unit 4 - molecular genetics
DESCRIPTION
Unit 4 - Molecular Genetics. DNA Replication Protein Synthesis Transcription Translation Cell Cycle. 1928 – Griffith. 1944 – Avery, McCarty, & McCleod. Bacteriophage. Viruses that attack bacterial cells (“bacteria eaters”). 1952 – Harvey & Chase. 1953 Watson & Crick (and Franklin). - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Unit 4 - Molecular Genetics](https://reader035.vdocuments.net/reader035/viewer/2022062315/5681645e550346895dd63447/html5/thumbnails/1.jpg)
Unit 4 - Molecular Genetics
• DNA Replication• Protein Synthesis– Transcription– Translation
• Cell Cycle
![Page 2: Unit 4 - Molecular Genetics](https://reader035.vdocuments.net/reader035/viewer/2022062315/5681645e550346895dd63447/html5/thumbnails/2.jpg)
• 1928 – Griffith
![Page 3: Unit 4 - Molecular Genetics](https://reader035.vdocuments.net/reader035/viewer/2022062315/5681645e550346895dd63447/html5/thumbnails/3.jpg)
• 1944 – Avery, McCarty, & McCleod
![Page 4: Unit 4 - Molecular Genetics](https://reader035.vdocuments.net/reader035/viewer/2022062315/5681645e550346895dd63447/html5/thumbnails/4.jpg)
Bacteriophage
• Viruses that attack bacterial cells (“bacteria eaters”)
![Page 5: Unit 4 - Molecular Genetics](https://reader035.vdocuments.net/reader035/viewer/2022062315/5681645e550346895dd63447/html5/thumbnails/5.jpg)
• 1952 – Harvey & Chase
![Page 6: Unit 4 - Molecular Genetics](https://reader035.vdocuments.net/reader035/viewer/2022062315/5681645e550346895dd63447/html5/thumbnails/6.jpg)
• 1953 Watson & Crick (and Franklin)
![Page 7: Unit 4 - Molecular Genetics](https://reader035.vdocuments.net/reader035/viewer/2022062315/5681645e550346895dd63447/html5/thumbnails/7.jpg)
• 1958 – Meselson & Stahl
![Page 8: Unit 4 - Molecular Genetics](https://reader035.vdocuments.net/reader035/viewer/2022062315/5681645e550346895dd63447/html5/thumbnails/8.jpg)
DNA Structure
• Nucleotides – the building blocks of DNA (nucleic acids)
![Page 9: Unit 4 - Molecular Genetics](https://reader035.vdocuments.net/reader035/viewer/2022062315/5681645e550346895dd63447/html5/thumbnails/9.jpg)
Base Pairing
• A-T (double) • G-C (triple)
![Page 10: Unit 4 - Molecular Genetics](https://reader035.vdocuments.net/reader035/viewer/2022062315/5681645e550346895dd63447/html5/thumbnails/10.jpg)
3’ vs. 5’ ends of DNA
![Page 11: Unit 4 - Molecular Genetics](https://reader035.vdocuments.net/reader035/viewer/2022062315/5681645e550346895dd63447/html5/thumbnails/11.jpg)
• Gene – a portion of DNA that codes for a specific protein
![Page 12: Unit 4 - Molecular Genetics](https://reader035.vdocuments.net/reader035/viewer/2022062315/5681645e550346895dd63447/html5/thumbnails/12.jpg)
![Page 13: Unit 4 - Molecular Genetics](https://reader035.vdocuments.net/reader035/viewer/2022062315/5681645e550346895dd63447/html5/thumbnails/13.jpg)
DNA Function• Transmission of genetic material to offspring• Basis of all cell processes (DNA RNA Protein)• Structure relates to function!– DNA structure provides a perfect template for semi-
conservative replication
![Page 14: Unit 4 - Molecular Genetics](https://reader035.vdocuments.net/reader035/viewer/2022062315/5681645e550346895dd63447/html5/thumbnails/14.jpg)
Leading vs. Lagging Strands• Nucleotides can only be added to the 3’ end of a
DNA molecule– THUS - DNA elongates only in the 5’ 3’ direction
![Page 15: Unit 4 - Molecular Genetics](https://reader035.vdocuments.net/reader035/viewer/2022062315/5681645e550346895dd63447/html5/thumbnails/15.jpg)
DNA Replication1. Starts at an origin of replication (ori)– Bacterial DNA is circular (only 1 ori)– Eukaryotic DNA is linear (multiple ori’s)
![Page 16: Unit 4 - Molecular Genetics](https://reader035.vdocuments.net/reader035/viewer/2022062315/5681645e550346895dd63447/html5/thumbnails/16.jpg)
2. RNA primase (enzyme) recognizes an ori site on DNA, “sits” down on DNA, and synthesizes an RNA strand (5-10 nucleotides long) called a primer
