A chemical found in the nucleus

DNA

What was the name of the scientist who worked with mice, and what did he discover?

Griffiths (1928): – he studied pneumonia in mice

- he heated a deadly strain of pneumonia, injected it into the mice and they lived

- the mice inherited material that transformed them permanently

-he discovered that bacteria is capable of transferring genetic information

In 1944, Avery expanded on Griffith’s idea. What did he discover?

That DNA causes death NOT protein in viruses, and DNA is the genetic material that is responsible for being passed from one

generation to the next.

Why were scientists skeptical that DNA was the root of genetics?

It seemed too simple because it only had 4 nucleotides (ATCG)

Name the 4 nucleotides that are the building blocks or monomers of nucleic acid

Adenine, thymine, cytosine, guanine – these are the rungs of the DNA ladder

What does each nucleotide contain?

1 - a ring shaped structure called deoxyribose 2 – a phosphate group

3 - they all have a single or double ringed nitrogenous base

What is a virus?

1- it is not living2- it is not made up of cells

3 - it needs a host to reproduce4 – it injects DNA into a host cell and “hijacks” a

cell’s function5 – they cannot survive on their own

Name the scientists who discovered that viruses have protein coats that make up the outside

shell, and DNA on the inside

Hershey and Chase (1952) by using radioactive materials to track a virus’ movement

-protein never got into a cell-DNA was injected by the virus into the nucleus

of a cell and took it over

These viruses only attack bacteria

Bacteriophage

What is the shape of DNA?

Double helix

What are the full names of DNA and RNA and what is the difference between them?

Both are polymers:Deoxyribonucleic Acid – double helix that contains genetic codes

to make RNA

Ribonucleic Acid – 1/2 ladder that contains codes to sequence amino acids to make proteins

(picture on next slide)

Which nucleotides have single rings (shorter) and which have double rings (longer)?

guanine and adenine have double rings - longerthymine + cytosine have single rings - shorter

Who is credited with the discovery of the shape of DNA and its make up?

Cricks and Watson 1953(stole Rosalind Franklin’s photo #51)

What is it called when nucleotides are held together by covalent bonds that connect the sugar

of one nucleotide to the phosphate group of another nucleotide

sugar-phosphate backbone – the sides of the ladder

How long are nucleotide chains?

They can vary from a a few hundred to an infinite number

Why does adenine only pair with thymine and cytosine only pair with guanine?

The pairing is due to size—one long and one short and their ability to form hydrogen bonds.

How does DNA replicate?

A complex of enzymes called helicase “unzip” the base pairs - this occurs very quickly and accurately, and always with the original set of DNA

During DNA copying the two strands of the helix separate. Each single strand acts as a “negative” producing a new complimentary strand. What is this called?

The Template Mechanism

What enzyme is responsible for the “re-zipping” of a double helix?

DNA polymerase – it re-zips molecule and proof reads

What kind of bond holds the base pairs together?

Hydrogen bond