What is Evolution?
Change over timeDescent with modification
Proximate causality
Refers to "HOW" something works
Ultimate causality
Refers to "WHY" something works
What evidence supports evolutionary theory?
-Comparative anatomy and embryology -Homologies, analogies, vestiga -Fossil record -Compatative biochemistry
What is required for evolution?
a. Reproductionb. Heredityc. Variation in fitness of organismsd. Variation in individuals and traits
Genetic variation
The variety of different types of genes in a species or population.Sources of genetic variation 1. Mutations 2. Gene Flow 3. Sex
Genetic drift
Occurs when a population experiences random fluctuations in frequencies of genetic traits -RANDOM -Drift causes random changes in allele frequencies while allele frequency changes due to selection are never random
Population bottlenecks
-A population dramatically changes in size
Natural Selection
NOT RANDOM Variation in population, differential variation in population differential reproduction, heredity, adaptive change 1. variation 2. differential reproduction 3. heredity 4. adaptive change
Fitness
A measure of the contribution of a genotype to the gene pool of the next generation
Mutation
Variation in a gene sequence arises from mutation -Can be the change of just one base or even the entire chromosome - Causes: DNA fails to copy, external influences
Meiosis
The genome is divided in half into new cells, going from diploid to haploid to form gametes
Crossing over
Involves reciprocal exchange of segments of non-sister chromatids within a tetrad Result: a recombination of alleles on the chromosome
Independent Assortment
The process whereby 1 chromosome pair divides or assorts independently of any other chromosome pair -completely random -Important to increase genetic diversity
DNA contrast to RNA
RNA more diverse than DNA-RNA is single stranded -Has different sugar in its backbone
DNA
4 bases: Guanine (G), Adenine (A), Thymine (T), Cytosine (C) -Double strand molecule -Nucleotide: phosphate group + sugar + nitrogen base -Sugar involved is deoxyribose -A nucleic acid that contains the genetic instructions for the development and function of living organisms
RNA
Ribonucleic acid -1 strand -To carry information of amino acid sequence from the genes to where proteins are assembled on ribosomes in the cytoplasm -A product of transcription uses DNA as a template -Composed of nucleic acids. (A,U,G,C) -During translation, the nucleic acids are read in groups of 3 bases called a codon-Each codon represents an amino acid -Ribose sugar is the RNA backbone
Transcription
4 nucleotides of DNA (A,C, G, T) are rewritten in the form of RNA (U, G, C, A)
Translation
Transcribed mRNA code into a linear string of amino acidsAmino acids: coded for by a codon and linked together through peptide bonds
Meiosis 1
DOES NOT involve fertilization-Location: gonads -one cell to 4 cells -diploid to haploid -independent assortment -crossing over and recombination Follows DNA replication Interphase 1: Duplication of chromosomes into sister chromatids Prophase 1: chromosomes condense and tetrads form (crossing over occurs) Metaphase 1: Tetrads line up vertically and go through an independent assortment Anaphase 1: reductive division (diploid to haploid)Tetrads are pulled apart and split into 2 different cells Metaphase 2: Chromosomes again align vertically in the new cell ( now there is only one pair of sister chromatids from each homologous pair).Anaphase 2: Sister chromatids are pulled apart Telophase 2 and Cytokinesis: 4 new daughter cells are formed. They are haploid meaning that they are only have one of each kind of chromosome
Meiosis 1 vs Meiosis 2
Meiosis I includes crossing over or recombination of genetic material between chromosome pairs, while meiosis II does not
Meiosis 2
Is not preceded by DNA replication chromatid pairs seperate
Costs of sex
-Energetic costs -Risk of disease-Producing half offspring as asexual
Muller's Ratchet
The hypothesis for the existence of sex, sexual reproduction is better able to eliminate harmful mutations from the genome
Red Queen Hyothesis
Sex exists as a mechanism for keeping up with rapidly coevolving pathogens
Codon
-Each codon represents an amino acid
Proteins
Polypeptides" - A string of amino acids -The product of translation uses RNA as a template
Expression
Process of going from DNA to protein
Genes
Unit of heredity that determines the specific trait of a person -Made of nucleic acids/bases (A,T,G,C) Nucleic acids: are composed of nucleotides, are very large and complex organic molecules that contain the genetic code for that organism.-Codes for proteins
DNA is transcribed into RNA which is translated into amino acids/proteins
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Genotype
Total set of genes Example: AA, Aa,aa
Allele
1 or 2 or more alternative forms of a gene that are found on the same place on a chromosome
