Lesson Overview Mutations

What types of

mutations are you

familiar with?

Lesson Overview Mutations

Videos

• Bozeman Mutations: https://youtu.be/eDbK0cxKKsk

• Amoeba sisters mutations: https://youtu.be/GieZ3pk9YVo

• White board, mutations: https://youtu.be/qxXRKVompI8

• Cystic fibrosis story: https://youtu.be/-a-WHZoTX0E

• CF explained: https://youtu.be/FMAOEOmLoUE

• Cf story 2: https://youtu.be/ORURXnKjCso

• Huntington’s disease explained: https://youtu.be/4HgFUvVyHYQ

Lesson Overview Mutations

Terms to know

1. Mutations

2. Point mutations

3. Substitutions

4. Insertions

5. Deletions

6. Frameshift mutations

7. Chromosomal deletion, duplication, inversion, and translocation

8. Mutagens

9. Sickle cell disease

10.Cystic fibrosis

11.Huntington’s disease

12.Nondisjunction

13.Down syndrome

14.Polyploidy

Lesson Overview Mutations

Preview

• Review p. 148. Draw and explain the three main types of chromosomal mutations: deletion, duplication, inversion and translocation.

• Review p.328 (black bio book). Draw and explain the two main types of gene mutations: point mutations including; base substitution, missense mutations, nonsense mutations, insertions/deletions, and frameshift mutations.

Lesson Overview Mutations

Types of Mutations

Now and then cells make mistakes in copying their own DNA,

inserting the wrong base or even skipping a base as a strand

is put together.

These variations are called mutations, from the Latin word

mutare, meaning “to change.”

Mutations are heritable changes in genetic information.

Lesson Overview Mutations

Types of Mutations

All mutations fall into two basic categories:

Those that produce changes in a single gene are known

as gene mutations.

Those that produce changes in whole chromosomes are

known as chromosomal mutations.

Lesson Overview Mutations

Gene Mutations

• Mutations that involve changes in one or a few nucleotides are known as

point mutations because they occur at a single point in the DNA

sequence. They generally occur during replication.

• Point mutations include substitutions, insertions, and deletions.

Lesson Overview Mutations

Substitutions

In a substitution, one base is changed to a different base.

Substitutions usually affect no more than a single amino acid,

and sometimes they have no effect at all.

Lesson Overview Mutations

Insertions and Deletions

• Insertions and deletions are point mutations in which one base is

inserted or removed from the DNA sequence.

• If a nucleotide is added or deleted, the bases are still read in groups of

three, but now those groupings shift in every codon that follows the

mutation.

Lesson Overview Mutations

Insertions and Deletions

Insertions and deletions are also called frameshift mutations because

they shift the “reading frame” of the genetic message.

Frameshift mutations can change every amino acid that follows the point

of the mutation and can alter a protein so much that it is unable to

perform its normal functions.

Lesson Overview Mutations

Lesson Overview Mutations

Chromosomal Mutations

• Chromosomal mutations involve changes in the number or structure of

chromosomes.

• These mutations can change the location of genes on chromosomes

and can even change the number of copies of some genes.

• There are four types of chromosomal mutations: deletion, duplication,

inversion, and translocation.

Lesson Overview Mutations

Chromosomal Mutations

Deletion involves the loss of all or part of a chromosome.

Lesson Overview Mutations

Chromosomal Mutations

Duplication produces an extra copy of all or part of a

chromosome.

Lesson Overview Mutations

Chromosomal Mutations

Inversion reverses the direction of parts of a chromosome.

Lesson Overview Mutations

Chromosomal Mutations

Translocation occurs when part of one chromosome breaks off

and attaches to another.

Lesson Overview Mutations

Mutagens • Some mutations arise from mutagens, chemical or physical agents in

the environment.

• Chemical mutagens include certain pesticides, a few natural plant

alkaloids, tobacco smoke, and environmental pollutants.

• Physical mutagens include some forms of electromagnetic radiation,

such as X-rays and ultraviolet light.

