Changes in DNAcan produce variation

Section 5.2

DNA sequence can change

• Differences in DNA are what make one organism different from another

• The number of differences between two species is large

Human3 billion

Base pairs

Yeast cell12 MillionBase Pairs

DNA sequence can change

• The number of differences between 2 individuals of the same species is small

• (<0.1% variation)

DNA sequence can change

• There is a large number of DNA bases in any organism that need to be copied

• Errors can occur when DNA is copied or affected by environment– UV radiation– X-rays– Toxins

DNA sequence can change

• Mutation – any change in DNA• Cells have ways of fixing mistakes in DNA• However some mistakes are not fixed

Possible outcomes when error occurs in genes

No effect – Some amino acids have more than one code and may not change resulting protein

– May have enough protein being produced

Possible outcomes when error occurs in genes

• Mutation is minor– May only cause a change in appearance

Possible outcomes when error occurs in genes

Mutation is great– Could be good (Resistant to disease)

– Could be bad (genetic disorder or disease)

• Only 5% of human DNA is in genes

• If mutation occurs in a non-coding region, then chances are that the mutation is neutral

Genetic Disorders

• Disease or condition caused by mutations that affect normal functions of the cell– Can be inherited (Tay-Sachs)– Can occur during a person’s life (Cancer)

Genetic Disorders• A person can carry a tendency for a disease

(diabetes)

• Sometimes a person’s behavior can prevent the disease (smoking)

Genetic Disorders

• Mutations can have more than one effect– Sickle cell anemia• Recessive disorder• Prevents blood from carrying oxygen• Prevents malaria

Genetic Disorders

• Pedigree – shows a family relationship for 2 or more generations

Cancer

• A group of disorders• Characterized by uncontrolled division of cells• Cells can spread to other tissues• Causes– Inherited– Carcinogens– Radiation– Series of mutations