1. Genes and Gene Technology
Chapter 7

2. What do Genes Look Like? 1869- DNA isolated from a cell nucleus
Unclear of function, or role in inheritance
75 years later 1944-Oswald T. Avery
Discovered DNA is the carrier of genetic information
Each strand of DNA contains 9 billion base pairs
If you could print a book with genetic information of one cell it would be 500,000 pages long
Uncoiled DNA about 2m long

3. Pieces of a puzzle Traits are determined by genes
Genes are passed from one generation to another
Genes are located on chromosomes
DNA is short for deoxyribonucleic acid
Genes material must carry out two functions
Supply complex instructions for cell processes and for building cell structures
Must be copied each time a cell divides
Ensures heredity information is passed to next generation
1940 genes of bacteria and viruses are made of DNA

4. Nucleotides- Subunits of DNA
DNA is made of 4 subunits-called nucleotides
Nucleotides have 3 different types of material
A sugar
A phosphate
A base
Nucleotides are identical except for the type of base present and slightly different shape
Four bases
Adanine (A)
Thymine (T)
Guanine (G)
Cytosine (C)

5. Nucleotides
Can you imagine
how they might
fit together?
(sugar)

6. Chargaff’s Rules 1950 biochemist Erwin Chargaff
Studied samples of DNA from different organisms
Amount of adenine in DNA always equals the amount of thymine
Amount of guanine in DNA always equals the amount cytosine
Chargaff’s rules are represented as follows
A=T
G=C
Ratio of units in a DNA strand differ between organisms

7. Picture of DNA Chemist Rosalind Franklin
Created images of DNA molecules
X-ray diffraction
X-ray hits a particle within the molecule
Ray bounces off the particle
Pattern is captured on film
DNA has a spiral shape

8. James Watson and Francis Crick
Built models of DNA
DNA resembles a twist ladder shape known as a double helix
Used model to predict how DNA is copied
Crick is said to have exclaimed
“We have discovered the secret of life”

9. DNA Structure Refer to page 154 (picture) DNA structure
Two sides of the “ladder” made of alternating sugar and phosphate molecules
Rungs are made of a pair of nucleotides
Adenine always pairs with thymine
Guanine always pairs with cytosine
(remember Chargaff’s rules)
Bases must pair up a certain way
If a mistake happens, the gene will not carry the correct information

10. Making copies of DNA
Remember adenine always bonds with thymine and guanine always bonds with cytosine
Bases on one side of the molecule become a template (pattern) for the other side
One side is complimentary to the other side
Example ACCG would have the sequence TGGC on the other side to form a new complimentary side
Creates two identical molecules of DNA
DNA molecules are split down the middle where the two bases meet
Each side of the ladder is able to pair with additional nucleotides that are free in the nucleus
See photo pg. 155

11. Trait to Gene Bases on one side of a molecule can be put in any order
Enormous variety of genes
Each gene has a string of bases, the order of the bases gives the cell information about how to make each trait
DNA functions the same way for all organisms
Faulty or missing genes cause disease
Cystic fibrosis
Sickle cell anemia
Scientists hope to be able to treat genetic disorders someday by altering genes within body cells
Refer to picture on page

12. Traits
Mendel’s findings uncovered basic principles of how genes are passed from generation to generation
Incomplete dominance
Mendel found that different traits did not blend together to produce an in between form
Since then researcher have found that sometimes different traits are equally dominant
Each allele has its own degree of influence (incomplete dominance)
Ex. red and white snapdragons-produce pink snapdragons

13. Traits One gene can influence many traits Ex. white tiger
White fur influenced by a single gene
This gene also influences eye color

14. Many genes can influence a single trait
Several genes acting together influence
Skin color
Hair color
Eye color
Difficult to tell sometimes if a trait is the result of a dominant or recessive trait
You may have blue eyes, probably a different shade than the blue eyes of a classmate
Different alleles result in slight differences in the amount of pigment present

15. Environment
Genes aren’t the only thing that influences your development
Consider the importance of:
Healthy diet
Exercise
Examples set by adults
Genes may determine that you can grow tall
Must receive the proper nutrition to reach
your potential height
Talent may be inherited but must be developed