Exam 1 Flashcards
What are the steps of central dogma?
DNA synthesis (replication)-. RNA synthesis (transcription)-> protein synth (translation)
What is DNA composed of
2 strands of nucleotides
How are the nucleotide strands held together
hydrogen bonding
what are the 4 nitrogenous bases
A C G T
what does anti-parallel mean
opposite 5 to 3 and 3 to 5’
What are the prymidines
cytosine (C), thymine (T, DNA), and Uracil (U, RNA)
what are the purines
Adenine (A) and Guanine (G)
Do G to C have 2 or 3 hydrogen bonds
3
whats the ratio for nucleotides and amino acids in the genetic code
4 nucleotides encode for 20 amino acids of proteins
what is a complete set of info of DNA
genome
How is eukaryotic DNA packaged
into discrete chromosomes (23)
DNA in combination with organization proteins is
chromatin
what are homologous chromosomes
chromosome pair (maternal and paternal) minus sex chromosome
what specialized DNA sequence links duplicate chromosomes during cell division
centromere
What organisms have larger genome
more complex organisms (minus amoeba)
what proteins are involved with compaction
Histones
combination of protein and DNA
chromatin
how many histones form a protein bead
8
what is it called when DNA coils around these protein beads
nucleosome
what is an octamer
nucleosomes that have 2 of each histones
What does the H1 histone do
further compacts the “beads on the string”
what uses ATP hydrolysis to slide DNA around a histone
chromatin- remodeling
How does DNA replicate
chromosome is duplicated using itself as a template
how is DNA semi-conservative
daughter molecule contains one of the parent strands
where does DNA replication start
origin of replication
How is DNA split during cell replication
with specialized enzymes
where are replication origins typically enriched?
A-T because they only share 2 hydrogen bonds
what begins splitting the DNA
the replication fork
which strand is continous and which is fragmented
leading= continuous
lagging has Okazaki fragments
how is the replication fork asymmetrical
there is a leading and lagging strand
what unwinds the double strand
DNA helicase
what prevents the formation of the double helix
single-stranded binding proteins (SSB)
What does primase do
creates short RNA primer so the DNA polymerase can begin
What synthesizes new DNA by adding nucleotides to existing strand
DNA polymerase
what corrects some errors made by DNA polymerase
exonuclease
what does primase make
RNA
difference betweenn making DNA and RNA
DNA needs primers
What fills in the gaps after the RNA primers are digested
ligase
What did Meselson and Stahl discover
that DNA is semiconservative
What keeps DNA polymerase attached to DNA
sliding clamp protein
what attaches the clamp protein
clamp loader protein
what separates RNA primer from DNA strand
nuclease
repair polymerase
Replaces RNA with DNA
what creates temporary breaks in DNA strand to relieve torsional stress
topoisomerases
What is a permanent error in DNA
mutation
negative consequences of mutations
leads to diseases
positive consequences of mutations
can cause resistant to infections (malaria)
what happens in mismatch repair
errors by the replication machine remove the new synthesized DNA and DNA polymerase and ligase fix gap
what are the three types of mutations
substitution, insertion, and deletion
substitution
changes from one base to another
insertion
extra base pairs are inserted into genome
deletion
base pairs are removed from genome
what happens during a frameshift
insertion and deletion cause the genetic code to read incorrectly during translation and transcription
what happens during depurination
loss of A or G, can be repaired or become permanent mutation
what happens in deanimation
loss of amino group on C/U
steps to DNA repair pathway
- removal of erroneous nucleotides via nucleases
- DNA repair polymerase fills gaps using the undamaged strand
- ligase seals the nick on the repaired strand
what causes double strand breaks
radiation, chemicals, errors around replication fork
gene expression
transcription converts DNA to RNA and the translation converts RNA to proteins
how does RNA differ from DNA
- RNA contains ribosomes, not deoxyribose
- RNA contains U instead of T
- RNA is typically single-stranded
what does RNA polymerase do
builds an RNA strand one nucleotide at a time, doesn’t require a primer
whats mRNA
RNA that will be converted to amino acids (proteins) called messenger RNA
rRNA
component of ribosomes (protein machine)
tRNA
move amino acids to ribosomes, match them to appropriate codons
microRNA
regulate gene expression by base pairing to mRNA silencing them by cutting them apart
what is a promoter
a specific sequence within DNA that signals the start of a gene for transcription
what is the terminator
where transcription ends the polymerase encounter
what does RNA polymerase ll do
trnasribe genes that code for mRNA and miRNA
what does RNA polymerase l and lll do
transcribe genes that code for tRNA and rRNA
what does RNA polymerase ll require
transcription factors
what does transciption factor TFllD do
binds to a promoter region known as a TATAbox (composed mainly of A and T nucleotides
what does mRNA need to receive before translation
it needs further processing. must receive a 5’ cap and 3’ polyA tail –> to stabilize mRNA and for it to be transferred out of the nucleus
Eukaryotic RNA need an extra step
needs introns and exons
what do introns do
a noncoding sequence that are interspersed in a coding sequence
what do exons do
coding region between introns
what do spliceosomes do
carry out RNA splicing in the cell and recognize common introns
what cuts out the introns
lariat (lasso)
alternative splicing do
transcripts several different ways to produce a variety of proteins from a single transcipt
where is mRNA exported
from the nucleus to the cytoplasm
what degrade mRNA after use
RNAses
which mRNA lifespan is shorter bacterial or eukaryotic
bacteria (3 min), eukaryotic last (30 min- 10 hours)
what is the genetic code
-set of rules that describe how a nucleotide sequence of a gene encodes a protein through mRNA
what is a codon
a set of 3 nucleotides code for a single amino acid
t/f the genetic code is redundant
true
what does the genetic code being redundant mean
most amino acids have more than one codon that codes for them
what are the three stop codons
UAA, UAG, UGA
what translates genetic code to proteins
tRNA
what links amino acid to tRNA
aminoacyl-tRNA synthetases
what are the protein manufacturing machines
ribosomes
where does the RNA message decode
ribosomes
what is the ribsome made of
a large and small subunit
what are the three binding sites for tRNA
E, P, and A site
function of E site
discharged tRNA exit at this site
function of P site
tRNA at this site carry the growing peptide chain
function of A site
accepts incoming charged RNA
what do release factors do
bind to stop codons instead of tRNA- waters added abd peptide chain is releases and ribosomal complex falls apart
what is needed to start protein synthesis
initiator RNA
where is intiator tRNA loaded
P site
how is translation started with ribosomes
- subunit attaches to mRNA until encounters start codon
- initator factprs fall away and large ribosomal binds
- begin protein synth woth tRNA added to A site
clusters of genes that direct different steps in the same process that are transcribed together in same mRNA
operons
what increases the rate of translation for each mRNA
polyribosomes
what destroys proteins by breaking peptide bonds between amino acids
protease
what do ‘stoppers’ do
bind to proteins tp be degrade, unfolded, and thread into inner chamber
what disrupts prokaryotic protein synth
antibiotics
