Protein Synthesis Flashcards
Protein Synthesis
Process of creating new proteins
Where are the instructions for synthesizing proteins found?
DNA
Genes
Sequences of DNA that code for protein
Protein synthesis occurs in what 2 stages?
Transcription
Translation
Transcription
First stage of protein synthesis; DNA template carrying protein is transcribed into mRNA
What does the enzyme RNA polymerase attach to?
Promoter
Promoter
Beginning region of gene that allows for protein attachment
TATA box
Promoter sequence so common that it has been given special name (found in 25% human genes)
What does RNA have in place of thymine?
Uracil
Uracil
Identical to thymine but uses extra methyl group on its base
How does RNA polymerase join RNA nucleotides together?
By forming sugar-phosphate backbone
What is added to first RNA nucleotide to prevent degradation?
5’ cap
Poly (A) tail and what 2 things does it do?
Long string of adenosine nucleotides
Protects RNA from being degraded at 3’ end and allows for transport across nuclear envelope
Polyadenylation
Process of adding a poly (A) tail
Once an RNA strand has formed what breaks the DNA-RNA hydrogen bonds?
Helicase
mRNA
Transports protein instructions from nucleus to cytoplasm
What happens to mRNA before it leaves the nucleus?
RNA splicing
RNA splicing
Removes introns leaving behind exons
Exons are spliced together to form final translated form of mRNA
Where does RNA splicing occur?
Spliceosomes
Spliceosomes
Molecules containing combo of RNA and protein located inside nucleus
Introns
Sequences that don’t get converted into proteins
Exons
Sequences that code for protein
Translation
Second and final stage of protein synthesis mRNA code is used to make new protein
What is the ribosome responsible for?
Performing translation
Where does translation occur?
Inside cytoplasm or along rough ER
Composition of ribosomes
1/3 protein
2/3 rRNA
2 subunits of eukaryotic ribosomes
40s subunit
60s subunit
Job of 40s subunit
Attached to and reads mRNA
Job of the 40s subunit
Attached to and reads mRNA
Job of 60s subunit
Recruits tRNA and amino acids
mRNA enters the ribosome through which side?
40s 5’ side first
Codon
3-letter sequence of mRNA
Is the first start codon always AUG?
YES
What amino acid does AUG code for?
Methionine
5’ untranslated region
Everything before the start codon
3’ untranslated region
Everything in between stop codon and poly (A) tail
Which region in an mRNA sequence contains the exons?
Coding region
4 steps of protein synthesis in translation
-60s recruits tRNA
-once in ribosome, tRNA transfer the amino acid to the growing polypeptide
-Proteins are synthesized from N terminus to C terminus
-Once stop codon is reached ribosome detaches and new protein is released to cytoplasm
How many amino acids are used by humans?
20
What do amino acids differ in?
R group
What 5 things does amino acid composition affect?
Shape
Hydrophobicity
Charge
Solubility
Enzymatic abilities
What is the first amino acid in every protein?
Methionine
How many essential amino acids can’t be coded in our body and where do we get them from?
8
Acquired through protein in our diet
How can mutations be classified? (6 points)
-Whether they help, harm or have no effect on organism
-Whether a nucleotide is added, removed or changed
Missence mutations
Substitution mutations where change in nucleotide alters one of the amino acids in a protein
Nonsense mutations
Substitution mutations where new nucleotide causes amino acids to be replaced by a stop codon
Frameshift mutations
Insertion or deletion mutations that cause all subsequent amino acids to be altered
Gene expression not only controlled by genes, what else is it caused by?
Both genetics and environment
Epigenetics
Study of how gene expression is altered through factors other than DNA code
What is the most common way gene expression is decreased?
Methylation
Methylation
Process of adding methyl group to DNA so RNA polymerase can’t easily attach
