1. Chapter 8
DNA and GENES
Biology Notes

2. Information Storage in Cells
Instructions for cell functions are stored in the nucleus within the chromosomes
Chromosomes are made of DNA molecules
DNA stands for:
DEOXYRIBONUCLEIC ACID

3. What is DNA? Genetic information that determines an organism’s traits.
Controls by proteins: skin, muscles, bones, etc.
Proteins = Enzymes

4. Watson & Crick
DNA is made of two chains of nucleotides joined together by the nitrogen bases.
Proposed DNA is shaped like a long zipper that is twisted.
Double Helix has two twisted strands that form a spiral.

5. Structure of DNA Very long molecule made up of nucleotides
Each nucleotide consists of :
One deoxyribose sugar (simple sugar)
One phosphate group (phosphorus surrounded by 4 oxygen atoms)
3) One nitrogen base

6. Nitrogen Bases Carbon ring structure w/ four nitrogen atoms.
Will be one of four possible bases:
Cytosine = C
Guanine = G
Adenine = A
Thymine = T

7. Nitrogen Base Pairs
Nitrogen Bases pair with a specific partner: (Complimentary Pairs)
Adenine = Thymine (A – T)
Guanine = Cytosine (G – C)
Hydrogen bonds between the nitrogen bases bond them together

8. A Cytosine Nucleotide P S C

9. Today’s DNA molecule Referred to as a double helix
Visually it is like a long twisted ladder:
Sides are made up of phosphate – sugar groups
The steps are made of pairs of nitrogen bases

10. C - G
Phosphate and sugar groups
G - C
T - A
T - A
G - C
A - T
G - C

11. DNA Replication
When a cell reproduces in the nucleus it must make copies of itself
Each new cell must have same info as the parent cell
Occurs during Interphase

12. DNA Replication Process:
An enzyme breaks the Hydrogen bonds between nitrogen bases (“Unzipping” the double helix)
Free floating nucleotides, surrounding the DNA molecule, are bonded to the exposed nitrogen bases. (Base Pairing)

13. Another enzyme bonds the nucleotides into a chain
Another enzyme bonds the nucleotides into a chain. (Creates the backbone to the new chain)
Process continues until there are 2 new DNA molecules that are identical to one another. (Final product, 2 from 1)

14. Process of Replication
T A
G C
G C TA
A-T
T-A
G-C
2. A-T A-T
A-T A-T
T-A T-A
G-C G-C
G-C G-C
T-A T-A
DNA Helix
New bases come in
Begin to split

15. Final step of Replication 2 identical DNA molecules
A-T A-T
T-A T-A
G-C G-C
T-A T-A

16. Reading the DNA molecule to make proteins.
Protein Synthesis
Reading the DNA molecule to make proteins.

17. How DNA controls cell functions
DNA instructs cell ribosomes to make proteins. It tells them what kind and how many to make.
Some of the proteins are enzymes

18. How DNA controls cell functions
Enzymes control what a cell will do
Enzymes control the cells chemistry
All proteins are made up of smaller units called Amino Acids. There are 20 different types of Amino Acids

19. By combining amino acids in different sequences different proteins can be made
DNA controls the sequence of amino acids in a protein
Therefore it controls what kinds of proteins are made by the cell ribosomes

20. How DNA controls amino acid order in a protein
Order of bases in 1 strand of DNA ( called master strand) determine order of amino acids in a protein.
Order of bases in master strand is called the Genetic Code
Code is read as a sequence of 3 bases called triplets
Each triplet determines which amino acid is to be placed where in a protein

21. Small segment of DNA master strand could have following genetic code
G----T----C----A----A----T----G----G----C
There are 3 triplets in this code
GTC, AAT, GGC
GTC is the triplet code for amino acid glutamine
AAT is triplet code for amino acid Leucine
GGC is triplet code for amino acid Proline

