Genomes Flashcards
why are genomes different sizes in diff organisms
lol we dont know it’s just how it is,
C paradox
how much % of our DNA encodes for proteins
3%
~20,000 genes
how much % are regulatory genes
10%
how much is junk in our genome %
~85%
45% is repetitive elements
what did Barbara McClintock suggest
that genes can move about on chromosome
won nobel prize for it
what’s the name for mobile genetic elements
transposons
what do transposons do
sequences of DNA that can move in the genome
some produce transposase
= enables ‘ungluing’ at either end and can ‘jump’ to where it wants
what is retrotransposons
produce RNA which is reverse transcribed into the genome
they kinda insert themselves somewhere else
remnant of retroviruses
what can movement of a transposon cause
produce mutations
can be involved in cancers, developmental disorders etc.
how can transposons prevent their own transposition
produce small interfering RNA
see one note for fish example on translocation
:)
how have retroviruses lead to the us bein gbal eot make placenta
genes that once encoded for the envelope of the retrovirus
was harnessed
now used to make syncitins
which is a protein needed to make placenta
how did cows get 25% of their genome frmo snakes
ticks
sucked blood from snake
one day the tick bit the ancestor of the cow
then it goes into bloodstream
eventually finds its way into the sex cells
is passed down
example of horizontal gene transfer in humans
mitochondiral DNA integrated into our nulcear DNA
what is typically needed for horizontal gene transfer in multicellular organisms
an intermediate
ie a parasite or some kind of symbiote
example of horizontal gene transfer that led to red colouration in pea aphids
usually green but some are red
the gene to turn red acquired from fungus
what are some examples of genes taht are necassary to be an animal
homeobox developmental genes
cell adhesion molecules
receptors
what is environmental DNA
exctraction of sequences without the organism
mainly from soil, water, air etc
non invasive observational technique
when can eDNA be useful
to identify kinds of organisms down in deep ocean from bits of DNA collected
why is collecting eDNA difficult
needs careful amplication and bioinformatic identification
cuz could easily be contaminated
on average, how much do humans differ to each other by
0.1% (only about 3 million base pairs)
why was human genetic variation initially underestimated
cuz all samples were european volunteers
what part of the world has the most genetic variation in humans
those with african descent
have ~10% more DNA than the ‘reference’ DNA (from the european sample)
example of humans still evolving: tibetans
study comparing tibetans (who’ve lived at high altitude for longggg time) and han chinese (who are migrants so only recently moved)
showed the tibetans more liekly to have EPAS1 gene
controls RBC production so better at high alt
only 9% on han chinese had it
example of humans still evolving: bajau people
they dive for long periods of time to fish
they have much bigger spleens that acts as a resovoir of RBCs
and another gene that lets them hold breath for longer
evidence of an ancient coronavirus?
studied DNA of genes for proteins that interact with coronaviruses in indegenous people (cuz they have less mixing of genes and stuff)
strong sign of selection for a gene that prevents or promotes replication in the lungs from around 20,000 yrs ago
obvs those that could prevent survived and that gene is seen in populations today
how might dark and light skin vary in different environments
dark skin protects from UV
lighter skin enable vit D biosynthesis wherever the sun is weaker
~how many genes involved in skin colouation
at least 15 genes hence the amount of variability in skin colours
