DNA: The Secret of Life. Mendel s laws show the rules of heredity (1866, rediscovered in 1900) Inheritance occurs in packets of information

Transcription

1 DNA: The Secret of Life Mendel s laws show the rules of heredity (1866, rediscovered in 1900) Inheritance occurs in packets of information

2 Developments in the 20th century 1933: Thomas Hunt Morgan wins the Nobel prize for demonstrating that chromosomes are the fundamental unit of inheritance. Demonstrated that here is an observable, physical nature to cellular information

3 The experiment X Breed mutant flies Look at their chromosomes

4 Observed Traits can often be inherited together. There are the same number of trait groups as there are chromosomes. In rare cases when chromosomes are not inherited normally, the traits are also not inherited normally. Inheritance is on chromosomes- things you can see in a microscope.

5 Developments in the 20th century 1944: Avery, McCarty and McLeod published a paper that stated "Deoxyribonucleic acid (DNA) plays a central role in determining specific characteristics in the course of reproduction. " There is a chemical substance, DNA, that holds genetic information

6 Discovery of DNA Function Fred Griffith - Discovered hereditary transformation Oswald Avery - DNAase blocks transformation Hershey and Chase - Bacteriophage injects DNA--not protein--into bacterium

7 Discovery of DNA Function Griffith s experiments Transfer of hereditary material from dead S cells to living R cells (transformation)

8 Discovery of DNA Function Hershey-Chase Radioisotope label protein and DNA of bacteriophage Radioactive phophorus is detected inside of bacteria

9 Developments in the 20th century 1946: Hermann Müller wins a Nobel Prize for his work on the genetic effects of radiation. The information can be changed through physical processes

10 The experiment X-rays Broken chromosomes Mutant chromosomes Mutant offspring

11 Rosalind Franklin

12 X-ray diffraction from DNA crystal Showed that DNA is a double helix Showed that the bases are on the inside More info on this at:

13 Francis Crick and Jim Watson (1953)

14

15 5' 3' Watson-Crick DNA Model (1953) 5' 3' Antiparallel double helix DNA bases in the middle Sugar Phosphate backbone running along the outside n

16 Watson-Crick DNA Model (1953) Antiparallel double helix DNA bases in the middle Sugar Phosphate backbone running along the outside Bases are paired with each other

17 DNA Structure Monomer: Nucleotides Deoxyribose Phosphate Group Nitrogen base: purines: Adenine A Guanine G Pyrimidines: Thymine T Pairing Arrangement A - T C - G Cytosine C

18 Components of DNA Four types of nucleotides Adenine (A) (base with double ring) Guanine (G) (base with double ring) Thymine (T) (base with single ring) Cytosine (C) (base with single ring Amount of A=T and C=G

19 Patterns of Base Pairing DNA consists of two strands of nucleotides held together at bases by hydrogen bonds Two kinds of base pairs form: A-T and C-G Base with double-ring structure always binds with base with single-ring structure

20 DNA Replication and Repair Enzyme regulated Unwinding Hydrogen bonds broken by DNA Helicase Complimentary pairing: Attachment of nucleotides to new strands by DNA polymerases Continous and discontinous: leading and lagging strand (Okazaki fragments) DNA ligase makes new hydrogen bonds, glues two strands together New strand is half old, half new

21 Detailed Look at Replication Strand assembly is continuous on one strand, discontinuous on other Nucleotides can only be added in the 5 to 3 direction

22 Creating Clones Dolly the sheep was first mammal to be cloned from a differentiated cell Nucleus from sheep udder cell was transferred into enucleated unfertilized egg Egg grew into sheep by mitotic divisions Mice and cows have now also been cloned from adult cells