Cell Structure & Genetics Principles

Genetics: Study of heredity and variation in traits through generations.
Inheritance: Transmission of genetic traits from parents to offspring, driving evolution.
DNA: Genetic code, identical in plants and animals, double helix structure, composed of nitrogenous bases.
Gene: Segment of DNA, contains instructions for protein synthesis.
Chromosome: Coiled DNA, carrying genetic information for specific traits, varying numbers per species.
Locus: Position of a gene on a chromosome.
Centromere: Region of chromosome where sister chromatids attach; divides chromosome into two "arms".
Sister Chromatids: Identical copies of each chromosome.

Asexual Reproduction: Identical offspring from a single parent, fast, simple.
- Mitosis: Cell division in all somatic cells, produces two identical cells.
  - Interphase: Cell growth and DNA replication phases
  - Prophase: Chromosomes condense, nuclear envelope breaks down
  - Metaphase: Chromosomes align at the cell's center.
  - Anaphase: Sister chromatids separate.
  - Telophase: Chromosomes decondense, nuclear envelopes reform.
  - Cytokinesis: Cytoplasm divides, forming two cells.
- Binary Fission: Simple division in prokaryotes via cell splitting.
- Spores: Single cells produced by specific cells (spore mother cells).
- Budding/Fragmentation: New organisms develop from the body of the parent.
- Cloning: Production of a genetically identical copy of an organism.
Sexual Reproduction: Combining genetic material from two parents via gametes (sex cells).
- Meiosis: Cell division producing gamete cells (haploid) from diploid cells.
  - Meiosis I: Reduces chromosome number to half, homologous chromosomes separate.
  - Meiosis II: Sister chromatids separate to create four haploid cells.
Gamete Formation:
- Spermatogenesis (male): Four sperm produced from one diploid cell
- Oogenesis (female): One egg and three polar bodies from one diploid cell.

Sex: Biological characteristics that differentiate male and female.
Gender: Cultural and societal roles associated with biological sex.
Genotype: Genetic makeup (allele combinations).
Phenotype: Observable traits determined by genotype.
Karyotype: Visual representation of an organism's chromosomes.
Homologous Chromosomes: Chromosomes with same genetic information.
Autosomes: Non-sex chromosomes.
Sex Chromosomes: Chromosomes that determine sex.
Diploid: Two copies of each chromosome (2n).
Haploid: One copy of each chromosome (n).
Polyploid: Multiple sets of chromosomes (more than 2n)
Sex Determination:
- Mammals (XX-XY system)
- Birds (ZW-ZZ system)
- Reptiles (Temperature-dependent)
- Fish (Age or Social structure dependent)
- Insects (Dependent on fertilization)
- Earthworms (Hermaphroditic)

Gregor Mendel: Developed laws of inheritance through experiments on pea plants..
Monohybrid Crosses: Crosses involving one trait.
Law of Segregation: Alleles separate during gamete formation.
Alleles: Different forms of a gene.
Dominance: Dominant allele masks the recessive allele's expression.
Homozygous: Having identical alleles.
Heterozygous: Having different alleles for a trait.
Incomplete Dominance: Phenotype is blend of both alleles.
Codominance: Both alleles are expressed fully.
Multiple Alleles: More than two alleles for a gene.
Polygenic Inheritance: Multiple genes control a single trait.
Dihybrid Crosses: Crosses of two traits simultaneously (F2 Generation)
Law of Independent Assortment: Alleles of unlinked genes separate independently during gamete formation.

Miescher: Isolated DNA, calling it “nuclein.”
Levene: Proposed basic structure of nucleotides (sugar, phosphate, base).
Hammerling: Experiments suggesting nucleus contains genetic information.
Chargaff: Discovered base-pairing rules (A=T, G=C).
Avery, MacLeod, McCarty: DNA, not protein, is the “transforming principle” in heredity.
Hershey-Chase: Further evidence of DNA as the hereditary material.
Franklin: X-ray diffraction images crucial for Watson and Crick.
Watson and Crick: Determined the DNA double helix structure.

Mutation: Change in DNA sequence.
- Spontaneous: Occur naturally during DNA replication.
- Induced: Caused by environmental factors.
- Point: Substitution of one base for another.
- Basepair: A single nucleotide pair is exchanged.
- Frameshift: Insertion or deletion of a nucleotide (can alter the entire protein sequence).
- Chromosomal: Changes to whole sections of chromosomes (inversions, translocations, deletions, duplications).
- Jumping genes (transposons): Segments of DNA that can move around the genome.

Human Genome Project: Project to map and sequence the human genome.
Epigenetics: Study of heritable changes in gene expression without changing the DNA sequence.