Untitled Notes

Definition: DNA replication is the process of producing two identical copies of DNA from one original DNA molecule.
Historical Note: In their paper describing the structure of DNA (1953), Watson and Crick noted that specific complementary base pairing suggests a copying mechanism.

After DNA replication, daughter strands have an identical nitrogenous base sequence as the parent strand, ensuring genetic stability across generations.
Because of complementary base pairing, each single strand contains the information necessary to reconstruct its partner strand (e.g., if one strand has AGGCTA, the complementary strand must be TCCGAT).

Semi-Conservative Nature: The new daughter DNA molecule consists of one original strand and one newly synthesized strand.

Cell Division: Essential for mitosis and meiosis, before cell division, DNA must double to ensure each daughter cell has a full set of genetic instructions.
Growth and Tissue Repair: Necessary for multicellular organisms to grow and repair tissue by increasing cell numbers, requiring genomic copies for each new cell.
Reproduction: Ensures faithful transmission of genetic information through sexual or asexual reproduction.

Each single strand contains information for reconstructing its partner strand; for new bases to be added to the daughter strand, they must fit the exposed nitrogenous bases of the parent strand:
- Adenine (A) & Thymine (T): Form hydrogen bonds due to their chemical groups positioned compatibly in two places.
- Cytosine (C) & Guanine (G): Form hydrogen bonds in three compatible positions. Mis-pairing (e.g., C with A) will lead to repelling charges preventing stable connections.

Process: DNA double helix must unwind and unzip—parent DNA separates into complementary strands to act as templates for replication.

Function: Breaks hydrogen bonds between base pairs, unwinding the double helix; it's an enzyme that requires energy from ATP hydrolysis for its action.

After unwinding, DNA polymerase catalyzes synthesis of complementary daughter strands:
- Moves along the template strand, adding correct free nucleotides based on complementary base pairing.
- Catalyzes condensation reactions creating covalent bonds forming the DNA backbone.
Separate DNA polymerase molecules work on each strand simultaneously:
- Leading Strand: Follows helicase, moves towards the replication fork.
- Lagging Strand: Works in the opposite direction (away from the replication fork).

Function: PCR amplifies specific DNA sequences, creating millions of copies from just a few original molecules. This technique is crucial in molecular biology for analysis and sequencing.

Denaturation (94-96°C): Heats double-stranded DNA to separate strands by breaking hydrogen bonds.
Annealing (50-65°C): Short DNA primers bind to complementary sequences on each strand, marking amplification start and end points.
Extension (72°C): Taq polymerase synthesizes new DNA strands by adding nucleotides to primers, creating complete target copies.

Definition: A technique used to separate DNA fragments based on size and charge.
Procedure: Prepare agarose gel by mixing agarose powder in buffer, heating, and solidifying. Pipette DNA samples with loading dye into wells.
Mechanism: On applying an electric current, DNA fragments migrate towards the positive electrode due to the negative charge of DNA. Smaller fragments travel faster and farther than larger ones.

DNA profiling for paternity and forensic investigations.
DNA Profiling: A technique creating unique patterns based on analyzing variable noncoding regions (Short Tandem Repeats - STRs).
- Steps include isolating DNA, PCR amplification, cutting DNA with restriction enzymes, and separating with gel electrophoresis.

Identifying genetic relationships (ancestry, forensic investigations, mass disaster victims, wildlife conservation, archaeological studies, medical diagnostics, food safety testing, research applications).

STRs are sequences of 2-6 repeated base pairs, showing variation among individuals.
Inheritance leads to unique combinations of STR alleles.
Analysis is crucial in paternity testing where shared alleles must match between a child and parents.

Comparing multiple STRs increases the confidence in DNA profiling, reducing random match chances. Analyzing multiple markers results in a highly specific profile.

Initiation: RNA polymerase binds to promoter, DNA strands separate.
Elongation: RNA polymerase moves along template strand, linking nucleotides to form mRNA.
Termination: mRNA is released, and DNA reforms.

Mutations: Changes in DNA that can lead to genetic variation, evolution, or disorders.
Types of Mutations:
- Point Mutations: Changes in a single nucleotide, including substitutions, insertions, deletions, causing frameshift mutations.
- Consequences of Mutations: Silent, missense, nonsense; can vary in severity from benign to serious impacts on function.

Caused by a single point mutation leading to the production of abnormal hemoglobin.
Provides advantages in malaria prevalence regions as it confers resistance.

Types: Mitosis (asexual) produces identical daughter cells, meiosis generates gametes (sex cells) featuring genetic diversity.

Two major divisions reducing chromosome number from diploid to haploid, facilitating genetic diversity through crossing over and independent assortment.

Mendelian Genetics: Explored traits via controlled breeding experiments (e.g. pea plants). Dominant and recessive traits, genotypes, phenotypes detailed.
Punnett Squares visualize inheritance patterns and probabilities of offspring genotypes.
Pedigree Charts used to predict inheritance patterns of genetic disorders in families.

Key examples include recessive disorders like cystic fibrosis and dominant disorders such as Huntington's disease, which can affect health and development.