DNA and Molecular Genetics
early 1900s to start of WWII
scientists still unsure if DNA or proteins were genetic material of cell
thought it was proteins since they had a bigger "alphabet"
many discoveries proved that DNA in fact was the genetic material of the cell
extracted DNA from fish sperm and pus of open wounds
named it nuclein
name changed to nucleic acid then to deoxyribonucleic acid (DNA)
discovered that fuschin dye stained DNA
DNA discovered in all eukaryotic cells
found that DNA was made of sugar, phosphate, and 4 nitrogenous bases
came up with idea of nucleotide monomer
incorrectly concluded that bases' proportions were equal and that tetranucleotide was the molecule's repeating structure
early 1900s
link between Mendel's work and cell biologists' work led to the theory of inheritance
proposed the link between genes and "inborn errors of metabolism"
question formed of what is a gene?
studied difference between infectious S strain covered by capsule and non-infectious exposed R strain
injected them into mice and ones with the S strain died
heat-killed S strain did not kill the mice
heat-killed S strain with R strain led to S strain in mice that killed other mice when injected into them
-found in Griffith's later experiments -turned R strain to S strain
-discovered that DNA is the transforming factor in Griffith's experiment -strong but not totally conclusive evidence -favor for proteins as genetic material
bacteriophage is virus attacking bacteria
studied one attacking E. coli
virus injects DNA into cell, then DNA "disappears" while taking over bacteria and making new virus
after 25 mins the host cell bursts, releasing hundreds of new bacteriophage
phages have DNA and proteins → ideal for resolving nature of hereditary material
labeled DNA radioactive phosphorus
32 and protein with sulfur-32 (DNA has phosphorus and not sulfur, protein has sulfur and not phosphorus)
radioactive S stayed on the outside but radioactive P was passed down
analyzed nitrogenous bases in many organisms
number of purines doesn't always equal the number of pyrimidines (Levene's idea)
scientists knew DNA was genetic material but not how it did its job
must carry information between generations, be chemically stable, relatively unchanging, and mutate (causing evolution)
gathered data
Franklin and Wilkens's X-ray diffractions of crystalline DNA
Linus Pauling helically coiled structure
Chargaff's base data
won Nobel Prize
ball and stick model
originally a triple helix
disproven after realizing that A:T ratio was not 1:1 (Chargaff) and it required too much magnesium
they realized it must be a double helix with antiparallel strands
leading them to find possible replication mechanisms and information coded in triplets of bases
sugar-phosphate nucleosides on sides and nitrogenous bases on the inside connected by hydrogen bonds
complementary strands twist around each other in double helix
A pairs with T/C pairs with G
deoxyribose sugar
nitrogenous base + sugar
-sugar, phosphate, nitrogenous base
-nucleic acid monomer
cytosine, thymine, uracil
1 ring
Mnemonic: King Tut and Cleopatra (with U for uracil) live in a Pyramid with 1 top
2 pyrimidines too small to bond in DNA
Adenine and Guanine
2 rings
2 purines too big to bond in DNA
somehow produces an entirely new DNA strand during replication
two DNA molecules
each had 1/2 the original DNA and an entirely new complementary strand
existing strands were complementary templates for new strand
involved the breaking of the parental strands during replication
somehow, a molecular reassembly mixing original and new fragments on each DNA strand
grew E. coli on heavy (Nitrogen-15) and light (Nitrogen-14) mediums
first generation on heavy then transferred to light
if DNA replication is semiconservative, then DNA grown on light medium would be intermediate between heavy and light
it was
requires a lot of ATP regenerated in G2 phase
occur once per cell generation
50 nucleotides/second in humans
500 nucleotides/second in prokaryotes
occurs in the S phase
unzip the helix by the nucleus
breaking hydrogen bonds between bases
forms replication fork at origin of replication (specific nucleotide set)
places new nucleotides in the replication fork
an unwound and open region of a DNA helix where DNA replication occurs
1 in prokaryotes, multiple in eukaryotes
entire DNA molecule's length is replicated as the bubbles meet DNA copying direction
5' to 3' (carbon 5 in first sugar down to carbon 3 in last sugar)
reads from 3' to 5' (because strands are antiparallel)
opposite directions on each strand (because they are antiparallel)
polymerase has to attach to the OH (hydroxyl) group
copied in fragments
DNA Polymerase started near the end and has to continuously go farther back to carry the rest of the DNA
Small fragments of DNA produced on the lagging strand during DNA replication
joined later by DNA ligase to form a complete strand.
enzyme that joins the Okazaki fragments
places nucleotide pairs in uncompleted parts to create 1 continuous strand
strand where DNA is copied continuously without breaks in the middle
synthesizes new lagging strand
compatible and opposite electrical charges
2 hydrogen bonds
compatible and opposite electrical charges
3 hydrogen bonds
done by nucleosomes
wrapped around histones
stack into solanoids
extended, condensed, then turned into mitotic stage
approx 2m of DNA in 10 um cells
packs and organizes DNA for cell division and gene expression
when permanent, allows cell specialization
active chromatin transcription promoted or inhibited by associated histones
catalyzes phosphodiester bonds between sugars and phosphate groups
proofreads complementary base pairings
mistakes about once per billion
carry nucleoside diphosphates
removes the RNA primer and replaces it with DNA
puts RNA primer in gaps
leads to DNA synthesis
short piece of RNA needed for DNA polymerase to start
10 base pairs of RNA nucleotides
attachment and initiation for DNA polymerase III
relaxes supercoiling ahead of the replication fork
prevents strands from rejoining
no hydroxyl group
missing the 3' hydroxyl (OH group)
terminate DNA replication since the DNA polymerase III cannot bond with them
early 1900s to start of WWII
scientists still unsure if DNA or proteins were genetic material of cell
thought it was proteins since they had a bigger "alphabet"
many discoveries proved that DNA in fact was the genetic material of the cell
extracted DNA from fish sperm and pus of open wounds
named it nuclein
name changed to nucleic acid then to deoxyribonucleic acid (DNA)
discovered that fuschin dye stained DNA
DNA discovered in all eukaryotic cells
found that DNA was made of sugar, phosphate, and 4 nitrogenous bases
came up with idea of nucleotide monomer
incorrectly concluded that bases' proportions were equal and that tetranucleotide was the molecule's repeating structure
early 1900s
link between Mendel's work and cell biologists' work led to the theory of inheritance
proposed the link between genes and "inborn errors of metabolism"
question formed of what is a gene?
