GeneticsGenetics

Core principles governing how traits are transmitted from parents to offspring, formulated using Pisum sativum.

• Law of Segregation: Also known as Mendel's First Law; states that allele pairs separate during gamete formation and randomly unite at fertilization.
• Law of Independent Assortment: Mendel's Second Law; states that allele pairs separate independently during the formation of gametes, applying primarily to genes on different chromosomes.
• Monohybrid and Dihybrid Crosses: Monohybrid cross yields a phenotypic ratio of 3:1 and genotypic ratio of 1:2:1 in F2 generation; Dihybrid cross yields a phenotypic ratio of 9:3:3:1.
• Test Cross: A cross between an organism with an unknown genotype and a homozygous recessive parent to determine if the organism is homozygous or heterozygous.

Detailed study of nucleic acids, genetic code, transcription, translation, and replication mechanisms.

• DNA Structure: Deoxyribonucleic acid is a double-stranded helix where purines (Adenine, Guanine) pair with pyrimidines (Thymine, Cytosine) via hydrogen bonds (A=T, G≡C).
• Central Dogma of Molecular Biology: Proposed by Francis Crick, it describes the directional flow of genetic information: DNA -> mRNA -> Protein (with reverse transcription as an exception in retroviruses).
• Genetic Code Characteristics: The code is triplet, universal, degenerate (multiple codons for one amino acid), non-overlapping, and comma-less. AUG acts as the start codon (Methionine).
• Types of RNA: mRNA carries genetic message from DNA; tRNA brings specific amino acids during translation; rRNA forms the structural core of ribosomes.

Pathological conditions arising from mutations in single genes or numerical/structural changes in chromosomes.

• Down Syndrome (Trisomy 21): Caused by an extra copy of chromosome 21; characterized by intellectual disability, epicanthic folds, and a flattened facial profile.
• Turner Syndrome (45, X0): A monosomy condition in females where one X chromosome is missing, leading to short stature, webbed neck, and sterility.
• Klinefelter Syndrome (47, XXY): Affects males with an extra X chromosome; characterized by gynecomastia, small testes, and reduced fertility.
• Hemophilia and Color Blindness: X-linked recessive disorders where Hemophilia impairs blood clotting and color blindness affects red-green color differentiation.

Advanced techniques involving recombinant DNA technology, gene cloning, PCR, and transgenic organisms.

• Polymerase Chain Reaction (PCR): Invented by Kary Mullis; used to amplify a single or few copies of a piece of DNA across several orders of magnitude, generating millions of copies.
• Restriction Endonucleases: Known as 'molecular scissors', these enzymes cut DNA molecules at specific palindromic nucleotide sequences.
• Recombinant DNA Technology: Involves joining together DNA strands ('molecular cloning') to create useful biological products, pioneered by Boyer and Cohen in 1973.
• CRISPR-Cas9: A revolutionary gene-editing tool derived from bacterial defense systems, allowing precise addition, removal, or alteration of genetic material.