Evolution exam 2: genomic evolution and development

genome architecture

structure and organization of a species complete DNA code

genomic size

total DNA base pairs

a metric of genome architecture

viruses small, eukaryotes larger but no pattern

genome content

proportion coding DNA

why do multicellular eukaryotes have such a high proportion of noncoding DNA?

1. introns

2. transposable elements/ transposons/ mobile elements

introns

noncoding region within genes

unique to eukaryotes

transposons

DNA sequences that have the ability to move from location to location in the genome

this makes up most of DNA of the intergenic regions

noncoding DNA but sometimes effect phenotype

intergenic

between gene regions

__% of human genome is transposons

45

absent in many unicellular organisms

transposons considered ___. why?

genomic parasites

IDK WHY

transposons __ and paste

CUT AND PASTE

retrotransposons

leave the copy of themselves behind

COPY AND PASTE

in unicellular organisms, mutation rate ___ with genomic size

decrease

negative correlation

in multicellular organisms, mutation rate ___ with genomic size

increase

positive correlation

Lynch suggested what about evolution of mutation rates?

lower limit on mutations set by interplay of natural selection and drift

evolution of mutation rates exam graph

Lynch 2 graphs combined into single pattern

a negative correlation graph

pop small and selection is weak = subject to drift

mammals have smaller pop than bacteria

in bacteria selection keeps mutations down

but in small pop mammals, drift happens and selection isn’t getting rid of bad mutations

gene duplication

the creation of a second copy of a gene

2 methods

2 methods of gene duplication

1. unequal crossing over

2. retroposition/ retroduplication

unequal crossing over

occurs during meiosis 1

results when homologous chromosomes misalign

when chromosome gains a copy of the gene(s)

retroposition/ retroduplication

processed mRNA reverse-transcribed into double-stranded DNA by reverse transcriptase

how corgis made - genes inserted far from original gene found in all dogs

pseudogenes

non-functional genes

product of most duplication events

lacking regulatory sequence that initiate transcription

4 different fates for duplicated genes

1. neofunctionalization

2. subfuncationalization

3. gene conservation

4. nonfunctionalization

neofunctionalization

gene copy mutates and by chance aquires new beneficial function

new + full

subfunctionalization

ancestral gene had 2 separate functions; duplicated copy lost one function and other gene lost other function

full/dead + dead/full

gene conservation

copy and original maintain function

full + full

nonfunctionalization

copy or original lose function but other copy keeps working full function

dead + full

gene families

sets of genes descended from single common ancestor gene

from multiple duplication events

not identical but similar

gene conversion

sequence info from one locus is transferred unidirectionally to other members of gene family

results in

• all gene copies to have same sequence

• concerted evolution

converted evolution

same gene product from multiple loci

development

processes by which an organism grows through its life cycle to reproduction and all stages in-between

evolutionary development biology

study of mechanisms by which development has evolved

EVO-DEVO = developmental and evolutionary processes

Saltationists

believed major jumps in phenotype via mutations to produce large effect

structuralist

believed physical and math directed growth

not true

gene expression

production of a protein or RNA from a DNA sequence

gene regulation

what genes are getting turned on or off during development

explains why so much variation

evo- devo

evolution and development biology

homeotic genes

induce the formation of particular parts of organism

like flies having different structures

homeodomain

amino acid sequence that forms a DNA binding fold

proteins are transcription factors

transcription factors

regulate the transcription of other genes

spatial colinearity

correspondence between gene order on chromosome and spatial locations of expression along body axis

developmental constraint

bias in the production of phenotypic variation

due to developmental factors

heterochrony

evolutionary changes in the timing of development

important in morphological evolution

paedomorphic traits

child like traits

pleiotropy

single gene affects more than one trait

pleiotropic genes during development

same gene affects different traits at different times during development

why we change

developmental trade-off

one feature of an organism can only be promoted at the expense of another feature