Phenotype
Observable trait determined by the genotype Ex: hair color, eye color, mouth shape
Chromosomes
Made up of genes -DNA wound tightly around proteins called histones -23 pairs in humans
Ploidy
Refers to the number of sets of chromosomes an organism possesses
Diploid
2 sets of chromosomes (human cells) or 2 copies of alleles of each gene -Copies can be different or the same A or a
Haploid
1 set of chromosomes (gametes)
Aneuploidy
A condition resulting in cells having more or less than the usual number of chromosomes -occurs during cell division if the chromosomes do not divide evenly - Lethan in humans except for sex chromosomes and chromosome 21
Trisomy of chromosome 21
Down syndrome
Homologous
When 2 chromosomes have the same genes -1 chromosome came from the mother and the other from the father -Have the same genes but can have different allelesEx: AA or aa
Humans are diploid so have homologous pairs
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Karyotype
A picture of all the chromosomes in a cell
Heterozygous
If different then heterozygous for that gene EX: Aa
Complete Dominance
One allele completely masks the other, thus one allele is dominant and the other recessive Dominant: T Recessive: t
TT will have the same phenotype as Tt because only need 1 dominant allele to express dominant phenotype
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Incomplete Dominance
Heterozygous genotype ends up having an intermediate phenotype/new phenotype Ex: AA red flower, Aa pink flower, aa white flower
Co-dominance
Both allies express their trait without making a new phenotype Ex: Mr. Potato Head activity AA=hat only aa=shoes only Aa= hat and shoes only
Linkage
Two genes are linked if they are on the same chromosome -Genes that are close to each other tend to stick together and rarely undergo independent assortment -Crossing over can still occur-Decreases the diversity of gametes because it decreases the possible allele combinations
Sex-linked
Means X-linked
Males only have 1 X chromosome, that they receive from their mother so they will express whatever phenotype the genes on that chromosome code for
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Polygenic Inheritance
Body size, skin color+
Multifactoral Inheritance
Traits that are influenced both by environment and genetics
Homologous structures
Anatomically features that different organisms share as a result of a common ancestor
Analogous structures
Anatomical features that different organism share but NOT a common ancestor -change because of similar environment
Founder Effect
Results when a small part of the population moves to a new location
Prokaryotes
Generally single celled (bacteria)
Eukaryotes
Complicate cell structure (any sexually reproducing organisms)
Hirsutism in woman
Gene-Protein-Phenotype -Testosterone in woman -Mutation in TEBG-Single gene mutation -Can skip generations
Why sex?
-DNA repair and recombination -Sex eliminates bad mutations
Convergent evolution
Organisms share features as a result of similar enviormental pressures
Gene Flow
Or migration occurs when individuals move between populations
Adapatation
Any feature that benefits an individual in its present environment is adaptive
Scientific theory difference from scientific hypothesis
A theory is a well supported explanation for a very good general observation Hypothesis treats more specific observation
Phylogeny
Evolutionary history of a speciesPhylogentics: the study of phylogenetic relationships and the use of phylogenetic trees to elucidate the evolutionary phenomenon
Amino Acid
Building blocks to form a protein
3 types of RNA involved in protein synthesis
mRNA, tRNA, rRNA
mRNA
(messenger RNA)-Convey's DNA genetic message in from of an RNA transcript
tRNA
(transfer RNA) aligns the mRNA transcript with amino acids, building blocks of a protein -each amino acid has tRNA molecule, itself complementary to bases in mRNA
rRNA
(ribosomal RNA) comprises much of the ribosome, 2 unit cellular structure that is site of protein synthesis
Types of Mutations
1. Substitution: simply involves the replacement of 1 nucleotide for another 2. Insertion: results from the addition of one or more nucleotides 3. Deletion-caused by removal of one or more nucleotides
The genetic information contained within a DNA molecule is determined by the
Linear sequence of a nucleotide bases in molecule
Asexual reproduction
A reproductive process that involves only one parent and produces offspring that are identical to the parent.-Type: 1. Budding: new organism develops from an outgrowth or bud due to cell division at one particular site.2. Parthenogenesis: females reproduce without males 3. Binary fusion: organism split in half (bacteria)4. Cloning: identical copy of 5. Spore formation: multiple fission (org. breaks up into a number of pieces6. Fragmentation: multi cellular colonial org.
