DNA

1928

Brittish Biologist Frederick Griffith

Researches bacteria and mice

1. Something made the harmless bacteria lethal

2. All descendants of bacteria were lethal3. Something must have been transferred

from the dead lethal bacteria to the living non-lethal bacteria

4. WHAT WAS THE TRANSFORMING FACTOR?????

HMMMMMMMM????????

1944 American Biologist Oswald Avery Thought maybe proteins were the

transforming factor Treated Griffith’s mixture w/ protein

destroying enzymes Mice still died

Thought maybe DNA was the transforming factor Treated Griffith’s mixture w/ DNA destroying

enzyme Mice lived

Avery concluded DNA was the transforming factor.

1952 Alfred Hershey & Martha Chase Did tests using viruses

VIRUS a nucleic acid surrounded by a protein coat Not living Not made of cells Can only reproduce by infecting living cells

Bacteriophage: a virus that only infects bacteria

Hershey & Chase knew DNA or proteins were the hereditary material Which one??

HMMMMM???

DNA was what caused the bacteria to make new phages Not proteins

DNA is the hereditary material

Double Helix Two twisted strands with complementary base pairs Watson & Crick (1953)

The heritable genetic information of an organism—stores, copies, and transmits genetic information

YOUR instruction manual Deoxyribonucleic acid A type of nucleic acid A polymer

Made of nucleotides (monomers)

The building blocks or subunits (monomers) of nucleic acids

So what are nucleic acids? Polymers (large, repeating molecules) made

of nucleotides 4 types of nucleotides make up DNA

Each nucleotide is made up of:1.Sugar2.Phosphate3.Nitrogenous Base (A, C, T, or G)

The four nucleotides that make up DNA differ only by their bases:

Adenine Cytosine Guanine Thymine

Nucleotides are joined together by covalent bonds Connect sugar—phosphate—sugar—phosphate

Sugar-phosphate backbone

Adenine always pairs/bonds with Thymine 2 Hydrogen bonds

Guanine always pairs/bonds with Cytosine 3 Hydrogen bonds

So which is easierto break?

A=T G=C

AAGCTACGGTTCACATGATCAACTTGA TTCGATGCCAAGTGTACTAGTTGAACT

GATACA CTATGT

AGCATTAGGAATTACAG TCGTAATCCTTAATGTC

%A=%T %G=%C Practice: 30%T=

A G C

Small, distinct sections of DNA are called genes. These genes control specific traits. A genome is all of the different genes in one organism (a complete set of

genetic material). Your genetic code is your sequence of nucleotides (ex. AATTCGCTCGG), which in

turn, determine genes, create genes and ultimately make you who you are. The environment in which you

live also

The environment in which you live also influences gene expression. For example, proper nutrition can make you taller and sun exposure can make you tan or cause skin cancer. Triggers in the environment (like chemicals) can turn genes on or off.