EE10 Flashcards
What is the C-value?
Total amount of DNA in a haploid genome
- this varies dramatically.
What is the C-value paradox explained by?
non-coding junk DNA
What are the possible reasons for the presence of excess/non coding DNA?
Transposition
- DNA seq that can change its position in genome, often duplicates as well
Replication Slippage
-mutation that leads to tri/dinucleotide expansion
Unequal crossing over
-gene deletion in one strand replaced with duplication from sister chromatid
Polyploidy
-more than two paired sets of chromosomes
-chromosomal duplication
What are orthologs?
Genes related by vertical descent from a common ancestor
- encodes proteins with same function in different species.
Homologous.
What are paralogs?
homolgous genes that have evolved by duplication and code for proteins with similar but not identical functions
How common is gene duplication?
relatively common,
=0.01 per gene per myr
-most are lost or silenced
- few diverge to new functions
What are multigene familes?
Give an example
groups of genes from same organism that encode proteins with similar sequences.
- can be tandemly repeated, (adjacent repetition) or dispersed in gene clusters
eg. Globins arose from single orgin - allows production of different types of haemoglobin, embryonic, foetal, adult with different O2 affinities.
How do selfish genetic elements work?
via inheritance bias in their transmission.
- should rapidly become fixed in a population unless opposed by evolution.
What can cause inheritance bias?
- Gonotaxis
- orientating to germline - interference
- scuppering competition - Over replication
- replicating more than once in cell cyle
What is the B chromosome?
An extra chromosome that occurs in 10-15% of plant and animal species that is transmitted at a higher than expected frequency.
It is found in 50% of British individuals.
Inherited d=0.8 through females.
stable frequency of chromsome is due to equilibrium between selection and accumulation.
What affect does presence of 2B in M.maculatus (a cricket) have?
the cricket becomes very unfit.
slows down development into adulthood.
causes sperm dysfunction
What is Ty1-copia?
a retrotransposon that is abundant in species like algae, byophytes, gymnosperms, angiosperms. etc.
What is Ty3-gypsy?
retro element
wide distribution in gymnosperms and angiosperms
What are LTR retroelements?
Long terminal repeat retroelements
- endogenous (originate within organism)
- retrovirus- DNA seq derived from virus ancesterally inserted
- not in humans
Give examples of the effects of LTR on host.
- beneficial
- neutral
- deleterious
- eg. RAG1/RAG2 genes are essential for generation of mature lymphocytes
- eg. variegation (colour changes) in morning glory flower.
- Mainly they are deleterious.
eg. p-element in drosophilia
eg. 0.1%-0.2% if human diseases are caused by mutations due to insertion of retrovirus
What are the structural domains of
NON LTR retroelements
LTR retroelements
Retrovirus
Non LTR -gag-en-rt- LTR -LTR-gag-int-rt-LTR Retrovirus -LTR-gag-rt-int-env-LTR
gag- core particle components en - endonuclease rt - reverse transcriptase ltr - long terminal repeat int - intergrase env- envelope glycoprotein (essential for virus entry into host)
What was discovered about sticklle back scale growth in marine and freshwater?
stickleback which go marine become heavily armoured
freshwater = lightly armoured
-found ectodyspasin gene responsible for difference,
secreted signal molecule known to effect scale growth
- 4 AA change between plated and non plated.
What does the Forkhead box protein gene FOXP2 do in humans?
language gene
mutations cause speech, language disorder
add to mouse by GIM - changed vocalisation, increased learning
shared with neanderthals
