DNA Replication and Recombinant DNA

Study Notes

DNA Replication

Purpose: DNA replication creates identical copies of DNA molecules for cell division.
Site: Replication occurs in the nucleus.
Semi-conservative Replication: The new DNA molecule consists of one original strand and one newly synthesized strand.
Steps:
- Unzipping (DNA Helicase): Enzymes (DNA helicase) unwind and separate the DNA double helix, creating replication forks.
- Complementary Base Pairing (DNA Polymerase): Free-floating nucleotides align with their complementary bases on each separated strand. DNA polymerase adds these nucleotides to the new strand.
- Joining (DNA Ligase): DNA ligase seals the gaps between short DNA segments (Okazaki fragments) - important for completing the newly synthesized strand.

Recombinant DNA

Definition: Recombinant DNA is DNA that has been artificially created, combining DNA from different sources.
Enzymes Involved: Specific enzymes are used to cut and paste DNA.
Uses:
- Producing pharmaceuticals.
- Gene Therapy.
- Enhancing crop production.

Protein Synthesis

Process Overview: The sequence of DNA dictates the sequence of amino acids in proteins. This process occurs in two main steps: transcription and translation.
Transcription: Creates a messenger RNA (mRNA) copy of a DNA gene sequence.
Translation: mRNA is used to produce a polypeptide chain (protein) in the ribosome.
Key Players:
- DNA: Stores the genetic code.
- mRNA: Carries the genetic message from DNA to the ribosome.
- tRNA: Carries amino acids to the ribosome.
- Ribosomes: The protein synthesis machine in the cell.
Steps (General):
- Initiation: Starts the process.
- Elongation: Amino acids are added to the growing chain.
- Termination: Stops the process.

Mutations in DNA

Effects: Mutations in DNA change the DNA sequence, which can change the amino acid sequence of a protein, leading to genetic disorders.
Environmental Mutagens: Examples include certain chemicals and radiation.
Example: Sickle cell anemia is a genetic disorder caused by a mutation in the DNA sequence, which changes a single amino acid.
Codon/Anticodon: mRNA codons (3-base sequences) specify amino acids. tRNA anticodons (complementary to codons) bring the corresponding amino acids to the ribosome.
Genetic Code: The relationship between DNA/mRNA codons and the amino acids they code for.
- The genetic code is degenerate meaning that some amino acids can be coded for by more than one codon.
- The genetic code is universal meaning that it's the same in most organisms.

Description

This quiz covers the fundamental processes of DNA replication and the concept of recombinant DNA. You will explore the steps involved in DNA replication, including the roles of various enzymes, as well as the definition and significance of recombinant DNA. Test your understanding of these key biological concepts essential for cell division and genetic engineering.