6.1.1 Cellular control Flashcards
What are the 3 components of a nucleotide?
Phosphate, deoxyribose sugar, base
Which bases are purines or pyrimidines?
A and G are purines.
T and C are pyrimidines.
What is a gene?
A sequence of bases, it codes for the production of amino acids which fold into proteins.
What is the fixed position of a gene called?
The locus.
What does it mean by the code being degenerate?
It means that more than one codon that codes for each amino acid.
What does it mean that the code is non-overlapping?
Each base is only read once.
What does it mean by the code being universal?
The same codon codes for the same amino acid in all organisms.
What is a mutation in a gene?
The change in the sequence of bases in DNA.
What are the 3 key types of mutation?
Substitution, insertion, deletion.
What are the features of a substitution mutation?
One nucleotide is substituted for another. EG ATC turns to AGC. The code is degenerate so sometimes this has no effect.
A change in the base sequence can cause a change in the amino acid sequence which can change the primary, secondary and tertiary structure of the protein.
What are the features of an insertion mutation?
An extra nucleotide may be added. Eg ACT may change to ACGT.
What are the features of a deletion mutation?
A nucleotide is removed.
What type of mutations cause a frame shift?
Deletion, insertion.
What is a frame shift?
It changes all of the codons after the mutation as it shifts the sequence of bases.
It causes all further amino acids to be changed including start/stop codons.
It results in a protein that will no longer perform it’s correct function in the cell.
What are the 3 effects a mutation can have?
Nonsense - the mutation results in one of the three stop codons.
Mis-sense - results in a different amino acid sequence being coded for, EG GTC changes to GTT.
Silent mutation - The same amino acid is coded for despite the mutation, could be the two codons code for the same amino acid or it occurred in non- coding region of DNA.
What are the 3 phenotypic effects mutations can have?
Neutral - Normal functioning proteins are still synthesised - phenotype of organism is unchanged.
Harmful - Proteins aren’t synthesised or are non-functional. Negatively impacts the phenotype.
Beneficial - Proteins synthesised with new and beneficial characteristics in the phenotype.
What effect can mutations have on enzymes?
Many proteins coded for by genes are enzymes which regulate metabolic pathways.
Mutations can cause the active site to be changed.
Enzyme activity can be slowed or stopped altogether.
What are mutagens?
They increase a mutation’s appearance.
What are the 3 mutagens?
Physical, chemical and biological mutagens.
What are chromosome mutations?
Where do they usually occur?
What can cause them?
They are mutations that affect whole chromosomes or number of chromosomes.
Usually occur in meiosis.
They can be caused by mutagens.
What effects do chromosome mutations have?
They can be silent but also lead to developmental difficulties.
What changes in chromosome structure can chromosome mutations have?
Deletion - section breaks off.
Duplication - section duplicated.
Translocation - section breaks off, and joins another homologous chromosome.
Inversion - section breaks off, is reversed, then joins back on.