biochem: rna(s) and mutations

Question 1

Mrna cap and poly-a-tail

Answer 1

in 5’ terminus it is capped by 7-methyl guanosine triphosphate

-protects mrna and for stability

poly-a-tail= 20-250 adenine nucleotides
-stabilize mRNA against degradation and helps the ribosome recognize mRNA

Question 2

rRNA

Answer 2

60s subunit and 40s subunit
(small and large subunit)

s=how fast particle travels in centrifugal field

add up to 80s ribosomes

Question 3

microRNA miRNA

Answer 3

mRNA silenced instead of broken and building it again (anabolic- takes E)

miRNA attached to mRNA to silence it temporarily (not read by ribo) so no overpopulation

miRNA= small rna that are cut down by specific ribonucleases to give the final product

Question 4

mutations: deamination

Answer 4

occurs at rate of 1/10^7 bases per 24h

dna repair enzymes work at removing U’s to replace by correct c

if dna used u instead of T, repair enzymes wont know diff between correct U and incorrect U

this is why dna use T not U

Question 5

mutations: depurination

Answer 5

occurs at rate of 1/10^5 bases per 24h

removal of purine base from phosphodiester bond

req constant repairs

Question 6

mutations: uv light

Answer 6

formation of 2 diff photoproducts in places where the dna has 2 consecutive (stacked) thymines

less flexible, no helical turn, no same major/minor grooves

Question 7

oxidative damage by h202 and free radicals

Answer 7

compounds w/ unpaired e-
ex; oh and o

Question 8

chemicals

Answer 8

ex: base analogs (AZT)
looks like base but is not, tricks enzymes into using them making nucleic acids made useless

Question 9

mutagenic agents

Answer 9

carcinogens (cancer-causing agents). allows uncontrolled growth (tumours). overpopulation (replicate/build quickly)