LS: I will be able identify and describe the different types of mutations.
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Transcript of LS: I will be able identify and describe the different types of mutations.
MutationsLS: I will be able identify and describe the different types of mutations.
Mutations
Mutations are changes in the genetic material (changes in the genes)
The DNA code can have a base(or more than one) missing, added, or exchange in a
codon.Mutations occur at a frequency of about 1
every 1 billion base pairs
Everybody has about 6 mutations in each cell in their body!
Can we see
mutations?
Mutations are not always seen.The affected gene may still function.
Mutations may be harmful.Mutations may be beneficial.Mutations may have no effect on the organism.
How are mutations beneficial?Mutations are a major source
of genetic variation in a population’s increasing biodiversity.
Some variation may help them to survive better.
When will I see a
mutation?
Only mutations in gametes (egg and sperm) are passed onto offspring
Mutations in body cells only affect the organism in which they occur and are not passed onto the offspring
Types of Mutations
Point mutation: occurs when the base sequence of a codon is changed. (ex. GCA is changed to
GAA)
There are 3 types:
SubstitutionDeletionInsertion
Deletion and Insertion are
also Frameshift mutations!
Ex: Substituti
onSubstitution Mutations
Normal DNA: CGA - TGC - ATC
Alanine - Threonine - Stop
Mutated DNA: CGA - TGC - TTC Alanine - Threonine -
LysineWhat has happened to the
DNA?
Do these look the same?
THE FAT CAT ATE THE RATTHE FAT HAT ATE THE RAT
Do these phrases make sense? What happened?
Changes the thought of the sentence. The effect will depend on where the substitution happened.
Ex: Insertion Mutation
Normal DNA: CGA - TGC - ATC Alanine - Threonine -
StopMutated DNA: CGA - TAG - CAT - C Alanine - Isoleucine -
Valine
What has happed to the DNA?
Further explanation!!
An insertion mutation adds to the sequence: 1. Causes the triplet “frames” to shift2. It always affects the amino acids and,
consequently, the protein formed
Ex: Deletion
Mutated DNA: CGA - TCA - TC Alanine -
SerineWhat has happened to the DNA?
Further explanation!!
A deletion removes from the sequence.1. Causes the triplet “frames” to shift2. It always affects the amino acids and,
consequently, the protein formed
1. ____________ are changes in the ___________ material.2. Mutations are a major source of genetic __________.3. In a ____________ mutation one nucleotide is replaced for another.4. In a ____________ mutation a nucleotide is removed from the sequence.5. In a ____________ mutation a nucleotide is added to the sequence.
LET’S RECAP…
Missense vs. Nonsense Mutations
A point mutation in which a single
nucleotide change results in a codon that codes for a different
amino acid
Missense
Mutation
A Point mutation in a sequence of DNA that results in a premature
stop codon.
Nonsense Mutation
How do these mutations affect the organism?
Substitution has the least affect:a. Changes only one amino acid or it may change no amino acid
Least
affected Example: Sickle cell anemia
1. Only one amino acid changes in the hemoglobin
2. The hemoglobin still functions but it folds differently changing the shape of the red blood cell
Insertion and deletion
a.Affect many amino acids
b.Consequently affecting the whole protein
Greates
t affectExample: Huntington’s Disease (caused by insertion mutation)
a. People with this disorder have involuntary movement , loss of motor control
b. Eventually there is memory loss and dementia
c. The disease is terminal
d. Located on chromosome 4
The greatest
affect on the
organism!
When the mutation occurs in the gamete (egg or sperm) or early in embryonic development (in stem cells or first few days)
Chromosome Mutations
Chromosomal mutation: a mutation involving a long segment of DNA
There are 5 TypesDeletionInversion
TranslocationNondisjunction
Duplication
Deletion vs. Duplication
Deletion 1. A segment breaks off and is lost
Duplication1. Occurs when a gene sequence is repeated on the chromosome
Inversion vs. Translocation
Inversion1. Chromosome segment
breaks off2. The segment then flips
around backward3. The segment then
reattaches Translocation1.Involves two
chromosomes that aren’t homologous
2.Part of one chromosome is transferred to another chromosome
Nondisjunction 1. Failure of chromosomes to
separate during meiosis2. Causes gamete to have too
many of too few chromosomes
3. Disorders:1. Down Syndrome – three
21st chromosomes2. Turner Syndrome –
single X chromosome3. Klinefleter’s Syndrome –
XXY chromosomes
Causes of Mutation
Inherited1. Hereditary
mutations or germline mutations
2. This type of mutation is present throughout a person’s life in virtually every cell in the body
Acquired 1. Or somatic mutations2. Occur in the DNA of
individual cells at some time during a person’s life
3. Caused by environmental factors
4. Can’t be passed on to the next generation
Causes of Mutations
Mutations are caused by either natural errors or an environmental
eventA mutagen is something that
causes the DNA code to change—X-ray, chemicals, UV light,
radiation, etc.
1. During a ___________ mutation a premature stop codon is formed.2. ________________ results when two non-homologous chromosomes exchange segments.3. ________________ is the failure of chromosomes to separate during meiosis.
LET’S RECAP…