Genetics and Evolution Mary Susan Mardon

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

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.

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.

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

RNA Function The function of RNA is protein synthesis. Three basic steps to protein synthesis: 1.DNA segment must be copied in the nucleus. 2.The code must be carried from the nucleus into the cytoplasm and to a ribosome. 3.The protein is assembled from the code and released from the ribosome.

Single stranded Ribose Adenine bonds with Uracil Cytosine bonds with guanine Three types of RNA: 1.Transfer 2.Messenger 3.Ribosome

Events of the Cell Cycle Interphase is composed of G 1 phase-----Cell growth, synthesize new proteins, organelles S phase-----Chromosomes replicated, DNA synthesized G 2 phase-----production of molecules and organelles, shortest of the 3 phases

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

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).

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)

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.

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)

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)

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

Directiona l Stabilizing Disruptive GENERATIONSGENERATIONS GENETIC VARIATIONS Eliminated Mean Eliminated Mean Eliminated Mean

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.

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

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.

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

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

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

Continued… Embryonic Developmental Similarities:

Continued… Fossil Record:

Continued… Extinction 1.Ecological extinction: species does not have a large enough population to sustain genetic diversity; ex. Florida panther, mountain lion 2.Mass extinction: large population becomes extinct in a short period of time