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Punjab (PTB) · Chapter test · Free

2nd Year Biology Chapter 7 TestCHROMOSOME AND DNA

30 marks · 40 minutes · 21 questions. Covers: CHAP 19: CHROMOSOME AND DNA.

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2nd Year Biology Chapter 7 Test

2nd Year · Biology · Punjab (PTB)

Name: ____________Roll No: ________Class/Section: ________Date: ________Total marks: 30Time: 40 minutes

Q1. Multiple choice questions (Attempt all · 10 × 1 = 10)

  1. How many initial bases of the new mRNA strand form a temporary hybrid helix with the template DNA strand?

    1. 5 bases

    2. 12 bases

    3. 20 bases

    4. 35 bases

  2. What is another name for the secondary constriction of a chromosome that helps produce nucleoli?

    1. Nuclear Organizer Region (NOR)

    2. Telomere Region

    3. Centromeric Sequence

    4. Sister Chromatid Core

  3. What are the short, separate pieces of DNA synthesized on the lagging strand called?

    1. Primers

    2. Replicons

    3. Okazaki fragments

    4. Termination sites

  4. What cellular event occurs when nucleotide sequences misalign during homologous chromosome pairing?

    1. A portion of one strand loops out

    2. The transcription bubble freezes permanently

    3. The cell splits into four identical parts

    4. Helicase stops unzipping the double helix

  5. What unexpected result occurred when a mixture of heat-killed S-type and live R-type bacteria was injected?

    1. The mice remained completely healthy

    2. Only heat-killed R-type was found in the blood

    3. The polysaccharide coat dissolved

    4. The mice developed pneumonia and died

  6. What are the non-coding regions of an immature mRNA molecule that must be removed?

    1. Exons

    2. Promoters

    3. Introns

    4. Caps

  7. Which of the following looks like beads on a string?

    1. Chromosomes

    2. Chromatin

    3. Nucleosomes

    4. Heterochromatin

  8. How does ionizing radiation like X-rays and gamma rays cause physical damage to DNA?

    1. By creating temporary RNA primers

    2. By breaking phosphodiester bonds of the DNA strand

    3. By accelerating the speed of DNA Polymerase III

    4. By dissolving the lipid membrane of the nucleus

  9. Which property represents the ability of DNA to be copied with high accuracy?

    1. Variability

    2. Stability

    3. Mutation

    4. Evolution

  10. Phenylketonuria is a genetic metabolic disorder associated with a normal gene present on which chromosome?

    1. Chromosome 11

    2. Chromosome 12

    3. Chromosome 16

    4. Chromosome X

Q2. Short questions (Attempt any 6 of 8 · 6 × 2 = 12)

  1. What is a replication origin site, and how does its quantity differ between prokaryotes and eukaryotes?

  2. Describe the structural dimensions and nucleotide count of DNA in an average human chromosome

  3. What is chromatin fibre? How is it formed during condensation of chromatin?

  4. Define a replicon.

  5. Why did Griffith initially think the S-type bacteria were virulent compared to the R-type?

  6. Explain the molecular structure of daughter DNA strands according to the Dispersive model.

  7. Differentiate between the Conservative and Semi-conservative models of DNA replication.

  8. List the requirements mentioned at the top of the page that a molecule must meet to be considered genetic material.

Q3. Long questions (Attempt any 2 of 3 · 2 × 4 = 8)

  1. DNA Polymerase III is a highly efficient proof-reader that fixes its own mistakes. What happens to a cell if the gene for the "proof-reader" enzyme itself gets a mutation?

  2. After isotopic labelling of the starting DNA with15N, Meselson and Stahl continue their experiment to at least two rounds of replication instead of stopping the experiment after only one round of replication. Justify their decision to continue to at least two replications.

  3. How many types of tRNA molecules are necessary for a living cell, if the genetic code is a triplet code?