Discovering DNA

A bacteriophage is a virus that infects bacteria The bacteriophage attaches to the bacteria and its genetic material then enters the bacterial cell. The bacterial cell treats the viral genetic material as if it was its own and subsequently manufactures more virus particles DNA inside protein coat Hollow sheath Question: what infects the bacterium, the protein or the DNA? Tail fiber

Hershey and Chase show protein does not infect the bacterium (1952) virus particle labeled with 35S DNA being injected into bacterium Hershey and Chase show protein does not infect the bacterium (1952) 35S remains outside cells

Hershey and Chase show DNA infects the bacterium virus particle labeled with 32P DNA being injected into bacterium Hershey and Chase show DNA infects the bacterium 32P remains inside cells

Types of Cell Reproduction Asexual reproduction involves a single cell dividing to make 2 new, identical daughter cells Mitosis & binary fission are examples of asexual reproduction Sexual reproduction involves two cells (egg & sperm) joining to make a new cell (zygote) that is NOT identical to the original cells Meiosis is an example

Types of Cell Reproduction Asexual Sexual

Cyclins Oncogenes and Cancer

Life Cycle of a Cell Mitosis is the division of somatic/autosomal (body) cells

Interphase Interesting things happen! Cell preparing to divide Genetic material doubles

The Cell Cycle DNA Copied Cells prepare for Division Cells Mature Daughter Cells Cell Divides into Identical cells

Chromosomes in Dividing Cells Duplicated chromosomes are called sister chromatids & are held together by the centromere Sister Chromatids

Mitosis Prophase (Sister Chromatids pair up ) Metaphase (meet in the middle) Anaphase (apart) Telophase (two)

Prophase Chromosome pair up! Chromosomes thicken and shorten -become visible -Sister chromatids are joined by a centromere and are ready to begin cell division Centrioles move to the opposite sides of the nucleus Nucleolus disappears Nuclear membrane disintegrate

Prophase

Metaphase Chromosomes meet in the middle! Chromosomes arrange at equator of cell Become attached to spindle fibers by centromeres Homologous chromosomes do not associate

Metaphase

Anaphase Sister chromatids get pulled apart Spindle fibers contract pulling chromosomes to the opposite poles of the cell

Anaphase

Telophase Now there are two! Chromosomes uncoil Spindles disintegrate Nucleolus reappears Nuclear membrane reappears CYTOKINESIS occurs Chromosomes reappear as chromatin

Telophase