Genetics: Inheritance Patterns

• Genetics is the study of heredity and variation of inherited characteristics
• Explores how traits are passed from parents to offspring and how these traits vary within and between populations

Inheritance Patterns

• Mendelian inheritance describes the inheritance of traits controlled by single genes with two alleles, one dominant and one recessive
• Mendel's laws include the law of segregation, stating that allele pairs separate during gamete formation
• The law of independent assortment states that alleles of different genes assort independently of one another during gamete formation
• Non-Mendelian inheritance patterns include incomplete dominance, where the heterozygote phenotype is intermediate between the two homozygous phenotypes
• Codominance occurs when both alleles are simultaneously expressed in the heterozygote
• Multiple alleles exist when a gene has more than two alleles in a population
• Sex-linked traits are traits controlled by genes located on sex chromosomes
• Polygenic inheritance involves traits controlled by multiple genes, resulting in a continuous range of phenotypes
• Epigenetics: the study of changes in gene expression that do not involve alterations to the DNA sequence itself
• These changes can be influenced by environmental factors and can be heritable

Gene Expression

• Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product
• Transcription is the process of synthesizing RNA from a DNA template
• Translation is the process of synthesizing a protein from an mRNA template
• The central dogma of molecular biology describes the flow of genetic information from DNA to RNA to protein
• Gene regulation controls the timing, location, and level of gene expression
• Promoters are DNA sequences where RNA polymerase binds to initiate transcription
• Enhancers are DNA sequences that increase the rate of transcription
• Silencers are DNA sequences that decrease the rate of transcription
• Transcription factors are proteins that bind to DNA and regulate transcription
• Small non-coding RNA molecules such as microRNAs (miRNAs) and small interfering RNAs (siRNAs) can regulate gene expression by binding to mRNA and inhibiting translation or promoting mRNA degradation
• Epigenetic modifications, such as DNA methylation and histone modification, can alter gene expression without changing the DNA sequence

Biotechnology Applications

• Biotechnology uses biological systems, living organisms, or derivatives thereof, to make or modify products or processes for specific use
• Genetic engineering involves manipulating an organism's genes
• Recombinant DNA technology combines DNA from different sources
• Polymerase chain reaction (PCR) amplifies specific DNA sequences
• DNA sequencing determines the nucleotide sequence of a DNA molecule
• Gene therapy introduces genes into cells to treat or prevent disease
• Genetically modified organisms (GMOs) have altered genomes through genetic engineering
• CRISPR-Cas9 is a gene editing technology that allows precise modification of DNA
• Applications in medicine include drug development, diagnostics, and personalized medicine
• Applications in agriculture include crop improvement, pest resistance, and increased yield
• Applications in environmental science include bioremediation and pollution control
• Ethical considerations include safety, environmental impact, and social justice

Genetic Mutations

• Genetic mutations are alterations in the DNA sequence
• Mutations can be spontaneous or induced by mutagens
• Point mutations are changes in a single nucleotide base
• Insertions add one or more nucleotide bases to a DNA sequence
• Deletions remove one or more nucleotide bases from a DNA sequence
• Frame-shift mutations alter the reading frame of a gene, leading to a completely different protein sequence
• Mutations in somatic cells are not heritable, while mutations in germ cells (sperm and egg) can be passed on to offspring
• Mutations can be harmful, beneficial, or neutral
• DNA repair mechanisms correct errors in DNA replication and repair DNA damage
• Mutations drive evolution by providing genetic variation that natural selection can act upon
• Mutations can cause genetic disorders and increase the risk of certain diseases

DNA Structure

• DNA (deoxyribonucleic acid) is the molecule that carries genetic information
• DNA is a double helix composed of two strands of nucleotides
• Nucleotides consist of a deoxyribose sugar, a phosphate group, and a nitrogenous base
• The four nitrogenous bases in DNA are adenine (A), guanine (G), cytosine (C), and thymine (T)
• Adenine pairs with thymine (A-T), and guanine pairs with cytosine (G-C) through hydrogen bonds
• The two DNA strands are antiparallel, meaning they run in opposite directions (5' to 3' and 3' to 5')
• The 5' end of a DNA strand has a phosphate group, while the 3' end has a hydroxyl group
• The sequence of bases in DNA encodes genetic information
• DNA is organized into chromosomes, which are structures that carry genes
• The human genome consists of approximately 3 billion base pairs and 20,000-25,000 genes