nucleic acids Flashcards
nucleic acid is present in
nucleus, mitochondria and chlorophlast
building blocks of nucleic acids
nucleotides- pentose sugars, nitrogenous base and phosphate group
pentose sugar
5 carbon atom
ribsose
RNA
deoxyribose
DNA, second carbon atom has no OH which makes it less reactive so its more stable
Nitrogenous bases
purines, pyramidines
purines
adenine
guanine
double ring
pyrimidines
cytosine
thymine (only DNA)
uracil (only RNA)
single ring
phosphate group
phosphoric acid, H3PO4
Structure of DNA in Deoxyribose
nucleoside- pentose sugar + nitrogenous base
nucleoside formation in purines
H20 and N glycosidic bond formed
Nitrogenous base is attached to the 1st carbon atom of deoxyribose sugar by N-glycosidic bond- condensation reaction- removed by water
nucleoside formation in pyrimidines
H20 and N glycosidic bond formed
Nitrogenous base is attached to the 1st carbon atom of deoxyribose sugar by N-glycosidic bond- condensation reaction- removed by water
nucleotide-
nucleoside + phosphate group
nucleotide formations in purines
phosphate group is attached to the 5th carbon atom of deoxyribose sugar by condensation reaction. phosphodiester bond is formed
nucleotide formations in pyramidines
phosphate group is attached to the 5th carbon atom of deoxyribose sugar by condensation reaction. phosphodiester bond is formed
nucleotide
2 nucleotides are joined by
phosphodiester bond
if a free phosphate group is present in
the 5th carbon atom of deoxyribose sugar it is called 5’ end of polynucleotide, if a free OH group is present in the 3rd carbon atom then it becomes the 3’ end of polynucleotide
features of DNA
made up of 2 polynucleotide chains
backbone of DNA is made up of sugar and phosphate
the 2 chains move in antiparralel direction
if one chain is moving from 5’ to 3’ direction, the other moves in 3’ to 5’ direction
purine always base pairs with
pyramidine
pitch of a helix is
3.4nm
in a pitch where 10 base pairs are present
distance between 2 base pairs is 0.34Nm
Chargoffs rule
he proposed complementary base pair ruling, purine always base pairs with pyrimidines, 2 ring structure base pair with 1 ring. distance between 1 pair is the same
importance of hydrogen bond
provide 3D structure to the molecule
many H2 bond gives stability but not easily separated
individual hydrogen bond can be broken so that the 2 strands are separated during replication/transcription
Hydrogen bond is formed between specific bases so less changes of mistakes
hydrogen bond is formed without any chemical reactions
importance of DNA being stable
maintains genetic information
same genetic information passed into daughter cells
sequence will not change
proteins produced will be functional
Replication
copying of information from parental DNA to daughter DNA during replication, both strands act as a template
New DNA molecule will be identical to each other
the daughter DNA produced will have 1 parental strand and synthesised strand due to this replication is called as semiconservative
enzymes involved in replication
topioisomes
helicase
DNA polymerase
DNA ligase
topoisomerase in replication
uncoils/unwinds DNA/ cuts the backbone( sugar+ phosphate)
helicase in replication
breaks the hydrogen bonds between the complimentary base pair, makes DNA strand available as template
DNA polymerase in replication
used DNA as a template to catalyze the polymerisation of DNA nucleotides, it catalyses the formation of new strand 5’ to 3’ direction
DNA ligase in replication
join okazaki fragments
replication fork due to
high energy requirements takes place in a small portion of DNA
parental stand with the polarity 3’ to 5’
is called the leading strand and synthesis of DNA in continuous. the parental strand with polarity 5’ to 3’ is called a lagging strand, synthesis is discontinous . it takes place in small fragments called okazaki fragments
okazaki fragments are joined by DNA ligase
it helps in making the phosphodiester bond between the fragments
binding proteins
binds to DNA, sterilizes the single-stranded structure generated by helicase. it does not allow parental strand to come down to each other( prevents complimentary base pairing)
RNA primers
to start DNA replication a small portion of RNA primers is required (18-22 bases). DNA polymerase can add nuleotides to an existing strand only. a primer contains a free OH group or the third carbon of sugar to which the phosphate group is attached. at end of replication the primer is removed
gene
a sequence of nucleotides/bases that is part of DNA that codes for a polypeptide
role of DNA polymerase
complimentary base pairing , join nucleotides by phosphodiester, proof read, Rpair
activated nucleotide
present in nucleoplasm during replication they give off 2 phosphate group so that nucleotides many bond with other nucleotide
Central Dogma of molecular biology
transcription
copying of information from DNA to RNA
why only one strand of DNA is copied to mRNA
if both the strands of DNA code for mRNA , 2mRNA molecules will be produced and they are complimentary to each other and form a double helix RNA
this prevents the translation of RNA ( protein synthesis)
if both the DNA strands act as a template, they will cools for 2 mRNA with different sequence which in turn code for 2 different polypeptide chains
enzymes involved in transcription
topoisomerase
helicase
RNA polymerase
RNA polymerase in transcription
produces a new strand 5’ to 3’
DNA strand with polarity 3’ to5’ act as template
transcribed strand. the other strand of DNA with polarity 5’ to 3’ is called as a non-transcribed strand
RNA polymerase binds to the promoter region
and the process of transcription begins..
