who are you? ch 30
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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. - PowerPoint PPT PresentationTRANSCRIPT
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!!