Molecular Genetics (Unit 3) - chapter 6 Flashcards
Recall _______ experiments with pea plants
in the 1800’s
Mendel’s
He proposed a “factor” for each trait that was
passed on from parents to offspring – ______
genes
A ____ is the coding region of DNA that
contains instructions to build a protein
gene
Some fundamental genes are shared by almost
all living organisms (T/F)
TRUE
There is a lot of _____ that needs to fit inside every
single cell of an organism
DNA
This is accomplished same or differently in prokaryotes and eukaryotes
differently
In eukaryotes, DNA coils around ______ proteins
to form complexes that combine to form
______
histone
chromatin
Eukaryotes also have small amounts of DNA in
their _______ and _______, which is
similar in structure to that found in prokaryotes
mitochondria and chloroplasts
DNA in archaea and bacteria is found in
simple _____________
loop-shaped chromosomes
The _______ consists of the entire set of DNA in
an organism
genome
They may also contain ______, small
accessory loops of DNA
plasmids
Bacterial DNA is found in an area called the _______
nucleoid
Humans and many other eukaryotes are _____ –
their chromosomes occur in homologous pairs
diploid
Bees, wasps, and ants are _______: the
females are diploid, while the males are haploid
haplo-diploid
Plants can be _____ …
haploid, diploid, triploid, tetraploid,
hexaploid…
In 1868, he studied
the composition of the
nucleus
Meischer
Meischer Extracted an unknown substance
that was _____ and contained ______
Named it “_____”
acidic, phosphorus
nuclein
Meischer Collected ____ from
bandages (mostly
WBC’s)
pus
In 1928, he studied pneumonia bacteria
(epidemic in Europe at the end of WWI)
Griffith
___-strain (smooth) vs.
___-strain (rough)
S-strain (smooth) vs.
R-strain (rough)
Griffith research Showed some sort of
hereditary transmission - _______
transformation
Griffith Injected ____ with each
strain and various
combinations
mice
Based on Griffith’s
findings, they carried
out similar studies in
1944 using
Streptococcus
Avery, McLeod,
&McCarty
Possible transforming
substances were ___, ____ and _____
DNA, RNA, and proteins
Results showed that
____ was the hereditary
substance (went against
current thinking –
proteins)
DNA
In 1952, they attempted
to verify if DNA or
protein was the genetic
material
Hershey &
Chase
Used _______
and E. coli bacteria
bacteriophages
Labelled _______
of phosphorus (DNA)
and sulfur (protein) to
determine what part
was being affected
(DNA or protein coat)
radioisotopes
Found radioactivity
only inside cells : _____
DNA
An organic chemist
Disagreed with
common thinking that
there was an equal
concentration of A, T,
C, and G
Chargaff
In 1950, he discovered
that the bases occur in
definite ratios where
A= ___ and C = ____
Now known as
Chargaff’s Ratios
A= T and C = G
Purine example
A and G
Pyrimidines example
T and C
Used X-ray crystallography to study
shape of DNA molecule
Wilkins & Franklin
____ produced clearer crystallographs
than Wilkins, whose work showed a ____ structure
Franklin
helical
X shape suggested _______ rotating
______, with _______ backbone on the outside
double helix
clockwise
sugar-phosphate
In 1952, they were building a variety of models of DNA to determine the structure
Watson & Crick
Wilkins revealed some of Franklin’s work, which helped them realize that a double helix model fit all of the known information
Strands must run _______
anti-parallel
Due to the work of ______ (4 ppl), an accurate model of DNA was determined in the 1950s
Watson, Crick, Franklin, and
Wilkins
DNA has a _____helix structure, with the “sides”
consisting of alternating _______ and
________
double
deoxyribose sugars
phosphates
The “rungs” consist of ______ base pairs (A, T, C,
&G)
nucleotide
The strands run _________ to each other
antiparallel
The _____ on the 3’ carbon of deoxyribose is at one end of the strand
hydroxyl
The ________ on the 5’ carbon is at the other end
phosphate
The strands run in _______ directions
opposite
In 1958, Meselson and Stahl verified that DNA
replication was _________
semiconservative
Then transferred colonies to a growth medium
of _______, allowed to _____ for one or
two rounds
normal N
replicate
Used “heavy” _____of nitrogen (15N) to
label E. coli bacteria (lots of N in DNA!)
