Presentation on theme: "Molecular Structure & Function of Genetic Material"— Presentation transcript:
1Molecular Structure & Function of Genetic Material Professor Janaki Natalie Parikh
2D.N.A. StructureD.N.A.: deoxyribonucleic acid: is a double stranded (dbl helix) polymer of a nucleotidesResides in the nucleus (eukaryotes)Made of 3 molecules:Phosphate, Sugar &nitrogenous base
3DNA 4 bases in D.N.A.: Adenine, Guanine, Thymine & Cytosine Rules for pairing bases together:Adenine Thymine Guanine CytosineOur DNA is composed of literally billions of bases!Genes are long sections (segments) of D.N.A.
4D.N.A. Function 1. D.N.A. can make a copy of itself, handy during? Mitosis & meiosis2. D.N.A. contains the code for protein synthesis, the manufacture of proteinsProblem, where does protein synthesis take place?Ribosomes, located? Outside the nucleus. D.N.A. can’t leave the nucleus.So how does this get done?
5R.N.A.R.N.A.: ribonucleic acid, single stranded, free floating throughout the cellSimilar bases, w/ 1 important diffc.Adenine, Guanine, Uracil & CytosineAdenine Uracil Guanine CytosineR.N.A assists in completing protein synthesis
6Protein Synthesis Proteins: polymers as well, but difft. components? Amino acids. How many are there?20 total. Of these 11 are naturally occuring, the other 9 must be consumed through food, those are known as “essential amino acids” (in kids 10 are essential, 1 loses this status once we produce it)How do we get these essential amino acids?
7Protein Synthesis Recall our logistical dilemma? Making proteins: multi-step taskCheesy analogy: outside of thenucleus is the “hood”, the nucleus: gated commtyD.N.A.: Doesn’t kNow About the hoodHowever, D.N.A.’s cousin, R.N.A. is another storyR.N.A.: Really kNows About the hood
8Steps of Protein Synthesis 1.transcription: m.R.N.A. enters nucleus, produces a transcript of D.N.A. code (in R.N.A. language)Let’s try part of a sequence:D.N.A. reads: A T A G A G mRNA?m.R.N.A.: U A U C U C2. translation: t.R.N.A. reads the mRNA transcript & translates the info one codon at a time
9Codons & Genetic CodeCodons: base triplet that codes for an amino acidNotice: genetic redundancy: more than 1 codon codes for thesame amino acid(we’ll discusssignifcance ofthis redundancysubsequently)
10Protein Synthesis Back to our 2nd step: mRNA: U A U C U C tRNA: A U A G A GAmino acid: Isoleucine, Glutamic Acid
11Genetic Redundancy Sometimes mistakes occur in this process (mutation) Problem: even 1 incorrect base can render a protein useless junk (loss of function)Remember genetic redundancy? It’s purpose:Serves as an built-in security mechanism, reducing the chance that a base substitution resuls in loss in protein function
12Mutations Overview Mutagens: accelerate the rate of mutations Mutations are completely random accidentsMost mutations result in loss in protein function (junk protein), some are neutral, Rarely: new protein function producted(Ecstasy q:
13Mutations Point mutations: involve 1 single base Base substitution: swapping of nucleotide baseCan possibly be neutral due to genetic redundancyAddition or deletion: extra base insert or a base is omitted from correct sequenceResults in a frameshift mutation (affects multiple amino acids) & can never be neutral
14Chromosomal Mutations Chromosomal mutations (macrolesions): occur during meiosis, larger scale of significance since whole chromosome involvedNondisjunction: chromosome pair failed to splitResults in a gamete w/ too many, or too few chromosomes
15Trisomy & Monosomy Trisomy: presence of 3 chromosomes instead of the normal 2 in ahomologous pairMonosomy: presence of 1 chromosome instead ofthe normal 2 in a homologous pairExamples?Down’s syndrome: trisomy of #21
16Syndromes Klinefelter’s Syndrome: XXY or XXXY Turner’s Syndrome: X0
17Mutations & Evolutionary Significance In order for a mutation to have an evolutionary impact, it must be inheritable (happens in the gametes)Next, we’ll examine a specific point mutation that had a major impact on human populations