Protein Synthesis Flashcards
What is a gene?
A sequence of nucleotides bases found in DNA that codes for one or more polypeptides
What is a DNA dictionary
A grid showing the base triplets on the DNA reference Strand that code for each amino acid
What do genes code for
Polypeptides which have structural roles such as keratin and collagen,and metabolic rolls such as channel proteins, enzymes, antibodies and haemoglobin.
How is the sequence of amino acids in a polypeptide chain determined simply?
By the sequence of nucleotides bases on the Gene
How many different types of nucleotides bases are found in DNA and what are the ?
Four different types A, T, C, G
What kind of code do we call the genetic code and why is it called this?
The genetic code is a triplet code which means three bases code for one amino acid. This results in 64 different triplet codes
Why is the genetic code described as degenerate ?
Because most amino acids have more than one code (codon - meaning a collection of 3 bases….?) As there are only 20 amino acids used in protein synthesis. Some codons correspond to stop codes which indicate the end of the polypeptide chain
What does the term non overlapping mean in regard to the genetic code?
It means each triplet is read separately and no triplet is used for the same Gene
What does the term universal mean in regard to the code?
It means the triplet code is widespread and universal for all organisms and viruses.
What are prokaryotic genes like in terms of continuous and non continuous genes?
genes are usually continuous, lacking non-coding sequences (introns)
What are eukaryotic genes like in terms of continuous and non continuous genes?
The genes are usually discontinuous genes with coding exons and non-coding introns
What does Gene expression mean
Transcription and translation
What does the enzyme RNA polymerase do
It catalyses the formation of the mRNA molecule by: forms new hydrogen bonds , forms the RNA’s sugar phosphate backbone and catalyses the free nucleotides joining onto the template.
What does the term non-template Strand mean?
A coding Strand
What does the term ribonucleotide mean?
It’s another name for the free nucleotides
5’ and 3’?
This refers to the carbons in the shape. Transcription occurs 3’ to 5’ off the DNA strand, forming an RNA molecule that is 5’ to 3’
Comparison of tRNA and mRNA
Made of the same sugar and mRNA bases but tRNA structurally forms a different shape.
Comparison of DNA vs tRNA and mRNA
DNA has T, not U.
DNA has a different sugar- deoxyribose, not ribose
What does DNA helicase do ?
It works the same way as the direction of transcription, breaking hydrogen bonds.
What do pre mRNA and mature mRNA mean?
pre mRNA is the result of transcription and is still in the nucleus. Mature mRNA is the result of pre mRNA having undergone post transcriptional modification - just exons left. Mature mRNA is what leaves the nucleus. Both are single stranded.
What happens in post transcriptional modification?
Introns (non-coding triplets/codons) are spliced out by an enzyme. This is initiated by primers. Does not occur in prokaryotes. DNA ligase makes the remaining triplets join / ‘ligated’ together.
What are introns
The non coding areas of a gene
How does RNA polymerase know when to stop transcribing
There is a stop-transcribing sequence, at which point RNA polymerase leaves the DNA
What do ribosomes consist of
rRNA and protein
What happens to make the amino acid attach to a TRNA molecule
It is activated by ATP and then attaches to the specific trna molecule
What is usually the start codon on Mr n a?
AUG
Where can polypeptides be further modified and and potentially combined with other polypeptides to create complete protein?
Golgi body
Define exon
A section of pre-mrna, transcribed from DNA, which will code of the protein
Define intron
A section of pre-mrna, that is removed in post-transcriptional modification
Define the one Gene one polypeptide hypothesis
This hypothesis suggests that there is a specific, separate Gene that codes to each polypeptide and that they exist on a one-to-one ratio basis.
What are the three types of mutation?
Deletion, insertion, substitution
Deletion
A base is lost or deleted
Insertion
An extra base is added or inserted
What is a frameshift mutation
Where the reading frame changes, changing the amino acid sequence from this point forward. It can be caused by deletion or insertion
Substitution
Where one base is substituted for another. If a substitution changes the amino acid, it’s called a missense mutation . if the substitution does not change the amino acid, it’s called a silent mutation. If a substitution changes the amino acid to a stop it’s called a nonsense mutation
Where are DNA fragments broken in regards to 5’ and 3’? (…?)
on the 5’ side…?
What are pyrimidines?
cytosine and thymine
What are purines?
adenine and guanine
