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