Molecular Basis of Inheritance Flashcards
____ is the genetic material
DNA
_____ work together in DNA replication and repair
many proteins
what does a chromosome consist of
a DNA molecule packed together with proteins
the molecule of inheritance
DNA
what is the most celebrated molecule of our time
DNA
what is hereditary information coded by
DNA
hereditary information is reproduced in
all cells of the body
what does the DNA program direct the development of
biochemical, anatomical physicological and behavioral trait s
who introduced the double-helical model of DNA
James Watson and Francis Crick
when is DNA copied
during DNA replication
can cells repair their DNA
YES
T H Morgan’s group showed that
genes are located on chromosomes
what became candidates for genetic material
proteins and DNA
a key factor for determining genetic material was
choosing appropriate experimental organisms
how was the role of DNA in heredity first discovered
studying bacteria and viruses
can a genetic trait be transferred between different bacterial strains
YES
transformation
change in genotype and phenotype due to assimilation of foreign DNA
only____ worked in transforming harmless bacteria into pathogenic bacteria
DNA
bacteriophages
viruses that target bacteria
what is a virus
DNA that is enclosed by a protective coat
what is the protective coat of a virus mostly made from
proteins
can viruses be RNA
YES
does a protein enter a phage
NO
does DNA enter a phage
YES
is Protein or DNA the genetic material of phage T2?
DNA
DNA is a polymer of
nucelotides
each nucleotide consists of
- nitrogenous base
- sugar
- phosphate group
DNA composition _____ from one species to the next
varies
what made DNA a more credible candidate for genetic material
the evidence of diversity
Chargaff’s rule
- base composition of DNA varies between species
- the number of A and T bases are equal
- the number of G and C bases are equal
what led to the understanding of base pairing rules
discovery of double helix
what end do you add nucleotides to
3’ end
what is located at the 3’ end that allows binding of nucleotides
OH
what end contains a phosphate
5’ end
what makes up the backbone
sugar and phosphate group
what makes up the branches in DNA
nitrogenous bases
what was the challenge of the DNA structure
how it accounts for role in heredity
what was used to study the molecular structure of DNA
Z-ray crystallography
who produced a picture of the DNA molecule
Rosalind Franklin
what allowed Watson to deduce the DNA helical structure
Franklin’s X-ray crystallographic image
DNA double helix was suggested based on
DNA molecule made up of two strands
one full turn of DNA is in
10 base pairs
1 nucleotide causes the DNA to turn
36 degrees
diameter of double helix
2 nm
bases are _____ apart
0.34 nm
covalent _________ bonds link
sugar-phosphate AND the nucleotides of each strand
hydrogen bonds are between
nitrogenous bases
what kind of bond holds the stands together
hydrogen bonds
Van de Waals interactions are between
stacked bases pairs
Van der Waals interactions help
hold the molecule together
where are base pairs located in DNA
interior of the molecule
what makes the outer structure of DNA
two outer sugar-phosphate backbones
antiparallel
subunits run in opposite directions
what did Watson and Crick first think about base pair linkage
they would link like to like (A with A)
what happened when base pairs are linked in the like-to-like way
did not have a uniform width
how must base pairs link
purine with a pyrimidine
why must a purine pair with a pyrimidine
makes a uniform width
what happens when two PURINES link
width is too large
what happens when two PYRIMIDINES link
too narrow
what nucleotides are purines
A and G
what nucleotides are pyrimidines
T and C
what is smaller, pyrimidines or purines
pyrimidines
what is larger, pyrimidines or purines
purines
Adenine must pair with
thymine
guanine must pair with
cytosine
the amount of A equals
amount of T
the amount of G equals
amount of C
Adenine and thymine pair with a
doube bond
Guanine and Cytosine pair with a
triple bond
what base pair linkage will have a stronger link
guanine and cytosine
where is structure and function of DNA manifested
double helix
DNA strands are
complementary
with DNA strands being complementary, each acts as a
template for building a new strand
DNA replication has the ______ unwinding
parent molecule
two daughter strands are built based on
base-pairing rules
semiconservative model of replication predicts
when a double helix replicates, each daughter molecule will have ONE parental strand and ONE newly made strand
three alternative models of DNA replication
- conservation model
- semiconservative model
- dispersive model
conservative model
the two parent strand rejoin
dispersive model
each strand is a mix of old and new strands
What model of DNA replication is this?
Dispersive
What model of DNA replication is this?
Conservative
What model of DNA replication is this?