3. DNA polymerase (enzyme) finds this primer and begins replication – Adds nucleotides in a 5’ 3’ direction only!
![Page 17: Unit 4 - Molecular Genetics](https://reader035.vdocuments.net/reader035/viewer/2022062315/5681645e550346895dd63447/html5/thumbnails/17.jpg)
Replication fork – spots where DNA double strand “forks”• DNA helicase (enzyme) – unzips the DNA
double helix
![Page 18: Unit 4 - Molecular Genetics](https://reader035.vdocuments.net/reader035/viewer/2022062315/5681645e550346895dd63447/html5/thumbnails/18.jpg)
3a – Leading Strand• As the helix is unzipped, the 3’ end of leading
strand is synthesized continuously• Only 1 RNA primer and 1 DNA polymerase is
needed!
![Page 19: Unit 4 - Molecular Genetics](https://reader035.vdocuments.net/reader035/viewer/2022062315/5681645e550346895dd63447/html5/thumbnails/19.jpg)
3b – Lagging Strand• Lagging strand is synthesized BACKWARDS in
short chunks called Okazaki fragments with each getting: – RNA primer (thus RNA primase)– DNA polymerase (to synthesize DNA)
• DNA ligase – enzyme that ligates (“sticks together”) Okazaki fragments together to form a single DNA strand
![Page 20: Unit 4 - Molecular Genetics](https://reader035.vdocuments.net/reader035/viewer/2022062315/5681645e550346895dd63447/html5/thumbnails/20.jpg)
![Page 21: Unit 4 - Molecular Genetics](https://reader035.vdocuments.net/reader035/viewer/2022062315/5681645e550346895dd63447/html5/thumbnails/21.jpg)
![Page 22: Unit 4 - Molecular Genetics](https://reader035.vdocuments.net/reader035/viewer/2022062315/5681645e550346895dd63447/html5/thumbnails/22.jpg)
![Page 23: Unit 4 - Molecular Genetics](https://reader035.vdocuments.net/reader035/viewer/2022062315/5681645e550346895dd63447/html5/thumbnails/23.jpg)
DNA Replication Video
• http://www.youtube.com/watch?v=teV62zrm2
![Page 24: Unit 4 - Molecular Genetics](https://reader035.vdocuments.net/reader035/viewer/2022062315/5681645e550346895dd63447/html5/thumbnails/24.jpg)
A few essential ideas to remember:
1. DNA copies itself almost always without error. (Approximately 1 true error per 10 billion bp; actually 1 error in 10,000 bp but DNA polymerases proof-read and fix)
2. Eukaryotic DNA replicates @ 50 nucleotides/second; bacterial DNA replicates much faster (10x)
![Page 25: Unit 4 - Molecular Genetics](https://reader035.vdocuments.net/reader035/viewer/2022062315/5681645e550346895dd63447/html5/thumbnails/25.jpg)
Proof-reading & Repair• DNA polymerases proof-read each strand
against the parent template.• If error goes unrepaired by DNA polymerases,
then other repair mechanisms kick in.• There are 130 different DNA repair enzymes in
humans!
![Page 26: Unit 4 - Molecular Genetics](https://reader035.vdocuments.net/reader035/viewer/2022062315/5681645e550346895dd63447/html5/thumbnails/26.jpg)
An example…
![Page 27: Unit 4 - Molecular Genetics](https://reader035.vdocuments.net/reader035/viewer/2022062315/5681645e550346895dd63447/html5/thumbnails/27.jpg)
Telomeres• Telomere- a 100 to 1000 base-pair section at
the tips of Eukaryote’s chromosomes (DNA)• Repeating sequences of TTAGGG (humans)• Function to protect the end of genes from being
shortened by successive rounds of replication but telomeres themselves are shortened after each round of replication
![Page 28: Unit 4 - Molecular Genetics](https://reader035.vdocuments.net/reader035/viewer/2022062315/5681645e550346895dd63447/html5/thumbnails/28.jpg)
![Page 29: Unit 4 - Molecular Genetics](https://reader035.vdocuments.net/reader035/viewer/2022062315/5681645e550346895dd63447/html5/thumbnails/29.jpg)
• Telomeres can only be shortened so much (thus a cell can divide only so many times) and then the cell dies via apoptosis (programmed cell death)
• Get this:– Certain cells (e.g. germ cells) have telomerase, an
enzyme that catalyzes the repair of telomere DNA damaged after replication
– Certain types of cancer cells overexpress telomerase which allows those cells to continuously divide w/o consequence