2 lecture 6 Flashcards
recall the structure of DNA
Double-stranded
Each nucleotide composed of deoxyribose, phosphate, and nitrogenous base
what are the bases of DNA
4 bases: adenine, thymine, guanine, cytosine
what is the structure of RNA
Single-stranded
Nucleotides comprised of ribose, phosphate, and nitrogenous base
What are the bases of RNA
4 bases: A, C, G, and U (uracil)
what do genes do
encode proteins
what is a gene
is a sequence of DNA that contains information to make a protein
what does DNA do
the DNA stores information required to make every protein in the cell
what does a messenger RNA (mRNA) do
a messenger RNA (mRNA) extracts this information (from the DNA) and delivers it to a ribosome
What does the ribosome do
the ribosome “translates” the mRNA code into a sequence of amino acids
what is the process to encode proteins
the DNA stores information required to make every protein in the cell
a messenger RNA (mRNA) extracts this information and delivers it to a ribosome
the ribosome “translates” the mRNA code into a sequence of amino acids
what is The flow of genetic information
DNA → RNA → protein
how does the flow of genetic information occur
in 2 steps
what are the steps of The flow of genetic information
Transcription
Translation
what is transcription
(DNA → RNA)
what is translation
(RNA → Protein)
what is coded information is used for
coded information is used for protein synthesis
what is always true about the coding strand of DNA
coding strand is always 5 prime, 3 prime
an the opposite complimentary strand is 3 prime, to 5 prime
what is the start code for gene structure
ATG
what is the stop code for gene structure
TAA
whites the mRNA start code for genes structure
AUG
what is the mRNA stop code for gene structure
UAA
does transcription occur n bacteria?
yes
does it occur in the nucleus?
No— bacteria do not have a nucleus
where does Transcription occur
in the nucleus
is there an exception to where Transcription occurs
yes, it is only in the nucleus in eukaryotic cells
how does the RNA polymerase know where to to start
the promoter region–
thats how it knows where to start, then it zips down the DNA between the start and end code
matches the complimentary DNA to the RNA
it knows the difference between different edna sequences
it will open up the hydrogen bonds so it can read off of a single coding strand instead of 2
how does RNA polymerase work
RNA polymerase binds to the promoter region of the gene RNA polymerase zips down the length of gene, matching RNA nucleotides with complementary DNA nucleotides this forms messenger RNA (mRNA
where does translation occur
translation occurs in the cytoplasm
what does translation require
translation requires:
mRNA (made during transcription),
amino acids (20 different types)
transfer RNAs (tRNAs, for each amino acid)
energy (ATP) to bond an amino acid to a tRNA
ribosomes
what is The ribosome is composed of
The ribosome is composed of ribosomal RNA (rRNA
has a small and a large subunit that must work together to build a polypeptide
how does the Transfer RNA work
Transfer RNA: tRNA carries amino acids and matches its anticodon with codons on mRNA
how long are codons
Codons are 3 nucleotides long
how is a protein put together
A protein is put together one amino acid at a time
how does translation work
A protein is put together one amino acid at a time
the ribosome attaches to the mRNA at the promoter region (before AUG)
the ribosome facilitates the docking of tRNA anticodons to mRNA codons.
when two tRNAs are adjacent, a peptidyl bond is formed between the amino acids.
and a chain of amino acids is formed (polypeptide)
how does the genetic code work
is based in codons
no ambiguity: this means the sequence of codons can be used to predict the sequence of amino acids in a polypeptide..
each codon is paired with what
each codon to specifies an amino acid
a codon is comprised of what
a codon is comprised of three nucleotides = 64 possible combinations (43 combinations)
how many codons are there
61 codons for amino acids
what about the remaining 3 codons?
3 others are stop codons (UAG, UAA, UGA) which end protein synthesis
the genetic code is redundant
true or false
true
why is the genetic code redundant
multiple codons = one amino acid e.g. CUU CUC CUA CUG all of these are leu still, the only difference int he last letter but it doesn't make a big difference at all
what is the exception to the “genetic code is redundant”
AUG
can the sequence of amino acids in a polypeptide be used to predict the DNA sequence
apart from Met, the sequence of amino acids in a polypeptide CAN NOT be used to predict the DNA sequence
why is the code redundant
when these 2 molecules come together, it is very hard for them (energetically) to come together perfectly— because the process has to be fast and accurate, this third codon has been found to be dispensable for binding but very important to remain bound
is the genetic code generally universal
yes
what does it mean by the genetic code generally universal
this means similar DNA sequences = similar proteins
across many different organisms
what are mutations
Changes in genetic sequence = mutations
Changes in genetic sequence might do what
Changes in genetic sequence might affect the order of amino acids in a protein
what is Protein function dependant on
Protein function is dependent on the precise order of amino acids
what are the Possible outcomes of mutation
1 - no change in protein
2 - non-functional protein
3 - different protein
what is a Neutral mutation
mutation does not change the sequence of the protein, new codon = the same amino acid
example: the 3rd base in codon can vary for the same amino acid
what is a Base-substitution mutation
Substitution of one base for another can change codon; polypeptide sequence; and protein function
what is a frameshift mutation
Addition or deletion of a base, which changes the reading frame (sequence of codons)
incomplete or different protein
which cells in the human body have the same dna
each cell in your body (except sperm and egg cells) has the same DNA
but each cell only expresses a small percentage of all its genes
example: nerve and muscle cells perform very different functions, thus they use different genes
what is regulating gene expression
turning a gene or a set of genes on or off = regulating gene expression
how do cells “hit the off switch”
cells use repressors to regulate gene expression
repressors bind to the promoter and prevent the RNA polymerase from binding
how do cells “hit the on switch”
cells use activators to regulate gene expression
activators help the RNA polymerase bind to the promoter
how does Regulation by chromosome condensation occur
Folding up of the chromosomes prevents transcription
how does Regulation by mRNA degradation
occur
Nucleases cut mRNA
how does Regulation of Translation
occur
Slowing of binding of the mRNA to the ribosome
how does Regulation of Protein Degradation
occur
Proteases degrade proteins
