Bio study chap. 13

DNA replication

Allowing genetic information to be inherited

Gene

Unit of heredity of specific DNA sequence

A major challenge for 20th century biologists

The identification of molecules of inheritance

T. H. Morgan

Showed genes on chromosomes

Griffith (1928)

Discovered harmless R strain of pneumoniae could be transformed into virulent S strain by S strain’s chemicals

Griffith’s conclusion

A chemical substance from one cell is capable of genetically transforming another

Avery (1944)

Discovered that DNase sample only had R strain

Avery’s conclusion

DNA is the chemical nature of the transforming substance

Hershey and Chase (1952)

Radioactive coloring on protein and DNA of T2 bacteriophage

Hershey and Chase’s conclusion

DNA was successful in entering the bacteria and directing the assembly of new viruses.

Thymidine

Precursor for thymine

Watson and Crick (1953)

Displayed double helix of DNA from using Franklin’s X-ray crystallography data

Feature No. 1 of DNA

Double-stranded helix of uniform diameter

Feature No. 2 of DNA

Strands are antiparallel

Feature No. 3 of DNA

Complementary base pairing: AT and CG

Feature No. 4 of DNA

H bonds hold strands together

Chargaff’s two rules (1950)

1. Base composition varies between species.

2. Percentage for A and T is equal, and same for C and G

Purines

A and G

Pyrimidine

C and T

2 hydrogen bonds holding

Between A and T

3 hydrogen bonds holding

Between C and G

3.4 nm

Length of one full turn helix

0.34 nm

Length between bases

3 end

—OH

5 end

—OPO-3

S phase

Where DNA replicates

Semiconservative

Having both old and new DNA

Conservative

Pestering the original one and generating an entire new one

Dispersive

New and old interspersed along each strands

What experiment for semiconservative

Heavy 15 medium for parent replication and light 14 medium for daughter or new

Basic concept of DNA replication

Separate parents strands into templates and add complementary nucleotides to those

Origins of replications

Sites where replication begins and DNA separates to form bubbles

Replication fork

Region of DNA unwound as templates

Topoisomerase

Protein that breaks, swivels, and rejoins parental DNA

Helicase

Protein that unwinds and separates parental DNA breaking hydrogen bonds

Primase

Synthesizes RNA primers that bind to origin of replications

DNA polymerase

Bind to RNA primers and add new DNA nucleotides only to the existing 3 end

Leading strand

Continuous synthesis toward the fork replication

Lagging strand

Sections called Okazaki fragments in opposite direction of fork replication

DNA polymerase I

Replaces RNA primers with DNA

Ligase

Seals and links Okazaki fragments

Why do normal cells progressively shorten

No replaceable end piece due to lacking 3 end

Telomerase

Repairing ends by filing in gaps

Telomere

Repetitive nucleotide sequence at the end of chromosomes to postpone erosion (TTAGGG)

DNA proofreading

Correcting mismatching bases needing nuclease, polymerase I, and ligase

Excision repair

When DNA is damaged

Nucleic acid hybridisation

Base pairing of one strand of nucleic acid to another

DNA cloning

Multiple copies of genes

Plasmids

Circular DNA separate from DNA chromosome

Heat stable DNA polymerase

Taq polymerase

Steps of PCR

Denaturation (separating), annealing (binding to primers), and extension (adding nucleotides)

Restriction enzymes

DNA cutting enzyme that recognizes specific sites in DNA

Transformation

Change in phenotype and genotype due to assimilation of a cell’s external DNA

Antiparallel

In opposite direction

Sing strand binding protein

Stabilize the unwound tempslte strand

Primer

Initial nucleotide chain