Genetics and Biotechnology Quiz

Grade 12 · Science · Quiz

Assess your understanding of inheritance patterns, molecular genetics, and modern biotechnological applications.

Questions

1. Which base pairs with adenine in DNA?

   1. Guanine
   2. Cytosine
   3. Uracil
   4. Thymine
   Show answer

   Answer: Thymine

   In DNA, adenine (A) pairs with thymine (T) via two hydrogen bonds; guanine pairs with cytosine. In RNA, uracil replaces thymine.

2. A woman who is a carrier for an X-linked recessive disorder and a normal man have children. What is the probability that their son will be affected?

   1. 0%
   2. 25%
   3. 50%
   4. 100%
   Show answer

   Answer: 50%

   Sons inherit their X chromosome from their mother. A carrier mother has a 50% chance of passing the affected X, so 50% of sons will be affected.

3. What does a restriction enzyme recognize and cut?

   1. Any single-stranded RNA sequence
   2. Specific short palindromic DNA sequences
   3. The promoter region of a gene
   4. Telomeric DNA repeats
   Show answer

   Answer: Specific short palindromic DNA sequences

   Restriction enzymes are endonucleases that recognize specific palindromic sequences (typically 4-8 bp) and cut both DNA strands, creating sticky or blunt ends.

4. Which of the following best describes gene therapy?

   1. Replacing damaged tissues using stem cells
   2. Introducing functional genes into cells to correct genetic defects
   3. Cloning an organism from somatic cells
   4. Sequencing an entire genome
   Show answer

   Answer: Introducing functional genes into cells to correct genetic defects

   Gene therapy involves delivering a correct copy of a defective gene into a patient's cells, often using viral vectors, to restore normal protein function.

5. During which stage of meiosis does crossing over (recombination) primarily occur?

   1. Metaphase I
   2. Anaphase II
   3. Prophase I
   4. Telophase II
   Show answer

   Answer: Prophase I

   Crossing over occurs during Prophase I when homologous chromosomes are paired as bivalents; non-sister chromatids exchange segments at chiasmata.

6. What is the function of a promoter sequence in transcription?

   1. It codes for the start amino acid methionine
   2. It signals the ribosome to begin translation
   3. It is the DNA sequence where RNA polymerase binds to initiate transcription
   4. It marks the end of a gene
   Show answer

   Answer: It is the DNA sequence where RNA polymerase binds to initiate transcription

   The promoter is a regulatory DNA region upstream of a gene where RNA polymerase and transcription factors bind to initiate transcription.

7. CRISPR-Cas9 can be used to both delete and insert specific DNA sequences in a genome.

   Show answer

   Answer: True

   CRISPR-Cas9 creates double-strand breaks; the cell's repair machinery can then introduce deletions (via NHEJ) or precise insertions (via HDR with a template).

8. The physical expression of an organism's genetic makeup is called its _____.

   Show answer

   Answer: phenotype

   The phenotype is the observable characteristics resulting from the interaction of genotype and environment; genotype is the underlying allele combination.

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