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.