22. Glutamine----Leucine----Proline
Protein being made form genetic code on master strand would have the following amino acid sequence
Glutamine----Leucine----Proline
G----T----C----A----A----T----G----C----C
Glutamine
Leucine
Proline

23. How are proteins made? RIBONUCLEIC ACID
DNA is in the cell nucleus, ribosomes (where proteins are made) are in the cell cytoplasm
Transfer of information from nucleus to ribosomes
Requires another type of nucleic acid
It is called RNA:
RIBONUCLEIC ACID

24. RNA is different than DNA in many ways
There is only 1 strand
Has a ribose sugar
4 nitrogen bases are
Cytosine
Guanine
Adenine
Uracil
RNA uses the DNA as a template to read the code in order to produce the right proteins.

25. Three Different kinds of RNA
m-RNA (messenger RNA)
1. Carries genetic information from DNA to ribosomes
2. Builds the physical sequence of amino acids

26. t-RNA (transfer RNA)
1. Transports Amino Acids into
place.
r-RNA (ribosomal RNA)
1. Connects the protein (amino acids) together
2. Makes up the Ribosome (with Proteins)

27. Transcription: Transfer of information from DNA to Ribosomes
DNA Molecule unzips, and unpaired bases are exposed
RNA NUCLEOTIDES attach to bases on one of the DNA strands (master strand)
 Cytosine to guanine C—G or G—C
 Adenine to uracil A—U
RNA nucleotides combine (develop backbone)
DNA reconnects and RNA is sent to the cytoplasm

28. Translation – Making Protein
Using codons in m-RNA as blueprint to line up amino acids in protein molecule
t-RNA molecules attach to amino acids in cytoplasm
Carry amino acids to Ribosomes
End of t-RNA molecule opposite end attached to amino acid has 3 base sequence called an anticodon

29. DNA and m-RNA A T G T C A G A C G (Master DNA)
U A C A G U C U G C (m-RNA Strand)
3 base sequence in m-RNA is called a codon
DNA and m-RNA molecules separate and the m-RNA molecules travel to the ribosomes

30. Translation continued
Anticodon of t-RNA match and bond to correct codon on m-RNA molecule
t-RNA molecules detach from m-RNA and amino acids
Process is repeated until whole protein molecule is produced

31. Errors in Stored Information
Cells may make proteins that have amino acids in the wrong order
Errors are the result of change in base sequences in a DNA molecule
These errors are called MUTATIONS

32. Mutations in Reproductive Cells
Mutations affect the reproductive cells of an organism by changing the sequence of nucleotides in a gene in the egg or sperm
If these cells take part in fertilization, the changed gene would be part of the genetic makeup of the offspring
This mutation may produce negative results ( death of embryo) or positive results in vary few cases ( faster or stronger individuals)

33. Mutations in Body Cells
If radiation hit a body cell such as your skin tissue, this would not be passed on to your offspring. However, severe effects may result for the individual such as cancer.
Aging is the result of a buildup of cells that do not work properly
Some mutations effect cell division which results in cells either dividing rapidly or not dividing at all.

34. There are 3 types of Mutations
Point Mutation – A change in a single base pair Ex. CAT to CAR = incorrect Amino Acid (replaced)
Frameshift – A single base is either added or deleted. Results in an entirely new amino acid sequence. (addition or deletion)
Chromosomal – Affect the distribution of genes to gametes during meiosis. They cause non-disjunction: the failure of chromosomes to separate

35. All 3 mutations will cause defective proteins to be produced
Cells or organism with mutation will not work correctly
Cells or organism with mutation may die

36. Causes of Mutations Many occur naturally
May be influenced by the environment:
1. Chemicals
2. Ultraviolet light
3. Radiation ( large amt. of energy = bursts DNA)
4. High temperatures
Materials causing mutations are called mutagens.

37. Assignment
Mini Lab pg 306
Do a lab write up, answer the analysis ?’s 1-3 and write a conclusion statement.
Problem Solving lab – pg 305
Answer the Thinking Critically Questions 1-4