- Which of the following terms refers to the failure of homologous chromosomes or sister chromatids to separate properly during meiosis?
a) Crossing over
b) Independent assortment
c) Non-disjunction
d) Linkage
Answer: (c) Non-disjunction
Explanation: Non-disjunction occurs when chromosomes fail to separate properly during meiosis I (homologous chromosomes) or meiosis II (sister chromatids). This results in gametes with an abnormal number of chromosomes, which can lead to conditions such as Down syndrome (trisomy 21) or Turner syndrome (45, X).
- What is the phenotypic ratio in the F2 generation of a dihybrid cross (AaBb x AaBb)?
a) 1:2:1
b) 3:1
c) 9:3:3:1
d) 1:1:1:1
Answer: (c) 9:3:3:1
Explanation: In a dihybrid cross, where two heterozygous individuals are crossed for two traits, the phenotypic ratio in the F2 generation is 9:3:3:1. This means that 9 offspring show both dominant traits, 3 show the dominant form of one trait and the recessive form of the other, another 3 show the opposite pattern, and 1 shows both recessive traits.
- Which of the following terms refers to the exchange of genetic material between homologous chromosomes during meiosis?
a) Independent assortment
b) Segregation
c) Crossing over
d) Non-disjunction
Answer: (c) Crossing over
Explanation: Crossing over is the process where homologous chromosomes exchange genetic material during prophase I of meiosis. This increases genetic diversity by creating new combinations of alleles in the resulting gametes.
- Which of the following best describes the law of independent assortment?
a) Each allele segregates independently of the others during gamete formation
b) The two alleles for a single trait separate during gamete formation
c) Genes located on the same chromosome are inherited together
d) Chromosomes fail to separate properly during meiosis
Answer: (a) Each allele segregates independently of the others during gamete formation
Explanation: Mendel’s law of independent assortment states that alleles for different genes are distributed independently of one another during the formation of gametes. This is true only if the genes are located on different chromosomes or far apart on the same chromosome.
- Which of the following traits is an example of polygenic inheritance?
a) Blood type
b) Height
c) Hemophilia
d) Color blindness
Answer: (b) Height
Explanation: Polygenic inheritance occurs when a trait is controlled by multiple genes. Height is an example of this, as it is determined by the interaction of several genes, each contributing to the overall phenotype. Blood type is controlled by a single gene with multiple alleles, and hemophilia and color blindness are examples of single-gene disorders.
- A cross between a red-flowered plant (RR) and a white-flowered plant (rr) produces all pink offspring. This is an example of:
a) Codominance
b) Incomplete dominance
c) Epistasis
d) Pleiotropy
Answer: (b) Incomplete dominance
Explanation: In incomplete dominance, the heterozygous offspring have a phenotype that is intermediate between the two parental phenotypes. In this case, crossing a red-flowered plant (RR) with a white-flowered plant (rr) results in pink flowers, as neither allele is completely dominant.
- Which of the following genetic disorders is inherited in an autosomal dominant manner?
a) Sickle cell anemia
b) Cystic fibrosis
c) Huntington’s disease
d) Hemophilia
Answer: (c) Huntington’s disease
Explanation: Huntington’s disease is caused by a dominant allele, meaning that only one copy of the mutated gene is required for the disorder to be expressed. Autosomal dominant disorders typically appear in every generation, and affected individuals have a 50% chance of passing the disorder to their offspring.
- Which of the following conditions is characterized by trisomy 13?
a) Down syndrome
b) Turner syndrome
c) Patau syndrome
d) Klinefelter syndrome
Answer: (c) Patau syndrome
Explanation: Patau syndrome is caused by trisomy 13, where individuals have three copies of chromosome 13. This leads to severe developmental issues and a low survival rate. Down syndrome is caused by trisomy 21, Turner syndrome by a missing X chromosome, and Klinefelter syndrome by an extra X chromosome in males (XXY).
- In a population that is in Hardy-Weinberg equilibrium, the frequency of the recessive allele is 0.4. What is the frequency of heterozygous individuals?
a) 0.16
b) 0.24
c) 0.48
d) 0.36
Answer: (c) 0.48
Explanation: The Hardy-Weinberg equation is p² + 2pq + q² = 1, where p is the frequency of the dominant allele and q is the frequency of the recessive allele. Given that q = 0.4, p = 1 – 0.4 = 0.6. The frequency of heterozygous individuals is given by 2pq = 2 × 0.6 × 0.4 = 0.48.
- Which of the following is true for a genetic disorder inherited in an autosomal recessive manner?
a) The disorder skips generations
b) Both males and females are equally affected
c) Individuals with one copy of the mutated allele are carriers
d) All of the above
Answer: (d) All of the above
Explanation: Autosomal recessive disorders require two copies of the mutated allele for the disorder to be expressed. These disorders often skip generations because carriers (heterozygous individuals) do not show symptoms. Both males and females are equally affected because the disorder is not sex-linked.
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