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 – 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 Chemicalsfoods Drugsviruses UV lightSTD’s X-raysrock 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 Expression You 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 & 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!!