DNA discovery (Phát hiện ADN)

DNA’s Discovery and StructureHonors Objectives SOL.BIO.6f... Today’s Objectives: TSW investigate and understand the common mechanisms of protein synthesis, including the structure of D

DNA’s Discovery and Structure

Honors Objectives SOL.BIO.6f

Today’s Objectives:

 TSW investigate and understand the common mechanisms of protein

synthesis, including the structure of DNA and its discovery.

Our Genetic Code

 The genetic code is a sequence of nucleotides in the of eukaryotic cells.

 There are two polymers of nucleic acids, _ and .

Important Scientists that

determined DNA’s Importance

 Frederick Griffith – bacterial transformation

 Oswald Avery – DNA = key to

transformation

 Alfred Hershey & Martha Chase

– Bacteriophage transformation

experiment

 Erwin Chargaff – base-pairing rules

Important Scientists in the “Race for the Double Helix”

 Maurice Wilkins & Rosalind Franklin

 James Watson & Francis Crick

DNA’s Structure

 DNA is a double helix

 DNA contains four nucleotide bases:

– adenine (A)

– cytosine (C)

– guanine (G)

– thymine (T)

Chargaff’s Rule

 The bases form the “rungs” on the

DNA ladder by complementary pairing

A == T

C == G

T == A

G == C

A == T

T == A

Sugar-phosphate backbone

DNA Replication

 Replication = Duplication

– Happens in the S phase of Interphase

– Must replicate before mitosis or meiosis I

 Part of the double helix is unwound

 Replication in small pieces (Okazaki fragments)

 Enzyme stitches pieces together later

Semi-Conservative Replication

new molecule of

DNA is old

(template

strand)

molecule of

DNA is new

(complementary

strand)

What is a Gene?

 A length of DNA on a chromosome

 May be in several parts

sequence

expressed

 Parts are cut, put together and then used

to make RNA and proteins

Odd Types of Genes

 Multigene families

 Transposons (Barbara McClintock)

 Protective Genes

 Viruses may give us new DNA that can

be kept over time to cause new

evolutionary changes!