RNA polymerase moves along the
template strand and add nucleotides opposites to the template strand following complimentary base pair ruling
when RNA polymerase reaches the termination region
it leaves the DNA forming a primary transcript of mRNA. the 2 strands of DNA are joined again by hydrogen bond, primary transcript/ pre mRNA undergoes processing
primary transcript of mRNA contains
coding sequnece (eexon) and non codinh sequence (intron) during processing, introns are looked out by the process of slicing and all the exons are joined by ligase, at 5’ end, guanine is added and at 3’ end adenin is added
similarity between exons and introns
both are part of primary transcript
exons
coding sequence, involved in transalation/required for the formation of polypeptides
not removed from primary transcripts joined to form mRNA. leaves the nucleus and goes to ribosomes
Not involved in regulating activity of gene
introns
non coding sequence
not involved in transalation
removed from primary transcript joined to form mRNA
not part of mRNA
remains in nucleus
may e involved in regulatory activity of gene
codon
sequence of 3 nitrogenous bases in mRNA which code for an amino acid
features of genetic code
totall of 64 codons- 61 code for amino acids,3 stop codon (UAA, UAG,UGA)
AUG has dual function
it codes for methionine and acts as a start codon
genetic code is degenerate
1 amino acid can have more than 1 codon
genetic code is universal
same for prokaryotes and eukaryotes
genetic code is read in
continous manner
reverse transcription
(mRNA makes DNA) - making DNA from RNA with the help of enzyme reverse transcription
mutation
a sudden inheritable change in DNA sequence that can lead to the formation of a dejective polypeptide
substituition
one or more nitrogenous base is changed with another
types of mutations
misence
silent
noncence
miscence
one nitrogenous base changed, one codon changed, a different amino acid appears in the sequence, primary structure changed, it shows that the genetic code is specific
CAC
his
CAA
gen
silent
one nitrogenus base change, one codon changed but codon for same amino acid so no change in primary structure, it shows that the genetic code is degenerate
GAG
Glu
UAG
stop
nonense
comes in between the sequence resulting in a shortness of polypeptide
insertion
adding a nitrogenous base in between the sequence
deletion
removing a nitrogenous base from the sequence. both results in frame shit as a result 0 this, the whole reunite after the mutation changes, a stop codon can come later the eenxyme ventilating in formation of shot
tramelation
takes place in cytoplasm, tRNA leaves the neuleus after transcription through nuclear pore and binds to the ribosome, mRNA caused
Role of tRNA
tRNA Carries amino acids to ribosomes
each type of tRNA carries a specific amino acid
anticodon on tRNA binds to codon on mRNA
tRNA molecules hold amino acids in place for peptide bond formation
tRNA molecules reused
semiconservative replication
each strand of DNA acts as a template for the synthesis of a complementary strand, new DNA has one parental strand and one daughter strand
process of exocytosis
Exocytosis is an active process that requires ATP, process by which materials are removed from cells by the fusion of vesicles containing the substance with the membrane, finally the contents are secreted out of the cell
process of DNA replication
DNA ( double helix) unwinds, hydrogen bonds break between base pairs, complementary base pairing, phosphodiester bonds form, both strands are used as templates, producing 2 identical DNA molecules,
outline how a mutation in GYS1 can lead to the formation of an altered polypeptide where a different amino acid replaces one amino acid
mutation causes the gene to be altered as base substitution changes the sequence of nucleotides so an altered mRNA is produced during transcription and mRNA codon is changed, tRNA brings different anticodons and different amino acid is formed
function of nucleolus
assembles ribosomes for polypeptide synthesis
function of mitochondria
synthesis ATP to supply energy for transcription of GYS1
the function of RER or Golgi body
folds and modifies synthesised polypeptide to produce functioning glycogen synthase
RNA serves as the
genetic material in some plant viruses
similarities between DNA and RNA
- both are macromolecules ( polynucleotides)
- both are build-up of nucleotides
- both can be found in the nucleus
- both contain sugar-phosphate backbone
- both contain N- bases C, G, and A ( purines and pyrimidines)
- their sugars are linked to a phosphate group at one end and a nitrogenous base at the other end
DNA occurs in
nucleus, it is also present in mitochondria and chlorophlast
sugar present in DNA
deoxyribose sugar
Nitrogenous bases in DNA
adenine, guanine ( purines), cytosine and thymine (pyrimidines)
