Presentation on theme: "How Many Scientists Does it Take to Discover a Molecule?"— Presentation transcript:
1 How Many Scientists Does it Take to Discover a Molecule?
2 Erwin Chargaff (Born 1905) Russian Moved to the U.S.Discovered that there could not be only one base attachedThere was always an equal number of A’s to T’s and C’s to G’s.There could be different amounts of these two groupings.
3 Rosalind Franklin (1920 – 1958) British Worked under Maurice WilkinsUsed X-ray diffraction to get images of DNAHer work was passed along to Watson and Crick by Wilkins.She did not get recognized for her work possible because she was a woman in science when it was not fully acceptable
5 Watson and Crick Crick (Born 1916) British Watson (Born 1928) American Used images and papers produced by FranklinDiscovered double helix shapeThey got theNobel Prize in1953 along withWilkins
6 DNA ReplicationDNA replicates when the cells divide and when the sex cells are formedGroups of proteins guide the process, but DNA polymerase is the major functioning enzyme.
7 Three major events to begin DNA replication The two nucleotide chains must separate forming a replication fork.The chains are separated by enzymes called helicasesDNA polymerase binds to the separated chains of DNA and assembles complimentary nucleotides to the old strandThe new strand of DNA hydrogen bonds with the old strand and winds back to form a helix
9 Checking the SystemIncoming nucleotides bind to the DNA polymerase and the polymerase checks to see if the incoming nucleotide pairs correctly with the DNA template.Error rate is about 1 error in base pairs (108)
10 Direction of Replication Replication takes place in both directions.DNA polymerase begins replication simultaneously at many points along the separated nucleotide.
11 The Other Nucleic Acid Remember that: DNA is located in the nucleus and under no circumstances can leave the nucleus.Proteins are manufactured in the cytoplasm at the ribsomes.DNA is the instructions for making those proteins.
12 RNA: Ribonucleic Acid Sugar: Ribose Phosphate group Nitrogen bases Single StrandedMade of nucleotidesSugar: RibosePhosphate groupNitrogen basesThe nitrogen bases in RNA have one difference.Thymine is replace by uracilSo A pairs to U; G pairs to C
14 Three Types of RNA Messenger RNA (mRNA) Transfer RNA (tRNA) Carries the code from DNA to the ribosomeTransfer RNA (tRNA)Picks up individual amino acids in the cytoplasm and carries them to the ribosome to be deliveredRibosomal RNA (rRNA)Helps bind mRNA and tRNA together during protein synthesis
15 RNA TranscriptionDNA transcribes a copy of mRNA in the nucleus of the cell. The mRNA takes the DNA code out of the nucleus and to the ribosomes.
16 Steps of Transcription RNA polymerase makes RNA copies of specific segments of DNA.This begins at a promotor site on DNAOnly the DNA template is used for transcription
17 Steps of Transcription RNA polymerase adds complimentary RNA nucleotides to form a new RNA molecule.Complimentary base pairing determines the nucleotide sequence
18 Steps of Transcription Transcription ends at the DNA terminator. Both DNA and RNA are released by the RNA polymerase.All three types of RNA molecules are transcribed by this process.
20 Protein Synthesis – Structure and Composition Proteins are polymers made of amino acids bonded by peptide bondsProteins are made up of specific sequences of amino acidsThere are 20 kinds of amino acids
21 Protein assemblyCodon (AUG) means “Start” or can code for the amino acid methinoneMRNA codon is paired with tRNA anticodonAmino acids are bonded with peptide bonds and the polypeptide chain grows into a proteinAt the stop codon (UAA, UAG, UGA) translation ends and the protein is finishedThe protein folds upSeveral ribosomes can translate the same mRNA transcript at the same time
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