Unit 1: Human Cells - Key Area 4 - Mutations Flashcards
What is a mutation?
Mutations are changes in the DNA, either in a gene or a chromosome, that can result in no protein at all or an altered protein being synthesised.
Are mutations rare and random?
Yes
What are mutations the only source of?
Mutations are the only source of new variation in populations.
What can mutations be for an organism?
Sometimes a mutation can be useful but many mutations have a harmful and lethal effect on an organism,
What is a mutant?
An organism which has been effected by and is the result of a mutation.
What are the two main types of mutation?
Gene and chromosome mutations.
What do single gene mutations involve?
A single gene mutation involves a change in the number or sequence of bases in a gene.
What are the three types of gene mutation?
Substitution, Insertion and Deletion.
What are substitution mutations?
Substitution mutations are point mutations and involve one base being exchanged for another. They will only affect one codon.
What are insertion and deletion mutations? (CAT CAT)
Insertion and deletion are frame-shift mutations and effect every single codon after the mutation. This involves whole sections of DNA being misread.
What results in frame-shift mutations?
Nucleotide Insertion and Deletion.
What are the 3 types of substitution mutation?
Missense, Nonsense and Splice-Site.
What are the 2 frame-shift mutations?
Insertion and Deletion.
What is the description of a Missense mutation?
A type of substitution mutation which changes the codon for an amino acid so that a different amino acid is inserted into the protein.
What is the effect on the protein from a Missense mutation?
Different amino acid is inserted into the protein meaning a different protein is produced.
What is an example of a condition caused by a Missense mutation?
Sickle cell anaemia.
What is the description of a Nonsense mutation?
A mutation which results in a codon for a specific amino acid being changed to a stop codon.
What is the effect on the protein from a Nonsense mutation?
It causes the protein to be stopped prematurely and a shorter protein being produced.
What is an example of a condition caused by a Nonsense mutation?
Duchenne muscular dystrophy.
What is the description of a Splice-Site mutation?
Mutations in the area that makes the start or end of an intron, may lead to one or more introns not being removed. This will lead to the creation of a protein that does not function properly.
What is the effect on the protein from a Splice-Site mutation?
The protein does not function properly.
What is an example of a condition caused by a
Splice-Site mutation?
Thalassemia
What is the description of a Insertion mutation?
A nucleotide is added to the strand.
What is the effect on the protein from a Insertion mutation?
Every amino acid after the mutation is affected so the protein is usually non-functional.
What is an example of a condition caused by an Insertion mutation?
Tay Sachs
What is the description of a Deletion mutation?
A nucleotide is removed/missing from the strand.
What is the effect on the protein from a Deletion mutation?
Every amino acid after the mutation is affected so the protein is usually non-functional.
What is an example of a condition caused by an Deletion mutation?
Cystic fibrosis
Why do insertion and deletion tend to have a greater effect on the protein produced than substitution mutations?
Every amino acid after the mutation is effected in Insertion and Deletion so the protein is usually non-functional which can be lethal, rather than just one codon being changed in substitution which has less effect.
What are gene mutations?
Gene mutations are a change in the number or sequence of nucleotides/bases in a gene.
What are chromosome mutations?
Chromosome mutations are a change in the number or sequence of genes in a chromosome.
Why can the broken end of a chromosome join to another broken end?
The broken end of a chromosome is ‘sticky’.
What are the 4 type of chromosome mutations?
Deletion, Duplication, Inversion and Translocation.
What happens in a Deletion chromosome mutation?
In a deletion chromosome mutation one or more genes are removed from the chromosome, resulting in the chromosome being shorter.
What is an example of a deletion chromosome mutation and how is this caused?
An example of a chromosome deletion mutation is Cri-Du-Chat.
What happens in an Inversion mutation?
Part of the chromosome is flipped over/reversed/re-orientated (different order)and put back into the chromosome.
What is an example of a condition caused by an Inversion mutation?
Hemophilia A
What happens in a duplication mutation?
One or more genes are copied/replicated and inserted into the same part of the chromosome. (Repeated within the chromosome).
What does a translocation mutation involve?
A translocation mutation involves a section of a chromosome breaking off and becoming attached to another chromosome (not its matching/homologous partner).
What is a homologous chromosome?
Genes in the same area/region/location.
What is the difference between reciprocal and non - reciprocal translocation mutations?
In reciprocal translocation mutations a section of chromosome breaks of two different chromosome and they switch/ swap places but don’t go to their homologous partners, whereas in non - reciprocal translocation mutations a section of chromosome breaks off one of the chromosomes and attaches to a non - homologous partner but no chromosome is received/ broken off the chromosome which received the chromosome( they are are not shared only one gives part of the chromosome away).
What are the 2 types of translocation mutation
Reciprocal and non - reciprocal.
What is an example of a condition caused by a Duplication mutation?
Charcot-Marie-Tooth
Why are chromosome mutation so lethal?
Chromosome mutations are so lethal as they often involve such a substantial change to the chromosomes structure.
What is an example of a condition caused by a translocational mutation and what genes are translocated?
Chronic Myeloid Leukaemia. It results from the translocation of genes on chromosome 9 and 22.
Familial Down’s Syndrome. This results from the translocation of chromosome 21 into 14.
