DNAStructure and Replication

DNA Rap Song

http://www.youtube.com/watch?v=d1UPf7lXeO8

Student Expectations

B 6.A1

Identify components of DNA.

DNA Structure

DNA stands for Deoxyribonucleic Acid

Shape: Double helix

Monomers: Nucleotides (has 3 parts) Sugar, (deoxyribose), phosphate nitrogenous base

Bases are held together by hydrogen bonds.

Four Nitrogenous Bases Adenine (A) Guanine (G) Cytosine (C) Thymine (T)

Purines (double ring) Adenine and Guanine

Pyrimidines (single ring) – Cytosine and Thymine

Chargaff’s rule: Adenine pairs with thymine. A –T T – A Guanine pairs with cytosine. G – C C – G

Nucleotides: Purines Pyrimidines

Adenine Guanine

Cytosine Thymine

Phosphate group

Sugar:

Deoxyribose

Thymine Cytosine

Build a DNA molecule

http://learn.genetics.utah.edu/content/begin/dna/builddna/

A Closer Look at DNA: Page 294

Hydrogen bonds

Nucleotide

Sugar-phosphate backbone

Key

Adenine (A)

Thymine (T)

Cytosine (C)

Guanine (G)

A closer look at DNA:How DNA condenses

Chromosome

Supercoils

ChromatinHistones

DNA

double

helix

Centromere

Student Expectation

B 5.A1

Describe the stages of the cell cycle, including

deoxyribonucleic acid (DNA) replication.

What is Replication?

The process of copying DNA during S phase of interphase in the nucleus

Makes sure that a daughter cell will have a complete set of chromosomes

Original strand of DNA serves as a template for 2 new strands Template: a pattern; an original model

Each new strand will be identical to the original strand because of Chargaff’s rule.

How does replication work?

1) Helicase unwinds the double helix, forming a “replication fork,” where replication takes place

2) DNA polymerase bonds the necessary nucleotides to the original DNA strand to complete 2 new DNA molecules

3) DNA polymerase also “proofreads” the new DNA strand to make sure it is an exact copy of the original DNA

DNA Replication Facts:

DNA polymerase can only work in one direction so: 2 new strands of DNA are made in opposite

directions One strand is made in sequence of nucleotides The other strand is what we call the “lagging

strand” because nucleotides are added in fragments

DNA Replication: Page 298

Growth

Growth

Replication fork

DNA polymerase

New strand

Original strand DNA

polymerase

Nitrogenous

bases

Replication

fork

Original strand

New strand

Videos

http://www.youtube.com/watch?NR=1&feature=fvwp&v=bW5JnYZImJA

http://www.youtube.com/watch?v=5VefaI0LrgE&feature=related