BIO 200 Exam 2 Review

1. BIO 200 Exam 2 Review May the curve be ever in your favor

2. Evidence from Genetics – Mendel • Mendel – pea experiments • Blending inheritance – NO • Particulate inheritance – YES • 3:1 phenotype ratio for monohybrid cross • 9:3:3:1 phenotype ratio for dihybrid cross • Legacy • Particle Theory of Inheritance • Law of Segregation • Law of Independent Assortment

3. Evidence from Genetics – After Mendel • Most traits are polygenic • Some genes are pleiotropic • Genes arranged in linear array on chromosomes • We see chromosomes when stained before cell division • Polyploidy possible, often in plants • Genes on same chromosome are linked • Distribution of chromosomes and crossover between sister chromosomes during meiosis lead to genetic recombination

4. Evidence from Biochemistry • DNA • Double stranded, Purines – A+G, Pyrimidines – C+T • Held together by hydrogen bonds • Know DNA replication concept • Repairs – proofreading, mismatch repair, excision repair • Know central dogma • Hox genes are super important

5. Mutations/Molecular Clocks • Types of mutations • Structural changes – loss/duplication of whole genes, changes in gene arrangement • Numerical changes in chromosomes • Point mutations • Protein chain length modifiers • Homeotic Genes • Regulate/control clusters of genes • Similar sequences in all multicellular organisms • Causes/Effects of Mutation • When do mutations affect evolution?

6. Acquired Characteristics/Epigenetics • Epigenetics • Changes in expression of genes without changing DNA sequence • Adding methyl groups to cytosine – inactivates gene, heritable • Histone modification of chromatin • Environmentally-induced

7. Population Genetics • H-W Equilibrium – p2+2pq+q2=1 and p+q=1 • No mutation • No selection • No gene flow • Infinite population size • Random mating • THIS DOESN’T OCCUR IN REAL LIFE – this is just a standard against which we compare to show that evolution is occurring

8. Selection • Stabilizing vs. directional vs. disruptive • Microevolution – short term changes in allele frequencies within populations • Macroevolution – long-term patterns/changes • Environment chooses whether or not trait is favored

9. Interspecies Relationships • Types of interactions – predator/prey, parasite/host, mutualism, competition, commensalism, ammensalism • Coevolution – “evolutionary arms race” • Defense to avoid predation – camouflage, chemical repellants, types of mimicry • Competition – intraspecific • Caused by limited resources, results in reduced growth and reproduction rates • Competition – interspecific • Usually fighting over some sort of resource – can be alleviated via resource partitioning

10. Speciation • Species definitions – morphological, reproductive (biological), lineage • Barriers and gene flow • Allopatric speciation – physical barrier • Sympatric speciation – no physical isolation, but speciation anyway • Reproductive Isolation • Prezygotic – mechanical, temporal, behavioral, habitat, gametic • Postzygotic – low hybrid zygote viability, low hybrid adult viability, hybrid infertility • Adaptive radiation – rapid speciation from a common ancestor; each new species specialized for different niche (e.g. when dinosaurs became extinct)

11. The Origin of Life • Miller-Urey demonstrate that organic molecules can be created in environment present on early Earth • First cells – Szostak shows that fatty acids in water form a “huddle,” creating a lipid bilayer – “Protocells” • First cells probably used catalytic RNA – “RNA World Hypothesis” – DNA evolved from RNA • First organisms – blue-green bacteria • TIMELINE • Big Bang (13.8 bya) --- Formation of our solar system (4.6 bya) --- Oldest rocks (4.4 bya) --- Chemical fossils (3.8 bya) --- Fossils (3.5 bya)

12. Viruses • Most abundant “life form” numerically – depend on cellular organisms • Same form of genetic information storage and transmission as cellular organisms • Retroviruses • Some viral DNA gives us new functions when incorporated into our genome • Bacteriophage – inserts genetic material into host cell and turns it into a virus factory; some viruses enter cells intact, shed coat, take over cell machinery • Lytic vs Lysogenic Life Cycle • HIV – enveloped retrovirus, rapid emergence of drug-resistant strains