GE 70-Week 3 Lectures
GE 70-Week 3 Lectures GE 70B
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General Education Cluster 80A Frontiers in Human Aging
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This 6 page Class Notes was uploaded by Sarah Doberneck on Sunday January 24, 2016. The Class Notes belongs to GE 70B at University of California - Los Angeles taught by Dr. Friscia in Winter 2016. Since its upload, it has received 39 views. For similar materials see Evolution of Life and the Cosmos in General at University of California - Los Angeles.
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Date Created: 01/24/16
Old structure new function Fossils reveal an evolutionary transition this time from jaw to ear bones on the phylogeny of vertebrates Evolution has essentially tinkered with existing parts to create a new function Monotremes are strange but are they primitive The platypus and 4 species of echidna are the only extant species Egg layers crude lactation Almost like transition fossils that never went extinct but are they primitive Characters may be primitive but an extant species by de nition is not A species with primitive characters has been evolving just as long as one with derived characters Different combinations of primitive characters mean monotremes are no more primitive than us Feathered dinosaurs take ight In the evolutionary transition from dinosaurs to birds Feathers were present long before ight The molecules of evolution 0 Darwin was convinced inheritance was real but had no evidence for a mechanism Blending inheritance was largely hypothetical yet widely accepted Fleming Jenkin did some math to show how blending heritage undermined the theory of natural selection Darwin39s solution He speculated the idea of pangenesis 0 Atom sized quotgem mulesquot produces throughout the body by cells 0 Only carried info about the body parts from which they came 0 Problems 0 No solid evidence 0 Suggested that acquired traits could be passed on o What about innovationnovel traits August Weismann experimentally erupted Lamarckism o Developed germ plasm theory 0 Inheritance only occurs via germ cells gametes sperm and eggs 0 Germ cells distinct Mendelian inheritance o Traits as discrete units 0 Recessive vs dominant o Showed traits don39t necessarily blend Mendel39s laws 0 Law of dominance when both alleles are present dominant is expressed recessive is not 0 Law of segregation every diploid individual possess a pair of alleles for a given trait Each parent passes only one copy to offspring selected at random 0 Law of independent assortment alleles for different traits are inherited independently Genes sort randomly and independently during gamete formation Gametes from one individual may Xlinked inheritance In mammals sex is determined by X and Y chromosomes 0 Two X means female Males have one x and one y Affected father 0 Carries one recessive allele 0 Expresses trait o Passes recessive allele to half his kids Unaffected mother 0 Passes dominant allele to all kids Unaffected father 0 Carries one dominant allele 0 Can39t express trait 0 Can39t pass recessive allele to kids Unaffected carrier mother 0 Carries one recessive allele and one dominant allele 0 Does not express trait o Passes recessive allele to half of kids dominant allele to other half Unaffected father 0 Carries one dominant allele 0 Can39t express trait 0 Can39t pass recessive allele to kids Affected mother 0 Carries two recessive alleles o Expresses trait o Passes recessive allele to all kidskin h o All sons have disease no daughters have it but are carriers Inheritance of discreet genetic units Illustrates Mendelssohn laws of inheritance DNA as the stuff of inheritance How did we go from men Searching for DNA structure in the 19505 Rosalind Franklin discover end that DNA was a double helix by taking a picture of DNA 0 Watson and some other old white dudes stole her work and got credit before she did 0 Double helix is a twisted ladder with covalent bonds creating a strong back bone 0 Hydrogen bonds are the rungs of the ladder and are very weak Rna vs DNA 0 RNA has an extra oxygen molecule 0 RNA uses uracil in place of thymine RNA is always single stranded and therefore less stable Base pairing rule AT and CG The central dogma DNA replication 0 Each strand of DNA acts as a template to create two new strands 0 Base pairing rule allows you to make copies without losing info Transcription from DNA to mRNA 0 One Sid elf the DNA ladder acts as a template for single strand RNA 0 Translation of mRNA to protein 0 Transfer RNA has anticodon at one end corresponding amino acid at the other end How DNA is stored Prokaryotes 0 Single chromosome 0 Circular free owing o Smaller ringlets of DNA called plasmids 0 Exchange plasmids via horizontal gene transfer recall the ring of life Eukaryotes 0 Multiple chromosomes 0 Chromosomes wrap around his tones 0 Isolated by nucleus 0 Organelles of prokaryotic origin The hidden genome Central dogma doesn39t explain as much as we thought 0 We have about 