DNA is mostly ___ stranded
double
DNA is the
genetic material
DNA transcribes
genetic information to RNA
DNA quantity
is fixed for a cell
DNA can be hydrolyzed
by an enzyme DNA-base
DNA replicates to form
new DNA molecules
hydrogen bonds are formed between
complementary nitrogen bases of the opposite strands of DNA
DNA is of only
one type
DNA shows regular
helical coiling
in DNA purine-pyrimidine bases
are in equal number
RNA is found in
cytoplasm, nucleus and nucleoplasm
sugar present in RNA
is ribose sugar
Nitrogen bases in RNA
adenine, guanine(purines), cytosine and uracil ( pyrimidines)
RNA is mostly __ stranded
single
RNA generally performs
nongenetic functions related with protein synthesis
RNA translates the
transcribe messages for forming polypeptides
RNA quantity
variable
RNA can be hydrolyzed
by an enzyme RNA-ase
RNA cannot
replicate itself except in RNA-RNA viruses
in RNA base pairing
through hydrogen bonds occurs only in coiled parts
RNA is of three types
rRNA, tRNA, mRNA
no regular coiling in RNA
excepts in parts of tRNA
in RNA purine-pyramidine
bases are not in equal number
messeneger RNA
mRNA
mRNA description
- it represents about 5 to 10% of the total RNA
- it is synthesized from DNA as and when necessary
mRNA function
mRNA has a significant role in genetic code, it carries the genetic information in the form of a specific sequence of nitrogen bases arranged in triplet codons, which are copies from the code in DNA
transfer RNA
tRNA
tRNA description
- it represents about 10 to 15% of the total RNA in the cell
- It has the shortest molecule having only about 80 to 100 nucleotides.
- the polynucleotide chain is folded on itself to have the shape of a cloverleaf
- the anticodon loop bears a triplet combination of nitrogen bases called anticodon, it is complementary to a codon of mRNA
tRNA function
tRNA is responsible for transferring amino acids to the site of protein synthesis ( ribosomes)
ribosomal RNA
rRNA
rRNA description
- it represents nearly 80% of the total RNA in the cell
- it is joined to proteins in ribosomes
- there are at least 20 different sorts of tRNA molecules, each with a particular triplet of bases at one end and able to attach to a specific amino acid at the other end ( there are 20 different types of essential amino acids)
mRNA sugar
ribose
mRNA has urcacil and no
thymine
mRNA is _ strannded
single
mRNA has __ bonds
no hydrogen
mRNA is not a
helix , it is a straight chain
mRNA ratio
of A+G to C+T varries
mRNA has _ base pairing
no base pairing within molecules
mRNA base pairing A-U with
tRNA/anticodon
mRNA length compared to DNA
shorter
mRNA found in
cytoplasm
mRNA is attached to
ribosomes
mRNA is __ lived
short
mRNA short function
transfer of information ( to ribosome)
mRNA codes for
one polypeptide
mRNA produced by
transcription
DNA sugar
deoxyribose
DNA has thymine but no
uracil
DNA is _ stranded
double
DNA has _ bonding
hydrogen bonding
DNA has _ helix
double
DNA ratio of A+G to C+T =
1
DNA has _ pairing
base
DNA base pairing is A-
T
DNA length compared to RNA
Longer
DNA found in
nucleus
DNA is not attached to
ribosomes
DNA is _ lived
long
DNA function short
information storage
DNA codes for
more than one polypeptide
DNA produced by
semiconservative replication
Transcription
genetic code on DNA is copied into mRNA, the double helix of DNA unwinds ( in the region to be copied) , complementary nucleotides line up along the coding strand of DNA, A to U and C to G, assemble to make a complementary strand of mRNA, under the influence of RNA polymerase, mRNA unzips from DNA template and passes to ribosomes
Replication occurs in
late interphase/ s phase/ prior to mitosis
Replication is catalyzed by
DNA polymerase enzymes
Replication complimentary base pairing
A-T
In replication both strands act as
template
in replication
all the DNA molecule is copied
in replication free activated DNA nucleotides serve as
raw material
in replication
2 DNA molecules produced and they are double stranded
Replication is important in
mitosis/ meiosis
in replication okazaki fragments
and joining of DNA required
Replication occurs along the
strands of DNA. it involves unwinding and splitting of the entire DNA molecule (chromosome)
Replication involves copying of the
entire genome
Replicated DNA strand remains
hydrogen bonded to its template DNA strand
in replication 2 double-stranded DNA molecules are
formed from one DNA molecule
in replication products remain
within the nucleus and are broken down
Replication requires RNA primer
to start replication
replication produces
normal DNA molecule that do not need any processing
transcription occurs in
the G1 and G2 phases of the cell cycle
transcription is catalyzed
by RNA polymerase enzyme
transcription base pairing is
A-U
in transcription only _ strand involved
one
in transcription genes are
