How DNA Works

• DNA is found in the cells of all organisms, from mosquitoes to bacteria to humans

• Each organism has a unique set of DNA, but DNA functions the same way in all organisms.

Unraveling DNA

• 1) DNA is often wound around proteins, coiled into strands, and then bundled up even more

• 2) In a cell that lacks a nucleus, each strand of DNA forms a loose loop within the cell

• 3) In a cell with a nucleus, the strands of DNA and proteins: are bundled into chromosomes

See the Difference!

• 4) The order of the bases on one side of the molecule is a code that carries information.

• 5) A gene consists of: a string of nucleotides that gives cell information

Genes and Proteins

1) DNA code reads like a book—from 1 end to the other, in 1 direction

2) Bases form the alphabet of the code. Groups of 3 bases are the codes for specific amino acids.

3) Example: 3 bases CCA form proline.

4) A long string of amino acids forms a protein. Thus, each gene is usually a: set of instructions for making a protein.

Proteins and Traits

1) Proteins are found throughout cells and cause: most differences you see.

2) Proteins act as chemical triggers and messengers.

3) A single organism may have thousands of genes that code for thousands of proteins.

Help From RNA

1) RNA: ribonucleic acid, a molecule that is present in all living cells and plays role in protein productions

2) RNA is so similar to DNA that is can serve as: temporary copy of a DNA segment

Making of a Protein (Figure 2):

Changes in Genes

1) Mutation: Changes in the number, type, or order of bases on a piece of DNA

1) Deletion: base is left out

2) Insertion: extra base added

3) Substitution: wrong base is used

Do Mutations Matter?

• Three possible consequences to changes in DNA:

1) An improved trait

2) No change

3) Harmful trait• When error is found, it is usually fixed• If the mutation occurs in the sex cells, the

changed gene can be passed from one generation to the next.

How Do Mutations Happen?

1) Mutations happen regularly because of: random errors when DNA is copied

2) Also, damage to DNA can be caused by abnormal things that happen to cells

3) Any physical or chemical agent that can cause a mutation in DNA is called a mutagen.

4) Examples of mutagens: X-rays, UV radiation, cigarette smoke

Uses of Genetic Knowledge

• Genetic Engineering1) Genetic engineering:

when scientists manipulate individual genes within an organism

2) New products created: drugs, food, fabrics

3) For example, bacteria may be used to make the proteins found in a spider’s silk

Genetically engineered peanut plant

• Genetic Identification

1) Your DNA is unique, so it can be used like a fingerprint to identify you.

2) DNA fingerprinting identifies: the unique patterns in an individual’s DNA

1) Identical twins have truly identical DNA. Scientists are now able to create something like a twin, called a clone. A clone is a new organism that has an exact copy of another organism’s genes.