BIOL SCI 215 Lecture Notes - Lecture 5: Main Sequence, Cistron, Tata Box
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Primers: Helicase, Primase, DNA pol, Ligase
DNA is a polymer, its monomer is called dNTP
Triphosphate is a high energy bond which helps to facilitate the reaction, taking 3’
Hydroxyl (from the base) and make a covalent bond
Primer is made of RNA
Lagging strand - with Okazaki fragment going backwards for 5’ to 3’, whereas for
leading strand, you can just continue
End replication problem for linear chromosomes
oSolution: Generate arbitrary sequence which will add the base pairs to the
ends of the sequence using polymerase
oTelomere lengthening: RNA held within telomerase which is able to bind to
the base sequence. Enzyme does a reverse step making them
complementary DNA. Transcription in Reverse
oEnd is synthesized with primase
Every eukaryote has a telomerase - important in cancer progression. WIthout it,
chromosomes will become smaller than coding genes will become lost
Transcription
Problem 1: DNA is in nucleus but proteins are synthesized in the cytosol [Solve by
making intermediate RNA]
Problem 2: Nearly all cells in an organism have identical DNA content but can
express different proteins due to a developmental program or in response to their
environment [A selectively produced messenger: RNA] RNA is same as DNA but is a
form that can be read out by ribosome to create proteins
RNA has a NTP (Has a 2’ Hydroxyl and U instead of T) while DNA has a dNTP.
oRibonucleic used instead of Deoxyribonucleic
To make RNA through transcription, you would need a template strand, similar to
DNA polymerization.
o5’ → 3’ of the new strand
oRNA is synthesized by RNA polymerases
oTop strand is called the coding strand [Same as DNA], mRNA is called the
template strand (Opposite bases as RNA)
omRNA - goes on to make proteins
orRNA - Forms part of ribosomes and are involved in protein synthesis
(Translation)
otRNA - Adaptors used in protein synthesis (translation)
oSmall RNAs - used for splicing
Promoter sequences specify transcription initiation, terminator sequences end
transcription [RNA polymerase to stop]
On bacteria: Sigma factor binds to promoter, DNA and reproofs RNA polymerase and
RNA polymerase starts transcription
oPromoter sequences: -35 and -10, specific DNA sequences which the sigma
factor recognizes
Already starting transcription
Elongation:
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Document Summary
Dna is a polymer, its monomer is called dntp. Triphosphate is a high energy bond which helps to facilitate the reaction, taking 3". Hydroxyl (from the base) and make a covalent bond. Lagging strand - with okazaki fragment going backwards for 5" to 3", whereas for leading strand, you can just continue. Enzyme does a reverse step making them complementary dna. Transcription in reverse: end is synthesized with primase. Every eukaryote has a telomerase - important in cancer progression. Without it, chromosomes will become smaller than coding genes will become lost. Problem 1: dna is in nucleus but proteins are synthesized in the cytosol [solve by making intermediate rna] Rna has a ntp (has a 2" hydroxyl and u instead of t) while dna has a dntp: ribonucleic used instead of deoxyribonucleic. To make rna through transcription, you would need a template strand, similar to. Promoter sequences specify transcription initiation, terminator sequences end transcription [rna polymerase to stop]