Transformation Lab Flashcards
Frederick Griffith
studied strains of pneumonia in mice (S) Smooth Strain, (R) Rough Strain
Alfred Hershey, Martha Chase
studies showing that DNA is the genetic material of phage known as T2
Edwin Chargaff
analyzed base (ATCG) to prove DNA is the genetic material
Rosalind Franklin
Took photo 51, showing the double helix, a discovery that was essential in unlocking the mystery of how life is passed down from generation to generation.
Structure of DNA
AT CG sugar attached to phosphate group through covalent bonds. Hydrogen bonds (weak) connect the two nitrogenous bases together
Semi-conservative
after one round of replication, every new DNA double helix would be a hybrid that consisted of one strand of old DNA bound to one strand of newly synthesized DNA.
Process of DNA replication
1) DNA double helix
2) Hydrogen bonds break and the helix opens
3) Each strand of DNA acts as a template for the synthesis of a new, complementary strand
4) Replication produces two identical DNA double helicases, each with one old and one new strand
Leading and Lagging
During DNA replication, one new strand (the leading strand) is made as a continuous piece. The other (the lagging strand) is made in small pieces.
5’ and 3’ carbon ends
For instance, if you know that the sequence of one strand is 5’-AATTGGCC-3’, the complementary strand must have the sequence 3’-TTAACCGG-5’. This allows each base to match up with its partner:
DNA polymerase only synthesizes DNA in the 5’ to 3’ direction only
5’ ends with the phosphate, and 3’ ends with the deoxyribose sugar.
Helicase
untwists and separates strands
single strand binding proteins
holds DNA strands apart
primase
enzymes whose continual activity is required at the DNA replication fork
DNA polymerase
adds DNA nucleotides to new strand
DNA ligase
joins DNA fragments together
If two pieces of DNA have matching ends, ligase can link them to form a single, unbroken molecule of DNA
DNA pol 1
removes RNA primer and replaces with DNA
Okazaki fragments
segments of lagging strand
Gel electrophoresis
a technique used to separate DNA fragments according to their size
DNA primer
a short nucleic acid sequence that provides a starting point for DNA synthesis
Mismatch repair enzymes
detect distortions caused by mismatched bases inserted during DNA synthesis
nuclease in DNA proofreading and repair
A nuclease enzyme cuts the damaged DNA strand at two points and the damaged section is removed. Repair synthesis by a DNA polymerase fills in the missing nucleotides. DNA ligase seals the Free end of the new DNA To the old DNA, making the strand complete.
telomeres
A telomere is a region of repetitive DNA sequences at the end of a chromosome. Telomeres protect the ends of chromosomes from becoming frayed or tangled. Each time a cell divides, the telomeres become slightly shorter. Eventually, they become so short that the cell can no longer divide successfully, and the cell dies.
significance of telomeres in regular and cancerous cells
Dont contain genes; DNA typically consists of multiple repetitions of one short nucleotide sequence
Distinguish between heterochromatin and euchromatin.
More condensed, non-transcribed = heterochromatin
Less condensed, transcribed = euchromatin
Describe how the packing of chromatin changes during the course of the cell cycle
In interphase, the chromatin is highly extended. Preparing for mitosis, the chromatin coils or condenses and forms chromosomes in metaphase.
Topoisomerase
relieves strain caused by unwinding
