genes and how they work!. genetic code how does the order of nucleotides in dna encode information...
TRANSCRIPT
![Page 1: Genes and how they work!. Genetic Code How does the order of nucleotides in DNA encode information to specify the order of amino acids?](https://reader036.vdocuments.net/reader036/viewer/2022062422/56649eca5503460f94bd82a9/html5/thumbnails/1.jpg)
Genes and how they work!
![Page 2: Genes and how they work!. Genetic Code How does the order of nucleotides in DNA encode information to specify the order of amino acids?](https://reader036.vdocuments.net/reader036/viewer/2022062422/56649eca5503460f94bd82a9/html5/thumbnails/2.jpg)
Genetic Code
• How does the order of nucleotides in DNA encode information to specify the order of amino acids?
![Page 3: Genes and how they work!. Genetic Code How does the order of nucleotides in DNA encode information to specify the order of amino acids?](https://reader036.vdocuments.net/reader036/viewer/2022062422/56649eca5503460f94bd82a9/html5/thumbnails/3.jpg)
Genetic Code
• Crick 1961 – elucidated the genetic code
• Logic used - How many bases (nucleotides) are needed to code for 20 amino acids?
• One base can code for 4 amino acids (41)
• Two bases can code for 16 amino acids (42)
• Three bases can code for 64 amino acids (43)
• Therefore a sequence of three bases is the most reasonable number for a coden!
![Page 4: Genes and how they work!. Genetic Code How does the order of nucleotides in DNA encode information to specify the order of amino acids?](https://reader036.vdocuments.net/reader036/viewer/2022062422/56649eca5503460f94bd82a9/html5/thumbnails/4.jpg)
![Page 5: Genes and how they work!. Genetic Code How does the order of nucleotides in DNA encode information to specify the order of amino acids?](https://reader036.vdocuments.net/reader036/viewer/2022062422/56649eca5503460f94bd82a9/html5/thumbnails/5.jpg)
• 3 bases constitutes a codon (codes for an amino acid) with no space/markers between codons.
![Page 6: Genes and how they work!. Genetic Code How does the order of nucleotides in DNA encode information to specify the order of amino acids?](https://reader036.vdocuments.net/reader036/viewer/2022062422/56649eca5503460f94bd82a9/html5/thumbnails/6.jpg)
Codons and their amino acids
• Nirenberg – used synthetic mRNA
• Eg. UUUUUUU phenylalanine
• Did not take long to determine amino acids
and the corresponding 3 nucleotide sequence
![Page 7: Genes and how they work!. Genetic Code How does the order of nucleotides in DNA encode information to specify the order of amino acids?](https://reader036.vdocuments.net/reader036/viewer/2022062422/56649eca5503460f94bd82a9/html5/thumbnails/7.jpg)
![Page 8: Genes and how they work!. Genetic Code How does the order of nucleotides in DNA encode information to specify the order of amino acids?](https://reader036.vdocuments.net/reader036/viewer/2022062422/56649eca5503460f94bd82a9/html5/thumbnails/8.jpg)
• Codon/amino acid relationship almost universal
• e.g. Codon AGA arginine in Bacteria, Humans and all other organisms
• except for Mitochondria and Chloroplasts and a few ciliates
• What does this tell you?
![Page 9: Genes and how they work!. Genetic Code How does the order of nucleotides in DNA encode information to specify the order of amino acids?](https://reader036.vdocuments.net/reader036/viewer/2022062422/56649eca5503460f94bd82a9/html5/thumbnails/9.jpg)
How does DNA make Proteins?
