The Molecular Basis of Inheritance (3) Flashcards
DNA strands are
Complimentary
Complementary strands
Each strand of DNA has the information it needs to make the other strand because of Chargaff‘s rule
Replication
 duplication process of DNA The DNA molecule splits into two strands and produces two complementary strands
How many steps are there in replication
2
 What is the first step of replication
Two strands of DNA are separated forming to replication forks
What is the second step of replication
as the new strand forms new bases are added following the rules of base pairing
Replication is carried out by
Enzymes
What is the principal enzyme of replication
DNA polymerase
DNA polymerase
An enzyme that joins individual nucleotides to, produce a new strand of DNA produce sugar phosphate bonds, proofreads new strands
Telomeres
DNA at the tips of chromosomes that are nonsensical so that you don’t need it and its just there to chop off and it extends at the 3’ side
Telomerase
Special enzyme that adds short repeated DNA sequences to telomeres 
What does telomerase do
Helps to prevent genes from being damaged your loss during replication in embryonic cells stem cells and other rapidly dividing cells
Telomerase is often switched off in
Adult cells
What form is DNA in in prokaryotes
Singular circular chromosome
When does replication occur in prokaryotes
Replication occurs when regulatory proteins bind to a starting point on the chromosome they trigger s phase to occur
In prokaryotes replication starts in____
spot
One
In what direction does replication occur in prokaryotes
Replication starts in one spot and proceeds in opposite directions
What happens after replication in prokaryotes
Often to DNA attach to different sides of the cell and separate during cytokinesis
How is DNA stored in eukaryotes
Tightly package with histones to form chromatin which is stored in the nucleus
Where does replication begin on DNA
Replication may begin at many places on DNA
In what direction is replication occur in eukaryotes
Replication can start in many spots and proceed in opposite directions
Damaged regions of DNA sometimes copied which may…
Alter certain genes
Semiconservative DNA replication
When DNA replicates the new DNA is made up of one daughter and one parent DNA strand
How many problems does DNA polymerase have
3
What is the first problem of DNA polymerase
DNA polymerase cannot start a new strand enough unless there is an existing nucleotide in place
What is the solution to the first problem of DNA Polymerase
Primase
Primase
Enzyme that puts down and RNA primer so that DNA polymerase can build the rest of the strand
What is the second problem of DNA polymerase
DNA polymerase can only work in a five prime to three prime direction
What is the solution to the second DNA polymerase problem
Okazaki fragments
How do Okazaki fragments work
Okazaki fragments form starting from about 100 to 200 base pairs away from the RNA primer
After Okazaki fragments form DNA polymerase takes away
The primer
What connects Okazaki fragments
DNA ligase
How does DNA ligase connect Okazaki fragments
DNA ligase connects the Okazaki fragments fragments by forming covalent bonds between the sugar and phosphate groups
The strand that goes from 3 prime to 5 prime is called the
Leading strand
The strand going from 5 Prime to 3 prime is called the
Lagging strand
What is the third problem of DNA polymerase
Every time the DNA replicates DNA gets shorter because when the DNA polymerase takes away the primer there is nothing to replace it
What is the solution to the third problem of DNA polymerase
Telomerase produces telomeres which are useful so when the DNA strands shorten you are not losing useful DNA
The telomeres produced by telomerase are
Nonsensical Nucleotides are just there so but don’t affect anything
when does replication occur
occurs during s phase in interphase
Conservative model of DNA
the parental double helix remains intact and al new copy is made
PARENT
/ \
PARENT NEW
/ \ / \
Parent New New New
Semiconservativemodel of DNA
the two strands of the parental molecule separate and each function as a template for synthesis of a new complementary strand
PARENT
/ \
both both
/ \ / \
both New New both
Dispersive model of DNA
each strand is made of both daughter and parent strands in odd newly synthesized parts
PARENT
/ \
mix mix
/ \ / \
mix mix mix mix
heterochromatin
loops on scaffold proiten
euchromatin
most unwound form of DNA – js the nucleosomes together
origin of replication
where they get the signal thingie and where the replication forks form
replication bubble
the whole replication bubble thing
how many replication bubbles does a prokaryote have
one
how many replication bubbles do eukaryotes have
multiple
Helicase
the enzyme that separates the strands and starts the bubble
single strand binding proteins
proteins that temporarily block bases so that they can’t attract each other – they do this by preventing H bonds
Topoisomerase
alleviate stress on the DNA bc as the helicase unwinds the DNA bc it builds up stress (imagine pulling a rope part) by cutting and putting back DNA so that helicase can keep doing its thang
why is the lagging strand called a lagging strand
bc of okazaki fragments
how do you get energy for polymerization
all of the bases start as ATP, GTP, etc. so when the 2 phoshates break off to provide energy
how are the 5’ and 3’ end determined
the one with the 5 carbon standing up is the 5’ side and vice versa for 3’
lagging grows ____ separation
away
leading grows ____ separation
towards
after a new daughter strand is made what happens to the RNA primer
it leaves bc it doesn’t mix with DNA properly
mismatch repair
enzymes that check DNA, look for mistakes, change, and sometimes they cause mistakes bc they remove the wrong thing
nucleotide excision repair
enzymes that cut out some segments of DNA and polymerasge adds good bases by gluing them with ligase and for larger mistakes they add a thymine dimers which distorts the DNA in order to break it and add the good DNA
which side of the DNA is always shorter and why
5’ end bc nonsense side so it gets shorter during every replication
