Lecture 6- Genomes Flashcards
when was the first human genome sequenced
2000
how many base pairs in the human genome
3 x 10^9 base pairs
what percentage of the human genome codes for proteins
3%
what percentage of the human genome is regulatory genes
10%
what percentage of the human genome is junk
85%
transposons
sequences of DNA that can move in the genome
(mobile genetic elements)
retrotransposons
produce RNA, then reverse transcribed into DNA and then inserted into genome
what are transposons agents of
evolution and disease
what are transposons remnants of
retrovirus in DNA
characters that prevent transposition
methylation (favoured to prevent mutation) and small interfering RNAs (produced by some transposons)
process of the creation of new genes
- duplication in non coding regions creating long string of 3 AAs
- overtime, changes in base sequences (mutations) causes tagging as secretory
- translocation brings sequence near promoter region
example of new genes in fish
fish living in polar seas have antifreeze glycoproteins
evolution of the placenta
syncitins (needed for the placenta) once coded for the envelope of a retrovirus
overtime, mammals have reused these genes to develop the placenta and regulate gene activity
horizontal gene transfer
transfer of genetic material from an organism to another organism that is not it’s offspring
-mainly in prokaryotes
-in multicellular organisms, involves parasite or symbiote
limitations of horizontal gene transfer
minor source of genetic variation
implications of horizontal gene transfer
can lead to adaptations
e.g spodoptera moth acquired an immune barrier through a virus that lives in a parasitic wasp
e.g genes involved in carotenoid biosynthesis acquired from fungus
how many groups of genes are necessary to be an animal
25
environmental DNA
extraction of sequences without an organism mainly from soil, water or air
-non invasive observational technique
-requires careful amplification and bioinformatic identification
what percentage do human genomes differ from each other
0.1% (3 million bases)
how many nuclear muations are present that aren’t present in our parents
70
example of how genetic variation is severely underestimated
910 individuals of recent African decent had 10% more DNA than in the reference genome including some being protein encoding genes
evidence of natural selection in humans: Tibetans
mutation of EPAS1 gene (regulated RBC production) found in 87% Tibetans (lived in high altitudes with 40% less oxygen) compared to only 9% Han Chinese shows clear genetic evidence of natural selection in humans adapting to low oxygen environments
evidence of natural selection in humans: Bajau people in S-E Asia
able to dive for long periods
-selection on PDE10A gene= larger spleens (resevoir of RBC)
-selection on BDKRB2 gene= involved in diving reflex
how many genes are involved in skin colour
atleast 15 genes
does skin colour correlate with other traits
no
