Genetics: Heredity, DNA and Chromosomes

• Genetics studies heredity and variation in organisms
• Explores trait inheritance from parents to offspring
• Includes genes, DNA, and chromosome study

Basic Concepts

• Genes, the basic heredity units, contain protein-building instructions
• Genes consist of DNA
• DNA (deoxyribonucleic acid) carries genetic instructions for organisms/viruses
• DNA has a double helix structure with nucleotide strands
• Nucleotides include a sugar, phosphate group, and a nitrogenous base
• DNA's four nitrogenous bases: adenine (A), guanine (G), cytosine (C), thymine (T)
• RNA (ribonucleic acid) is typically single-stranded, similar to DNA
• In RNA, uracil (U) replaces thymine (T)
• RNA is vital in protein synthesis
• Chromosomes in cells contain DNA
• Humans possess 46 chromosomes in 23 pairs
• Chromosome sets are inherited from each parent
• Alleles are gene versions
• Individuals inherit two alleles per gene, one from each parent
• Genotype: individual's genetic makeup
• Phenotype: observable traits from genotype/environment interaction

Mendelian Genetics

• Gregor Mendel: modern genetics father
• Mendel's pea plant experiments explained inheritance
• Mendel's experiments led to inheritance laws
• Law of Segregation: individuals have two alleles per trait, separating during gamete formation
• Law of Independent Assortment: genes for different traits are inherited independently
• Dominant allele expresses its trait over a recessive allele
• Recessive allele expresses its trait only when paired with another recessive allele
• Homozygous: two identical alleles for a gene (e.g., AA or aa)
• Heterozygous: two different alleles for a gene (e.g., Aa)
• Punnett square predicts offspring genotypes/phenotypes

Molecular Genetics

• Molecular genetics studies gene structure/function
• Explores DNA replication, transcription, and translation processes
• DNA replication copies DNA
• Replication ensures each daughter cell gets complete genetic instructions
• Transcription transcribes DNA into RNA
• RNA polymerase synthesizes RNA complementary to the DNA template during transcription
• Translation translates RNA into protein
• Ribosomes read mRNA sequence and assemble a protein chain during translation
• The genetic code translates genetic material information into proteins
• Each three-nucleotide sequence (codon) specifies an amino acid/stop signal

Gene Expression and Regulation

• Gene expression synthesizes a functional gene product using the information encoded in a gene
• Gene regulation controls when, where, and how much of a gene product is made
• Gene regulation is essential for development, cell differentiation, and adaptation
• Regulatory elements are DNA sequences influencing gene expression
• Transcription factors bind to regulatory elements and modulate transcription rate
• Epigenetics involves changes in gene expression not due to DNA sequence alterations
• Epigenetic modifications include DNA methylation and histone modification
• These modifications alter chromatin structure and affect gene accessibility

Mutations

• A mutation is a DNA sequence change
• Mutations occur spontaneously or via mutagens
• Mutagens increase mutation rate (e.g., radiation, chemicals)
• Point mutations change a single nucleotide
• Point mutation types: substitutions, insertions, deletions
• Frameshift mutations alter mRNA reading frame via insertions/deletions
• Chromosomal mutations change chromosome structure/number
• Mutations' effects range from no effect to harmful/beneficial

Genetic Engineering

• Genetic engineering manipulates an organism's genes
• Recombinant DNA technology creates genetic material combinations
• Restriction enzymes cut DNA at specific sequences
• DNA ligase joins DNA fragments
• Plasmids are vectors that carry genes into cells
• Polymerase chain reaction (PCR) amplifies DNA
• Genetically modified organisms (GMOs) have altered genetic material
• Genetic engineering applies to medicine, agriculture, and industry

Population Genetics

• Population genetics studies populations' genetic composition
• Examines allele/genotype frequencies in a population
• The Hardy-Weinberg principle describes conditions for constant allele/genotype frequencies
• The principle assumes no mutation, no gene flow, random mating, no natural selection, and a large population size
• Deviations from Hardy-Weinberg equilibrium indicate evolutionary forces acting on the population
• Genetic drift randomly fluctuates allele frequencies due to chance events
• Gene flow moves genes between populations
• Natural selection favors organisms with advantageous traits for survival/reproduction

Genomics

• Genomics studies entire genomes
• It involves sequencing, mapping, and analyzing the complete set of DNA in an organism
• Genome sequencing technologies have advanced rapidly
• Bioinformatics analyzes large biological datasets with computational tools
• Comparative genomics compares genomes to understand evolutionary relationships and gene function
• Functional genomics determines gene functions

Applications of Genetics

• Genetic testing diagnoses genetic disorders, assesses disease risk, and predicts drug response
• Gene therapy introduces genes into cells to treat/prevent disease
• Personalized medicine tailors treatment to an individual's genetic makeup
• Forensic genetics uses DNA analysis to identify individuals in criminal investigations
• Plant/animal breeding uses genetic principles to improve crop yields/livestock traits