Nucleic acids & Protein synthesis Flashcards by Joshua Parnaby

Two Types of nucleic acids

Deoxyribonucleic acid(DNA) & Ribonucleic acid(RNA)

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Describe nucleic acids

Composed of nucleotides, A monosaccharide 5 carbon atoms, phosphate group, nitrogenous base

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Purine Nitrogenous bases

A & G (look like pyrimidine)

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Pyrimidine Nitrogenous bases

C,T & U (1ring)

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what is the 5’ end

phosphate

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what is the 3’ end

monosaccharide (OH)

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Describe DNA structure

two polynucleotide chains that wind around a common axis to form a double helix

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What is antiparallel

Two polynucleotide chains have opposite orientations 5’=>3’ & 3’=>5’

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What are the 2 groves in DNA

Major and Minor

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What is the pairing of bases in DNA and how many bonds

A-T 2 H bonds
C-G 3 H bonds

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What is Chromatin

Double helix wrapped around histones

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Describe Genes

Codes for RNA that codes for a protein, on a specific location on DNA called a LOCUS

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Describe RNA

Single stranded polymer of nucletides joined by phosphodiester bonds, Made with ribose

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differences of RNA

sugar is ribose, nitrogen bases U(uracil) instead of T(thymine)

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What type of replication is DNA replication

semiconservative- half of new double helices are original strand half new strand

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3 stages of DNA replication

Initiation, Elongation, Termination

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Describe Initiation stage (dna rep)

Protein recognise origin sites and form prereplication complexes then form a replication bubble(initiation complex)

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Describe the Stages of Initiation stage(enzymes)

TOPOISOMERASE- unwinds coiling of double helix
HELICASE- binds to origin of replication, establishes replication fork, unzips to make single strand
SINGLE-STRANDED DNA BINDING PROTEINS- prevent coiling

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DNA Primase (elongation) role

makes RNA primer (5-10 nucleotides) provides 3’end

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DNA Polymerase (elongation) role

Add nucleotides to 3’ end, catalyse bonds of nucleotides , 1 per chain

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Describe Leading strand

5’=>3’, continuous process, ε polymerase

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Where is DNA Polymerase ε used

Leading strand

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Describe lagging strand

3’=>5’, discontinuous process, backstitching mechanism (multiple RNA primers) (okazaki fragments), α & δ polymerase

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Where is DNA polymerase α & δ

lagging strand

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Describe Termination for leading strand

When two replication forks encounter each other head on, (HELICASE is modified by ubiquitin is removed from DNA), repair DNA polymerase and DNA ligase fill in gaps

Describe Termination for lagging strand(okazaki fragments)

RNAse removes primers after completion, DNA polymerase δ fills gaps, Nicks in the DNA are sealed by DNA ligase

What does DNA ligase do

Fill in gaps at the end of DNA replication

How many errors per nucleotide

1per10^7 nucleotide bases

Name the spontaneous DNA damage types

Depurination, depyrimidination, deamination, UV

Describe Depurination

loss of purine bases

Describe Depyrimidination

Loss of pyrimidine bases

Describe Deamination

loss of amino in cytosine C=>U

Describe UV radiation damage

causes covalent linkage between pyrimidine bases T,C

Name 2 major DNA repair pathways

Base excision, Nucleotide excision

Describe Base excision and what is it used for

remove a base/nucleotide then replace that one - for deamination

Describe Nucleotide excision and what used for

Remove set of nucleotides then replace- for depyrimidation

What does base excision repair

Deamination

What does nucleotide excision repair

depyrimidation

Name the mechanisms to repair double strand breaks

Nonhomologous end joining and Homologous recombination

Describe Nonhomologous end joining

Break repaired using DNA ligase to glue together with LOSS of nucleotides at repair sites

Describe Homologous recombination

Break repaired by DNA Polymerase and Ligase by using undamaged DNA as template with NO LOSS of nucleotides at repair site

Name types of DNA recombination

DNA repair, Meiosis

Describe DNA repair (recombination)

Fixes Double strand break by bringing the strands together using new nucleotides based of the template undamaged strand and using base-pairing

Describe Meiosis DNA recombination

Strand breaks programmatically and then they crossover and resemble

Describe DNA recombination is repair vs meiosis

DNA recombination in DNA repair primarily maintains genome integrity by accurately repairing double-strand breaks, while in meiosis, it promotes genetic diversity by exchanging genetic material between maternal and paternal sister chromatids.

How many amino acids

What groups are on a amino acid

amino group, carboxyl group, hydrogen atom and r-group

How many amino acids to be called a protein

50<

How many amino acids to be called a peptide chain

<50

What does genetic code determine

number and sequence of amino acids

What reaction occurs to form peptide bond

condensation reaction

5 stages of Protein synthesis

DNA, Transcription, RNA, Translation, Protein

Describe Transcription

DNA unwound by RNA polymerase then binds to specific section of gene called promoter sequence, triplets have start stop sequences

What Strand does RNA polymerase copy

3'-5' strand(template strand) through complementary base pairing resulting in a copy of the non template strand

Name the 4 steps of posttranscriptional modification (pre-mRNA)

Splicing, editing, 5'capping, polyadneylation

What is splicing

removing introns (dont code for proteins)

What is editing

Changing the length/shape of nucleotide bases

What is 5'capping

Adding on something(head) to the start to prevent it breaking down and allow ribosome to identify mRNA

What is polyadenylation

adding a tail of adenine bases to signal to end of mRNA

3 stages of translation

initiation, elongation, termination

What is initiation (translation)

Transitional complex forms and tRNA brings first amino acid in polypeptide chain to bind to start codon on mRNA

What is Elongation (translation)

tRNA bring amino acids one by one to add to polypeptide chain

What is Termination (translation)

Release factor recognizes stop codon translation complex dissociates and completed polypeptide is released

Name the 4 steps of posttranslational modifications

Primary, secondary, tertiary, quaternary

What is Primary protein structure

sequence of a chain of amino acids

What is Secondary protein structure

Alpha helix/ Beta pleated sheet Where hydrogen bonding causes the chain of amino acids to fold into repeating pattern

What is Tertiary protein structure

3 dimensional folding pattern of a protein due to interactions such as disulfide bridges, ionic bonds, hydrophilic/phobic interactions etc

What is Quaternary protein structure

protein consisting of more than one amino acid chain