6 NUCLEIC ACIDS & Protein Synthesis Flashcards
(9 cards)
- “central dogma”
- rna
- rna structure
- atp, adp
- protein synthesis
- transcription overview
- rna processing
- introns & exons
- SPLICING overview
- triplets
- translation
- translation overview
- dna => rna => protein
transcription, translation - rna: a complementary copy of a dna strand as instructions for protein synthesis. 3 types: rRNA (ribosomal RNA; synthesised in nucleolus), mRNA, tRNA (transfers amino acids to ribosomes)
- rna structure: nucleotide monomers into polymer
-single stranded
-ribose sugar instead of deoxyribose
-extra hydroxyl group make it less stable than dna.
-uracil instead of thymine
-form base-pair with adenine. - transcription (+ rna processing), translation.
- Promoter sequence identified [initiation] - RNA Polymerase recognises the promoter region on DNA, specific to it
> DNA double helix unwind/unzip - RNA Polymerase unzips DNA. TRANSCRIPTION BUBBLE forms where RNA polymerase unwinds DNA ahead of time & rewinds DNA behind it. Temporarily single-stranded for RNA synthesis.
> form template strand and coding strand - ONLY TEMPLATE strand is used for mRNA synthesis. CODING strand (non-transcribed strand) used to
> COMPLEMENTARY mRNA STRAND FORM TEMPLATE STRAND - elongation. RNA polymerase adds complementary nucleotides to template strand (A-U, C-G), 5’ to 3’ direction
> TERMINATION; RNA polymerase recognises terminator region on DNA. so mRNA detaches from DNA template. - post-transcriptional processing ; mRNA needs to be checked and changed to make it functional; LESS STABLE than dna, so MORE PRONE TO MUTATIONS.
-misreading nucleotide/adding wrong etc - introns: taken out; NON-CODING REGIONS FOR mRNA STABILITY ETC ;; exons: coding regions for coding amino acids (so proteins).
[only ~1-2% of DNA code in human genome actually code for proteins] - > pre-mRNA introns spliced out; carried out by an enzyme complex called spliceosome
5’ cap is added to pre-mRNA to prevent degradation
poly-A tail added to 3’ end of pre-mRNA to prevent degradation
exons combine to form mature mRNA - COVALENTLY bond (alternative splicing; protein isoforms after translation)
mature mRNA leaves nucleus (move from nucleus to CYTOPLASM; through NUCLEAR PORES in nuclear membrane)
(transcription ends) - dna code is read in triplets;
each triplet codes for the same amino acid;
a triplet is termed a CODON on mRNA - TRANSLATION:
> sequence of bases in mRNA is converted into sequence of amino acids in a polypeptide
>ribosomes (big+small) made of rRNA and protein.
-tRNA = transfer RNA,
trna: carries anticodon to ribosome
rRNA = part of ribosome, mRNA = genetic code from DNA
12.
> ribosome binds to and scans mRNA: ribosomal units assemble together on mRNA strand. ATTRACT tRNA molecules towards mRNA
> start codon on mRNA identified: INITIATION; only one START codon AUG. Codes for the first amino acid in the polypeptide chain, Methionine (Met)
> tRNA matches its anticodon with mRNA codon
ELONGATION. tRNA loop contains specific anticodons that match with codons on mRNA.
Correct tRNA enters ribosome with correct amino acid.
> AMINO ACID FORMS; elongation, ribosome moves to the next codon on mRNA, tRNA molecules carry amino acids to translation area
ANTICODON = COMPLEMENTARY BASES
> polypeptide chain forms: TERMINATION, ribosomes form peptide bonds to link amino acids.
ribosome identifies STOP codon
-release factor binds instead of tRNA, and chain is released
> END: end products of protein synthesis is PRIMARY STRUCTURE of protein; a sequence of amino acids bonded together by peptide bonds.
AUG start, UAA UAG UGA STOP.
dna atcg double
rna single aucg
DEFINITION MUTATION
change in
DNA BASE SEQUENCE
that may lead to changes in phenotype
mutation types
- point mutation
- frameshift mutation; causes everything to shift as it skips to next base
- DELETION
SUBSTITUTION
INSERTION
-
SUBSTITUTION mutation outcomes
- point ;; change to a base in DNA (affects amino acids); small scale
- frameshift: changes how DNA sequence is read; large scale
-
deletion: nitrogen base is removed; frameshift mutation
subst.: replaced; point mutation (no shift caused)
insertion: add base; frameshift mutation
-
subst outcomes:
1. same-sense (silent) - NO change in protein, mutation might not change amino acid bc of redundancy (of last amino acid)
2. missense mutation - YES change in protein, leads to different amino acid formed in polypeptide sequence
3. nonsense mutation - creates a stop codon; a STOP codon halts sequence reading, early termination of protein, COMPLETELY NON-FUNCTIONAL = premature stop.
mutation outcomes
-harmful
-beneficial
-neutral
harmful: eliminates poorly adapted organisms to environmental conditions like diseases, disorders
beneficial: exhibit greater fitness in current environment, hence live longer (adaptive advantage)
neutral: may have benefit/harm in the future if environment changes.
nucleic acids
-nucleic acid eg dna and rna
-they’re macromolecules
-polymers ;; subunit monomers are nucleotides
-DNA AND RNA also “POLYNUCLEOTIDES”
nucleotides [3]
-nitrogenous base
-pentose sugar (5 carbon atoms)
-phosphate group
nucleotide structure RNA AND DNA DIFFERENCES.
pentose sugar: in DNA DEOXYRIBOSE, in rna RIBOSE
bases: adenine, thymine, cytosine, guanine and IN RNA, adenine, uracil, cytosine, guanine
number of strands: in dna DOUBLE-STRANDED DOUBLE HELIX, in rna SINGLE-STRANDED.
ATP
adenosine triphosphate (ATP)
[adenosine: a nucleoside - a base – adenine, attached to a pentose sugar]
-energy-carrying molecule
-providing energy to drive living processes in cells
-ATP: another type of nucleotide
-structurally similar to nucleotides making up DNA AND RNA
-ATP: a PHOSPHORYLATED nucleotide
-1 P: adenosine monophosphate (AMP)
purines & pyrimidines
- nitrogenous base molecules that are found in the nucleotides of DNA (A, T, C, G) and RNA (A, U, C, G) occur in two structural forms: purines and pyrimidines
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