dna intro. & replication (s phase) dna = deoxyribonucleic acid objective: d3 - identify the...

DNA Intro. & Replication (S phase)

DNA = deoxyribonucleic acidObjective: D3 - Identify the components of DNA and describe…DNA replication

I. History of DNAA. Avery, Oswald (1944)

Discovered that the nucleic acid, DNA, stores and transmits the genetic information from one generation of an organism to the next

B. HERSHEY & CHASE (1952)CONCLUDED THAT THE GENETIC

MATERIAL OF THE BACTERIOPHAGE WAS DNA, NOT PROTEIN

C. Chargaff, ErwinDiscovered a relationship in the nitrogenous bases

ADENINE (A) = THYMINE (T) GUANINE (G) = CYTOSINE (C) D. Rosalind Franklin (1952)

TOOK AN X-RAY OF THE DNA STRUCTURE SO THE PATTERNS COULD BE SEEN

THE X-RAYS SHOW THAT DNA IS TWISTED AROUND EACH OTHER LIKE A HELIX AND HAS 2 STRANDS

E. Watson and Crick (1953) Studied the structure of the DNA by

building a 3-D model AFTER using clues from Franklin’s x-ray of DNA

proposed that DNA is made up of 2 chains of nucleotides & that the 2 strands are twisted together in a shape called a double helix

Nucleus

II. Overview of DNA

*Chromosomes are made up of super coiled DNA*

Histone ProteinsDNA

(double

helix)

Base pairs

Sugar-phosphate backbone

Structure of DNA

Made up of nucleotides

Nucleotides have 3 parts:o Phosphateo Sugaro Nitrogen base

Traits are carried in the sequence of nitrogen bases

Common to all organisms

Adenine always pairs with Thymine

Cytosine always pairs with Guanine

DNA Base Pairing Rules

Copying process by which a cell duplicates its DNA

DNA molecule separates into two strands, then produces two new complementary strands following the rules of base pairing Each strand of the double helix of

DNA serves as a template for the new strand

DNA – Genetic Information DNA – Deoxyribonucleic acid

III. DNA Replication (S phase)

How Replication OccursEnzymes unzip DNA by breaking the weak hydrogen bonds between the base pairs, which produces two replication forksDNA polymerase Joins individual nucleotides

to make a new strand Proofreads each new strand

Chromosome Number The number of chromosomes are the same at the end of mitosis

Practice: If one strand of DNA looks like this, ATC GTA CCG, what will the complementary side look like?

TAG CAT GGC If the number of chromosomes in a human skin cell is 46, how many chromosomes will there be in a skin cell after mitosis? 46

ATC GTA CCG___________