Who are you?Ch 30

Karyotype

Chromosome Theory• Walter Sutton

– Saw mitosis of grasshopper cells•Mendel’s “factors” = chromosomes•Chromosome theory – genes are

sections of chromosomes•Chromosomes are made of DNA

wrapped around a protein “blob”

The Genetic Code• DNA - Deoxyribo Nucleic Acid• Made of 3 major parts:

•Phosphate•Sugar•Any one of 4 Nitrogen containing

Bases–Adenine (A)–Thymine (T)–Guanine (G)–Cytosine (C)

Structure of DNA– James Watson and Francis Crick (1953)

• Use X-ray photograph of DNA crystals created by Rosalind Franklin

– Discovered structure • double helix (twisted ladder)

– Sides made of sugar & phosphate

• Complementary base pairing make up the “steps”

A – TG - C

Importance of structure?

• Structure determines HOW DNA gets copied or replicated for new cells

• nucleotide letters make up our genes– Genes determine our traits– Changes to DNA structure mean

changes to our traits •mutations

DNA Replication

• Makes an EXACT copy of the DNA– Passed to a new cell

•Interphase of cell cycle

DNA vs. RNA• DNA in the nucleus

– DNA “letters” are the directions to make proteins

– We are made of proteins

• Proteins made at the ribosome– In the cytoplasm– RNA copy of DNA takes the message out of the

nucleus and brings it to the ribosomes

– 2 step process• Transcription• Translation

Transcription

• Make an RNA copy of DNA

• RNA copy is complementary to DNA– No thymine in RNA– Substitute T with uracil (U)

• DNA - AAGCCGATARNA -

Translation

• How to ‘read’ the DNA/RNA code– Every 3 letters of RNA = a CODON

– RNA Codon translated into an amino acid

– Lots of amino acids make a protein (polypeptide)•Proteins are: structural, enzymes,

hormones

Translation

• DNA – A A G C C G A T ARNA – U U C G G C U A U

Amino Acid translation:UUC = phenylalanineGGC = glycineUAU = tyrosine

Together, it ‘means’ build ______ using these 3 amino acids

Changes in the Code

• Mutation– Mistakes in the code– Can be caused by

• chromosome errors• Deletions, inversions, substitutions

• Mutagens– Things that cause mutations

• Chemicals foods• Drugs viruses• UV light STD’s• X-rays rock n’ roll

Cancer & DNA

• Cells “gone wild”• Mutagens that

cause cancer– carcinogens

Human Genetics

• Genetic counselors– Medical professionals who test and

counsel people for the possibility of genetic disorders•Use family history•Use clinical tests

Gene ExpressionYou must have been a beautiful

baby…

When do genes need to be transcribed/translated?

• Needs of the cell

• Energy conservation

• Developmental “milestones”

• Environmental signals

Why are cells different?• Gene expression

• All somatic cells have same DNA code

• Through development, cells become differentiated as they morph – Morphogenesis & differentiation

• Not all gene codes are “turned on” , some genes are “turned off”– environmental signals– Cell location & tissue type

Pluripotency & cloningDifferentiation leads to different cell types – regeneration is based on de-differentiating

cells• turning gene codes back on

all cells have the ability to be pluripotent – anything they want to be!

– THIS is the basis for cloning and future gene manipulation!!