Transcript Unit 3- Section 2

Unit 3: Molecular Genetics
Section 2-Mutations
I. Chromosomes
a.
b.
c.
Made of tightly wound DNA.
Most of the code is useless
Useful code=genes
Genes code for proteins
b. EX: Melanin
a.
d.
Each person has different forms of genes=alleles
Everyone has gene for melanin
b. Some produce more than others
a.
II. Mutation
a.
b.
c.
A change in the DNA or RNA sequence
Caused by mistakes in mitosis and meiosis
Caused by mutagens-UV light, carcinogens
III. Two types
a.
Germline
Occurs in germ cells-egg and sperm
b. Passed on to next generation
a.
b.
Somatic
Occurs in typical body cells
b. Not passed on
a.
IV. Chromosomal Alterations
a.
Occurs when mistakes are made in
mitosis and meiosis
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Deletion-A portion of the chromosome is lost and
the information is lost with it.
Duplication-A portion from the homologous
chromosome is added
Inversion- A portion is added but it attaches in the
reverse direction
Insertion- additional information is added
Translocation-A portion of a chromosome attaches
to a different chromosome, completely messing up
the genetic code.
V. Other mutations
a.
Point mutations
One nitrogenous base is changed
b. Affects the resulting protein by one amino acid
a.
b.
Frameshift mutations
A nitrogenous base is added or deleted
b. Affects the whole amino acid sequence
a.
VI. Effects of mutation
a.
Genetic disorders
Proteins are assembled incorrectly
b. Sickle-cell anemia-hemoglobin
c. Colorblindness
a.
b.
Harmful mutations
a.
c.
Disappear in the gene pool
Beneficial mutations
Become common in gene pool
b. Provide adaptationevolution
a.
d.
Cancer
a.
Caused by carcinogens