Lesson 2 - Molecular Genetics

Lesson 2: Molecular Genetics - Q&A

1. Define Molecular Genetics:
It is a branch of biology that focuses on the structure and function of genes at the molecular level, studying how genes replicate, express, and mutate.
2. Define a nucleotide and list its components:
A nucleotide is the basic unit of nucleic acids. It consists of a nitrogenous base, a pentose sugar, and a phosphate group.
3. Define semiconservative replication:
It is a type of DNA replication where each new DNA strand contains one original strand and one newly synthesized complementary strand.
4. What is a codon?
A codon is a sequence of three RNA bases in mRNA that codes for a specific amino acid during translation.
5. Define genetic mutation:
A mutation is a permanent change in the DNA sequence, which may affect the gene's function and can be beneficial, harmful, or neutral.
6. What evidence shows that genes are made of DNA?
In 1944, Avery and colleagues proved through bacterial transformation experiments that DNA is the hereditary material, not protein.
7. List the revisions of the "One Gene-One Enzyme" hypothesis:
- Some enzymes are made of multiple polypeptides encoded by different genes.
- Some genes code for non-enzymatic proteins.
- Some genes do not code for any proteins.
8. List the main functions of genes:
- Accurate replication.
- Directing RNA and protein production.
- Accumulating mutations for evolution.
9. List types of genetic mutations:
- Base substitution.
- Base deletion.
- Base insertion.
- Large-scale mutations that may inactivate the gene.
10. How does a defective gene affect protein production?
A defective gene may lead to an abnormal or missing protein, which can disrupt the function of the cell.
11. Explain the Watson and Crick double helix model:
DNA is composed of two strands twisted into a double helix. The nitrogenous bases pair via hydrogen bonds: A with T, and G with C.
12. Describe transcription and translation:
Transcription: The process where DNA is copied into RNA inside the nucleus.
Translation: The process where mRNA is decoded by ribosomes in the cytoplasm to form a protein.
13. Explain the relationship between mutations and evolution:
Mutations create genetic variation. If a mutation is beneficial, it can be passed on, contributing to evolutionary change.
14. What is the difference between small and large mutations?
Small mutations may change one base or amino acid, while large mutations can remove or insert large DNA segments, possibly inactivating the gene.
15. Compare transcription and translation:
Feature Transcription Translation
Location Nucleus (in eukaryotes) Cytoplasm
Main Enzyme or Machinery RNA Polymerase Ribosome and tRNA
Starting Material DNA mRNA
Product RNA (usually mRNA) Polypeptide (Protein)
Purpose Copy genetic code into RNA Build proteins based on mRNA code
16. Compare a normal gene and a defective gene:
Gene Type Description
Normal Gene Produces a functional protein that performs its expected role in the cell. It contributes to normal development and metabolism.
Defective Gene May produce a nonfunctional or harmful protein, or fail to produce a protein altogether. This can lead to diseases or disorders.