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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.
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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 – T G - 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 - AAGCCGATA RNA -
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 A RNA – U U C G G C U A U Amino Acid translation: UUC = phenylalanine GGC = glycine UAU = 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
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 & cloning Differentiation 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!!
