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25 Cards in this Set

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  • Back
Why do different cells have different functions if they all have the same genetic make-up?
they have selective reading of DNA or gene expression
What is the central dogma of gene expression?
DNA goes through transciption to produce RNA which then goes through translation to produce proteins
What is transcription?
it is the process of copying one portion of 1 strand of DNA into mRNA
What is translation?
it is the process in which the mRNA is used to sequence or direct protein synthesis
What types of RNA are involved in gene expression?
mRNA providing instructions for amino acid sequence for building proteins

rRNA for ribosmes composed of rRNA and proteins that help to synthesis more proteins

tRNA linke betweens mRNA sequence and amino acid production of proteins
Where does the gene expression occur in the cells of prokaryotes?
transcription and translation occurs in the cytoplasm of the nucleus because that is where prokarotes store their DNA
Describe prokarotic gene transcription?
RNA polymerase reads the DNA from 3'-5' and makes a complementary strand of mRNA sequence from 5'-3' using uracil in place of thymine
Why would the non-transcribed strand be called the coding strand?
because it is the same sequence as the mRNA
How does RNA polymerase know where to start?
in prokarotic cells the are promoters located at the start sites on the DNA template strand
How does RNA polymerase know when to stop?
it uses the common prokarotic stop signal? GC hairpin loop
What is the process of transcription in eukarotic cells?
it is similar to the process in prokaryotic cells only more complex

-iniation occurs where transcription factors bind to the promoter and assemble the initiation complex controlled with activators anjd repressors
What are some ways in which eukaryotic transcription is different from prokaryotic transcription?
in eukaryotic transcription and translation are seperated transcription occurs in nucleus the other out of nucleus

initiation complex forms at promoter in eu

and RNAs are modified after transcription
List the steps of modification of eu mRNA?
1 5' capping
2 3' poly A tail makes mRNA more stable
3 removal of introns to make mature mRNA
What are introns and exons?
intron is a portion of the mRNA that is removed before the mature mRNA is translated into a protein

exon a portion of DNA that is both transcribed and translated into a protein

exons are scattered DNA that will code for amino acids and introns are noncoding segments that the exons are scattered on
What are the steps in producing mature mRNA or RNA splicing?
1. transcription of primary sequence ALL DNA introns + exons
2. intron sequence are cut out
3. remaining exons are spliced together
What is a codon in regards to the genetic code?
it is a triplet of nucleotides that specifiy an amino acid that make up the genetic code
Describe whene translation begins?
it begions when mRNA binds to rRNA in a ribosome that contains rRNA and protein 2 subunits large and small that sandwich the mRNA
What are the steps of translation?
- start signal
- initiation complex



- stop signals
What is the start and stop signal for translation?
AUG or methionine
uaa is stop
What are the steps of initiation in translation?
mRNA binds to small unit on ribosome

tRNA binds to AUG condon on mRNA

initiation factors

large subunit
Describe the steps of elongation in translation?
tRNA is in P position of ribosome

second tRNA binds to ribosome at A position site

peptide bond forms between 1st and 2nd amino acid
Describe translocation in translation?
ribosome moves along mRNA

1st tRNA exits from E site

new tRNA enters A site
How does a gene mutation occur?
from either insertions or deletions i.e. frame shift

single base substitutions
What are different types of base mutations?
missense mutations - new base alters codon resulting in different amino acid i.e. sickle cell

nonsense mutation - new base changes a codon into a stop signal

silent mutation - new base changes a codon to one which encodes the same amino acid as original codon
What are the difference between Prokaryotic and Eukaryotic gene expression?
eu genes posses introns

eu mRNA must pass across the nuclear membrane before translation

bacterial mRNA often contains transcripts of several genes

eu have introns and exons