• Central dogma:
• DNA RNA Protein Transcription Translation
![Page 10: Genes and how they work!. Genetic Code How does the order of nucleotides in DNA encode information to specify the order of amino acids?](https://reader036.vdocuments.net/reader036/viewer/2022062422/56649eca5503460f94bd82a9/html5/thumbnails/10.jpg)
![Page 11: Genes and how they work!. Genetic Code How does the order of nucleotides in DNA encode information to specify the order of amino acids?](https://reader036.vdocuments.net/reader036/viewer/2022062422/56649eca5503460f94bd82a9/html5/thumbnails/11.jpg)
RNA
• Ribosomal RNA (rRNA) – made of several RNA molecules and over 50 proteins
• Messenger RNA (mRNA)
• Transfer RNA (tRNA)
![Page 12: Genes and how they work!. Genetic Code How does the order of nucleotides in DNA encode information to specify the order of amino acids?](https://reader036.vdocuments.net/reader036/viewer/2022062422/56649eca5503460f94bd82a9/html5/thumbnails/12.jpg)
Transcription (making mRNA)
• Promotor – short sequence on DNA template strand where RNA polymerase binds.
• Initiation – binding by RNA polymerase and starts unwinding DNA (17 base pairs long)
• Elongation – 50 nucleotides added per second, no proof reading by RNA polymerase, therefore errors may occur.
• Why is this not a big problem?
![Page 13: Genes and how they work!. Genetic Code How does the order of nucleotides in DNA encode information to specify the order of amino acids?](https://reader036.vdocuments.net/reader036/viewer/2022062422/56649eca5503460f94bd82a9/html5/thumbnails/13.jpg)
![Page 14: Genes and how they work!. Genetic Code How does the order of nucleotides in DNA encode information to specify the order of amino acids?](https://reader036.vdocuments.net/reader036/viewer/2022062422/56649eca5503460f94bd82a9/html5/thumbnails/14.jpg)
![Page 15: Genes and how they work!. Genetic Code How does the order of nucleotides in DNA encode information to specify the order of amino acids?](https://reader036.vdocuments.net/reader036/viewer/2022062422/56649eca5503460f94bd82a9/html5/thumbnails/15.jpg)
![Page 16: Genes and how they work!. Genetic Code How does the order of nucleotides in DNA encode information to specify the order of amino acids?](https://reader036.vdocuments.net/reader036/viewer/2022062422/56649eca5503460f94bd82a9/html5/thumbnails/16.jpg)
Transcription (cont’d)
• Termination – stop sequences (series of GC forms a GC hairpin, slows down transcription.
• Followed by 4 A which attaches 4 U, which are weak bonds, strand disassociation occurs
![Page 17: Genes and how they work!. Genetic Code How does the order of nucleotides in DNA encode information to specify the order of amino acids?](https://reader036.vdocuments.net/reader036/viewer/2022062422/56649eca5503460f94bd82a9/html5/thumbnails/17.jpg)
![Page 18: Genes and how they work!. Genetic Code How does the order of nucleotides in DNA encode information to specify the order of amino acids?](https://reader036.vdocuments.net/reader036/viewer/2022062422/56649eca5503460f94bd82a9/html5/thumbnails/18.jpg)
mRNA• mRNA now needs to travel out into cytoplasm
• mRNA modified to prevent degradation by nucleases and phosphatases
• Terminal 5’ end (usually A or G) is removed and is replaced with an unusual 5’-5’ linkage with GTP forming a 5’ cap. Protects end from degradation by nucleases and phosphotases.
• 3’ end contain AAUAAA, poly A polymerase adds about 250 A’s to 3’ end long A tail. Needed to prevent degradation.
