PRE FI LEC 1: TRANSCRIPTION AND TRANSLATION Flashcards
A cell uses 2 processes to manufacture proteins using genetic instructions which are…
TRANSCRIPTION AND TRANSLATION
- Synthesis of RNA molecule that is complementary to 1 strand of the DNA double helix for a particular gene (DNA to RNA)
- copies DNA information into RNA.
TRANSCRIPTION
Uses the information in the RNA to manufacture a protein by aligning & joining specified amino acids (RNA to proteins)
TRANSLATION
Bridges gene and protein
RNA
Bases of RNA sequence is complementary to the strand of double helix which we called________
TEMPLATE STRAND
3 MAJOR TYPES OF RNA
- MESSENGER RNA (mRNA)
- RIBOSOMAL RNA (rRNA)
- TRANSFER RNA (tRNA)
- CARRIES A PARTICULAR INFORMATION that specifies a particular protein
- Each 3 mRNA bases in a row form a genetic code word called ______
- 500 -4500 bases long
- ENCODE AMINO ACID SEQUENCE
MESSENGER RNA (mRNA)
- Each 3 mRNA bases in a row form a genetic code word called CODON
- 100 to nearly 3,000 nucleotides long.
- Largest component of cellular RNA (80% - 90%)
- ASSOCIATE WITH CERTAIN PROTEINS to form a ribosome, (which structurally support and catalyze protein synthesis)
- Some catalyze the formation of the peptide bonds between amino acids (ribozyme)
- Some help align the ribosome and mRNA
RIBOSOMAL RNA (rRNA)
- BINDS AN mRNA CODON at one end and a specific amino acid at the other.
- Is only 75 to 80 nucleotides long
- One loop of it has 3 bases in a row that form the anticodon
- tRNA with a particular anticodon strongly bonds to a specific amino acid
TRANSFER RNA (tRNA)
One loop of the tRNA has 3 bases in a row that form the __________, which is complementary to an mRNA codon.
ANTICODON
STEPS OF TRANSCRIPTION
- INITIATION
- ELONGATION
- TERMINATION
STEPS OF TRANSCRIPTION
- beginning of transcription, when RNA polymerase & supporting proteins bind to the promoter
- RNA polymerase & its supporting accessory proteins assembled on DNA at a specific site (promoter)
- Control point that determines which genes are transcribed
INITIATION
a special sequence that signals the start of the gene, like a capital letter at the start of a sentence.
PROMOTER
STEPS OF TRANSCRIPTION
- addition of nucleotides to the mRNA strand
- enzymes unwind the DNA double helix locally
- RNA polymerase moves along the DNA strand, adding complementary nucleotides as dictated by the DNA template
ELONGATION
STEPS OF TRANSCRIPTION
- ending transcription, occurs when RNA polymerase crosses a stop (termination) sequence in the gene
- Ending of transcription & happens once the RNA polymerase transcribes a sequence
TERMINATION
a __________ will signal the end of transcription
TERMINATOR SEQUENCE
SETTING THE STAGE FOR TRANSCRIPTION TO BEGIN:
- DNA must be released locally from histones & the helix unwound, involve the participation of:
- DNA - BINDING PROTEINS
- HISTONE MODIFICATION ENZYMES
- RNA POLYMERASE
- TRANSCRIPTION FACTORS
1st transcription factor to bind
TATA BINDING PROTEINS
TATA BINDING PROTEINS is chemically attracted to ___________ which is the BASE SEQUENCE TATA surrounded by long stretches of G and C
TATA BOX
- Many identical copies of RNA are transcribed simultaneously
- Usually ___________ DNA bases lies between RNA polymerase
100 OR MORE
In eukaryotes, the newly made RNA ( primary transcript/pre - mRNA) is further processed before it is functional
mRNA PROCESSING
mRNA PROCESSING STEPS
- CAPPING
- POLYADENYLATION
- SPLICING
a cap blocs the eukaryotic mRNA at the 5’ terminu
CAPPING
ADDITION OF ADENOSINES to the 3’ end of mRNA with the help of polyadenylate polymerase enzyme
POLYADENYLATION
removal of intron (non-coding/intervening) sequences from mRNA
SPLICING
- Assembles a protein using the information in the mRNA sequence
- Particular mRNA codons corresponds to particular amino acids (genetic code)
- Takes place in the free ribosomes in the cytoplasm & in the ribosomes that are embedded in the endoplasmic reticulum
TRANSLATION
GENETIC CODE: GENERAL FEATURES
- The genetic code is written in LINEAR FORM
- The genetic code is TRIPLET
- The genetic code is UNAMBIGUOUS
- The genetic code is DEGENERATE
- The genetic code include CONTROLS
- NO INTERNAL PUNCTUATION (such as comma) is used in the code.
- The genetic code is NONOVERLAPPING
- The genetic code is nearly UNIVERSAL
- Uses the ribonucleotide bases that compose mRNA molecules as “letters”
- Ribonucleotide sequence is derived from the complementary nucleotides bases in DNA
THE GENETIC CODE IS WRITTEN IN LINEAR FORM
The number of bases in a codon is 3
THE GENETIC CODE IS TRIPLET
Each triplet specifies only a single amino acid
THE GENETIC CODE IS UNAMBIGUOUS
Redundancy: different codons specify the same amino acid
THE GENETIC CODE IS DEGENERATE
- Triplets that initiate & terminate translation
- AUG - signals “starts”
- UGA, UAA, and UAG - signify “stop”
THE GENETIC CODE CONTROLS
- Code is said to be commaless
- Once translation of mRNA begins, the codons are read one after the other, with no breaks between
NO INTERNAL PUNCTUATION (SUCH AS COMMA) IS USED IN THE CODE
Once the translation commence, any single ribonucleotide at a specific location within the mRNA is part only of 1 triplet
THE GENETIC CODE IS NONOVERLAPPING
- All species uses the same mRNA codons to specify the same amino acids, and therefore the same genetic code
- Universality of genetic code: All life evolved from a common ancestor
- Exceptions: Few codons in mitochondria and in certain single-celled eukaryotes (ciliated protozoa), almost all viruses, prokaryotes, archaea
THE GENETIC CODE IS NEARLY UNIVERSAL
Different codons that specify the same amino acid
Ex: GUG, GUA, GUC, GUU specify valine
SYNONYMOUS CODONS
Encode different amino acids
Ex: AAA (LYSINE) & AAC (ASPARAGINE)
NONSYNONYMOUS CODONS
BUILDING A PROTEIN
Requirements:
mRNA - MESSENGER RIBONUCLEIC ACID
tRNA - TRANSFER RIBONUCLEIC ACID
RIBOSOME
ENERGY-STORING MOLECULES (ATP - ADENOSINE TRIPHOSPHATE & GTP GUANOSINE TRIPHOSPHATE)
PROTEIN FACTOR /S
TRANSLATION process
INITIATION
ELONGATION
TERMINATION
beginning of translation, when the small ribosome subunit assembles with mRNA & then the large ribosomal subunit
INITIATION
- binding of charged tRNAs & formation of the peptide bond producing growing polypeptide
- Assisted by chaperones
ELONGATION
- ending of translation, occurs when the complex encounters a nonsense codon (UAG, UGA,& UAA)
- MESSAGE STOP HERE
TERMINATION
AMINO ACID STRUCTURE
CARBOXYL GROUP (COO-) - NON-POLAR
AMINO GROUP (NH2 GROUP BONDED TO THE CARBON ATOM) - POLAR
R (RADICAL) GROUP - CHARGE
CENTRAL C ATOM - CHARGE
Manner in which amino acids are bonded together
PEPTIDE BOND
2 amino acids linked together
DIPEPTIDE
3 amino acids
TRIPEPTIDE
10 or more amino acids linked together
PROTEIN STRUCTURE
POLYPEPTIDE
PROTEIN FOLDING
- Stabilize partially folded regions in their correct form & prevent a protein from getting “struck” in an intermediate form, which would affect its function
CHAPERONE PROTEINS
PROTEIN FOLDING
- Straighten and refold the misfolded protein
UBIQUITIN
PROTEIN FOLDING
- Degrade the protein into amino acids
PROTEASOME
PROTEIN MISFOLD IN 2 WAYS
- May CHANGE the amino acids sequence
MUTATION
PROTEIN MISFOLD IN 2 WAYS
- 2 forms of the same protein have identical amino acid sequences, but fold differently
Ex: PRION
HAVING MORE THAN ONE CONFORMATION
amyloid beta precursor protein, tau proteins
ALZHEIMER’S DISEASE
superoxide dismutase, TDP- 43
FAMILIAL AMYOTROPHIC LATERAL SCLEROSIS
tau proteins, TDP-43
FRONTOTEMPORAL DEMENTIA
Alpha synuclein
PARKINSON DISEASE
LEWY BODY DEMENTIA
huntingtin
HUNTINGTON DISEASE
PHENYLALANINE HYDORXYLASE
PHENYLKETONURIA (PKU)
PRION PROTEIN
PRION DISEASE
PRION DISEASES: TRANSMISSIBLE SPONGIFORM ENCEPHALOPATHIES (TSEs)
- 1st described prion disease
- Fatal, degenerative disease affecting the CNS of sheep & goats
- PrPSc (prion): its different conformation makes it resistant to normal cellular processes.
- Affected animals: behavioral changes,loss of coordination, tremors, weight loss, excessive itching/scratching behavior
SCRAPIE
PRION DISEASES: TRANSMISSIBLE SPONGIFORM ENCEPHALOPATHIES (TSEs)
- TRANSMISSABLE, neurodegenerative fatal brain disease of cattle
- Accumulation of PrPSc in the CNS
- Affected animals: behavioral changes, difficulty in coordination, abnormal movements, weight loss
BOVINE SPONGIFORM ENCEPHALOPATHY (BSE): MAD COW DISEASE
PRION DISEASES: TRANSMISSIBLE SPONGIFORM ENCEPHALOPATHIES (TSEs)
- Fatal,neurological illness deer, elk, moose and mink
- Accumulation of PrPSc in brain & other tissues
- Affected animals: wasting/progressive weight loss, behavioral changes, decreased coordination, tremors, an altered stance, emaciation, excessive salivation, & other neurological abnormalities
WASTING DISEASE
PRION DISEASES: TRANSMISSIBLE SPONGIFORM ENCEPHALOPATHIES (TSEs)
- 1st prion disease recognized in HUMANS
- Affected the native Fore people who lived in remote mountains in Papua New Guinea
- Wobbly legs, trembling, & whole body shaking; uncontrollable laughter laughing disease); speech slurred, thinking slowed & the person became unable to walk or eat; death came within a year
KURU
5 MAJOR HUMAN PRION DISEASES
- rapid mental deterioration, memory loss, personality changes, movement disorders & ultimately severe dementia
CREUTZFELDT-JAKOB DISEASE (CJD)
5 MAJOR HUMAN PRION DISEASES
- progressive and total inability to sleep, leading to severe insomnia; autonomic dysfunction, hallucinations, delirium, & motor abnormalities
FATAL FAMILIAL INSOMNIA (FFI)
5 MAJOR HUMAN PRION DISEASES
- ataxia (loss of coordination), dementia, muscle stiffness & involuntary movements
GERSTMANN-STRAUSSLER-SCHEINKER DISEASE (GSS)
