Chapter 12 - DNA Flashcards
Who concluded that bacteria could be transformed from harmless to disease causing by an unknown factor?
Griffith
Who concluded that DNA was the factor that caused one bacterium to transform into another?
Avery
Who concluded that the genetic material of a bacteriophage is DNA?
Hershey and Chase
Who discovered that percentages of Adenine and Thymine were almost the same in any sample of DNA. and the same occurred for Guanine and Cytosine?
Chargaff
called “Chargaff’s rule”
Who concluded using an x-ray that DNA was in the shape of a double helix and that nitrogenous bases are near the center of the DNA molecule?
Franklin
Who discovered the structure of the DNA molecule (based of Franklin’s work)?
Watson and Crick
What did Watson and Cricks model show about DNA?
The two strands of DNA run in anti parallel
Hydrogen bonds held together the two strands of DNA
Explained and gave proof to Chargaff’s rule
During DNA replication, the DNA molecule does what?
It separates into two strands
At the end of DNA replication how many NEW strands of DNA are there?
Two new strands
At the end of DNA replication, how many strands (new and original) are there?
Four strands
New DNA is replicated in strands complimentary to the Original DNA, because production of new DNA follows the rules of
base parings
What are DNA’s 3 jobs
Give instructions to assemble proteins
Direct REPLICATION of genes (meiosis)
Direct process of how genes pass from parent to offspring
What is DNA
a nucleic acid (polymer) made of nucleotides (monomers)
The nucleotides are joined by covalent bonds (sugar to phosphate)
Can be thousands of nucleotides long
What is a nucleotide made of
sugar, deoxyribose (a phosphate group), and a nitrogenous base
What are the four Nitrogenous bases?
Adenine (A), Thymine (T),
Cytosine (C), Guanine (G)
What bases always go together and have the same percentage (Chargaff’s rule)
A = T C = G
How do two strands of DNA join
They join by hydrogen bonds, because they are strong enough to hold it together, but weak enough to break apart when needed
what is the shape of DNA
double helix (twisted ladder)
What bases are Pyrimidines
Cytosine and Thymine. They both have one ring
1y=1 ring
what bases are Purines
Adenine and Guanine. They both have two rings.
2ns’=2 rings
why are the “rungs of the ladder” 3 bases wide?
so that DNA is more stable, more integrity, and resists damage. (A=2 + T=1 = 3) (G=2 + C=1 = 3)
what is the backbone of DNA made of?
the outside sticks of ladder
alternating sugars and phosphates
How are the DNA strands Anti parallel
3 prime on one end and 5 prime on other end of one strand means on other strand; 5 prime on end opposite of other 5 prime, and 3 prime on other end of strand, opposite of 3 prime of other end
How does the original strand act as a template for new strand?
the original is a template because the new strand must be complementary (using Chargaff’s rule) to original strand
First step of DNA replication
Enzymes identify DNA that needs to be replicated and unwinds double helix
what does the Helicase do? (step 2 in DNA replication)
Helicase “unzips” DNA by breaking the hydrogen bonds between the two Original strands. Creating two replication forks
what does DNA polymerase do? (step 3 in DNA replication)
attaches the complementary base to the template strand. It also “proofreads” the forming strand
Step four of DNA replication
The leading strand (the original 5’ to 3’ - nucleotides begin attached at the 3’ end of new) will build in a smooth progression
Step five of DNA replication
the lagging strand (the original 3’ to 5’ - nucleotides cant be attached at the 5’ end) builds piecemeal
what are okazaki fragments (step 6 in DNA replication)
short sections of bases brought together by DNA polymerase. (lagging side)
what are ligase (step 6.5 in DNA replication)
ligase bring together Okazaki fragments (lagging side)
step seven of DNA replication
When the replication is complete, the two new molecules of DNA are identical to each other. They then wind up and take the double helix form.
What are telomeres
the DNA at chromosome tips, they’re very delicate and can be damaged during replication
Replication in Prokaryotes
replication starts at one point and moves in both directions until ends meet and DNA separates. one origin two forks
Replication in Eukaryotes
starts at many points and all move in both directions until completely copied. many origins many forks
