dna rep Flashcards
(13 cards)
What is DNA replication, and why is it important? (3 marks)
A:
Definition: Production of exact copies of DNA with identical base sequences.
Purpose: Required for cell reproduction, enabling growth and tissue replacement.
Timing: Occurs during the S phase of interphase before cell division.
Result: Each chromosome consists of two identical sister chromatids post-replication.
: What is semi-conservative replication, and how does it work? (3 marks)
A:
Definition: Each new DNA molecule consists of one original template strand and one newly synthesized strand.
Mechanism:
Nitrogenous bases pair complementarily (A=T, G≡C).
Base sequences are conserved, ensuring accuracy.
What roles do helicase and DNA polymerase play in DNA replication? (4 marks)
A:
Helicase:
Function: Unwinds and separates the DNA double helix.
Mechanism: Breaks hydrogen bonds between base pairs.
DNA Polymerase:
Function: Covalently joins free nucleotides to the template strand.
Mechanism: Synthesizes new strands using condensation polymerization (anabolic process).
What is PCR, and what are its steps? (4 marks)
A:
Definition: Artificial method to amplify DNA sequences.
Steps:
Denaturation: Heat separates DNA strands (95°C).
Annealing: Primers attach to target sequences (55°C).
Elongation: Taq polymerase synthesizes new DNA strands (72°C).
Applications: Produces billions of copies within 30 cycles.
How does gel electrophoresis separate DNA fragments? (3 marks)
A:
Definition: Artificial method to separate DNA fragments by size.
Mechanism:
DNA fragments are placed in agarose gel and subjected to an electrical current.
Larger fragments move slower than smaller ones due to resistance.
Size determination uses reference fragments.
Applications:
DNA profiling.
Assessing fragment lengths post-PCR.
What are three applications of DNA technologies? (5 marks)
A:
DNA Profiling:
Uses short tandem repeats (STRs) for unique banding patterns.
Applications: Forensics, paternity testing.
Gene Cloning:
Process:
DNA and vector (e.g., plasmid) are amplified using PCR.
Cut with restriction enzymes and joined by DNA ligase.
Recombinant plasmid is introduced into a target cell.
Outcome: Creation of genetically modified organisms (e.g., transgenic crops).
Sequencing:
Modified PCR (Sanger method) incorporates chain-terminating nucleotides (ddNTPs).
Stops replication at specific points, revealing base sequence via fragment analysis.
DNA Profiling and STRs
What are STRs, and how are they used in DNA profiling? (3 marks)
A:
STRs: Non-coding DNA sequences with repeat patterns.
Reliability: Analyzing multiple STR loci increases profiling accuracy.
Uses:
Crime scene analysis.
Establishing biological relationships.