studied difference between infectious S strain covered by capsule and non-infectious exposed R strain
injected them into mice and ones with the S strain died
heat-killed S strain did not kill the mice
heat-killed S strain with R strain led to S strain in mice that killed other mice when injected into them
-found in Griffith's later experiments -turned R strain to S strain
-discovered that DNA is the transforming factor in Griffith's experiment -strong but not totally conclusive evidence -favor for proteins as genetic material
bacteriophage is virus attacking bacteria
studied one attacking E. coli
virus injects DNA into cell, then DNA "disappears" while taking over bacteria and making new virus
after 25 mins the host cell bursts, releasing hundreds of new bacteriophage
phages have DNA and proteins → ideal for resolving nature of hereditary material
labeled DNA radioactive phosphorus
32 and protein with sulfur-32 (DNA has phosphorus and not sulfur, protein has sulfur and not phosphorus)
radioactive S stayed on the outside but radioactive P was passed down
analyzed nitrogenous bases in many organisms
number of purines doesn't always equal the number of pyrimidines (Levene's idea)
scientists knew DNA was genetic material but not how it did its job
must carry information between generations, be chemically stable, relatively unchanging, and mutate (causing evolution)
gathered data
Franklin and Wilkens's X-ray diffractions of crystalline DNA
Linus Pauling helically coiled structure
Chargaff's base data
won Nobel Prize
ball and stick model
originally a triple helix
disproven after realizing that A:T ratio was not 1:1 (Chargaff) and it required too much magnesium
they realized it must be a double helix with antiparallel strands
leading them to find possible replication mechanisms and information coded in triplets of bases
sugar-phosphate nucleosides on sides and nitrogenous bases on the inside connected by hydrogen bonds
complementary strands twist around each other in double helix
A pairs with T/C pairs with G
deoxyribose sugar
nitrogenous base + sugar
-sugar, phosphate, nitrogenous base
-nucleic acid monomer
cytosine, thymine, uracil
1 ring
Mnemonic: King Tut and Cleopatra (with U for uracil) live in a Pyramid with 1 top
2 pyrimidines too small to bond in DNA
Adenine and Guanine
2 rings
2 purines too big to bond in DNA
somehow produces an entirely new DNA strand during replication
two DNA molecules
each had 1/2 the original DNA and an entirely new complementary strand
existing strands were complementary templates for new strand
involved the breaking of the parental strands during replication
somehow, a molecular reassembly mixing original and new fragments on each DNA strand
grew E. coli on heavy (Nitrogen-15) and light (Nitrogen-14) mediums
first generation on heavy then transferred to light
if DNA replication is semiconservative, then DNA grown on light medium would be intermediate between heavy and light
it was
requires a lot of ATP regenerated in G2 phase
occur once per cell generation
50 nucleotides/second in humans
500 nucleotides/second in prokaryotes
occurs in the S phase
unzip the helix by the nucleus
breaking hydrogen bonds between bases
forms replication fork at origin of replication (specific nucleotide set)
places new nucleotides in the replication fork
an unwound and open region of a DNA helix where DNA replication occurs
1 in prokaryotes, multiple in eukaryotes
entire DNA molecule's length is replicated as the bubbles meet DNA copying direction
5' to 3' (carbon 5 in first sugar down to carbon 3 in last sugar)
reads from 3' to 5' (because strands are antiparallel)
opposite directions on each strand (because they are antiparallel)
polymerase has to attach to the OH (hydroxyl) group
copied in fragments
DNA Polymerase started near the end and has to continuously go farther back to carry the rest of the DNA
Small fragments of DNA produced on the lagging strand during DNA replication
joined later by DNA ligase to form a complete strand.
enzyme that joins the Okazaki fragments
places nucleotide pairs in uncompleted parts to create 1 continuous strand
strand where DNA is copied continuously without breaks in the middle
synthesizes new lagging strand
compatible and opposite electrical charges
2 hydrogen bonds
compatible and opposite electrical charges
3 hydrogen bonds
done by nucleosomes
wrapped around histones
stack into solanoids
extended, condensed, then turned into mitotic stage
approx 2m of DNA in 10 um cells
packs and organizes DNA for cell division and gene expression
when permanent, allows cell specialization
active chromatin transcription promoted or inhibited by associated histones
catalyzes phosphodiester bonds between sugars and phosphate groups
proofreads complementary base pairings
mistakes about once per billion
carry nucleoside diphosphates
removes the RNA primer and replaces it with DNA
puts RNA primer in gaps
leads to DNA synthesis
short piece of RNA needed for DNA polymerase to start
10 base pairs of RNA nucleotides
attachment and initiation for DNA polymerase III
relaxes supercoiling ahead of the replication fork
prevents strands from rejoining
no hydroxyl group
missing the 3' hydroxyl (OH group)
terminate DNA replication since the DNA polymerase III cannot bond with them
