Transcript Genetics and Evolution

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.
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Single stranded
Ribose
Adenine bonds
with Uracil
Cytosine bonds
with guanine
Three types of
RNA:
Transfer
Messenger
Ribosome
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
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
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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
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Stabilizing
Disruptive
Eliminated
Eliminated
Eliminated
Mean
Eliminated
Mean
GENETIC VARIATIONS
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