Chapter 6

Genes and Gene Technology

DNA

Deoxyribonucleic acid Hereditary material that controls all

the activities of a cell contains the information to make new

cells provide instructions for making

proteins

Nucleotide

A subunit of DNA Consists of a sugar, a phosphate, and

one of the four nitrogenous bases A, C, T or G Nucleic acid- a biochemical that

stores information needed to build proteins

A, T, C, G

Adnenine – pairs with Thymine Thymine – pairs with Adenine Cytosine – pairs with Guanine Guanine – pairs with Cytosine

Ribosome

A small organelle in cells where proteins are made from amino acids

What Do Genes Look Like?

Chromosomes are made of DNA and proteins

Traits (appearance)are determined by genes (codes of DNA)

Genes are passed from generation to generation

Genes are located on the chromosomes

The gene material must

Able to supply instructions for cell processes and for building cell structures

Able to be copied each time a cell divides

Early Studies

Suggested that DNA was a simple molecule and therefore thought protein carried heredity information

1940’s – scientists discover that genes of bacteria are made of DNA

Chargaff’s Rules

1950’s – Erwin Chargaff found the amount in adenine in DNA always matches the amount of thymine

Also, the amount of cytosine always matches the amount of guanine Clue 1 to the structure of DNA

A Picture of DNA

Clue 2 for the shape of DNA Rosalind Franklin (1920-1958) Used x-ray diffraction (bombard the

DNA molecule with x-rays that bounce off and create a pattern)

Created a picture of DNA molecule

Franklin’s Picture

Died at the age of 38 due to cancer

Discriminated throughout her career by Wilkins and Watson

Watson and Crick

Discovered that DNA was helical in shape (double helix) Franklin’s picture

Spiral shape Chargaff’s rules

Bases in pairs Double strand

Watson and Crick

Won the Nobel prize in 1962 with Maurice Wilkins

Rosalind Franklin receive no mention because the Nobel Prize is not awarded posthumously

After her death, W and C gave her credit to their success

Because adenine always bonds with thymine, and cytosine always bonds with guanine, one side of a DNA molecule is complementary to the other.

If the DNA segment is

GATTACTTTAACCT

The complementary strand would be:

CTAATGAAATTGGA The complementary base pairing

allows DNA to REPLICATE or copy itself

DNA replicates by splitting down the middle where the nitrogen bases meet.

The bases on each side of the molecule are used as a template, or pattern for a new complementary side.

This creates two identical molecules of DNA.

DNA

DNA functions the same way for all organisms

DNA makes us the same and makes us unique

The bases on one side of the DNA molecule can be put in any order, allowing an enormous variety of genes.

Each gene consists of a string of bases.

The order of the bases gives the cell information about how to make each trait.

The double helix wraps around a protein known as a histone and coils and condenses until it appears as a chromosome

The Importance of Environment

Remember, genes only influence your development

Other things affect your growth and development Nutrition, exercise

Mutation?

Is this possible?

How about this?

Mutation

A change in the order of the bases in an organism’s DNA

Deletion –removing a base Insertion – adding a base Substitution – Switching bases

Insertion

Substitution

Mutation – Leucistic

Mutagen

Anything that can damage or cause changes in DNA