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Biological Molecules

• Enzymes: Biocatalysts that speed up biochemical reactions
• Haemoglobin: Transports oxygen
• Hormones: Chemical messengers that coordinate cell activity
• Antibodies: Immunity; fights pathogens for immunity
• Collagen: Muscle fiber that strengthens muscles; important for growth and repair

Genetic Variation

• Genetic similarities and differences can be compared within and between species
• Within a population (intraspecific): similarities show common ancestry, differences show genetic diversity
• Between populations (interspecific): similarities show evolutionary relationships, differences show species diversity

Sources of Variation

• Genome: The complete set of genes in a species
• Gene pool: The complete set of alleles (gene variations) in a species
• Genetic diversity: The total of all genetic characteristics in a species
• Sources of genetic variation:
  • Crossing over: Homologous chromosomes exchange genes, creating new combinations of alleles
  • Independent assortment: Homologous chromosomes arrange themselves and separate independently, leading to random allele combinations
  • Random fertilization: Non-identical male and female gametes fuse to create an offspring with a unique combination of alleles
  • Mutations: Produce new alleles to increase genetic variation
• Meiosis + Fertilization + Mutations = Recombination of genes → Genetic variation → Favourable adaptations → Natural selection → Reproductive maturity of fittest organisms → Inheritance of favourable variations → Genetic isolation → Speciation (new species) → Diversity

Gene Pool and Genotype

• Gene pool: Each gene has different variations or alleles; a collection of all alleles in a population
• Genotype: Every individual inherits 2 alleles per trait; each pair of alleles is a genotype
• Phenotype: Each genotype codes for 1 trait; the phenotypic expression of each genotype (or pair of alleles)

Single Nucleotide Polymorphism (SNPs)

• A nucleotide alteration that occurs in more than 1% of a population
• Most SNPs occur in non-coding regions of DNA
• SNPs can be used as:
  • Indicators of disease susceptibility
  • Determining genetic relatedness
  • Establishing evolutionary relatedness

Inheritance Patterns in a Population

• Population genetic patterns can be predicted with accuracy using DNA analysis and genetic technology
• Technologies used to determine inheritance patterns:
  • The Human Genome Project
  • Polymerase chain reaction (PCR)
  • DNA sequencing (Sanger method)
• Autosomal dominant and recessive inheritance patterns
• X-linked dominant and recessive inheritance patterns

Population Genetics

• The study of frequency of traits/characteristics in a population
• Changes in frequency → Change to population → Genetic variation → Evolution
• Studying population genetics allows us to:
  • Predict the survival of a species through genetic variation
  • Conservation management
  • Predict the inheritance of diseases and disorders in a population
  • Trace evolution

Mechanisms of Inheritance

• Chromosomes:
  • Autosomes: contain genes responsible for body traits (1-22nd pairs in humans)
  • Sex-chromosomes: contain genes for gender and secondary sexual characteristics (23rd pair in humans)
• Mutations:
  • Occur in both somatic and germline cells
  • Mutations in somatic cells → expression in individual → no inheritance
  • Mutations in germline cells → not expressed in individual → gametes → inheritance → expressed in offspring
• Autosomal inheritance:
  • Inheritance on germline cells where the genes inherited are on the 1st - 22nd pairs of chromosomes
  • Inheritance of body characteristics

Mathematical Model for Frequency

• 𝑁𝑜 𝑜𝑓 𝑡ℎ𝑎𝑡 𝑎𝑙𝑙𝑒𝑙𝑒/ 𝑔𝑒𝑛𝑜𝑡𝑦𝑝𝑒/ 𝑝ℎ𝑒𝑛𝑜𝑡𝑦𝑝𝑒 = 𝑇𝑜𝑡𝑎𝑙 𝑛𝑜.𝑜𝑓 𝑎𝑙𝑙𝑒𝑙𝑒𝑠/ 𝑔𝑒𝑛𝑜𝑡𝑦𝑝𝑒𝑠/ 𝑝ℎ𝑒𝑛𝑜𝑡𝑦𝑝𝑒𝑠