HSA # 1

Which of these is a the formula for Photosynthesis?

A. C02 + C6H12O6 H20 + O2

B. C6H12O6 + O2 H20 + C02

C. H20 + C02 C6H12O6 + O2

D. C02 + O2 C6H12O6 + H20

Turn in midterm

today!

Objective

SWBAT create a DNA model in order to

describe the structure and function of DNA

in living organisms.

Topic: DNA Structure and replication

Essential Question: What is DNA made of and

how does it replicate?

What is DNA? The Molecule of Heredity

• DNA makes up your genes. Genes determine what you look like, also known as your traits.

• Where did you get your genes from?

DNA stands for

Deoxyribonucleic acid

The complete instructions for synthesizing all the proteins for an organism.

Heredity

• Think back to the characteristics of life… What is heredity?

• Chromosomes are the condensed pieces of DNA.

• DNA/ chromosomes are ALWAYS located in the nucleus of a cell.

DNA: The Structure

The monomer (building block) of DNA molecules are nucleotides

3 Parts of a nucleotide

Sugar

Phosphate

Nitrogen bases

DNA is made up of only FOUR nitrogen bases…

they are abbreviated with the first letter of their name.

A = Adenine

T = Thymine

G = Guanine

C = Cytosine

A and T always pair together.

G and C always pair together.

Genetic Code : the importance of nucleotide sequences

All organisms have the same

4 bases

The order of the nitrogen bases causes the differences between organisms

Genetic Differences

No two people look exactly alike… except identical twins.

Why is that? What makes us all different?

Why do you think identical twins are… well… identical?

DNA: Shape

2 DNA strands twist into a double helix. Like a twisted ladder.

The sides or “backbone” of the molecule is made up of sugar and phosphates.

The “steps” are made of nucleotides.

The nucleotides

always pair up

the same way.

A always pairs

with what?

C always pairs

with what?

T

G

DNA to Chromosome

Replication of DNA

DNA is replicated before a cell divides so each new cell gets a complete set of chromosomes.

Replication of DNA

Process in which DNA is copied before cell division (Mitosis)

Name the phase of the cell cycle responsible for DNA Replication

Interphase

How DNA replicates

1) Enzymes break the hydrogen bond between nitrogen bases of the 2 DNA strands

2) This causes the 2 DNA strands to unzip

3) Free floating nitrogen bases in the cytoplasm attach to each side of the DNA strand

4) Another enzyme helps the free floating nitrogen bases attach to each side of the DNA strand

5) Continues until the entire DNA molecule is unzipped and replicated (copied)

6) End up with 2 sides copied and re-twisted

Each new double helix has one old strand and one new strand

Making a DNA model

• You will create a DNA model and complete the question sheet that goes along with that model.

• When your model is complete ask Ms. Cogswell to check your work. Then compete the work sheet.

• Take apart your model and place all parts back into the bag.