20000 genes that codes for proteins and that makes uo about 12 of the genome What the other 99 all about 0 Not junk 0 There is a lot of gene regulation as to where and what and when stuff can happen 0 Gene regulation may be more important than the proteins themselves because it adds to diversity Mutations generate variation 0 Point mutation 0 Changing one nucleotide to another Insertion 0 Adding in the genome Deletion o Removing Gene duplication o Duplicating part so that now there is twice as much of that speci c gene in a row Inversion 0 Sections get inverted and changes how the gene is read Chromosome fusion Genome duplication Codominance Both alleles are expressed equally 0 White mom brown dad cow caf is spots of white and brown not just a lighter brown cow Incomplete dominance Intermediate expression of the two alleles 0 With Iink owers they come from red and white owers yet still have the gene for red or for white and can still pass it on Polygenic traits Multiple genes affect one trait Ex Height or skin color Pleiotropy One gene affects several traits Ex Frizzle gene in chickens One gene give curlers feathers high metabolism and low body temp The central dogma says evolution happens primarily at the level of proteins and their genes gene regulation contradicts this It39s not the proteins that change it39s the way they are expressed Genotype to phenotype How see phenotype so related to genotypes It39s not simple or easy to do because of polygenic effects Pleitropy and environment Thursday January 21 2016 Polygenicheight is in uenced by more than one gene 0 Continuous traits are usually polygenic Environmental factors often in uence continuous traits Real world example of genetics 0 Diabetes 0 An inability of cells to absorb glucose due to problems with insulin 0 Affects 3 of the population 0 Two types lnsulin dependent juvenile or type I o No ability to produce insulin Produce autosomal recessive with 70 penetrance Noninsulin dependent type II or adult 0 Lack of sensitivity to insulin 0 Generic and environmental components 0 Using type I o If we assume everyone who is homozygous recessive has the disease only people with dd can have it This means that Tony39s dad was dd as were his aunts Tiny is Dd because he doesn39t have the disease This means his mother either had DD or Dd What is the probability of each of those two possibilities We know that 3 of the population have dd That is 003 o If qfd the frequency of the d allele in the population 0 003qquot255 Hardy Weinberg equilibrium 0 A statement of how allele frequencies relate to genotype frequencies under certain conditions 0 FDpfrequency of the dominant allele 0 Fdq frequency of the recessive allele 0 Pq1 Conditions 0 Random mating Large populations No migration No mutation OOO o No natural selection o If these aren39t met then gene frequencies will changeevoution Breaking HWE Non random mating Humans usually mate in groups 0 We nd mates similar to ourselves 0 13 of all marriages worldwide are between people born less than 10 mi Apart Nonrandom mating is due to 0 Cultural practices 0 Imperialismgenociderape Can lead to problems of consanguinity If you39re not mating with people far away and tend to keep all their genes in one community then at some point you39re going to marry someone you39re related to 0 Increased changes of diseases Small populations 0 Less genetic diversity More susceptible to random events 0 Genetic drift random changes in allele frequency due to the effect of limited genetic sampling with each generation 0 Starts with some YY YR RR Goes to RR mostly and some YR Ends with all RR Drunk guy analogy Alleles frequencyposition on platform relative to edges Timedistance walked 0 Population sizewidth of platform Allele is lost frequency 0 0 Drunk guy dies Allele is xed frequency 100 0 Drunk guy catches train and goes home Founder affect Applied to founding populations it is an unrepresentative sampling of the original population due to chance because of small populations Evidence for genetic drift 0 Has been demonstrated and quanti ed in lab experiments 0 Neutral changes in DNA that are uses to assess evolutionary relationships 0 Population bottleneck in the elephant seal 0 Elephant seal numbers were reduce by hunting to less than 25 individuals in the 18905 There are now more than 30000 but they show signi cantly less genetic variation loss of alleles relative to mammals with a similar population size 0 Their population grew faster than the DNA could create mutations More important in small populations and small populations are a concern for conservation biologists o Drift can result in loss of genetic variation number of alleles per gene in a population and can be made worse by inbreeding Selection Selection favors the ttest in the population e Those that have the most offspring Selection can be arti cial or natural This will change the gene frequencies in the population because the phenotype a that selection acts on are based on genotypes
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