Collinearity of Genes & Protein Flashcards
(32 cards)
How many genes usually encode for each protein?
One.
What is the central dogma of molecular biology?
DNA (genes) - mRNA- protein - function - cell / organism.
Information flows from DNA to RNA to make proteins. Can this be reversed.
Not usually, no. It is a unidirectional flow of information.
The DNA sequence corresponds to the amino acid sequence. True or false?
True.
…………….. are joined into ……………… chains, which are folded to make proteins. There are an average of 500-1,000 ……………. in every protein.
Amino acids, polypeptide, amino acids.
All amino acids have the same structure, apart from ………………… .
The R group.
What four atoms / molecules are bonded to the central carbon atom of an amino acid?
A hydrogen atom, an amino group (NH2), a carboxyl group (COOH) and an R group.
How many different amino acids are found in living cells?
Twenty.
What are the four categories of amino acids?
- Neutral and non-polar (hydrophobic).
- Neutral and polar (hydrophilic).
- Acidic (negatively charged).
- Basic (positively charged).
Which category do these nine amino acids belong to?
Glycine, alanine, valine, leucine, isoleucine, methionine, phenylalanine, tryptophan and proline.
Neutral and non-polar.
Their R groups can be aliphatic (a mixture of hydrogen and carbon atoms) or aromatic (more complicated).
Which category do these six amino acids belong to?
Serine, threonine, cysteine, tyrosine, aspargine, glutamine.
Neutral and polar.
The R groups of these amino acids are not charged but they can interact with water by hydrogen bonding.
Which category do these two amino acids belong to?
Aspartate, glutamate.
Acidic.
Their R groups have a negative charge.
Which category do these three amino acids belong to?
Lysine, arginine, histidine.
Basic.
Their R groups have a positive charge.
Where in proteins are neutral, non-polar amino acids likely to be found and why?
They are often found in the centre of proteins because they are hydrophobic.
The first evidence of how genes encode for specific proteins came from studies on which type of cells?
Red blood cells and haemoglobin.
Haemoglobin is a ………………. made of two …………. and two …………….. polypeptide chains. In inherited anaemia, sufferers have an altered ………….. caused by ……………….-…………….. mutations following Mendelian Laws.
Tetramer, alpha, beta, globin, semi-dominant.
When the mutation for sickle cell anaemia is homozygous, all of the haemoglobin is altered and the sufferer develops severe anaemia.
What happens if the sickle cell gene is heterozygous?
The sufferer will still have anaemia, but less severely, because only have of the beta-chains are altered. The haemoglobin is only partially defective.
Why can having the heterozygous sickle cell anaemia gene sometimes be an advantage?
Parasites cannot live in the slightly altered red blood cells so the hereterozygous form of sickle cell anaemia confer resistance to malaria.
In sickle cell anaemia, the sixth amino acid in haemoglobin specifically changes from glutamate to valine. Why is this change so drastic?
The change from glutamate to valine is a drastic one because glutamate is acidic, negatively charged and hydrophilic, whereas valine is neutral, uncharged and hydrophobic.
What is a silent mutation?
A mutation which does not cause any damage or change to the amino acid produced.
In the 1950s, Seymour Benzer isolated mutants of the trpA cistron in E.Coli, which allowed him to do what?
He mapped the positions of these mutations within the gene and compared them to the sequencing of the amino acids.
Tryptophan synthase (trpA) can be read in the same direction and with the same spacing as the corresponding amino acid sequence, which is evidence of collinearity.
What are operons?
Operons are unique to microbes and keep their genome compact.
More than one genetic mutation can affect the amino acid at a single position, BUT there can be recombination between the mutants. What does this prove?
That the original mutations must be at different nucleotide position - more than one nucleotide corresponds to each amino acid.
How do four nucleotides (adenine, thymine, guanine and cytosine) encode for twenty different amino acids?
Each amino acid corresponds to a triplet of nucleotides - a codon.
