Nucleic acid and protein synthesis and regulation Flashcards
what are the four basic genetic process that help produce and maintain the proteins and nucleic acids of a cell?
protein synthesis
DNA replication
DNA repair
genetic recombination
what are some steps involved in the synthesis of protein?
DNA transcription
mRNA translation
ribosomal assembly
what is the first step in protein synthesis?
transcription
what does transcription do?
process takes the genetic information from DNA and transcribes it into form of a messenger RNA
how is immature mRNA modified?
RNA splicing to remove introns
describe the process of RNA splicing
- done by enzyme RNA polymerase which recognize promoter sequence in DNA with help of transcription factors
- RNA polymerase binds to this sequence and then initiates transcription of downstream genes
what happens when RNA polymerase reaches the termination sequence?
dissociates from template DNA strand and releases newly synthesized immature mRNA to be modified by splicing
what are some components that can affect whether or not certain genes are transcribed?
gene regulatory component
histone acetylation/deacetylation
methylation
what are the three main types of RNA involved in protein synthesis?
mRNA
rRNA
tRNA
what is rRNA?
ribosomal RNA
- makes up the structure of the ribosome
what do ribosomes catalyze the formation of?
peptide bonds (connections between each amino acid in a protein)
what is tRNA?
transfer RNA
- RNA that carries specific amino acids based on the genetic code to the ribosome that creates peptides
How does the tRNA know which amino acid it needs to take to the ribosome to make protein?
anticodons
what are codons?
three-nucleotide sequence that correspond to specific amino acids
what is a group of three nucleotides considered and what does that mean?
reading frame
- means that when protein synthesis occurs, DNA code is read by three nucleotides
what is used when a tRNA transfers an amino acid corresponding to the genetic code?
anticodon (complimentary to the codon present in DNA)
- tells tRNA which amino acid is next in the polypeptide sequence
in prokaryotes, the 70S ribosome is made of which subunits?
30S and 50S
in eukaryotes, 80S ribosomes are made up of which subunits?
40S and 60S
what is the A site of the ribsosome?
part of the ribosome where tRNA delivers amino acid
what is the P site of the ribosome?
where the formation of the peptide bond is catalyzed
what is the E site of the ribosome?
where the peptide chain exits the ribosome as it is being synthesized
list the stop codons
UAG
UAA
UGA
what is the start codon and which amino acid does it correspond with?
AUG
methionine
in prokaryotes, what is the start codon and what is special about it?
fMET because it has a formyl group attached to it
how are disease causing mutations found in our cells usually eliminated from the population and only present at low rates?
natural selection
list types of mutations
silent
frameshift
missense
nonsense
what is point mutation caused by and which types of mutations are included in this?
caused by a single base pair change
- silent, missense, and nonsense
describe frameshift mutations and what does it produce?
- result in shift of reading frame
- causes production of short (truncated) protein or change up protein structure entirely due to addition of wrong amino acid
what are the DNA repair mechanisms that are commonly used in cells?
base excision repair
double stranded break repair
mismatch repair
describe base excision repair
- only the damaged nucleotide is removed and then replaced
- everything is glued back together using DNA ligase
describe mismatch repair
- mis-paired bases removed from DNA strand
~ done by proteins that first recognize mismatched area and then cut out that whole patch of DNA - DNA polymerase puts the new correct base
- DNA ligase glues pieces back together
describe double stranded break repair
- occurs when DNA has been damaged and a double stranded break has been created
- occurs when exposed to high-energy radiation
- repaired via non-homologous end joining (NHEJ) and homologous recombination (HR)
describe NHEJ in double-stranded break repair
- cell glues DNA back together at breakage point
- usually small mutation at the breakage site
why is NHEJ not the best way to repair?
the cell can lose some DNA at the breakage point or could be addition of new DNA at breakage point which results in small mutation at breakage site
describe HR in double-stranded break repair
information of damaged chromosome is found in homologous sister chromosome/chromatid, and information is used to repair DNA
what must happen in order to replicate DNA?
strand must be separated and each single strand is replicated by DNA polymerase
what is the purpose of primase?
RNA primer to start replication
what is the main idea behind DNA replication?
base pairing
what is base pairing?
explains which nitrogenous bases bond together
list which nitrogenous bases bond together
A (adenine) ——> T (thymine)
G (guanine ——-> C (cytosine)
how many hydrogen bonds are between A and T?
2
how many hydrogen bonds are between G and C?
3
If the DNA has a higher percentage of G and C base pairs, it will have a ______ melting point compared to DNA that has a ______ percentage of A and T base pairs.
higher
how does the DNA composition melt?
temperature at which it denatures or two strands separate
what DNA helicase work?
unzips DNA to make a replication fork
what is a replication fork?
point at which DNA transitions from being one double stranded molecule to two strands
the synthesis of the copy of DNA using the single strand as a ______ will begin
template
DNA polymerase only synthesizes DNA in which direction?
5’-3’ direction
describe the leading strand
- has normal DNA replication
- DNA synthesis will occur continuously in the 5’-3’ direction starting at the 3’ end of the template strand
describe the lagging strand
- DNA replication occuring in a discontinuous manner
- synthesis still occurs in 5’-3’ direction
- DNA polymerase will have to stop and then continue behind the previously synthesized fragment
what fills the space in between the okazaki fragments?
DNA ligase
what is the 3’-5’ exonuclease activity?
removes mis-paired/unpaired bases during replication
When DNA is unzipped by DNA helicase, sometimes upstream the DNA gets wound up into a ________.
supercoil
what enzyme removes supercoils that appear downstream of the DNA helicase?
DNA topoisomerase
how does topoisomerase remove coils?
creates a “nick” in the DNA to relieve tension and prevent DNA from breaking
- nick closed immediately because when DNA topoisomerase creates this break, its a reversible reaction
DNA topoisomerase I vs II
I- makes a single strand break
II- makes a double strand break
how do viruses replicate their genetic material?
they infect other cells and hijack their replicative machinery in order to replicate themselves
- genetic material can be either DNA or RNA, which can be linear, circular, double stranded, or single stranded
what is the result of genetic recombination?
increase in diversity of gene combinations in our chromosomes
what are the two types of genetic recombination?
- general recombination
- site-specific recombination
describe general recombination
- process involves double strand breakage of a segment of DNA on a chromosome which is then switched with homologous region on the homologous chromosome
- only occurs between two homologous regions on chromosomes
- used in homologous recombination
what does site-specific recombination require?
recombination enzyme that recognizes specific sequences that are present on the recombining DNA molecules which are the ones that are involved in recombination
- commonly occurs in bacteria
in prokaryotic and eukaryotic chromosomes, what are the mobile genetic elements that function in the same way as site specific recombination and how does it work?
transposable elements
- move around in the host genome using recombination enzyme
- elements can insert themselves in the middle of important genes, causing a disruption which may lead to disease
