BIOL 190A Practice Exam 3 Study Notes

BIOL 190A Practice Exam 3 Study Notes

Section 1: Mitosis and Cell Division

1. Mitosis
  • Definition: Mitosis is commonly thought to refer to cellular division but more accurately pertains to nuclear division.
      - True or False: Mitosis is a sexual process.
        - Answer: False (It is a asexual process.)
      - Identical Daughter Cells:
        - True or False: Identical daughter cells are created during mitosis.
          - Answer: Technically false. The daughter cells are genetically identical, but there may be slight variations due to mutations.
      - Cytokinesis: Mitosis is often mistakenly said to include cytokinesis; however, it is a separate process that occurs at the end.
        - True or False: Cytokinesis is part of mitosis.
          - Answer: False. Cytokinesis is a separate phase that follows mitosis.
2. Chromosomal Count in Different Phases
  • At the end of various phases:
      - A. Interphase (comprising G1, S, and G2): 92 chromosomes.
      - B. Entering mitosis: 92 chromosomes.
      - C. During cytokinesis: 46 chromosomes (the cytoplasm divides).
3. Chromosomes Information
  • Sister Chromatids:
      - True or False: Homologous chromosomes are called sister chromatids.
        - Answer: False. Homologous chromosomes are not the same as sister chromatids. Sister chromatids are identical copies of a single chromosome, created during replication.
4. Cancer Cells
  • The ability to evade normal cellular controls is an indicative characteristic of cancer cells.

Section 2: RNA and DNA Structure

5. Unique Bases in RNA
  • Question: Which base is only found in RNA?
      - Options:
        A. A
        B. T
        C. C
        D. G
        E. U (Answer: E)
6. Sugar-Phosphate Backbone Bonds
  • The bonds found in the sugar-phosphate backbone of DNA are covalent, while the bonds between nitrogen bases are hydrogen bonds.
  • Correct Answer: A. Covalent, hydrogen.
7. DNA Directionality
  • Definition: DNA runs in the 5' to 3' direction on one strand, which is counter to the 5' to 3' direction on the complementary strand.
      - The term used to describe this structure is Antiparallel.

Section 3: DNA Replication and RNA Processing

8. Directionality of Replication
  • True or False: Replication must run in the 5' to 3' direction.
      - Reason: This is because DNA polymerase adds nucleotides to the 3' end of the growing DNA strand.
      - Correct option: C. DNA polymerase adds nucleotides to the 3' end.
9. Complementary DNA Strand
  • Given the DNA sequence AACGTCAT, the complementary DNA strand would be TTGCAGTA (Option B).
10. Leading and Lagging Strands
  • Leading and lagging strands differ in the following ways:
      - Correct statement: A. The leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction.
      - The leading strand is synthesized continuously, while the lagging strand is synthesized in short fragments (Okazaki fragments) that are later joined.
11. mRNA Processing
  • mRNA processing includes the removal of introns and the addition of a methyl cap and a poly A tail to protect mRNA from degradation in the cytoplasm.

Section 4: Transcription and Translation

12. Transcription
  • The creation of an RNA molecule from a DNA gene template is referred to as transcription (Answer: B).
13. Translation
  • The process of using messenger RNA (mRNA) as a template for building a protein is known as translation (Answer: B).
  • The site of translation in the cell is the ribosome (Answer: B).
14. Enzymes in DNA Replication
  • Seven enzymes are crucial in DNA replication:
      - DNA Helicase: Unwinds the DNA helix.
      - Single-Stranded Binding Proteins: Bind to unwound DNA strands and prevent them from rejoining.
      - RNA Primase: Synthesizes a short strand of RNA at the 5' end of each DNA strand.
      - DNA Polymerase III: Elongates the newly formed DNA strands by adding nucleotides onto the RNA primer.
      - DNA Polymerase I: Removes the RNA primer and replaces it with DNA, adding to the 3' end.
      - DNA Ligase: Covalently links the 3' end of the DNA that replaces the primer to the rest of the newly formed DNA strand or joins the Okazaki fragments in the lagging strand.
      - Topoisomerase: Relieves strain ahead of the replication fork by placing nicks in the DNA strands and then later rejoins them.
15. Types of RNA
  • Three types of RNA involved in translation:
      - mRNA (messenger RNA): The copy transcribed from DNA.
      - tRNA (transfer RNA): Brings the amino acid to the ribosome for the growing polypeptide.
      - rRNA (ribosomal RNA): Part of the ribosome.
16. Genetic Code
  • The genetic code is described as universal and redundant, meaning:
      - A prokaryotic organism could create the same protein as a eukaryotic organism using the same codons (correct option: A).
17. Ribosome Sites
  • The site in the ribosome where peptide bonds are formed is the P site (Answer: B).
18. Mutations
  • If the codon AAA changes to AAG, and both still code for lysine, this is an example of a silent mutation. (Answer: C).

Conclusion

  • This study guide provides comprehensive coverage of key concepts in mitosis, DNA and RNA structure, DNA replication, transcription, and translation processes essential for understanding molecular biology in the context of BIOL 190A. Review and understand these details thoroughly for exam preparation.