Advantages of asexual reproduction
-Every offspring has 100% of parents genes -Cheap (energy not spent finding males) -No sexual cannibalism -No disease -No competition
Which point of mutation has the most catastrophic effect on the functioning of a protein?
Deletion of a single base
Examples of aneuploidy
-XO (Turner's syndrome) A chromosomal disorder in which a female is born with only one X chromosome-Klinefelter's syndrome: A genetic condition in which a male is born with an extra copy of the X chromosome (breast enlargement, less body hair)-XYY: Some may be taller than average and face learning difficulties or speech problems. They may also grow up with minor physical differences, such as weaker muscle tone-Down Syndrome: A genetic chromosome 21 disorder causing developmental and intellectual delays.
NOT part of evolution by natural selection
Traits acquired during an individual life are passed on to its offspring
Homologous structures in 2 species
Are modified from a structure in a common ancestor
Dolphins are recent descendants of terrestrial, four-legged mammals. Like fish, dolphins have streamlined bodies for ease of movement under water. The streamlined bodies of fish and dolphins are?
Analogous and adaptations to a common environmentAnalogous: are anatomical features that different types of organisms share but not as a result of an ancestor.
Populations can evolve through
Gene Drift, Mutation, natural selection
Lineage
A sequence of successive generations connected by reproduction
Meiosis is evolutionary significant and Mitosis is not
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Truth about homologous chromosomes?
They represent paternal and maternal chromosomes Represent the conjoined product of DNA
Coevolution
2 or more species affect each other's evolution -likely to happen when different species have close ecological interactions with each other
Parthenogenesis
Unfertilized birth or Virgin Birth
Eden is a woman with male DNA. What is the cause of this condition?
She has a mutation in a gene that responds to androgens
In protein synthesis, a linear sequence of nitrogenous bases is translated into a linear sequence of amino acids
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Fruit fly males release a "sex peptide," a proteinthat males produce and release with sperm inthe ejaculate. This can increase the male's fitnessbecause this protein
Encourages his mate to eat more and support his developing offspring
In the "Why Sex?" chapter, you readabout parthenogenic whiptail lizards.Parthenogenesis means
The embryos develop from unfertilized eggs
In human females, a version of hirsutism (malehair patterns) appears to be inherited in simpleMendelian fashion. This suggests that hirsutism is
Due to a single gene mutation - Explanation: mutation in the gene of testosterone A gene that produces a protein that normally binds testosterone Recessive allele causes some cases of hirsutism: - can skip generations
What is the probability a couple willproduce two sons in a row?
1/2x 1/2
When Ridley refers to the "costof males," he is referring to
Genetic cost of meiosis
Theories to account for the existence of sex
Weisman's, Fisher's and Muller's "speeds upevolution" idea• Decreases harmful mutations• evolution as imperative• group selectionist• sex occurs "for the good of the species"?
Compelling evidence for Muller'sRatchet hypothesis includes
B. Water fleas (Daphia) that accumulate more mutations when they are asexual than when they reproduce sexually
Steps:
1. A substitution mutation occurs in thehemoglobin gene 2. A mutant version of hemoglobin is produced at the ribosomes3. Mutant hemoglobin impairs oxygen delivery to your tissues4.Sickle-cell anemia results
What is the effect produced when a bee carries pollen from one coneflower population to another?
Gene Flow
A gene is...
A region of DNA with a particular phenotypic effect Gene has: -nitrogenous bases -sugars-hydrogen bonds -nucleotides
Population can evolve through
Genetic drift, Gene Flow or migration, and natural selection
Primary structure of a protein refers to
Linear sequence of amino acids