Biology Chapter: Translation and Genetic Code

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Questions and Answers

What defines a codon in the genetic code?

A sequence of proteins

A sequence of 3 nucleotides (correct)

A sequence of 4 nucleotides

A sequence of 3 amino acids

Which characteristic of the genetic code indicates that multiple codons can encode the same amino acid?

Degeneracy/Redundancy (correct)

Non-overlapping

Universality

Specificity

What is the consequence of frame-shift mutations?

They can change the reading frame of mRNA (correct)

They only affect non-coding regions

They always create longer proteins

They have no impact on protein synthesis

What disorder is associated with the trinucleotide repeat expansion of the CAG sequence?

Huntington disease Signup and view all the answers

Which of the following mutations is known to result in the deletion of three nucleotides?

Frame shift mutation Signup and view all the answers

How does fragile X syndrome primarily affect gene expression?

Through DNA hypermethylation Signup and view all the answers

What is the main feature of the genetic code regarding its universality?

It remains the same across all known species Signup and view all the answers

Which of the following accurately describes the 'commaless' characteristic of the genetic code?

Codons are uninterrupted by any additional signals Signup and view all the answers

What is the significance of the loss of Phe at the 508th position in the CFTR protein?

It is the most common mutation associated with cystic fibrosis in western Europe. Signup and view all the answers

Which component is essential for the activation of amino acids during protein synthesis?

Aminoacyl-tRNA synthetase Signup and view all the answers

What occurs during the termination phase of protein translation?

One of the three termination codons enters the A site. Signup and view all the answers

Which posttranslational modification involves the addition of carbohydrate groups to proteins?

Glycosylation Signup and view all the answers

What is required for the initiation of protein translation?

Assembly of ribosomal subunits and mRNA Signup and view all the answers

How many high energy bonds are broken per amino acid added during protein synthesis?

4 Signup and view all the answers

Which of the following describes the role of tRNA in translation?

It provides the amino acids in the order specified by mRNA. Signup and view all the answers

Which protein factor is involved in the initiation of translation in eukaryotes?

eIF Signup and view all the answers

Study Notes

Translation Overview

Translation is the synthesis of proteins from mRNA
The process requires nucleic acids, DNA replication, and transcription
It involves the structure of nucleic acids

The Genetic Code

Proteins with 20 different amino acids are coded by a mRNA sequence with only four nucleotides
A codon is a sequence of three nucleotides that encodes an amino acid
There are 64 possible combinations of codons

Codon Chart

A table showing the relationship between codons and amino acids
Page 4 of the images shows a detailed codon table

Reading Frames

A reading frame is a way of grouping nucleotides in threes to read the genetic message
Three possible reading frames in the mRNA sequence
These reading frames are non-overlapping on a single mRNA template

Mutations

Mutations are changes in the nucleotide sequence
Point mutations: changes in a single nucleotide, including a substitution, insertion, and deletion
Affects the amino acid chain if substitutions occur
Frame-shift mutations: addition or deletion of a base
These frame-shift mutations can alter the reading frame and create different amino acid sequences

Trinucleotide Repeat Expansion Mutations

Repeating sequences of three bases are amplified in the DNA
Within the coding region results in extra copies of amino acids
Within the non-coding region leads to a decrease in protein produced

Huntington's Disease

A disease caused by a trinucleotide repeat expansion mutation, increasing glutamine residues in the huntingtin protein
An example of triplet expansion disease

Cystic Fibrosis

Caused by a deletion mutation in the CFTR protein.
This results in the loss of a phenylalanine

Steps in Protein Translation

Initiation: involves the assembly of components of the translation system before peptide bond formation
- Two ribosomal subunits, mRNA, initiator tRNA, the aminoacyl-tRNA for the first codon, GTP, and initiation factors
Elongation: addition of amino acids to the carboxyl end of the growing chain
- Elongation factors bring in an aminoacyl-tRNA that pairs with the next codon, forming the next peptide bond.
- GTP is used and is then exchanged for GDP plus a phosphate.
Termination: occurs when one of the three termination codon moves into the A site. The termination codons are UAG, UAA, or UGA.
This process requires a release factor, with GTP being hydrolyzed

Post-translational Modification

Covalent alterations
Phosphorylation (adds phosphate)
Glycosylation (adds carbohydrates)
Hydroxylation (adds hydroxyl functional groups)
Biotinylation (adds biotin)
Farnesylation (adds farnesyl groups)
Trimming
Example modifications of polypeptide chains
Post translational modifications can happen after the peptide chain has been formed.

Energy Requirements of Translation

Four high energy bonds are broken per amino acid (a.a.) during protein translation
- Amino acid binding to tRNA
- Aminoacyl-tRNA to ribosome
- Ribosome translocation

Medical Relevance

Antibiotics attach to translational machinery to target prokaryotes
Diphtheria toxin affects eukaryotic translation

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Description

Explore the fascinating processes of translation and the genetic code in this quiz. Understand the intricacies of codons, reading frames, and mutations. Test your knowledge on how proteins are synthesized from mRNA and the implications of genetic variations.