Lesson Overview Mutations

Preview

• Go to p.147 and p.163

• Create a chart that lists the major symptoms of the following disorders:

A (p.163)

1. Cystic fibrosis

2. Huntington’s disease

3. Sickle cell disease

B (p.147)

1. Turners syndrome

2. Klinefelters syndrome

3. Down syndrome

Lesson Overview Mutations

Harmful Effects

• Sickle cell disease is a disorder associated with changes in

the shape of red blood cells. Normal red blood cells are

round. Sickle cells appear long and pointed.

• Sickle cell disease is caused by a point mutation in one of

the polypeptides found in hemoglobin, the blood’s principal

oxygen-carrying protein.

• Among the symptoms of the disease are anemia, severe

pain, frequent infections, and stunted growth.

Lesson Overview Mutations

Lesson Overview Mutations

Lesson Overview Mutations

Cystic Fibrosis

• Cystic fibrosis (CF)

• Most cases result from the deletion of just three bases in the gene for a

protein called cystic fibrosis transmembrane conductance regulator

(CFTR). As a result, the amino acid phenylalanine is missing from the

protein, causing the protein to fold improperly.

Lesson Overview Mutations

Cystic Fibrosis

• CFTR normally allows chloride ions (Cl−) to pass across cell

membranes.The loss of these bases removes a single amino acid—

phenylalanine—from CFTR, causing the protein to fold improperly.

• The misfolded protein is then destroyed.

Lesson Overview Mutations

Cystic Fibrosis

With cell membranes unable to transport chloride ions, tissues

throughout the body malfunction. Children with CF have serious

digestive problems and produce thick, heavy mucus that clogs their

lungs and breathing passageways.

Lesson Overview Mutations

Lesson Overview Mutations

Lesson Overview Mutations

Huntington’s Disease

• Huntington’s disease is caused by a dominant allele for a

protein found in brain cells.

• The allele for this disease contains a long string of bases in

which the codon CAG—coding for the amino acid

glutamine—repeats over and over again, more than 40

times.

• The symptoms of Huntington’s disease, namely mental

deterioration and uncontrollable movements, usually do not

appear until middle age.

• The greater the number of codon repeats, the earlier the

disease appears, and the more severe are its symptoms.

Lesson Overview Mutations

Huntington’s Disease

Lesson Overview Mutations

Chromosomal Disorders

The most common error in

meiosis occurs when homologous

chromosomes fail to separate.

This mistake is known as

nondisjunction, which means

“not coming apart.”

Nondisjunction may result in

gametes with an abnormal

number of chromosomes, which

can lead to a disorder of

chromosome numbers.

Lesson Overview Mutations

Chromosomal Disorders

• If two copies of an autosomal chromosome fail to

separate during meiosis, an individual may be born with

three copies of that chromosome.

• This condition is known as a trisomy, meaning “three

bodies.”

• The most common form of trisomy, involving three

copies of chromosome 21, is Down syndrome, which is

often characterized by mild to severe mental retardation

and a high frequency of certain birth defects.

Lesson Overview Mutations

Chromosomal Disorders

• Nondisjunction of the X

chromosomes can lead to a disorder

known as Turner’s syndrome.

• A female with Turner’s syndrome

usually inherits only one X

chromosome.

• Women with Turner’s syndrome are

sterile, which means that they are

unable to reproduce. Their sex

organs do not develop properly at

puberty.

Lesson Overview Mutations

Chromosomal Disorders

• In males, nondisjunction may cause

Klinefelter’s syndrome, resulting from the

inheritance of an extra X chromosome,

which interferes with meiosis and usually

prevents these individuals from

reproducing.

• There have been no reported instances

of babies being born without an X

chromosome, indicating that this

chromosome contains genes that are

vital for the survival and development of

the embryo.

Lesson Overview Mutations

Beneficial Effects (Copy the definition)

• Plant and animal breeders often make use of “good” mutations.

• The condition in which an organism has extra sets of chromosomes is called

polyploidy.

• Polyploid plants are often larger and stronger than diploid plants.

• Important crop plants—including bananas and limes—have been produced this

way.

Quiz

1. Define base substitution.

2. Draw a picture of a chromosomal deletion.

3. Why is it called “Sickle” cell disease?

4. What are the symptoms of Huntington’s disease?

5. Draw the sex chromosomes of someone with Turner’s syndrome (first) and Klinefelter’s syndrome (second).