Mutations in DNA
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Transcript of Mutations in DNA
Mutations in DNA
Mutations
• A mutation is a change in a DNA sequence. • Can happen if – There is a mistake in replication.– Bases change spontaneously due to random
movement of atoms in the DNA molecule. – In contact with chemicals, radiation, or
ultraviolent rays. They make more frequent errors in base pairing.
Types of Mutations
–Point Mutations or Substitutions: bases are mismatched
GAG CTC GAG Valine
Correct DNA Correct mRNA Correct AA
GCG CTC GGG Glycine
A should pair with T, but instead G is mismatched to T
Point mutation mutated mRNA Wrong AA
Mutations• Example: Sickle Cell Anemia• http://evolution.berkeley.edu/evolibrary/article/0_0_0/mutations_06
Insertion: one or more new nucleotide pairs are inserted into a gene.
Correct DNA: ATA CCG TGA TAT GGC ACT
Correct mRNA: UAU GGC ACU
Correct amino acids: Tyrosine Glycine ThreonineExtra inserted base shifts how we read the codons (3 bases), which changes the amino acids
Frameshift mutation ATG ACC GTG Ain DNA: TAC TGG CAC T
Mutated mRNA: UAC UGG CAC U
Wrong amino acids: Tyrosine Tryptophan Histadine
Deletion- One or more nucleotide pairs are deleted.
Mutations
• If a mutation happens in a sex cell (sperm or egg), it may be passed on to future generations.
• Frameshift Mutation: Deletions and insertions of one or two nucleotides can have catastrophic effects on genes because all the codons that follow the deletion or insertion will be altered.
Example
THE DOG SAW THE CATor
THD OGS AWT HEC AT
Overall Types of Mutationsadd to the bottom of note sheet
• Missense : ANY mutation that alters the codon so as to produce an altered amino acid in the protein
• Nonsense : ANY mutation that changes a codon that specified an amino acid to one of the STOP codons
• Silent : ANY mutation that causes no change in the protein and cannot be detected without sequencing the gene
Four Outcomes of Nucleotide Substitutions
1. The protein may be unchanged. 2. The new protein may be equivalent to the
original one. 3. Protein function may be changed by an
altered amino acid sequence. 4. Protein function may be destroyed by a
premature stop codon.
Rate of Mutations in Human Gametes.
• In humans, mutation rates range from about 1 in every 100,000 gametes to 1 in 1,000,000 gametes.
Mutations to control genes can transform one body part into another. Scientists have studied flies carrying Hox mutations that sprout legs on
their foreheads instead of antennae!
Sickle Cell Anemiahttp://evolution.berkeley.edu/evolibrary/article/0_0_0/mutations_06
Name Mutationshttp://www.nature.ca/genome/04/0413_e.cfm