Chapter-16-The molecular basis of inheritance

Chapter16-The Molecular basis of Inheritance

1953-James Watson and Francis Crick

Discovered the molecular structure of the DNA molecule.

Remember: Chromosomes and genes are the DNA molecule

Genes code for proteins. When a protein is needed by the body the gene that makes that protein is activated.

Proteins can be of various types: Structural, storage, transport, hormonal, receptor, contractile, defensive, enzymatic.

Frederick Griffith and Oswald Avery

Showed that DNA carries the genetic information (the genes)

Their experiments showed that transformation can occur between bacteria.

Transformation-a change in genotype and phenotype in bacteria due to the assimilation of external DNA by a cell.

Alfred Hershey and Martha Chase

They worked with Bacteriophages.

Bacteriophages-viruses that attack bacteria.The bacteriophages inject their DNA into bacteria in order to make 100’s of more copies of themselves.

By labeling the DNA of the Bacteriophages with radioactive phosphorous-32 they also proved DNA carries the genetic instructions

There are many enzymes that help DNA to duplicate

Helicase-unwinds the DNA molecule

Single-strand binding proteins-holds the unwound DNA strands apart

DNA polymerase and Ligase- synthesize and join the new strands to the old strands

DNA Can Repair Itself

Enzymes proofread DNA during its replication and fix any mistakes. Enzymes also repair damage in existing DNA.

Existing DNA can be damaged by-Chemicals, radiation, U.V. light. Fig.16-17

Xeroderma Pigmentosum-a condition in which the DNA repair enzymes in your skin are defective due to the inheritance of a defective gene. Can lead to skin cancer

Telomeres

Telomeres-protective structures at the ends of your chromosomes.

Telomeres protect the genes from being eroded or damaged during the many times a cell undergoes DNA replication during it’s lifetime.