- Which of the following techniques is used to separate DNA fragments based on size?
a) PCR (Polymerase Chain Reaction)
b) Gel electrophoresis
c) DNA sequencing
d) Cloning
Answer: (b) Gel electrophoresis
Explanation: Gel electrophoresis is a technique used to separate DNA fragments based on size. DNA fragments are placed in a gel and subjected to an electric field, which causes them to move. Smaller fragments move faster through the gel, allowing separation by size. PCR amplifies DNA, DNA sequencing determines the nucleotide order, and cloning produces copies of DNA.
- Which enzyme is responsible for sealing the gaps between Okazaki fragments during DNA replication?
a) Helicase
b) DNA polymerase
c) Primase
d) DNA ligase
Answer: (d) DNA ligase
Explanation: DNA ligase is the enzyme responsible for sealing the gaps between Okazaki fragments on the lagging strand during DNA replication. It forms covalent bonds between adjacent nucleotides to create a continuous strand of DNA. Helicase unwinds the DNA, primase synthesizes RNA primers, and DNA polymerase adds nucleotides to the growing DNA chain.
- Which of the following statements about genetic drift is true?
a) It results from natural selection
b) It has a larger effect in small populations
c) It increases genetic variation within populations
d) It only occurs in large populations
Answer: (b) It has a larger effect in small populations
Explanation: Genetic drift is a random change in allele frequencies in a population, and it has a greater effect in small populations because chance events can significantly alter the gene pool. Unlike natural selection, genetic drift does not necessarily lead to adaptation and can reduce genetic variation within populations over time.
- Which of the following phenomena results in the movement of alleles between populations?
a) Genetic drift
b) Gene flow
c) Natural selection
d) Mutation
Answer: (b) Gene flow
Explanation: Gene flow is the movement of alleles between populations, often due to migration. It can introduce new alleles into a population, increasing genetic diversity. Genetic drift is a random change in allele frequencies, natural selection favors beneficial traits, and mutation introduces new genetic variations.
- Which of the following disorders is caused by nondisjunction during meiosis?
a) Sickle cell anemia
b) Hemophilia
c) Down syndrome
d) Cystic fibrosis
Answer: (c) Down syndrome
Explanation: Down syndrome is caused by nondisjunction during meiosis, which results in an extra copy of chromosome 21 (trisomy 21). Nondisjunction occurs when chromosomes fail to separate properly during meiosis, leading to gametes with abnormal numbers of chromosomes. Sickle cell anemia, hemophilia, and cystic fibrosis are caused by specific gene mutations.
- Which of the following statements about the human genome is correct?
a) Humans have about 10,000 genes
b) The majority of the genome consists of protein-coding genes
c) Humans have 23 pairs of chromosomes
d) The Y chromosome is larger than the X chromosome
Answer: (c) Humans have 23 pairs of chromosomes
Explanation: Humans have 23 pairs of chromosomes, for a total of 46. The human genome contains about 20,000 to 25,000 genes, and the majority of the genome consists of non-coding DNA rather than protein-coding genes. The Y chromosome is smaller than the X chromosome.
- Which of the following describes the inheritance pattern of mitochondrial DNA?
a) Paternal inheritance
b) Maternal inheritance
c) Autosomal inheritance
d) X-linked inheritance
Answer: (b) Maternal inheritance
Explanation: Mitochondrial DNA is inherited exclusively from the mother because mitochondria are passed down through the egg cell. This type of inheritance is known as maternal inheritance. Paternal inheritance refers to traits passed down through the father, and autosomal and X-linked inheritance refer to nuclear genes.
- What is the main function of tRNA during translation?
a) Carries amino acids to the ribosome
b) Catalyzes the formation of peptide bonds
c) Synthesizes mRNA from a DNA template
d) Protects mRNA from degradation
Answer: (a) Carries amino acids to the ribosome
Explanation: Transfer RNA (tRNA) is responsible for carrying amino acids to the ribosome during translation. Each tRNA molecule has an anticodon that pairs with a specific codon on the mRNA, ensuring that the correct amino acid is added to the growing polypeptide chain. Ribosomes catalyze the formation of peptide bonds.
- Which of the following types of RNA is involved in splicing introns from pre-mRNA?
a) tRNA
b) mRNA
c) rRNA
d) snRNA
Answer: (d) snRNA
Explanation: Small nuclear RNA (snRNA) is involved in splicing introns from pre-mRNA during the process of RNA processing. This occurs in the spliceosome, where snRNA helps recognize the splice sites and remove introns. tRNA is involved in translation, mRNA carries genetic information, and rRNA forms part of the ribosome.
- Which of the following techniques is used to amplify a specific segment of DNA?
a) Gel electrophoresis
b) PCR (Polymerase Chain Reaction)
c) DNA sequencing
d) Restriction enzyme digestion
Answer: (b) PCR (Polymerase Chain Reaction)
Explanation: PCR is a technique used to amplify a specific segment of DNA, producing millions of copies of the target sequence. It involves repeated cycles of heating and cooling to denature the DNA, anneal primers, and extend the DNA with the help of DNA polymerase. Gel electrophoresis separates DNA fragments, DNA sequencing determines the sequence, and restriction enzymes cut DNA
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