Pharm 411: The genetic code and Protein Synthesis Flashcards Preview

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What is the tRNA do?

its the link between the two codes (DNA code and RNA code) since it carries the amino acid to the site of protein synthesis


How do you read mRNA?

ALWAYS from the 5' to 3' and the growing protein chain ALWAYS GROWS from the N-terminal residue


What is the basic unit of genetic code?

The codon; which is a group of three nucleotides, found in mRNA


What is the anticodon?

Part of the tRNA which has three bases and pairs with codon


What is a start codon?

signals the start of the protein and codes for the first amino acid (n-terminus) AUG


What is a stop codon?

End of protein synthesis UAA UAG UGA


Why do amino acids come in groups of three?

With only 4 bases, they wouldnt be able to code for all 20 amino acids alone, and two bases together could only code for 16 Using 3 bases means 61 codons specify an amino acid with 3 stop codons


What does it mean by amino acids are degenerate?

It means that amino acids often have more than one possible codon


What is a open reading frame?

Codons are read from a fixed starting position, three nucleotides at a time in the 5'-3' direction. The reading frame starts with a start codon and then ends with an end codon


Do we use overlapping or non-overlapping code?

We use non-overlapping (we always read in sections of 3)


What are the two types of mutations and what occurs with each?

Point mutation: change in ONE base with no effect on reading frame Frameshift mutation: One or two nucleotide insertion or deletion moves the reading frame out of register, which will give a shorter or longer protein with different protein sequence


What are the different types of point mutations?

Silent missense nonsense


What is a silent mutation?

Change in codon does not result a change in the amino acid sequence uUG-(leu) ---> cUG (leu)


What is a missense mutation?

Change in codon results in change in amino acid sequence UuG (leu) ----> UcG (ser)


What is a nonsense mutation?

Change in codon results in a premature stop codon UuG - (leu) ----> UaG (stop) leads to smaller protein


What can the result of mutations give?

A mutation could be positive, negative or neutral There is no way to know what effect a mutation will have but the majority of the time they will have a negative effect


What is an insertion mutation?

Frameshift When you insert one or two base pairs into the mRNA which will cause a shift in the reading frame


What is a deletion mutation

Frameshift When you delete a section of the mRNA and it shifts your reading frame


What does is meant by charging tRNA?

Its the process where an amino acid is attached to tRNA which will form an amioacyl-tRNA


Where is the amino acid added onto the tRNA?

Its attached on the 3' end of tRNA


What is responsible for charging tRNA?

aminoacyl-tRNA synthetases Each synthetase is specific for one amino acid and for one or more tRNA


Why is it important to have high specificity for amioacyl-tRNA synthetases?

to build the correct protein its very important to have the tRNA to have the correct amino acid attached so it can translate the genetic code to a protein


Where do edits of tRNA changing take place?

They happen within the synthetase; once the tRNA leaves the synthetase there is no way we can edit it or check it for accuracy.


How does the aminoacyl-tRNA synthetases make sure that it binds the correct amino acids?

It has an editing site as well as an acylation site -The acylation site will reject amino acids that are larger than the correct one -The editing site rejects amino acids that are smaller than the correct one **all the editing happens without dissociation of the tRNA from the synthetase


What does the term wobble mean?

Used for pairing between two nucleoti that do not follow watson-crick base pairing rules These is the reason for the last codon is most often different and why amino acids have degeneracy


What is the wobble position?

Base pairing between the first nucleotide of tRNA (5' end) and the third nucleotide of the mRNA codon (3' end) **ALWAYS AT 5' end of anticodon


What causes the formation of inosine?

the deamination of adenine


What are the 5 bases involved in wobble?

Inosine, Guanine, Uracil, Adenine and cytosine


What are the base pairings that happen during wobble>

Inosine can bind to every thing but guanine guanine can bind to uracil I-C I-U I-A G-U **they can also form their normal bonds


EX of wobble 3' UCG 5' (anticodon) what are the combos that can happen?

(codon) 5' AGC 3' U