Transcript Sometimes replication, transcription and translation don`t go as

Sometimes replication,
transcription and translation don’t
go as planned!
Replication, Transcription,
and Translation errors
result in mutations.
A mutation is any change in
the DNA of an organism.
Truths about mutations!
• MOST mutations are minor.
• Many mutations are harmful.
• Some mutations are lethal.
• Very few mutations are helpful.
Mutations can occur as…
Germ Mutations
mutations in gametes
Somatic Mutations
mutations in body cells
Two Types of Mutations
1. Chromosome
Mutations
2. Gene Mutations
Types of Mutations within
chromosomes
1. Deletion
2. Inversion
3. Translocation
4. Nondisjunction
Deletion
• a piece of a chromosome breaks off and is lost
Inversion
• a piece of a chromosome breaks off and
reattaches itself in reverse order
Translocation
• a broken piece attaches to a nonhomologous
chromosome
Nondisjunction
• a pair of chromosomes fail to separate during
Anaphase I of meiotic cell division
• results in trisomy or monosomy
Trisomy = three of one kind in a diploid cell
Monosomy = one of one kind in a diploid cell
Types of Gene Mutations
1. Point
2. Frame-shift
Point
• a change in a single nitrogen base in DNA
• Often referred to as a “nonsense” mutation
Frameshift
• the addition or deletion of a nitrogen base,
causing a shift in the sequence of codons
• the amino acid sequence is nonsense, coding
for all the wrong amino acids
What causes a mutation?
• Anything that causes a mutation is called a
mutagen
• Environmental mutagens include:
– Ultraviolet radiation
– Tars from tobacco
– Asbestos