Compare the processes and effects of point mutations and chromosomal mutations. Include examples in your answer. (8 marks)
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→ Mutations are the change in an individuals genome. Their effects are dependent on
-
- the location of the mutation. Mutations in coding DNA can affect proteins and have adverse physiological affects while mutations in non-coding DNA often have no affect, however may slightly impact cell activity.
- the type of cell it occurs in. Somatic cell mutations only affect the individual, while germ-line mutations occur in germ-line cells which go on to produce gametes, thus potentially affecting offspring.
→ Point mutations are mutations which change only a single base in a DNA sequence. They can be a single base substitution or the deletion or insertion of an extra base. Deletion or insertions are referred to as ‘frameshift’ mutations as they impact all codons proceeding it.
→ Sometimes substitution mutations are neutral and occur in non-coding DNA, code for an amino acid of very similar chemical composition or even code for the same amino acid. When a mutation does code for a dissimilar amino acid or a stop codon causing premature termination, this interferes with the shape of the polypeptide chain and the protein it becomes part of, rendering it faulty or completely unusable (e.g. sickle cell anaemia, NRAS mutation). The nature of frameshift mutations affecting every codon proceeding it are often more severe, as there is more potential to cause a faulty polypeptide chain (e.g. cystic fibrosis).
→ Chromosomal mutations can refer to the removal, insertion, translocation or inversion of large sections of a chromosome. These often affect genes by either splitting them up or relocating them to a new chromosome.
→ Chromosomal mutations can also refer to the relocation of entire chromosomes during meiosis of germ-line cells where they fail to separate. This is called non-disjunction and results in aneuploidy of two gametes, one which will result in having an extra chromosome (trisomy) and one will lack a chromosome (monosomy). Conditions such as Down’s syndrome (trisomy-21) or Turner syndrome (XO) are aneuploidy conditions but most often cause a miscarriage or unsuccessful zygote development.
→ Polyploidy is the complete development of an entirely new set of chromosomes. This is known to occur in strawberries which have 8 sets of chromosomes but cannot occur in humans.
→ While both can cause radical health defects, it is important to note that these mutations are the basis of evolution. Beneficial mutations are more likely to be carried through a species through generations according to natural selection.
→ Mutations are the change in an individuals genome. Their effects are dependent on
-
- the location of the mutation. Mutations in coding DNA can affect proteins and have adverse physiological affects while mutations in non-coding DNA often have no affect, however may slightly impact cell activity.
- the type of cell it occurs in. Somatic cell mutations only affect the individual, while germ-line mutations occur in germ-line cells which go on to produce gametes, thus potentially affecting offspring.
→ Point mutations are mutations which change only a single base in a DNA sequence. They can be a single base substitution or the deletion or insertion of an extra base. Deletion or insertions are referred to as ‘frameshift’ mutations as they impact all codons proceeding it.
→ Sometimes substitution mutations are neutral and occur in non-coding DNA, code for an amino acid of very similar chemical composition or even code for the same amino acid. When a mutation does code for a dissimilar amino acid or a stop codon causing premature termination, this interferes with the shape of the polypeptide chain and the protein it becomes part of, rendering it faulty or completely unusable (e.g. sickle cell anaemia, NRAS mutation). The nature of frameshift mutations affecting every codon proceeding it are often more severe, as there is more potential to cause a faulty polypeptide chain (e.g. cystic fibrosis).
→ Chromosomal mutations can refer to the removal, insertion, translocation or inversion of large sections of a chromosome. These often affect genes by either splitting them up or relocating them to a new chromosome.
→ Chromosomal mutations can also refer to the relocation of entire chromosomes during meiosis of germ-line cells where they fail to separate. This is called non-disjunction and results in aneuploidy of two gametes, one which will result in having an extra chromosome (trisomy) and one will lack a chromosome (monosomy). Conditions such as Down’s syndrome (trisomy-21) or Turner syndrome (XO) are aneuploidy conditions but most often cause a miscarriage or unsuccessful zygote development.
→ Polyploidy is the complete development of an entirely new set of chromosomes. This is known to occur in strawberries which have 8 sets of chromosomes but cannot occur in humans.
→ While both can cause radical health defects, it is important to note that these mutations are the basis of evolution. Beneficial mutations are more likely to be carried through a species through generations according to natural selection.