copied
in transcription, RNA nucleotides serve as
raw material
in transcription _ produced
messenger RNA/ mRNA/ pre mRNA
transcription is important in
protein synthesis
in transcription mRNA produced as
continuous molecules
transcription takes place along
one strand of DNA and involves unwinding and splitting only those genes which are to be transcribed
transcription involves
copying of certain individuals only
transcribed RNA strand
separates from the template strand
in transcription, A single one-stranded RNA molecule
formed from a segment of one strand
in transcription the greater part of the product passes from
nucleus into cytoplasm
in transcription products are
degraded after their function is over
in transcription
no primer is required
transcription produces
primary RNA transcript molecules which need processing to acquire final form and size
why do the two polynucleotides on a dna molecule run in opp directions
the 2 polynucleotides on a dna molecule run in opposite directions so
that the double helix formed has 2 strands that are parallel to each other
A separate tRNA molecule is not required for each of the ten amino
acids because
each of the tRNA molecules, specific to one of the four
kinds of amino acid, can be reused.
relate trna to no of diff amino acids
helicase - makes strands available as
templates
topoisomerase - enables tension caused by
unwinding to be
released
single-strand binding protein - prevents
original strands reforming
complementary base pairs
dna polymerase
adds dna nucleotides to the 3’ end of a growing
polynucleotide strand
before mrna leave nucleus, what events will have occured twice?
bonds break between cb and bonds form between cb
what makes the exact copying of dna molecules possible
base pairing
correct sequence of processes involved in formation of an enzyme
transcription → translation → condensation → ionic bonding
what happens if ribosomes r inactivated
peptide bonds will not form between adj amino acids in the growing
polypeptide
smallest unit of a dna molecule that can be altered by a mutation and
cause a change to the coding of a polypeptide?
nucleotide
no rna polymerase? :((
condensation reactions joining rna nucleotides will not take place to form
mrna
translation timeline
mrna binds to ribosome → trna enters ribosome → h bonds form →
peptide bond forms
max number of codon-anticodon interactions within one ribosome
2 yaaaaaaaas
define gene
a sequence of nucleotides that forms part of the dna molecule and
codes for a polypeptide
during dna replication, what must happen before a newly added
nucleotide is bonded to the next nucleotide in the strand
cb pairing and h bond formation
structure of atp
nitrogenous base (adenine), a ribose sugar, and three serially bonded
phosphate groups
3 bases make one
amino acid [ 3 nucleotides = 1 amino acid ]
tRNA contains
single stranded RNA which folds such that hydrogen
bonding occurs between regions of complimentary bases (it occurs
along some of the trna’s length)
dna is able to
remain stable due to the sugar-phosphate backbone
dna molcules has
reducing sugar [molecule has covalent and hydrogen
bonding]
sense strands / antisense strans are other words for
transcribed/ non-transcribed strand
sugar-phosphate bonds form after
complementary base pairing
only trna has a site to which a
only trna has a site to which a s
dna molecules differ in the
sequence of the nucleotides
in replication, both the dna strands act as
templates (parental dna is split
into 2 strands, each of which is replicated); but in transcription only one
acts as a template
if the parent molecule contains 40% guanine
so does the new dna
molecule because they are both identical
base pairs are of
equal length
when they say possible effects of mutated sequence, and they give u a
sequence just go by
that given sequence
role of dna polymerase is to make
polynucleotides and make sugarphosphate bonds
anticodon and dna triplet have the same
base sequence
State what is meant by a STOP:
Codon that terminates polypeptide synthesis / translation / transcription
Does not code for an amino acid
Has no complementary anticodon
Causes release of polypeptide chain
Compare the peptide bond formed during translation with the types of bond made during tertiary structure formation
similarity
peptide bond and disulfide bond are covalent bonds ;
differences
tertiary structure bonds are between, R groups / side chains, (of different amino acids ;
H bond / ionic bond / hydrophobic interaction, versus covalent peptide bond ;
A tertiary structure bonds apart from disulfide are not covalent
peptide bond, stronger / more thermostable, than, tertiary structure bonds / two named bonds;
peptide bond is between, carboxylic acid / COOH, and, amino / NH2, group (of the adjacent amino acid) ;
AVP ; detail of a tertiary structure bond e.g.
