Chapter 7 Notes (From Power-Point)
Chapter 7 Notes (from power-point)
Genes & Gene Technology
What do genes look like?
Cell nucleus chromosomes genes.
Genes & chromosomes contain DNA & proteins.
DNA = Deoxyribonucleic acid.
What do genes look like?
Genes have 2 functions:
1. has instructions for cell processes & building cell structures.
2. is able to be copied each time a cell divides.
What do genes look like?
DNA structure:
DNA is made of nucleotide subunits.
Nucleotide contains: sugar, phosphate, & base.
All nucleotides are the same, except the base.
4 different types of bases: adenine (A), thymine (T), guanine (G), & cytosine (C).
What do genes look like?
Chargaff’s Rule:
Amount of A’s and T’s (bases) are the same.
Amount of C’s and G’s are the same.
Conclusion: A always pairs with T, C always pairs with G.
What do genes look like?
A picture of DNA:
X ray diffraction: x rays hit the DNA molecule and when the x ray hits a particle, it ounces off the particle & this pattern is put on film.
Important because Rosalind Franklin’s x-ray diffraction picture showed that DNA has a spiral shape.
What do genes look like?
DNA structure:
Using other scientist’s work and additional information, James Watson & Francis Crick figured out a model of DNA.
The model of DNA resembles a twisted ladder shape = double helix.
Since A pairs with T and C pairs with G bases, one side of DNA is complementary to the other side of DNA.
What do genes look like?
Updated scientific findings on genes:
1. special case of genes: Incomplete Dominance:
When 1 trait does not dominate over another trait. In this case, no dominant & recessive alleles; special case in which both alleles dominate & are both displayed in the physical traits.
Example: Snapdragons
Red Snapdragon X white snapdragon
= Pink snapdragon.
Blending of the two physical traits
together.
What do genes look like?
Updated scientific findings on genes:
1. special case of genes: 1 gene can influence more than 1 trait.
Example: white tiger
1 gene controls both fur color (white) & eye color (blue eyes).
What do gene look like?
Updated scientific findings on genes:
1. special case of genes: Many genes that control 1 trait.
Example: eye color, hair color, skin color.
Several genes working together for 1 trait; this is why there is so much variety in eye, hair, & skin color in humans.
What do genes look like?
Genes do not control everything-
Our Environment controls much of how we will grow & change.
Examples: food/nutrition, practice (sports), decision making.
How DNA works
Genes & Proteins:
Proteins are made up of chains of amino acids.
3 bases = 1 amino acid.
Bases in DNA read like a book of instructions.
Different combination of 3 bases = different variety of amino acids.
Gene: section of DNA that contains instructions for stringing amino acids together to eventually make a protein.
Protein: important because it helps with all functions within the body.
How DNA works.
The making of a protein:
1. DNA is in the nucleus of a cell and it is copied = Replication.
2. DNA converts to RNA and moves from the nucleus to the cytoplasm of a cell = Transcription.
3. RNA (different version of DNA) is made into proteins = Translation.
How DNA works.
Steps of how RNA changes to a protein that the body can use:
1. copy of DNA (RNA) is feed through the ribosome (processing station in the cytoplasm of the cell).
2. transfer molecules deliver amino acids from the cytoplasm of the cell to the ribosome.
3. the amino acids are dropped off at the ribosome.
4. the amino acids are joined together in a long chain to make a protein.
How DNA works.
Changes in genes: Mutations = mistakes in the DNA base order; 3 types.
1. Deletion: a base is left out of the order of DNA bases.
2. insertion: extra base is added to the DNA base order.
3. Substitution: an incorrect base replaces a correct base.
How DNA works.
Mistakes happen:
Enzymes (type of protein) tried to repair all mistakes, but sometimes it does not.
Consequences to mistakes in DNA:
1. an improvement.
2. no change at all.
3. harmful change.
If the correct protein is not made, results can be fatal.
If damage is in the sex cells, then the mistake can be passed down to the next generations.
How DNA works.
DNA can be damaged in other ways:
Mutagens = can harm DNA by physical & chemical agents.
Physical agents = x-rays (high energy) & UV radiation.
Chemical agents = asbestos & cigarette smoke chemicals.
How DNA works.
Substitution of a base in DNA- example:
GAA = glutamic acid
(3 bases) = (1 amino acid)
Mistake: GTA = valine
-This 1 mistake can cause a disease: Sickle Cell Anemia.
-Sickle Cell Anemia = disease that causes red blood cells to change shape (sickle shape); RBC’s get stuck in blood vessels because of the shape.
-This causes dangerous & painful clots in the body.
How DNA works.
Genetic Counseling:
Example: Sickle Cell Anemia: child only inherits the disease from a defective gene in both parents.
Parents can get genetic counseling: information about their genetic history is analyzed to see if their children will have any diseases.
Pedigrees are used.
Pedigree: tool used for tracing a trait through generations of a family.
Applied Genetics
Selective Breeding = organisms with desirable characteristics are mated together.
Designer genes:
Genetic engineering: scientists transfer genes from 1 organism to another.
Genetic engineering used for:
1. manufacture proteins.
2. repair damaged genes.
3. identify individuals who carry a disease for a certain disease.
Applied Genetics
Living Factories:
When genes from 1 organism are put into another using genetic engineering, & the resulting DNA is called recombinant DNA.
Recombinant DNA is used to treat diseases.
Example: Diabetes-
Some people who are diabetic need insulin.
Scientists inject a normal human insulin gene into the DNA of certain bacteria.
Bactria become insulin factories: making huge amount of insulin.
Scientists take insulin created by these bacteria & use it for medicine.
Applied Genetics
DNA Fingerprints:
Each person’s DNA is unique.
In lab, DNA fragments are separated from each other by size.
Patterns of fingerprints are compared.
If patterns match = match of DNA.
Can be used to identify guilty suspects in court cases.
Applied Genetics
Human Genome Project:
A project by a team of scientists to create a map that shows the location & the whole human DNA sequence in all of genes.