CONVERGENT EVOLUTION. Def n acquisition of some biological trait but different lineages

Transcription

1 CONVERGENT EVOLUTION Def n acquisition of some biological trait but different lineages Living Rock cactus Baseball plant

2 THE QUESTION From common ancestor or independent acquisition? By Lineage By Convergence

3 ANOTHER QUESTION Why haven t prokaryotes developed the kind of complexity that eukaryotes show?

4 THE ANSWER It s all about energy mitochondria provide sufficient energy (about 200,000 times that of prokaryotes) that genetic complexity is not a hurdle

5 THE ANSWER Eukaryotes can afford to carry high diversity and with greater diversity comes greater opportunity For a prokaryote to employ respiration would be very costly

6 ANCIENT BACTERIA? 250 million years later, scientists revive life forms Thursday, October 19, 2000 U.S. researchers say they have revived bacteria that have been dormant for more then 250 million years, resurrecting micro-organisms that last wriggled before dinosaurs walked the Earth. In a paper published today in the journal Nature, scientists from West Chester University in Pennsylvania described how they isolated bacteria spores within 250-million- year-old salt crystals buried in a rocky deposit in New Mexico.

7 ANCIENT BACTERIA? "I just find it a silly and unbelievable report," said Dr. Tomas Lindahl, an expert on the stability of DNA who works at the Imperial Cancer Research Fund in London. There are no active repair enzymes in a spore, he said, and radioactivity alone would eventually break the DNA into pieces that would make a spore no longer viable.

8 ANCIENT BACTERIA? However, attempts to replicate of results involving DNA purported to be over a million years old have not succeeded. Theoretical studies suggest that DNA is unlikely to survive intact more than about 100,000 years

9 GENETIC TRANSFORMATION

10 GENETIC TRANSFORMATION Def n - change in genotype of one individual after exposure to another s DNA

11 2 NUCLEIC ACID CATEGORIES

12 ANOTHER FACT Each nucleotide has only one complementary base

13 A FACT A DNA molecule can be made up of any combination of nucleotides e.g. AAA, AGC, GTC, TTG, TGT, GCG, One triplet codes (indirectly)for one amino acid

14 HOW MANY DIFFERENT CODONS ARE THERE? ANSWER: 4 3 = 64 A doublet codon would give 4 2 = 16 Thus, a triplet code is the smallest word that can give codes for all amino acids

15 A FACT DNA is not translated into amino acids. It is transcribed into rna

16 RNA DIFFERS FROM DNA RNA sugar (ribose) has one more oxygen than does DNA (deoxyribose) Uracil replaces thymine as the complementary base to adenine RNA is typically single-stranded

17 ANOTHER FACT Each nucleotide has only one complementary base

18 ONE GREAT UNDERSTATEMENT It has not escaped our notice that the specific [base] pairing that we have postulated immediately suggests a possible copying mechanism for the genetic material

19 SEMI-CONSERVATIVE DNA REPLICATION 3 STEPS: The 2 DNA strands of the parental DNA unwind and separate Each parental strand acts as a template for production of a complementary daughter strand Each new daughter strand winds together with its mother strand

20 DNA REPLICATION

21 A PROBLEM In eukaryotic cells, DNA inhabits the nucleus whereas the protein that it codes for is synthesized the cytoplasm. in

22 GENETIC CODES U C A G U C A G UUU Phe UUC UUA Leu UUG CUU CUC Leu CUA CUG AUU AUC Ile AUA AUG GUU GUC Val GUA GUG UCU UCC Ser UCA UCG CCU CCC Pro CCA CCG ACU ACC Thr ACA ACG GCU GCC Ala GCA GCG UAU Tyr UAC UAA UAG CAU His CAC CAA Gin CAG AAU Asn AAC AAA Lys AAG GAU Asp GAC GAA Glu GAG UGU Cys UGC UGA UGG Trp CGU CGC Arg CGA CGG AGU Ser AGC AGA Arg AGG GGU GGC Gly GGA GGG U C A G U C A G U C A G U C A G

23 THE GENETIC LANGUAGE An example of a genetic sentence that codes for a protein: THEDOGFEDTHECATFORFUN

24 TRANSCRIPTION

25 ANOTHER PROBLEM Which DNA strand should be copied just one or both?

26 YET ANOTHER PROBLEM How to rapidly move polymerase enzyme along unraveled strand Nuclear molecular motors (myosin) similar to those used in the cytoplasm were recently discovered

27 TRANSLATION trna decodes the message carried by the mrna Translation takes places at ribosomes

28 TRANSLATION A complex series of steps: