Collinearity of the Gene and the Protein Flashcards
What is a gene ?
Segment of a DNA molecule
What does a gene specify ?
A protein
What is the function of most genes ?
to instruct the cell how to make a protein
What do you need to know to understand how genes work ?
Some simple protein biochemistry
Whats the process to get from DNA to cell ?
DNA - mRNA - Protein - function - cell organism
How are proteins made ?
-By joining together amino acids to form polypeptide chains
- The chains fold up to make a 3D structures
- Each amino acid in a protein has the same chemical structure except for its R group
What are the groups bonded to a central carbon atom in an amino acid ?
- Amino group
- Carboxyl group
- Hydrogen Atom
- R group ( different in each amino acid )
What are the 4 different classes of R groups ?
- Neutral and non-polar : 9
- Neutral and polar : 6
- Acidic : 2
- Basic : 3
What do amino acids join to form ?
peptide bonds
What is the primary structure and what is it determined by ?
Primary structure is an amino acid sequence and its determined by the genetic code of the mRNA
What is the secondary structure and what’s bonds and interactions does it have in it ?
-Folding and twisting of a single polypeptide chain
Results pf weak H-bonds and electrostatic interactions
What is the tertiary structure and what bonds does it contain?
Three dimensional shape of a polypeptide chain
Function of R-groups contained in the polypeptide
What is the quarternary structure and what does it occur in ?
Association between polypeptides in multi-subunit proteins
Occurs only with two or more polypeptides
Where did the first detailed evidence of how genes specify proteins come from ?
Studies on the oxygen binding protein found in red blood cells - haemoglobin
What is the structure of haemoglobin ?
It is made of four polypeptide chains ; two a-chains and two b-chains
What occurs to people with inherited disorders such as anaemia and thalassemia ?
- All of the sufferers have altered haemoglobin or more specifically a globin
- These disorders are caused by semi-dominant mutations obeying mendelian laws.
What occurs to the haemoglobin when a person has sickle cell anaemia ?
- When the gene defect is in homozygous form HbsHbs all of the haemoglobin is altered
-Some of the haemoglobin forms insoluble deposits in the red blood cells which become sickle shaped.
If the sickle cell anaemia gene defect is in heterozygous form hBShba does the person still suffer with the disease ?
Yes because the protein is a tetramer
What occurs to the haemoglobin in sickle cell anaemia - what does this change cause ?
-The sixth amino acid is changed from glutamine to valine
- This is a drastic change from an acidic, negatively charged, hydrophilic amino acid to a neutral, uncharged, hydrophobic one.
Why do changes of one amino acid for another destroy the function of a protein ?
- If the protein is an enzyme, the amino acid that carries out the reaction may be changed.
- The altered amino acid may have been involved in pairing with another amino acid to maintain the shape of the protein
What is a mutation that doesn’t affect the function of the gene ?
Silent mutations
What has the study of haemoglobin shown ?
That mutations in a gene can cause specific changes in a protein
What does it mean if the genetic map and the amino acid sequence are collinear ?
The mutations in the gene and the changed amino acids in the protein appear in the same relative positions.
How can 4 nucleotides ( G,A,T,C) encode for 20 different amino acids ?
In fact, each amino acid is specified by a triplet of nucleotides, known as a codon.
What can a mutation in a gene where one amino acid is changed for another cause ?
A mutation in a gene that causes a change of one amino for another can affect the function of a protein and can result in disease.
What are the protein sequence and the genetic map ?
Collinear
