Human Evolution Study Guide 1Scientific Method1. Observation2. Question3. Hypothesis4. Gather Data5. Analyze Data6. More HypothesisTheory in Science- Model for understanding natural phenomenon- Collection of concepts- Formal logic- Conforms to all available dataTheory in Evolution- 150 years of observations- Natural Selection Theoryo Individuals uniqueo Traits passed to offspringo Desirable traits more prevalent over timeFitness: ability to reproduce as measured by surviving offspringAdaptation: result of natural selection, neither permanent nor permanentFour Forces of Evolution:1. Mutationa. Only source of variation in individualsb. Many aren’t useful2. Migration/ Gene Flowa. New traits to different areas3. Genetic Drifta. Original Population Bottlenecking Event (Catastrophic) Surviving Population4. Natural SelectionDNA- Nucleotide baseo Sugar, Phosphate, Base o Adenine + Thymine, Cytosine + Guanine (sequence = Genes)- Double helix structure- Locus: location of genes on DNA- 23 pairs of chromosomes in nucleus (humans)Cell Division- Begin with DNA replication- Interphase: DNA replicating in nucleus, centrioles separate- Prophase: nuclear membrane breaks down, chromosomes condense, mitoticspindle begins to form- Metaphase: chromosomes align, mitotic spindle develops- Anaphase: chromosomes separate- Telophase: new nuclear membrane, cells pinch (cytokinesis), new daughter cells formed (mitosis – identical, meiosis- have half of genes)- Mitosiso Somatic (body cells) over lifespan (starts at fertilization)o One parent cell produces two identical daughter cellso Rate of division depends on where cell is locatedo Diploid cells produced (double copies of chromosomes – one from each parent- 23 pairs)- Meiosiso Sex cellso Females – begins in utero with chromosomes lining up, freeze until puberty, continues if egg is fertilized, stops with menopauseo Males – begins at puberty with no stopping pointo 4 Haploid cells produced (one copy of chromosome- 23 chromatids (singles))o 2 phases of division Prophase I - crossing over  Metaphase I – homologous chromosomes side-by-side, genetic recombination – chiasma (cross) formed, centromeres do no divide Anaphase I – sister chromosomes stay together Metaphase II – chromosomes end-to-end  Anaphase II – centromeres divide Telophase II – 4 haploid daughter cells- Gametogenesis- Oogenesis –egg cellso 3 polar bodies, 1 egg o 1 has enough cytoplasm to support lifeo 2 million eggs- Spermatogenesiso 4 sperm cellso 74 days to produceCentral DogmaDNAtranscription RNA translation ProteinRNA- mRNA (messenger) smaller than DNA- carries genetic code from nucleus to ribosome in cytoplasm- Uracil replaces Thymine- Codons: group of three bases, codes for amino acidso Start codon is AUG, methionineo 20 amino acids, 64 possibleGenetics- Genes made up of two alleles (one from each parent), codes for a traitLaw of Segregation: pairs of alleles separate during meiosis so that each gamete receives only one copy of a geneLaw of Independent Assortment: segregation of the alleles of one pair is independent of the segregation of the alleles of another pair- Punnett squares- Pedigreeso Diagram showing relationships to trace hereditary pattern of a particular traito Squares = male, circle = femaleo Autosomal traits equal Dominant (RR, Rr), recessive (rr), co-dominant (RS)o Sex-linked have gender bias Males are hemizygous (one X) Most likely to be expressed in males Females often