Molecular Biology: Translation and Genetics

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Questions and Answers

What is the function of a codon in the genetic code?

It specifies the sequence of nucleotides.

It encodes an amino acid. (correct)

It increases the rate of protein synthesis.

It replaces protein-coding sequences.

What characteristic of the genetic code allows multiple codons to encode the same amino acid?

Specificity

Universality

Redundancy (correct)

Non-overlapping

What can result from a frameshift mutation?

An entirely different amino acid sequence. (correct)

A protein devoid of any amino acids.

A protein with the exact same amino acid sequence.

An increase in the number of base pairs.

Which condition is associated with trinucleotide repeat expansion mutations?

Huntington disease Signup and view all the answers

What does the term 'non-overlapping' mean in the context of the genetic code?

Each nucleotide belongs to one codon only. Signup and view all the answers

What effect does the deletion of three nucleotides have in cystic fibrosis?

It leads to a truncated protein product. Signup and view all the answers

What is one consequence of point mutations in the genetic code?

It may result in a single amino acid change. Signup and view all the answers

Which of the following describes a characteristic of the genetic code known for its ability to function across almost all species?

Universal Signup and view all the answers

What is the result of losing Phe at the 508th position in the CFTR protein?

Destruction of CFTR protein Signup and view all the answers

Which molecule is primarily responsible for catalyzing the addition of amino acids to tRNA?

Aminoacyl-tRNA synthetase Signup and view all the answers

What is the primary sequence of events in protein translation?

Initiation, Elongation, Termination Signup and view all the answers

What is the primary function of tRNA in protein synthesis?

To carry amino acids to ribosomes Signup and view all the answers

Which of the following modifications can occur to polypeptide chains posttranslationally?

Hydroxylation Signup and view all the answers

What is the role of the A site in eukaryotic ribosomes during translation?

Attachment of aminoacyl-tRNA Signup and view all the answers

What occurs during the elongation phase of protein translation?

Amino acids are added to the growing polypeptide chain Signup and view all the answers

Which termination codon-related factor is present in eukaryotes?

eRF Signup and view all the answers

Study Notes

Translation Overview

Translation is the synthesis of proteins
It involves nucleic acids, DNA replication, and transcription
It's a crucial process in the central dogma of molecular biology

The Genetic Code

Proteins, with 20 different amino acids, are coded by mRNA sequences containing only 4 nucleotides
A codon is a sequence of 3 nucleotides encoding an amino acid
There are 64 possible combinations of codons

Codon Table

A table with 3 positions (First, Second, Third) to decode codons
Different codons translate into specific amino acids

Reading Frames

mRNA sequence can be read in different ways (frames 1-3)
This sequence impacts the amino acid sequence of the protein
Alterations through insertion or deletion mutations produce frame-shift mutations resulting in inaccurate amino acid sequences

Point Mutations

Point mutations change a single nucleotide in the DNA sequence and may be altered to a different amino acid (missense) or a stop codon (nonsense)
Point mutations can be silent if they change the codon to a synonymous codon that codes for the same amino acid

Trinucleotide Repeat Expansion

Mutations where a sequence of 3 bases is amplified
Results in extra amino acids within the coding region
Can lead to neurodegenerative disorders or reduced protein production in non-coding regions, like Huntington's disease

Cystic Fibrosis

A mutation in a gene coding for a protein (CFTR) leads to the malfunction of CFTR destroying the protein
The deletion of 3 nucleotides in the CFTR gene often results in a loss of phenylalanine at position 508

Protein Synthesis Requirements

Translation requires amino acids, tRNA, aminoacyl-tRNA synthetases, mRNA, ribosomes, protein factors, and energy (ATP and GTP)

tRNA Structure

tRNA carries amino acids to the ribosome for protein synthesis
It includes an anticodon sequence that base-pairs with the mRNA codon
It has an amino acid attachment site

Aminoacyl-tRNA Synthetase

Enzymes that accurately attach the correct amino acids to their corresponding tRNA molecules
This activation of amino acids is an energy-intensive step

Eukaryotic Ribosome

Ribosomes are the site of protein synthesis
Composed of rRNA and ribosomal proteins
Have binding sites for tRNA molecules carrying amino acids
Found in the cytoplasm or associated with the rough endoplasmic reticulum

Peptide Bond Formation

Peptidyl transferase catalyzes the formation of peptide bonds between amino acids
It's an enzyme within the ribosome, where the growing polypeptide chain is extended

Steps in Protein Translation (Initiation, Elongation, Termination)

Initiation involves assembly of components to begin translation
Elongation steps include adding amino acids to the growing polypeptide chain
Termination occurs when a stop codon is reached; signaling the release of the completed polypeptide chain

Post-translational Modifications

Trimming, Phosphorylation, glycosylation, hydroxylation, and carboxylation or acetylation, and addition of farnesyl groups are some post-translational alterations

Energy in Protein Synthesis

4 high-energy bonds are used per amino acid addition
These energies are required for aminoacyl-tRNA binding to the ribosome and ribosome translocation

Medical Relevance

Antibiotics like streptomycin, tetracyclines, and puromycin bind to prokaryotic ribosomes to inhibit bacterial protein synthesis
Diphtheria toxin inhibits eukaryotic protein synthesis

Additional Resources

Several YouTube videos are suggested for further learning

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Description

Explore the fundamental processes of translation and the genetic code in this quiz. Test your knowledge on RNA, codons, reading frames, and mutations that affect protein synthesis. Gain a deeper understanding of how genetic information is expressed in living organisms.