. In a cross between two individuals with genotypes AaBb x AaBb, the
probability of getting an offspring with the genotype AABb is:
- A) 1/16
- B) 1/8
- C) 1/4
- D) 1/2
Answer: A
Explanation: The probability of getting an AABb offspring is
calculated based on the possible genotypic combinations from the dihybrid cross,
which results in a 1/16 chance.
21. If a pea plant has a genotype of TtYy, what is the total number of
possible gametes that can be produced?
Answer: A
Explanation: For a dihybrid genotype TtYy, the plant can
produce four possible gametes (TY, Ty, tY, and ty).
22. In a cross between a homozygous dominant red-flowered plant and a
homozygous recessive white-flowered plant (RR x rr), all offspring will have:
- A) Red flowers
- B) White flowers
- C) Pink flowers
- D) Half red and half white flowers
Answer: A
Explanation: All offspring will inherit one dominant red allele
and one recessive white allele, so they will all exhibit the red flower
phenotype.
23. The term "genetic recombination" refers to:
- A) The random assortment of alleles
- B) The process of creating genetic variation in gametes
- C) The fusion of gametes during fertilization
- D) The mutation of genes in an individual
Answer: B
Explanation: Genetic recombination refers to the process of
generating genetic variation through the reshuffling of alleles during meiosis.
24. What does the term "X-linked inheritance" mean?
- A) Traits are inherited through the Y chromosome
- B) Traits are inherited through the X chromosome
- C) Traits are inherited independently of sex chromosomes
- D) Traits are inherited from both parents equally
Answer: B
Explanation: X-linked inheritance means that a gene responsible
for a trait is located on the X chromosome, and its inheritance pattern follows
sex-linked rules.
25. Which of the following is an example of epistasis?
- A) Coat color in dogs where one gene determines color and another gene masks the
color
- B) Blood group inheritance
- C) Sickle cell anemia
- D) Eye color in humans
Answer: A
Explanation: Epistasis occurs when the expression of one gene
is affected by the presence of another gene, as seen in coat color in dogs.
26. What is the phenotypic ratio of a dihybrid cross of two heterozygous
plants (AaBb x AaBb) for unlinked genes?
- A) 9:3:3:1
- B) 3:1
- C) 1:2:1
- D) 1:1
Answer: A
Explanation: The phenotypic ratio for a dihybrid cross of two
heterozygous plants (AaBb x AaBb) for unlinked genes is 9:3:3:1.
27. Which of the following is an example of multiple alleles?
- A) Blood groups in humans
- B) Height in humans
- C) Skin color in humans
- D) Eye color in humans
Answer: A
Explanation: The ABO blood group system is an example of
multiple alleles, where three alleles (A, B, O) determine blood type.
28. Mendel's second law of independent assortment applies to:
- A) Genes located on the same chromosome
- B) Genes located on different chromosomes
- C) Recessive traits
- D) Dominant traits
Answer: B
Explanation: Mendel's second law of independent assortment
applies to genes located on different chromosomes, where their alleles segregate
independently.
29. The F1 generation from a cross between a pure-breeding tall (TT) and
a short (tt) plant will be:
- A) Short
- B) Tall
- C) A mix of tall and short
- D) Heterozygous short
Answer: B
Explanation: All offspring in the F1 generation will inherit
one dominant allele from the tall parent and one recessive allele from the short
parent, resulting in all tall plants.
30. What will be the phenotypic ratio of the F2 generation of a dihybrid
cross (AaBb x AaBb)?
- A) 1:2:1
- B) 9:3:3:1
- C) 3:1
- D) 1:1
Answer: B
Explanation: The phenotypic ratio for the F2 generation of a
dihybrid cross of heterozygous individuals (AaBb x AaBb) is 9:3:3:1.
31. Which of the following is the correct genotype for a female carrier
of hemophilia?
- A) X^H X^H
- B) X^H X^h
- C) X^h X^h
- D) X^H Y
Answer: B
Explanation: A female carrier of hemophilia has one normal
allele (X^H) and one defective allele (X^h), making her genotype X^H X^h.
32. The law of dominance explains that:
- A) Only recessive alleles are expressed in a heterozygote
- B) Dominant alleles are always expressed
- C) Recessive alleles are never expressed
- D) Dominant alleles mask the expression of recessive alleles in a heterozygote
Answer: D
Explanation: The law of dominance states that dominant alleles
mask the expression of recessive alleles in a heterozygote.
33. In human males, the Y chromosome is inherited from the:
- A) Father
- B) Mother
- C) Both parents equally
- D) Only maternal side
Answer: A
Explanation: In humans, males inherit the Y chromosome from
their father, as females do not have a Y chromosome.
34. Which of the following statements about genetic linkage is true?
- A) Genes located on different chromosomes always assort independently
- B) Linked genes are inherited together
- C) Linked genes always show complete dominance
- D) Linked genes do not assort independently
Answer: B
Explanation: Linked genes, located on the same chromosome, are
inherited together more often than genes on different chromosomes.