Semiconservative
Does DNA replication follow conservative, semiconservative or dispersive model
semiconservative
first replication in the experiment produced a bond of hybrid DNA which eliminates
conservative model
second replication in the experiment produced both a light and hybrid DNA which eliminates
dispersive model
where does replication begin
origins of replication
origin of replication is the place where
two strands of DNA are separated and open up with a replication bubble
at the origin of replication, replication happens
in BOTH directions
where do the two new daughter strands START to form
origins of replication
a eukaryotic chromosome has
multiple origins of replication
what shape of the replication fork
Y shaped region
where do the new DNA strands elongate
replication fork
what is at the end of each replication bubble
replication fork
helicases
enzymes that untwist the double helix at replication forks
single-strand binding proteins
bind to and stabalize single-stranded DNA
single-strand binding proteins
bind to and stabilize single-stranded DNA
Topoisomerase
corrects “overwinding” (stress) ahead of replication forks
how does topoisomerase correct overwinding
by breaking, swivelling and rejoining DNA strands
what enzyme can we not replicate DNA without
topoisomerase
a double-stranded DNA has better
protection compared to single-stranded
primase is needed in _____ but NOT _____
DNA and RNA
primase allows
polymerase to start adding nucelotides
can DNA polymerase initiate synthesis of a polynucleotide
NO
DNA polymerase can only
add nucleotides to an existing 3’ end
initial nucleotide strand is
short RNA primer
______ can start an RNA chain and add RNA nucleotides one at a time
primase
how can primase add RNA nucleotides one at a time
using parental DNA as a template
what serves as the starting point for the new DNA strand
3’ end of short primer
DNA polymerase
catalyze elongation of new DNA at the replication fork
Is RNA polymerase involved in DNA synthesis
nO
what polymerase catalyzes the elongation of new DNA at replication fork
DNA
what do most DNA polymerases require
primer and DNA template strand
elongation is faster in
bacteria than human cells
what is each nucleotide added to a growing DNA strand
nucleoside triphosphate
nucleosides are missing the
phosphate group
dATP differs from ATP by the
sugar
dATP has a
deoxyribose
ATP has a
ribose sugar
dATP
supplies adenine to DNA
what happens every time a new nucleotide is added to the growing DNA strand
loses two phosphate groups
what is the molecule known as when a nucleotide loses two phosphate groups
pyrophosphate
the antiparallel structure of the double helix affects
replication
DNA polymerase adds nucleotides to the
3’ end
a new DNA strand can ONLY elongate in the
5’ to 3’ direction
Leading strand
continuously moving toward the replication fork
the leading strand is elongated in the ____ direction
5’ to 3’
Is C the leading or lagging strand
lagging strand
Is B a leading or lagging strand
Leading strand
how must ____ work to elongate lagging strands
DNA polymerase AND away from replication fork
the ____ strand is made up of Okazaki Fragments
lagging
the lagging strand is made up of
Okazaki Strand
how are Okazaki fragments joined
DNA ligase
what unwinds the parental double helix
helicase
what strand is synthesised continuously
leading strand
what do the proteins in DNA replication forming
DNA replication machine
the DNA replication machine may be ))))) during replication
stationary
DNA ligase
joins Okazaki fragments of lagging strand
what does DNA ligase do on the leading strand
joins 3’ end of DNA that replaces primer to rest of leading strand DNA
DNA Pol I
removes RNA nucleotides of primer from 5’ end and replaces them with DNA nucleotides
DNA pol III
using parental DNA as a template, synthesizes new DNA strand by adding nucleotides to an RNA primer or preexisting DNA strand
what proofreads newly made DNA and replaces any incorrect nucelotides
DNA polymerase
mismatch repair
repair enzymes correct errors in base pairing
nucleotide excision repair
a nuclease cuts out and replaces damaged stretches of DNA
is error rate after proofreading zero
NO
what happens to sequence changes that are permanent
passed to next generation
what are source of genetic variation
mutations
natural selection operates upon
mutations
what creates problems for linear DNA of eukaryotic chromosomes
limitations of DNA polymerase
does the usual replication machinery provide a way to complete the 5’ end
NO
what happens with repeated rounds of replication
shortening of DNA molecules at the ends
is shortening of DNA molecules at the ends a problem for prokaryotes
NO, they have round chromosomes
the ends of DNA molecules after repeated rounds of replication are
uneven
what do eukaryotic chromosomal DNA molecules have at their ends
telomeres
telomeres do what
postpone erosion of genes near the ends of chormosomes
do telomeres prevent shortening of DNA molecules
NO
what is connected to aging
shortening of telomeres
what would happen if germ cells became shorter in every cell cycle
genes would be missing from gametes produced
what catalyzes the lengthening of telomeres in germ cells
telomerase
what can protect cells from cancerous growth
telomeres
how can telomeres protect cells from cancerous growth
limits the number of cell divisions
what happens as telomeres shorten
there is a loss of cell viability
bacterial chromosomes are
double-stranded, circular DNA molecules
eukaryotic chromosomes are
linear DNA molecules
do eukaryotic or bacterial chromosomes have LOTS of proteins
eukaryotic
do eukaryotic or bacterial chromosomes have LITTLE of proteins
bacterial
where is DNA found in bacterium
nuceloid
chromatin
complex of DNA and protein
where is chromatin found
nucleus of eukaryotic cells
what undergoes a change in packing during the cell cycle
chromatin
what is chromatin like in interphase
organized into a 10 nm fibre or most is compacted into a 30 nm fibre
do interphase chromosomes become entangled
NO
what is chromatin like in interphase
loosely packed
what does chromatin do prior to mitosis
condenses
euchromatin
loosely packed chromatin
heterochromatin
centromeres and telomeres become highly condensed during interphase
what does dense packing make difficult
to express genetic information coded in these regions
what undergo chemical modifications that result in changes in chromatin organization
histones
histones
responsible for the first level of DNA packing in chromatin
