2. DNA – The molecule of Heredity
Chromosome -
Carrier of genetic material,
a long strand of coiled DNA
Gene –
a segment of DNA found
on a chromosome
1 gene =
code to make 1 polypeptide (protein)
What is DNA?
A molecule, Deoxyribonucleic Acid,
that holds the master copy of an
organism’s genetic code.

3. DNA – The molecule of Heredity
What is DNA?
Deoxyribonucleic Acid,
Who Discovered the structure of DNA?
Click here for video onDNA
Watson and Crick – 1953, discovered that DNA was made of two spiral strands, they called it a double helix.
Why is DNA important?
Knowledge of DNA is critical for understanding…
Birth Defects
Cancer
Genetic Engineering
Viral Diseases
Aging
Criminal Investigation

4. DNA – The molecule of Heredity
What are the building blocks of DNA?
- Subunits called Nucleotides make up DNA.
Nucleotides are made up of:
A simple sugar – deoxyribose
A phosphate group
A nitrogen base (one of four)
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)

5. A Closer Look at DNA Untwisted
The 2 strands are held together by a weak hydrogen bond.
The 2 strands are held together at the nitrogen bases.
Adenine will bond with Thymine
Cytosine will bond with Guanine
These are called complimentary base pairs
Deoxyribose
Sugar
Hydrogen Bond
Covalent Bond
Phosphate Group
Covalent Bond

6. DNA Replication
What process have we already discussed that involves DNA Replication?
The Cell Cycle!!!!!!!!!! (more specifically, interphase!)
Remember… DNA needs to replicate so that when the cell divides in half, the two daughter cells will have the same genetic information!

7. DNA Replication
DNA untwists

8. DNA Replication
2. Two chains unzip or separate

9. DNA Replication
3. Free floating nucleotides in the nucleus bonds to the unzipped strands by base pairing with the help of enzymes.

10. DNA Replication
4. Two identical DNA molecules are formed.

11. DNA Replication - RECAP
Process:
DNA untwists
DNA unzips and separates
Free floating DNA nucleotides in the nucleus come and bond to the unpaired strands of DNA.
2 identical DNA molecules are formed
Product:
2 DNA molecules that are exactly alike.
**Replication is Semi-Conservative – meaning that the 2 old DNA halves are used as patterns on which to build to new halves.

12. DNA Replication Active Art
Active Art Clip of DNA Replication

13. Double or Single Stranded
What is RNA?
RNA strands for Ribonucleic Acid
Differences in RNA and DNA:
DNA
RNA
Double or Single Stranded
Double
Single
Nitrogen Bases
Thymine
Uracil
Sugar
Deoxyribose
Ribose
RNA is used in the processes of transcription and translation.
There are 3 different types of RNA.
RNA
Function
mRNA – messenger RNA
A copy of DNA. Takes information from the nucleus to the ribosome.
tRNA – transfer RNA
Transports amino acids to the ribosome to be assembled into a protein
rRNA – ribosomal RNA
Makes up the ribosome; assembles proteins

14. We know that DNA is very important because it gives our bodies instructions to make proteins. But how does it do that???
To go from
DNA  proteins, DNA must first become RNA and then go through several processes to become a protein.

15. How does DNA turn into RNA and then make a protein?????
This happens through a process called protein synthesis.
Protein synthesis is made up of 2 main parts:
Transcription
Translation

16. Let’s look at what we know about proteins so far…
Proteins are made up of amino acids.
Proteins are in our foods, such as meats.
Enzymes are a type of protein.
Antibodies are a type of protein.
Considering all of that, we have already learned that proteins are pretty important.
Therefore, our DNA must be pretty important too!

17. Transcription Transcription: Making a copy of mRNA from DNA
mRNA (messenger RNA) = A copy of DNA. Takes information from the nucleus to the ribosome.
Transcription takes place in the nucleus of the cell!
Practice:
DNA TAC CGA GTA ACT
mRNA
AUG GCU CAU UGA

18. Transcription
DNA untwists

19. Transcription
2. Two chains unzip or separate

20. Transcription
3. Free RNA nucleotides pair with complementary DNA nucleotides on one of the DNA strands.

21. Transcription
4. mRNA breaks away as the DNA strands rejoin

22. Transcription - RECAP Process: DNA untwists DNA unzips and separates
Free floating RNA nucleotides in the nucleus come and pair with their complementary DNA pair.
The mRNA breaks away and the DNA comes back together.
Product:
1 single-stranded mRNA molecule
The same double-stranded DNA molecule that you started with.
Transcription video

23. Translation
Translation: converting the mRNA message into a sequence of amino acids to form a protein
tRNA (transfer RNA) = brings the amino acid to the ribosome
Each tRNA carries only 1 amino acid!
Translation takes place at the ribosomes in the cell!
Codon = 3 nitrogen bases on DNA or mRNA. Each codon represents 1 of 20 amino acids.
START CODON – AUG codes for the amino acid Methionine and starts protein synthesis
Anticodon = 3 bases on tRNA that bond to the codon of mRNA
Remind students that we already know that ribosomes help make proteins and that proteins are made up of amino acids.

24. Translation
mRNA attaches to the ribosome

25. Translation
2. tRNA anticodon pairs with mRNA

26. Translation
3. Amino Acids are joined together with peptide bonds to make a protein.

27. Translation – RECAP Process: mRNA attaches to the ribosome
tRNA anticodons pair with mRNA
Amino Acids are joined together with peptide bonds to make a protein.
Product:
Protein!!!!!!!!!!
(determined using a codon chart)
Video on translation

28. How can I tell which codons are used to make the protein?
Codon Chart

29. Protein Synthesis – RECAP

30. Replication and Protein Synthesis
Web Activity

31. If the order of bases change Genes will change
Just like everything else in our bodies, there is a chance that this process will mess up.
When replication, transcription or translation mess up, we call it a mutation.
If the order of bases change
Genes will change
Trait will be expressed differently

32. Mutations
Mutation – any mistake or change in the DNA Sequence, both random or from radiation/chemical exposure (only changes in the gametes will be passed on from parent to offspring)
Types of Mutations:
GENE MUTATION
If the order of bases changes
Amino Acid Sequence changes
Proteins function changes Changes Phenotype
a. Substitution or Point Mutation – change in a single base pair
b. Frameshift Mutation – addition or deletion of a single base pair