35. A characteristic of codominance is that:
- A) Both alleles are expressed equally
- B) Only one allele is expressed
- C) One allele is dominant over the other
- D) Both alleles are silenced
Answer: A
Explanation: In codominance, both alleles are equally
expressed, as seen in blood groups (AB).
36. Which of the following genetic conditions is an example of
pleiotropy?
- A) Marfan syndrome
- B) Blood type inheritance
- C) Sickle cell anemia
- D) Albinism
Answer: A
Explanation: Marfan syndrome is an example of pleiotropy, where
a single gene affects multiple traits such as height, limb length, and heart
problems.
37. Which of the following patterns of inheritance involves the
expression of traits based on sex chromosomes?
- A) Autosomal inheritance
- B) Sex-linked inheritance
- C) Incomplete dominance
- D) Codominance
Answer: B
Explanation: Sex-linked inheritance involves traits determined
by genes located on sex chromosomes (X and Y).
38. In a monohybrid cross of two heterozygous individuals (Aa x Aa), the
ratio of the offspring will be:
- A) 3:1
- B) 1:2:1
- C) 9:3:3:1
- D) 2:1
Answer: A
Explanation: The monohybrid cross between two heterozygous
individuals (Aa x Aa) will result in a 3:1 phenotypic ratio.
39. A person with the genotype AABb will have:
- A) Type AB blood
- B) Type A blood
- C) Type B blood
- D) Type O blood
Answer: B
Explanation: A person with the genotype AABb will have Type A
blood because the A allele is dominant over the B allele.
40. What is the main reason for genetic variation in sexually
reproducing organisms?
- A) Independent assortment of chromosomes
- B) Mutation
- C) Crossing over during meiosis
- D) All of the above
Answer: D
Explanation: Genetic variation is primarily due to independent
assortment of chromosomes, mutations, and crossing over during meiosis.
41. Which of the following is an example of incomplete dominance?
- A) Flower color in snapdragons
- B) Blood type in humans
- C) Skin color in humans
- D) Eye color in humans
Answer: A
Explanation: Incomplete dominance occurs when the heterozygous
phenotype is an intermediate of the two homozygous phenotypes, as seen in
snapdragon flowers (red and white producing pink).
42. Which term describes the physical appearance of an organism based on
its genetic makeup?
- A) Genotype
- B) Phenotype
- C) Homozygous
- D) Heterozygous
Answer: B
Explanation: The phenotype refers to the physical appearance of
an organism, determined by its genotype and environmental factors.
43. What does the term "homozygous" mean?
- A) Having two different alleles for a trait
- B) Having identical alleles for a trait
- C) Having one dominant and one recessive allele
- D) Having two recessive alleles for a trait
Answer: B
Explanation: Homozygous means having identical alleles for a
specific gene.
44. Which of the following crosses would produce offspring in a 1:1
ratio for a recessive trait?
- A) Heterozygous x heterozygous
- B) Homozygous dominant x homozygous recessive
- C) Homozygous dominant x heterozygous
- D) Heterozygous x homozygous recessive
Answer: D
Explanation: A heterozygous x homozygous recessive cross
produces a 1:1 ratio of dominant to recessive phenotypes.
45. The Law of Segregation states that:
- A) Two alleles for a trait segregate independently during gamete formation
- B) Alleles for different traits assort independently
- C) The dominant allele is always expressed
- D) Genes located on different chromosomes always assort independently
Answer: A
Explanation: The Law of Segregation states that each individual
has two alleles for each trait, which separate during gamete formation.
46. Which type of inheritance is observed in the case of color
blindness?
- A) X-linked recessive inheritance
- B) Autosomal dominant inheritance
- C) Autosomal recessive inheritance
- D) Y-linked inheritance
Answer: A
Explanation: Color blindness is an X-linked recessive trait,
which means it is carried on the X chromosome and expressed in males who have
only one X chromosome.
47. A trait controlled by a single gene and having only two alleles is
called:
- A) Polygenic inheritance
- B) Monohybrid inheritance
- C) Mendelian inheritance
- D) Multifactorial inheritance
Answer: C
Explanation: A trait controlled by a single gene with two
alleles follows Mendelian inheritance patterns.
48. In a dihybrid cross, the ratio 9:3:3:1 is indicative of:
- A) Codominance
- B) Independent assortment
- C) Incomplete dominance
- D) Epistasis
Answer: B
Explanation: The 9:3:3:1 ratio in a dihybrid cross is a result
of independent assortment of alleles.
49. The probability of a homozygous recessive offspring from a cross
between two heterozygous parents (Aa x Aa) is:
- A) 0%
- B) 25%
- C) 50%
- D) 75%
Answer: B
Explanation: The probability of a homozygous recessive (aa)
offspring from a cross between two heterozygous parents (Aa x Aa) is 25%.
50. Which of the following is a result of crossing over during meiosis?
- A) Genetic variation
- B) Reduction of chromosome number
- C) Formation of gametes
- D) None of the above
Answer: A
Explanation: Crossing over during meiosis increases genetic
variation by exchanging genetic material between homologous chromosomes.