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…