Nucleoid

Region in prokaryotic cells where DNA is located.

No membrane-bound nucleus in prokaryotes.

Organizes and protects bacterial genome.

Streptococcus pneumoniae

Bacterium in Griffith’s experiment.

Griffith Experiment on Rats

Demonstrated bacterial transformation.

Avery, MacLeod, and McCarty

Confirmed DNA as transforming principle.

Genetic Material in Viruses

Viruses can have DNA or RNA.

Bacteriophage Life Cycle

Attachment, injection, replication, assembly, release.

Why Radioactive Phosphorus and Sulfur

Used to label DNA and protein in experiments.

Hershey-Chase Experiment

DNA labeled with radioactive phosphorus is genetic material.

Supercoiling Differences

Positive supercoiling: Overwound DNA with increased tension.

Negative supercoiling: Underwound DNA with reduced tension.

Affects gene expression and DNA packaging.

DNA Packaging Importance

Fits long DNA into the nucleus.

Prevents tangling and damage.

Ensures access for cellular processes.

Nucleosome Model Proteins

Core histone octamer: H2A, H2B, H3, H4.

Wrapped by DNA in nucleosome.

Histone H1 binds to linker DNA.

Chromosome Types

Metacentric, submetacentric, acrocentric, telocentric.

Based on centromere position.

Search for Genetic Material

Early scientists sought inheritance substance.

Experiments to identify DNA or proteins.

Scientific Contributions

Mendel’s work on heredity.

Griffith, Avery, MacLeod, McCarty experiment showed that DNA is the substance that causes bacterial transformation

Hershey and Chase experiment led to proof of DNA as genetic material.

Features of Genetic Material

Stable, replicable, contains traits.

Subject to mutations for diversity.

DNA is genetic material in most organisms.

Griffith Experiment

Heat-killed bacteria transform live bacteria.