Genetics and Evolution

1. Genetics and Evolution Mary Susan Mardon

2. Nucleotides • Building blocks of DNA and RNA. • Each nucleotide contains: • phosphate group. • deoxyribose(DNA), ribose (RNA) • nitrogen base. * adenine * cytosine * thymine * guanine RNA only---Uracil

4. The Discovery of DNA’s Structure • Rosalind Franklin and Maurice Wilkins at King’s College in England used x-ray diffraction to study the physical structure of DNA. • James Watson and Francis Crick worked at Cambridge University in London, England created a structural model of DNA.

5. The Structure of DNA • Deoxyribonucleic acid(DNA) is located in the nucleus. • Double helix. • Each side of the helix is composed of a long strand of nucleotides. • DNA has four nitrogen bases--adenine, thymine, guanine and cytosine.

7. DNA Function • Provides genetic information in the form of a genetic code. • DNA splits in half • Codon is transcribed to mRNA • tRNA picks the message up and transfers to the ribosome where the message is translated into amino acids • Proteins are then formed

8. RNA Function • The function of RNA is protein synthesis. • Three basic steps to protein synthesis: • DNA segment must be copied in the nucleus. • The code must be carried from the nucleus into the cytoplasm and to a ribosome. • The protein is assembled from the code and released from the ribosome.

9. Single stranded • Ribose • Adenine bonds with Uracil • Cytosine bonds with guanine • Three types of RNA: • Transfer • Messenger • Ribosome

10. Events of the Cell Cycle • Interphase is composed of G1 phase-----Cell growth, synthesize new proteins, organelles S phase-----Chromosomes replicated, DNA synthesized G2 phase-----production of molecules and organelles, shortest of the 3 phases

12. Mitosis • Nuclear division. • Cell division results in two daughter cells. (2n)

13. Meiosis A process called reduction division in which the number of chromosomes in a human reproductive cell is reduced to 23 chromosomes. These cells are haploid (n).

14. Genetics and Probability • Gregor Mendel • Trait • Hybrid or Heterozygous—Hh • Purebred or Homozygous—HH, hh • Allele: variation of a gene • Dominant Trait—HH, Hh • Recessive Trait– hh • Gamete: Sex cells • Genotype: genes represented by letters (HH, Hh, hh)

15. Genetics and Probability continued • Phenotype: traits or characteristics you can see. • Punnett Square: A tool to calculate genetic probability. • Cross-pollinate: two different parents. • Self-pollinate: one parent. • True breeders: can self-pollinate to produce identical offspring.

16. Genetics and Probability continued • Principle of Segregation: The paired alleles separate so that each egg or sperm carries one form of the allele. • Principle of Independent Assortment: states that genes for different traits can segregate independently during the formation of gametes. • Principle of Dominance: states that some forms of a gene or trait are dominant over other traits, which are called recessive (hides or masks)

17. Genetics and Probability continued • Incomplete Dominance: one allele is not completely dominant over the other (RR, WW) • Co-dominance: Both alleles contribute to the phenotype (BW) • Polygenic Traits: more than one gene controls the trait (skin color)

18. Evolution: Change over time • Theory of Natural Selection: Organisms adapted to their environment survive and reproduce

19. Stabilizing Directional Disruptive G E N E R A T I O N S Eliminated Eliminated Eliminated Eliminated Mean Mean Mean GENETIC VARIATIONS

20. Types of Natural Selection • Stabilizing Selection: environmental change acts to eliminate extremes in a population • Directional Selection: occurs in either direction shifting the population towards a new norm. • Disruptive Selection: environmental change acts on the most common variety.

21. Requirements of a Species • Species: group of similar organisms that can breed and produce fertile offspring. • Genetic mutations (random changes in the DNA) • Genetic drift (change in frequency of alleles in a population) • Hybridization • Gene Flow: exchange of genes between two populations, development of geographic isolation, ex. Darwin’s finches

22. Animal Adaptation • Behavioral adaption for survival and reproduction • Territoriality is a behavioral adaption that ensures adequate space and resources for reproduction. • Courting behavior is a behavioral adaption that helps to ensure beneficial genes are passed along to offspring.

23. Patterns of Evolution • Gradualism: species change slowly over many generations; ex. body size of the water buffalo • Punctuated Equilibrium: sudden changes in a species; ex. light and dark peppered moth • Convergent Evolution: unrelated species develop similar characteristics; ex. porpoise and shark—streamlined bodies and fins • Divergent Evolution: many species develop from a common ancestor; ex. homologous structures (beaks) in Darwin’s finches

24. Patterns of Evolution, continued • Coevolution: two or more organisms in an ecosystem evolve in response to each other; ex. Orchid’s long tube and Hawk moth’s proboscis

25. Evidence of Evolution • Anatomical Similarities • Homologous structures; ex. human arm, wing of a bird, flipper of a whale • Vestigial organs; whales and some snakes have a pelvis and femurs • Molecular Similarities: overlap of DNA; ex. DNA of a Horseshoe crab is more closely related to a spider than a crab

26. Continued… • Embryonic Developmental Similarities:

27. Continued… • Fossil Record:

28. Continued… • Extinction • Ecological extinction: species does not have a large enough population to sustain genetic diversity; ex. Florida panther, mountain lion • Mass extinction: large population becomes extinct in a short period of time