Chapter 16: The Molecular Basis of Inheritance DNA- the Genetic Material Flashcards
composed of nucleotides
nucleic acids
what are nucleotides made of?
- 5 C simple sugar (deoxyribose or ribose)
- Phosphate Group
- Nitrogenous base
how many bases does DNA have?
4
what are the bases of DNA
Adenine
Guanine
Thymine
Cytosine
who studied bacteria?
Griffith and Avery
who studied Viruses
Hershey & Chase
what bacteria did Griffith study?
2 strains of Streptococcus pneumoniae
disease-causing
pathogenic
what kinds of strains did he use?
1 pathogenic
1 harmless
Exposure of harmless strains to the remains of the pathogenic strains caused a what?
a change, a transformationa transformation in in
the harmless variety the harmless variety
a change in genotype and phenotype due to
an assimilation of external DNAan assimilation of external DNA
Transformation
at molecule changes in the harmless strain
only DNA
who purified various chemicals from the pathogenic remains and added each individually to the harmless strain
Avery
was accepted as the genetic material
DNA
were using a technique called X-ray crystallography to study molecular structure
Maurice Wilkins and Rosalind Franklin
this was used to study molecular structure
X-ray crystallography
produced a picture of the DNA molecule
using this technique
Rosalind Franklin
enabled Watson to deduce that DNA was helical
Franklin’s X-ray crystallographic images of DNA
what did the x-ray images help Watson deduce?
that DNA was helical
the width of the helix
the spacing of the nitrogenous bases
the double helix
2 strands attached at their nitrogenous bases
Double helix
Who said this
“It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying postulated immediately suggests a possible copying mechanisms for the genetic material”mechanisms for the genetic material”
Watson and Crick
Nitrogenous bases pair up and attach by weak H bonds
Complimentary base pairing
which bases pair with which?
A and T
C and G
(you look at george clooney)
Complicated, highly organized process involving more
than a dozen enzymes and proteins contribute to DNA than a dozen enzymes and proteins contribute to what?
DNA Replication
DNA molecules are duplicated through a process
called what?
DNA Replication
Enzymes break apart the hydrogen bonds that hold the 2 strands of the double helix together
helicases
New nitrogenous bases attach to each original
exposed DNA strand and 2 new DNA molecules are exposed DNA strand and 2 new DNA molecules are formed
(semi-conservative process)
enzymes that attach free nucleotides to that attach free nucleotides to unwound portions of the unwound portions of the parent template
DNA polymerase
unwind the DNA strand so DNA DNA strand so DNA polymerases can go to work
DNA Helicases
where DNA replication begins
origins of replication
where the
two strands of DNA separate to form two strands of DNA separate to form
replication “bubbles”replication “bubbles”
origins of replication
a Y-shaped region where the new strands of DNA region where the new strands of DNA
are elongating
replication “fork”
Bind to and stabilize the unwound tabilize the unwound parental DNA
Single-strand binding proteins
relieves the strain of twisting of the double helix by breaking, swiveling, and rejoining
DNA strands
Topoisomerase
what is DNA composed of?
2 intertwined strands which
run in opposite directions
intertwined strands which
run in opposite directions = what
antiparallelrun
DNA is polar with a 5’ end
Phosphate group terminal
DNA is polar with a 3’ end
hydroxyl group terminal
nucleotides units are added where
from 5’ to 3’
the new DNA strand from one parental strand
Leading strand
follows in the direction of the fork
Leading strand
works along the other parental strand in
the opposite direction - away from the replication fork the opposite direction
the lagging strand
is the lagging strand first synthesized
Okazaki fragments
enzyme that fills in tiny gaps between the
new short stretches of nucleotides to form a new
continuous strand
DNA ligase
Joins the fragments together
DNA ligase
DNA polymerase can only add
nucleotides where
to the end of an
existing polynucleotide chain.existing polynucleotide chain.
what is used to overcome DNA polymerase only being able to add nucleotides to the end of an existing polynucleotide chain
primers
is a short stretch of RNA
primers
it functions as the original pre-existing
chain with which DNA polymerase can chain with which DNA polymerase can
interact
primers
joins RNA nucleotides
primers
how many primers are needed for the leading DNA strand
1
how many primers are needed for the lagging DNA strand
1 per fragment
what binds primers after they are converted to Dna
ligase
Enzymes what? the newly synthesized
DNA “looking” for mistakes and repairs
proof-read
how many Specialized DNA Repair Enzymes
discovered so far in humansdiscovered so far in humans
130
checks the sequence
as it progresses
DNA Polymerase
special enzymes find
mistake(s) (mispaired nucleotide), delete
and then correct nucleotide is inserted
mismatch repair
Nuclease cuts out a damaged area and repaired by DNA polymerase and ligase
Nucleotide Excision Repair
a region of repetitive nucleotides sequences at each end of the chromosome
telomere
