DNA to Proteins Flashcards
how is DNA to converted to RNA?
by transcription
how is RNA converted to protein?
by translation
what sugar is found in RNA?
ribose
what sugar is found in DNA?
deoxyribose
what makes up a nucleoside?
base + sugar
what makes up a nucleotide?
nucleoside (base + sugar) + phosphate group
what are the four bases in DNA?
Adenine Cytosine Guanine Thymine
what are the four bases in RNA?
A C G Uracil
what is the nucleoside containing adenine called?
adenosine
what is the nucleoside containing cytosine called?
cytidine
what is the nucleoside containing guanine?
guanosine
what is the nucleoside containing thymine called?
thymidine
what is the nucleoside containing uracil called?
uridine
what are the four building blocks of DNA?
dATP
dCTP
dGTP
dTTP
what are the four building blocks of RNA?
ATP
CTP
GTP
UTP
where does a phosphodiester bond form in DNA?
between a free 3’ OH group and a 5’ triphosphate
what does polymerisation of two nucleotides in DNA require?
two high energy bonds
where are new nucleotides added in a growing strand of DNA?
the free 3’ end
name a drug that is a nucleotide analogue
retrovir
which nucleotide is retrovir an analogue of?
thymidine
where is retrovir incorporated into when taken?
growing viral DNA
how does retrovir inhibit viral growth?
it lacks a 3’ OH growth so terminates chain elongation of the viral DNA
how does retrovir target only viral DNA and not human?
retrovir has a higher affinity for viral reverse transcriptase than it does for human DNA polymerases
what connects nucleotides in the same strand along the outside?
the sugar phosphate backbone
what bond forms between base pairs on complementary DNA strands?
hydrogen bonds
what are the complementary DNA base pairs?
A to T
C to G
how many hydrogen bonds form between A and T nucleotides?
two
how many hydrogen bonds form between C and G nucleotides?
three
how can the replication of DNA be described?
semi conservative
what unwinds DNA?
helicase
what enzyme catalyses DNA replication?
DNA polymerase
why does DNA have to be replicated before cell division?
to ensure daughter cells have a complete copy of the genome
what is required for DNA polymerase to begin replication and why?
an RNA primer as it can only add nucleotides to existing nucleotides
how is eukaryotic DNA replication bidirectional?
genomes have many origins of replication allowing it to begin simultaneously at several points
which strand of DNA is replicated continuously and why?
the leading strand
it always has a free 3’ strand
which strand of DNA is replicated discontinuously?
the lagging strand
what are the short segments replicated in the lagging strand called?
okazaki fragments
what enzyme synthesises the RNA primer needed for DNA synthesis?
primase
what enzyme looks for DNA damage and repairs it following replication?
DNA polymerase
what type of activity does DNA polymerase have that allows it to detect and repair DNA damage?
3’ to 5’ exonuclease activity
what is RNA?
ribonucleic acid
how many strands does RNA have?
one
what is a stem loop in RNA?
a local stretch of intramolecular base pairing
what are the three main classes of RNA?
rRNA
tRNA
mRNA
what is rRNA?
ribosomal RNA
what is tRNA?
transfer RNA
what is mRNA?
messenger RNA
what is the function of rRNA?
combines with proteins to form ribosomes where protein synthesis takes place
what is the function of tRNA?
carries amino acids to be incorporated into the protein
what is the function of mRNA?
carries the genetic information for protein synthesis
what base is different in RNA compared to DNA?
contains U instead of T
what enzyme makes RNA?
RNA polymerases
how many types of RNA polymerase does a prokaryotic cell have?
one
how many types of RNA polymerase does a eukaryotic cell have?
three
what are the three types of RNA polymerase called in eukaryotic cells?
Pol I
Pol II
Pol III
what RNA polymerase synthesises all mRNA?
Pol II
what acts as an adapter between the nucleic acid code and the amino acid code?
tRNA
what does an anticodon consist of?
three tRNA nucleotides
what is attached to the 3’ end of a tRNA anticodon?
a specific amino acid, depending on the anticodon sequence
what are the five steps of transcription?