hydrophobic between non-polar R groups
disulfide between sulphur-containing R groups
ionic between carboxyl and amino groups of R groups
H bond between oxygen on —CO groups and H on either the —OH or —NH groups of R groups
Explain how the structure of DNA enables it to replicate semi-conservatively.
- base pairing/A-T and C-G; A purine - pyrimidine
- ref to complementary/explained with ref to H bonds; R complementary in wrong context
- (free) nucleotides pair with both, strands/each strand/polynucleotides/sides;
- both strands act as templates;
- to produce two DNA molecules that are identical to one another;
Role of mRNA after leaving nucleus:
- translation ; R if transcription given as well, unless in correct context A use of, nucleotide / base, sequence, to make, amino acid chain / polypeptide / protein
I protein / polypeptide, synthesis - moves towards / combines with, ribosome ;
- ref to small and/or large sub-units ; I small / large ribosome
- codon(s) ; only accept in correct context
- transfer / t, RNA, bringing, amino acid(s), to mRNA / ribosome ;
- anticodon(s) ; only accept in correct context
- (complementary) base pairing ;
- any e.g. of codon:anticodon base pairing ; need six bases
- ref to polyribosome(s) / used by many ribosomes ;
- (mRNA short-lived) ref to production of protein for short period of time ;
Role of tRNA in protein synthesis:
- (tRNA) carries amino acid to ribosome ;
- ref. to specificity of amino acid carried ; A role in ensuring correct primary structure
- ref. anticodon (on tRNA): codon (on mRNA) binding ;
- ref. complementary / base pairing ; A A-U, C-G
- ref to tRNA binding sites within ribosome ;
- two tRNAs bound to, mRNA / ribosome, at same time ;
- amino acids held close to each other / AW ;
- (for) peptide bond formation ;
- (tRNA) can be reused / binds another amino acid ;
During interphase:
cells metabolically active / AW ;
protein synthesis ;
transcription ;
translation ;
gene expression ;
DNA / semi-conservative, replication ;
respiration ;
synthesising, organelles / named organelle(s) ; e.g. A centrioles replicate
synthesising, macromolecules / named macromolecule ;
Factors that increase the risk of cancer:
- chemical carcinogens ; A named carcinogenic chemical e.g. asbestos / tar / benzpyrene / aniline dyes / mustard gas / ethidium bromide ; allow two named chemicals for two marks
- virus, qualified ; e.g. with oncogene / ability to convert host proto-oncogene / named virus e.g. HPV / retrovirus / HIV / HTL
- ionizing radiation / X-rays / gamma rays / particles from radioactive decay / ultraviolet light / alpha particles / beta particles ; allow two named radiation examples for two marks
- free radicals ;
- hereditary predisposition / AW ;
- tobacco smoking ;
- obesity ; A qualified ref. to diet
- AVP ; e.g. if immunocompromised
How can mutation in gene lead to formation of altered polypeptide where one amino acid is replaced with a different amino acid*
(in DNA / gene) altered, sequence / AW, of, nucleotides / bases ;
base substitution or base / nucleotide, replaces another, base / nucleotide;
(mRNA synthesised) during transcription ;
(mutation leads to) altered / AW, mRNA / messenger RNA ;
(only) one (mRNA) codon changed / a different codon ; (A one DNA, triplet / codon, changed I ref. to codons changed)
tRNA, with / has, a different anticodon ;
7 (tRNA) brings, a different / a changed / the incorrect, amino acid, during translation / to the ribosome ;
codon-anticodon, binding / complementary / AW ; (A matches R amino acid with anticodon)
Role of anticodon in translation
The anticodon is complementary to the codon on mRNA hence it binds to the mRNA
The anticodon is specific to an amino acid. This ensures that the correct amino acid sequence is formed during translation.