isotopes
:. New DNA would contain “light”
N and ______ could be measured
density
Eukaryotic DNA replication is similar to
prokaryotic, but more complex due to its ________ and ________
linear configuration
sheer volume
DNA helicase Unwinds DNA by breaking apart _______ between base pairs
H-bonds
DNA replication Consists of 3 steps:
Strand separation
Building complementary strands
Dealing with errors
_______: Y-shaped region of
separation
Replication fork
Step 1: Strand Separation -
________ binds to specific nucleotide
sequences (replication origins)
DNA helicase
2 problems:
Tension on DNA behind fork (topoisomerase)
Separated strands tend to anneal (SSBPs)
Helicase will separate strands in both
directions, forming a __________
replication bubble
There can be many replication bubbles at any
given time on a strand of DNA (T/F)
TRUE
The replication bubble will extend until _______
they meet and merge
Step 2: Building Complementary Strands -
_________ are enzymes that add
nucleotides to build new DNA strands
DNA polymerases
It takes about ______ to replicate the entire
genome
an hour
DNA is replicated at a rate of ______ per
second at each fork
~50bp
_______ are added to the 3’ end of the existing
“template” strand, which is read in the 3’ to 5’
direction
Nucleotides
New strand: ___🡪 ___
5🡪3
DNA polymerases need ____, which comes
from the hydrolysis of 2 Pi from a _________ as it is added to the strand
energy
nucleoside triphosphate
strands are synthesized ___ to ____
5’ to 3’
Nucleotide = ______ + _____ + ______
Sugar + Base + Phosphate
DNA polymerase III can only add to the ___ end
of a strand, so ________ builds a short (10
– 60 bp) complementary RNA sequence called
an ______
3’
RNA primase
RNA primer
Nucleoside = _____ + _____
Sugar + Base
One strand will be able to be synthesized
continuously: ________
leading strand
_______ begins adding to the
primer in the 5’ to 3’ direction
DNA polymerase III
The other side must be made in smaller
fragments, using multiple RNA primers:
________
lagging strand
These DNA fragments on the lagging strand
are called _______ fragments
Okazaki
_______ long in eukaryotes
_______ long in prokaryotes
100-200 bp
1000-2000 bp
_________ removes the RNA
nucleotides and replaces them with those of
DNA
DNA polymerase I
As each fragment extends, it will run into the
_________ of the previous Okazaki fragment
RNA primer
________ catalyzes the formation of a
phosphodiester bond between the nucleotides
of the two fragments
DNA ligase
Step 3: Error Correction -
DNA polymerases also __________ the
newly synthesized strands
proofreads and corrects
For example, if there is a base pair mismatch (e.g. A
and C), ________ can’t continue
DNA polymerase III
It will back up, replace the ______, and continue
nucleotide
Sometimes, errors will be missed (1 in every
million bp) which __________
distort the shape of DNA
_________ has a repair mechanism that
can determine which is the original correct
template strand, and remove the incorrect bases so
they can be replaced
DNA polymerase II
Eukaryotic DNA Organization:
Negatively charged DNA is wrapped around
positively charged _______ proteins
histone
8 Histone proteins combine to form a
__________ which helps to wrap DNA
Nucleosome
Nucleosomes are further condensed to form
__________ (6 nucleosomes)
solenoids
Solenoids (also called chromatin fibres) are
further coiled and folded until they form
__________
chromosomes
DNA replication results in small amounts of
_____ DNA after each replication
lost
Prokaryotic DNA Organization:
Commonly only ____ chromosome that can be
circular
one
nuclear membrane or not? (in Prokaryotic DNA Organization)
NO
Smaller pieces of DNA float throughout the
cell and are called ______
Plasmids
can Plasmids be shared between bacteria
YES
a repeating sequence of DNA at the
end of a chromosome. Protects coding regions
from being lost during replication.
Telomere
twisting of prokaryotic DNA to
reduce the volume
Supercoiling
Telomeres help prevent the loss of ________
important parts of DNA
Telomeres during Replication:
Telomeres ______ after each division
shorten
The Several Functions of Telomeres:
Help to prevent chromosome ends from
______________
Prevent DNA degradation from _________
Assist ___________ in
distinguishing DNA breaks from
chromosomal ends
Determine how many times a cell can
_______
Help to prevent chromosome ends from
fusing to other chromosomes
Prevent DNA degradation from other
enzymes
Assist DNA repair mechanisms in
distinguishing DNA breaks from
chromosomal ends
Determine how many times a cell can
divide
Cells can only divide so many times before
they lose their ______ and important DNA
starts to become ___
telomeres
lost
Human cells can divide around ___ times before
telomeres become too short
50
the total number of times a cell
can divide
Hayflick Limit
______ must continue to divide and
produce more of them
Sex cells
adds more DNA to the shortening telomeres of sex cells so they can continue to divide
Telomerase
______ and some White Blood Cells
also use Telomerase
Stem Cells
As we age more and more of our cells
reach the ________ and begin to die
off
Hayflick limit
Cancer cells can continue to ________ because they produce large amounts of _______ and continue to repair their telomeres
divide indefinitely
Telomerase
