Gene to protein to phenotype Flashcards
What is a prion and what disease is a result of prions?
Prions are normal proteins that ref old into different dangerous infectious structures that kill brain and nervous cells. This is the case in Creutzfeld-Jakob disease vCJD or mad cow disease as its more commonly known.
A child who’s newborns urine turns black in air suffers from what disease and how is it inherited?
Alkaptonuria, an autosomal recessive trait linked to the inability to produce enzymes needed to metabolise homogentisic acid so their urine turns black.
Genes produce changes in … Through proteins
phenotype
The amount of genetic information held in a cell is a function of the number of nucleotides in a cell on the 46 chromosomes the cell holds. How many genes roughly are on a chromosome and how many nucleotides make up a gene?
Hundreds or thousands of genes on a chromosome. Genes are typically made up of several hundred to several thousands of nucleotides.
What is a protein?
A linear sequence of amino acid subunits folded into a specific 3D structure related to its function.
How many amino acids are commonly found in humans?
20
How many nucleotides code for an amino acid?
3
Note several different 3 nucleotides sequences may code for the same amino acid.
When you write the nucleotide code for amino acids do you write the DNA code or the RNA code for convention?
RNA code
What are the 4 special codons?
Start codon AUG (also codes for methionine)
Stop Codons UAA UAG UGA
A group of 3 nucleotides coding for an amino acid is called?
A codon
Transcription is…
The gene in the DNA being encoded into pre-messenger RNA in the nucleus.
Translation is…
In the cytoplasm the messenger RNA is converted into a sequence of amino acids in a polypeptide chain to from a protein.
What determines the structure and thus the function of a protein?
The amino acid sequence.
What is pre-messenger RNA?
The transcript made by the DNA template that will go on to be modified to messenger RNA.
What is messenger RNA?
A single stranded complementary copy of the amino acid coding nucleotide sequence of a gene.
(Modified pre-mRNA)
Where is pre-mRNA modified to mRNA?
In the nucleus.
Where does transcription initiation start?
The promoter region of the DNA sequence.
What is the name of the stage of transcription where the gene is read and complementary pre-mRNA is made?
Elongation
Describe transcription
RNA polymerase binds to the promoter region, one strand of DNA is used to make pre-mRNA. The polymerase moves along the DNA unwinding it and linking complementary RNA nucleotides into a strand . Opened DNA at the site of transcription is called the transcription bubble. Transcription is terminated at the 3’ termination sequence where the RNA polymerase dissociates.
What are the tree stages of transcription?
Initiation
Elongation
Termination
Define Introns
Nucleotide sequences in genes that do not code for amino acid sequences in proteins.
What are exons?
What is left in mRNA after introns have been spliced out. The sequence of bases that correspond to the amino acid chain of the protein.
What happens when pre-mRNA is converted into m-RNA?
Introns are spliced out leaving just the exon sequence.
A nucleotide cap is added to the 5’ end.
Poly-A tail is added to the 3’ end, this is a tail of 30-100 nucleotides.
The final product is a mature mRNA molecule.
How does mRNA leave the nucleus for translation?
Through nuclear pores
What is alternative splicing?
Exons can be retained or removed during splicing, allowing processed mRNA to contain different exon sequences- this allows one gene to code many different forms of a protein.
95% of pre-mRNA splicing has alternative slicing.
What are the three acteristic parts of amino acids?
Amino group (NH3) Carboxyl group (COOH) R Group- the side chain.
Where does a peptide bond form between amino acids?
Carboxyl group to amino group- forms in translation.
What is the free amino group at the end of a polypeptide known as?
N-terminus
What is the free carboxyll group at the end of a polypeptide known as?
C-terminus
By convention which way do we write poly peptide sequences?
N-terminus to C terminus
Peptide bond link a what to a what covalently?
C-N the OH on the C and the H on the N are lost as water.
Describe the role of rRNA in translation
The rRNA in the rage subunit acts as an enzyme linking amino acids together in the order specified by the mRNA codons.
What is transfer RNA?
Transfer RNA molecule bring amino acids to the mRNA ribosome complex for translation.
There are two parts to a tRNA molecule
-The anticodon (complementary 3 RNA bases to the codon on the mRNA)
-Site for amino acid attachment specified by the mRNA codon.
Describe translation.
The m-RNA binds to the small ribosomal subunit at the start codon for methionine AUG. Transfer RNA coding the anticodon for methionine binds and then the large ribosomal subunit binds. Transfer RNA carries amino acids with the anticodon dictated by the mRNA into the Ribosome at the A site of the ribosome. The large ribosome subunit contains rRNA which acts as an enzyme linking amino acids by making peptide bond in the P part of the ribosome. The transfer RNA then exits at the E site. The ribosome moves along the mRNA in this fashion throughout elongation. Termination occurs at the end codon which doesn’t code for any amino acids. Release factors (proteins) bind instead to the stop codon. The polypeptide, mRNA and tRNA release from the ribosome.
What is the first amino acid in all transcription?
Methionine
The initiation complex is
The tRNA blinded to the mRNAcodon for methionine in the ribosome- both small and large units.
What is a polysome?
After initiation has occurred new initiation complexes can form on the mRNA. One mRNA molecule with many ribosomes attached is called a polysome.
What does RNA stand for?
Ribo
Nucleic
Acid
Why do we cap pre-mRNA?
Protect against degradation
What is and why do we add polyAtails to pre-mRRNA
Lots of A’s added to protect from degradation
What is capping?
5’ to 5’ linking by 3 phosphates covalently bonded. This protects and has a function in translation.
What is a ribosome made up of?
Proteins and rRNA with two subunits.
We have a 40 subunit and a 60 subunit. We have 80s ribosomes
Prokaryotes have 30S and 50S known as 70S ribosome
What is the wobble position and what does it exhibit?
3’ of codon base and thus the 5’ anticodon on base is the wobble position.
In translation and inosine on the tRNA may bind to a U, C or A on the mRNA. This allows a singe tRNA to recognise multiple codons.
Does elongation in translation require energy?
Yes, in translocation