RNA polymerase binding DNA chain separation transcription initiation elongation termination
what is required for RNA polymerase binding?
transcription factors
what are initiation sites for transcription called on DNA?
promotors
what happens during transcription initiation of RNA?
selection of the first nucleotide of the growing RNA
what happens during elongation of RNA?
addition of further nucleotides to the RNA chain
what happens during termination of RNA?
release of the finished RNA
where does transcription start?
initiation nucleotide + 1
where is the TATA box found?
around 25 nucleotides before the transcriptional start (-25)
what is TBP?
TATA box binding protein
what does TBP do?
recognises the TATA box
what is TBP part of?
TFIID
what is TFIID?
a general transcription factor required for all Pol II transcribed genes
what direction is the RNA chain synthesised in?
5’ to 3’ direction
what does a newly synthesised RNA make when finished?
a stem loop structure followed by a stretch of U’s
what happens when finished RNA is cleaved off of the DNA template?
RNA is released
polymerase dissociates
what is a coding section of a gene called?
an exon
what is a non coding section of a gene called?
an intron
what needs to be removed before mRNA is translated into a protein and what is this process called?
introns by splicing
what are steroid receptors?
a family of transcription factors that are a subset of a family of nuclear hormone receptors
where are steroid receptors found and what state are they in?
the cell cytoplasm where they are inactive
what happens when a steroid binds to a steroid receptor?
the steroid moves to the nucleus and binds to DNA at a steroid response element (SRE)
what is an SRE?
steroid response elements
what happens to tRNA in translation?
the anticodons on tRNA molecules form base pairs with codons on mRNA
how many nucleotides are found in codons and anticodons?
three
how many amino acids are there?
20
what does each possible codon code for?
one amino acid or a stop
how many possible reading frames are there for translation of each RNA molecules?
three, depending on where translation starts
what is the function of an aminoacyl-tRNA synthetase?
bind amino acids specifically to their corresponding tRNA molecule
what is an If?
initiation factor
what provides energy for initiation?
hydrolysis of GTP
what initiates RNA translation?
a small ribosomal subunit binds to the 5’ end of the mRNA and moves until it finds the start codon
what is the start codon?
AUG
what amino acid does the start codon code for?
methionine
what is the tRNA sequence complementary to the start codon?
UAC
where is the initiator tRNA located at the end of initiation?
the P site
what brings the second aminoacyl-tRNA into a ribosome during translation?
Ef-1a, an elongation factor
what site does the second amino-acyl tRNA enter during translation?
the A site
what is EFBy?
a second elongation factor in translation
what is the function of EFBy?
regenerates Ef-1a to bring the next aminoacyl-tRNA for translation
what moves the ribosome along by one triplet during translation?
elongation factor EF-2
when does termination of translation occur?
when the A site of the ribosome encounters a stop codon
what are the three stop codons?
UAA
UAG
UGA
what binds to stop codons and what does this cause?
release factor (RF) causes GTP hydrolysis
how many rRNA molecules does a ribosome contain?
four
what are the three tRNA binding sites in a ribosome?
E = exit P = peptidyl A = aminoacyl
what are the two types of ribosomes?
free and bound
where is a free ribosome found?
in the cytosol
where is a bound ribosome found?
on the rough endoplasmic reticulum
what is a point mutation?
a change in a single base in DNA
what does a missense mutation cause?
a change of the amino acid sequence
what can a missense mutation change?
protein function
what is an example of a disease caused by a missense mutation?
sickle cell anaemia causing akterer haemoglobin
what is a silent mutation?
a mutation causes by degeneracy of the egentic code that has no effect on amino acid sequence
what are the two types of frameshift mutation?
addition or deletion of a base
what effect does a frameshift mutation have?
changes the reading frame of translation into a protein
name four types of chromosomal mutation
deletions
duplications
inversions
translocations
