Cellular Control Revision Notes
Gene Mutations
Mutations
-change to the genetic material (DNA)
-can be change to structure/number of chromosomes
-mutagen cause mutations (UV light, X-rays, Gammas rays and tobacco smoke)
-change to genes = change to proteins
-change to gametes = change is inherited
2 Types of Mutations
Point Mutation (1 base replaces another)
Indel Mutation (base is inserted/deleted)
Point Mutations
-occurs during transpiration
-3 Types - silent, missense or nonsense
Silent Mutations
-change to a base that still codes for same amino-acid
-it does not affect protein - primary, secondary and tertiary structure will be the same so it can carry out its function
Missense Mutations
-change to base that affects the sequence of amino acids
-change the primary structure which will change the tertiary structure – changing the function of the protein
(e.g. sickle cell anaemia – amino acid valine instead of glutamic acid)
Nonsense Mutations
-change to base that causes a stop codon to form
-protein may be shorter, changing the function of the protein
(e.g. Duchenne muscle dystrophy)
Indel Mutations
-2 Types – insertions or deletions (frameshift)
Insertions
-bases are added to the gene sequence
-as genetic code is non-overlapping the genes shift (frameshift) so it will code for different amino acids
- if 3 bases are added, then an extra amino acid is coded for
-therefore the correct protein is coded and cannot carry out its function
Deletions
-bases are removed to the gene sequence
-as genetic code is non-overlapping the genes shift (frameshift) so it will code for different amino acids
-if 3 bases are removed, then an amino acid is removed
-therefore the correct protein is coded and cannot carry out its function
Chromosome Mutations
-change to the chromosome or number of chromosomes
Deletion – a section of chromosome breaks off and is lost within a cell
Duplication – sections of chromosome are duplicated
Translocation – a section of one chromosome breaks off and joins a non-homologous chromosome
Inversion – a section of chromosome breaks off, is reversed, and re-joins the chromosome
Expanding Triple Nucleotide Repeats
-some genes have a repeating triplet code (CAG-CAG-CAG)
-sometimes it will increase in length due to mitosis and passing onto generations
-If repeated over a certain number it can lead to diseases (Huntington’s Disease)
Useful Mutations
-blue eyes have less iris pigment – help to see better at lower light intensities BUT high light intensity can develop cataracts
-black skin – higher light intensities withstand UV BUT low light intensities cannot produce vitamin D leading to rickets
-different shaped earlobes – no effect
Gene Mutations
Mutations
-change to the genetic material (DNA)
-can be change to structure/number of chromosomes
-mutagen cause mutations (UV light, X-rays, Gammas rays and tobacco smoke)
-change to genes = change to proteins
-change to gametes = change is inherited
2 Types of Mutations
Point Mutation (1 base replaces another)
Indel Mutation (base is inserted/deleted)
Point Mutations
-occurs during transpiration
-3 Types - silent, missense or nonsense
Silent Mutations
-change to a base that still codes for same amino-acid
-it does not affect protein - primary, secondary and tertiary structure will be the same so it can carry out its function
Missense Mutations
-change to base that affects the sequence of amino acids
-change the primary structure which will change the tertiary structure – changing the function of the protein
(e.g. sickle cell anaemia – amino acid valine instead of glutamic acid)
Nonsense Mutations
-change to base that causes a stop codon to form
-protein may be shorter, changing the function of the protein
(e.g. Duchenne muscle dystrophy)
Indel Mutations
-2 Types – insertions or deletions (frameshift)
Insertions
-bases are added to the gene sequence
-as genetic code is non-overlapping the genes shift (frameshift) so it will code for different amino acids
- if 3 bases are added, then an extra amino acid is coded for
-therefore the correct protein is coded and cannot carry out its function
Deletions
-bases are removed to the gene sequence
-as genetic code is non-overlapping the genes shift (frameshift) so it will code for different amino acids
-if 3 bases are removed, then an amino acid is removed
-therefore the correct protein is coded and cannot carry out its function
Chromosome Mutations
-change to the chromosome or number of chromosomes
Deletion – a section of chromosome breaks off and is lost within a cell
Duplication – sections of chromosome are duplicated
Translocation – a section of one chromosome breaks off and joins a non-homologous chromosome
Inversion – a section of chromosome breaks off, is reversed, and re-joins the chromosome
Expanding Triple Nucleotide Repeats
-some genes have a repeating triplet code (CAG-CAG-CAG)
-sometimes it will increase in length due to mitosis and passing onto generations
-If repeated over a certain number it can lead to diseases (Huntington’s Disease)
Useful Mutations
-blue eyes have less iris pigment – help to see better at lower light intensities BUT high light intensity can develop cataracts
-black skin – higher light intensities withstand UV BUT low light intensities cannot produce vitamin D leading to rickets
-different shaped earlobes – no effect
