Definition: Changes in the nucleotide sequence of DNA.
Occurrence:
Can happen in somatic cells (not passed to offspring).
Can happen in gametes (eggs & sperm) and be passed to offspring.
Consequences:
Some skin cancers and leukemia result from somatic mutations.
Some mutations can improve an organism's survival (beneficial).
Types of Mutations:
Chromosomal Mutations.
Gene Mutations.
Definition: Changes in chromosome structure or gain/loss of chromosome parts.
Types of Chromosome Mutations:
Deletion: A piece of a chromosome is lost due to breakage.
Inversion: A chromosome segment breaks off, flips around, and reattaches backward.
Duplication: A gene sequence is repeated, resulting in multiple copies.
Translocation: Part of one chromosome is transferred to a non-homologous chromosome.
Nondisjunction: Failure of chromosomes to separate during meiosis, leading to gametes with abnormal chromosome numbers.
Meiosis I: Starts normally; tetrads line up in the middle of the cell.
Nondisjunction Occurs: One set of homologous chromosomes does not separate.
Meiosis II: Occurs normally.
Outcome: All gametes have an abnormal number of chromosomes (one too many or one too few).
Definition: Change in the nucleotide sequence of a gene.
Characteristics:
May involve a single nucleotide.
Can be caused by copying errors, chemicals, viruses, etc.
Types of Gene Mutations:
Point Mutations: Change of one base in the sequence.
Substitutions: One base substituted for another.
Insertions: Addition of a base.
Deletions: Removal of a base.
Frameshift Mutations: Entire sequence is shifted due to insertions or deletions.
Definition: Involve the deletion, insertion, or substitution of a single nucleotide.
Impact: Inserting or deleting one or more nucleotides changes the “reading frame” of the gene, altering the entire sequence.
Example:
Original: "The fat cat ate the wee rat."
Frame Shift (deletion of "a"): "The fat cat tet hew eer at."
Amino Acid Sequence Change:
Original sequence: ATG GAA GCA CGT (Met Glu Ala Gly).
ATG GAA GCA CGT
After frameshift mutation: ATG AAG CAC GT (Met Lys His).
ATG AAG CAC GT