![Page 19: Genes and how they work!. Genetic Code How does the order of nucleotides in DNA encode information to specify the order of amino acids?](https://reader036.vdocuments.net/reader036/viewer/2022062422/56649eca5503460f94bd82a9/html5/thumbnails/19.jpg)
![Page 20: Genes and how they work!. Genetic Code How does the order of nucleotides in DNA encode information to specify the order of amino acids?](https://reader036.vdocuments.net/reader036/viewer/2022062422/56649eca5503460f94bd82a9/html5/thumbnails/20.jpg)
Structure of tRNA
![Page 21: Genes and how they work!. Genetic Code How does the order of nucleotides in DNA encode information to specify the order of amino acids?](https://reader036.vdocuments.net/reader036/viewer/2022062422/56649eca5503460f94bd82a9/html5/thumbnails/21.jpg)
![Page 22: Genes and how they work!. Genetic Code How does the order of nucleotides in DNA encode information to specify the order of amino acids?](https://reader036.vdocuments.net/reader036/viewer/2022062422/56649eca5503460f94bd82a9/html5/thumbnails/22.jpg)
![Page 23: Genes and how they work!. Genetic Code How does the order of nucleotides in DNA encode information to specify the order of amino acids?](https://reader036.vdocuments.net/reader036/viewer/2022062422/56649eca5503460f94bd82a9/html5/thumbnails/23.jpg)
Translation
• Making polypeptides
![Page 24: Genes and how they work!. Genetic Code How does the order of nucleotides in DNA encode information to specify the order of amino acids?](https://reader036.vdocuments.net/reader036/viewer/2022062422/56649eca5503460f94bd82a9/html5/thumbnails/24.jpg)
![Page 25: Genes and how they work!. Genetic Code How does the order of nucleotides in DNA encode information to specify the order of amino acids?](https://reader036.vdocuments.net/reader036/viewer/2022062422/56649eca5503460f94bd82a9/html5/thumbnails/25.jpg)
![Page 26: Genes and how they work!. Genetic Code How does the order of nucleotides in DNA encode information to specify the order of amino acids?](https://reader036.vdocuments.net/reader036/viewer/2022062422/56649eca5503460f94bd82a9/html5/thumbnails/26.jpg)
![Page 27: Genes and how they work!. Genetic Code How does the order of nucleotides in DNA encode information to specify the order of amino acids?](https://reader036.vdocuments.net/reader036/viewer/2022062422/56649eca5503460f94bd82a9/html5/thumbnails/27.jpg)
![Page 28: Genes and how they work!. Genetic Code How does the order of nucleotides in DNA encode information to specify the order of amino acids?](https://reader036.vdocuments.net/reader036/viewer/2022062422/56649eca5503460f94bd82a9/html5/thumbnails/28.jpg)
![Page 29: Genes and how they work!. Genetic Code How does the order of nucleotides in DNA encode information to specify the order of amino acids?](https://reader036.vdocuments.net/reader036/viewer/2022062422/56649eca5503460f94bd82a9/html5/thumbnails/29.jpg)
![Page 30: Genes and how they work!. Genetic Code How does the order of nucleotides in DNA encode information to specify the order of amino acids?](https://reader036.vdocuments.net/reader036/viewer/2022062422/56649eca5503460f94bd82a9/html5/thumbnails/30.jpg)
Advantage• In humans 1 to 1.5% of genome is exons
• 24% are introns, rest of genome (75%) is non-incoding
• Spliceosomes are large proteins that splice the exons together.
• Human genes can be spliced together differently by spliceosomes.
• Therefore 30,000 genes in humans can encode 120,000 different mRNA’s
![Page 31: Genes and how they work!. Genetic Code How does the order of nucleotides in DNA encode information to specify the order of amino acids?](https://reader036.vdocuments.net/reader036/viewer/2022062422/56649eca5503460f94bd82a9/html5/thumbnails/31.jpg)
Differences between Eukaryotic and Prokaryotic cells
![Page 32: Genes and how they work!. Genetic Code How does the order of nucleotides in DNA encode information to specify the order of amino acids?](https://reader036.vdocuments.net/reader036/viewer/2022062422/56649eca5503460f94bd82a9/html5/thumbnails/32.jpg)
Differences between Prokaryotes and Eukaryotes• Most eukaryotes posses Introns, Prokaryotes mostly do not!
• Eukaryote mRNA contain transcripts of one gene. Prokaryote mRNA transcripts of several genes.
• mRNA of eukaryotes must exit nucleus before translation can take place
• Prokaryotes – translation starts at AUG codon Eukaryotic,start is also AUG, mRNA has a 5’ cap where translation is initiated.
• Eukaryotic mRNA are modified, cap, tail and introns cut out
• Eukaryotic rRNA are larger than those of Bacteria