genetics and evolution
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
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. Transfer2. Messenger3. Ribosome
Events of the Cell Cycle
• Interphase is composed of G1 phase-----Cell growth, synthesize new proteins, organellesS phase-----Chromosomes replicated, DNA synthesizedG2 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
Directional Stabilizing Disruptive
GENERATIONS
GENETIC VARIATIONS
Eliminated
Mean
EliminatedEliminated
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…
• Extinction1. 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