chapter twenty-one/twenty-two Flashcards
how much of our genome is transcribed into mRNA, tRNA, and rRNA
1.5%
intergenic DNA
DNA between genes
- some unique, like pseudogenes
pseudogenes
former genes that have accumulated mutations and are nonfunctional
what is most DNA?
repetitive DNA
- present in multiple copies in the genome
types of repetitive DNA
- transposable elements and related sequences
- other repetitive DNA
transposable elements and related sequences
can move from one location to another within genome through recombination process
discovery of transposable elements
- geneticist Barbara McClintock
- worked with calico corn
- observed effects of mobile DNA pieces, moved from one site to another in cell’s DNA
- present in both proks/euks
2 types of transposable elements in eukaryotes
- transposons
- retrotransposons
transposons
- move via DNA intermediate
- cut/paste - no copy at original site
- copy/paste - leaves copy at original site
- requires enzyme transposes encoded by transposon
retrotransposons
- move via RNA intermediate
- converted back to DNA w/ reverse transcriptase
- always leaves copy at original site
- most
Alu-elements
transposable element-related DNA in humans/primates
- some transcribed, but function of RNA molecules unknown
- type of SINEs (short interspersed nuclear element)
LINEs
long interspersed nuclear elements
- type of retrotransposon
- like L1
- longer than Alu elements, low rate of transposition
what did other repetitive DNA probably arise from?
mistakes during DNA replication and recombination
types of other repetitive DNA
- long sequence duplications
- simple sequence duplications (STRs)
- multigene families
simple sequences duplications
many copies of tandemly-repeated units
- STRs
- common in centromeres and telomeres
STRs
short tandem repeats
- 2-5 nucleotide repeating units, repeating thousands of times
- repeat numbers can vary among sites within genome and btw ind
function of simple sequence DNA in centromeres and telomeres
- centromeres - separation of sister chromatids
- telomeres - protects against degradation, joining to other chromosomes
multigene families
collections of identical or very similar genes
- identical: rRNA genes clustered tandemly
- non-identical - globin gene families, dif forms of global expressed at dif times
polyploidy
extra sets of chromosomes
duplications and inversions
result from mistakes during meiosis
- unequal c-o during prophase I
what happens when gene family members get duplicated
some are used, other can accumulate mutations
exon duplication
can be duplicated on 1 chromosome and deleted from another
exon shuffling
mixing/matching of different exons within gene or between 2 dif genes
multiple transposable elements can facilitate recombination between different _________
chromosomes
how can transposable elements cause trouble?
if they insert within a protein-coding sequence of gene regulatory sequence
what does comparing distantly related species help us understand?
“ancient evolutionary events”
what can be studied in model organisms?
highly conserved genes
what can genetic differences between closely related species be correlated with?
phenotypic differences
human genome diversity
- SNPs
- CNVs
SNPs
single nucleotide polymorphism
- single base-pair sites where genetics variations found in a least 1% of pop
CNVs
copy-number variation
- variation in copies of a particular gene or genetic region
homeotic genes
specify identity of body segments in animal development
- all contain homeobox region
homeobox region
sequence that codes for homeodomain in the resultant protein
- important for development
what organisms are homeobox sequences found in?
vertebrates and invertebrates, related sequences in plants, fungi, prokaryotes
sometimes small changes in regulatory sequences of certain genes leads to what?
changes in body form
when was the Origin of Species published?
1859
The Origin of Species
focused attention on great diversity of organisms
- Darwin noted that current species are descendants of ancestral species
evolution
descent with modification
- where species accumulates differences from ancestors over time
Aristotle
viewed species as fixed and arranged them on Scala naturae
Old Testament
species individually designed by God and therefore perfect
Carolus Linnaeus
- interpreted organismal adaptations as evidence that Creator had designed each species for specific purpose
- founder of taxonomy
- developed binomial format for naming species
paleontology
study of fossils
- largely developed by French scientist Georges Cuvier
catastrophism
- Cuvier
- each boundary between starts represents a catastrophe
what did James Hutton and Charles Lyell claim?
that changes in earth’s surface can result from slow continuous actions still operation today
Lyell’s principle of uniformitarianism
states mechanisms of change are constant over time
- influenced Darwin’s thinking
Lamarck’s Hypothesis of Evolution
species evolve through use and disuse of body parts and inheritance of acquired characteristics
- unsupported by evidence
what did Darwin perceive adaptations to the environment and the origin of new species as?
closely related processes
what did Darwin do in 1844
write essay on natural selection as mechanism of descent with modification
- didn’t introduce theory publicly
natural selection
process in which ind. w/ favorable inherited traits are more likely to survive and reproduce
what 3 observations did Darwin explain in The Origin of Species
- unity of life
- diversity of life
- match between organisms and environment
artificial selection
humans have modified other species by selecting and breeding ind. with desired traits
Darwin’s 2 observations
- members of a population often vary in inherited traits
- all species can produce more offspring than the environment can support, and many of these offspring fail to survive and reproduce
Darwin’s 2 inferences
- ind. whose inherited traits give them a higher probability of surviving/reproducing tend to leave more offspring
- unequal ability of ind. to survive/reproduce will lead to accumulation of favorable traits in population over generations
who was Darwin influenced by?
Thomas Malthus
- noted potential for human population to increase faster than food supplies and other resources
individuals with certain heritable characteristics _________ and ________ at a higher rate than other ind.
survive and reproduce
what does natural selection increase over time?
adaptation of organisms to environment over time
what evolves over time?
populations, not individuals
what can only increase/decrease heritable traits that vary in a population?
natural selection
what varies with different environments?
adaptations
