Hebert 1-6 Flashcards
what percentage of our genome is repetitive?
50%
what percent of our genes actually codes for protein?
1.5%
what are the 5 classes of DNA?
repetitive
heterochromatin
regulatory
intronic
coding
what are the 3 classes of RNA?
protein coding
catalytic
regulatory
what is the significance of AT-rich regions on DNA?
it is where the origin of replication can happen because it is easier to break 2 hydrogen bonds rather than the 3 found in GC regions
SS DNA binding proteins
keep DNA single stranded and protect from nucleases
how do eukaryotes differ from bacteria in DNA replication?
it occurs at multiple sites in eukaryotes and only a single site in bacteria
helicase
enzyme that unwinds DNA at both replication forks
-requires ATP
topoisomerase
cut a nick in supercoil strand so it can unwind then uses ligase to restitch it back together
type I vs type II topoisomerase
-type I doesn’t require ATP, cuts only one strand
-type II cuts both strands and allows a double strand to pass through the break
what is the significance of the OH on the 3’ end?
DNA polymerase III binds in order to continue making DNA
DNA polymerase III
-reads parental strand from 3-5
-synthesizes new DNA from 5-3
okazaki fragments
multiple RNA primers in the lagging strand
DNA polymerase I
-removes primers in 5-3 exonuclease activity
what enzyme fuses the DNA ends together after the okazaki fragments have been cut out
ligase
telomeres
-ensure that genes are fully replicated
-protect ends of chromosomes
-shorten with age
why don’t telomeres shorten in cancer cells?
these cells express telomerase
telomerase
-an enzyme comprised of protein and a short piece of RNA
-reverse transcriptase activity (can make DNA from RNA template)
-maintains telomere length
-expressed in primary cell lines which makes them immortal
what is the approximate length of DNA?
6.5 feet
how do histones work
histones are positively charged and DNA is negative so they attract each other
-H1 binds the DNA between the nucleosome beads
what histone modifications can impact gene expression?
acetylation, methylation, and phosphorylation
mismatch repair reduces the error of replication to how many errors per replication?
3.2
repairs bulky lesions as those caused by pyrimidine dimers
nucleotide excision repair
-removes only the problem base
-takes care of bases lost to deamination
base excision repair
how are double strand breaks repaired?
nonhomologous end-joining (error prone)
homologous recombination (less error prone)
protein coding rna
mRNA
catalytic RNA
rRNA
tRNA
snRNA
snoRNA
scaRNA
regulatory RNA
miRNA
riboswitch
RNA modifications enable ~_________________genes in the human genome to produce ~_____________different proteins.
30,000
100,000
what percentage of RNA in a cell is mRNA?
5%
monocistronic vs polycistronic mRNA
-eukaryotes (mono): RNA carries info from 1 gene
-prokaryotes (poly): RNA carries info from more than 1 gene (operon)
rRNA accounts for what percent in a cell?
80%
-has unusual bases and intrachain pairing
-3 sizes in prokaryotes
-4 sizes in eukaryotes
rRNA