01 dna structure and replaction
DESCRIPTION
Lesson 1 - DNA Structure and replicationTRANSCRIPT
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.