Genetics Exam 3: Translation

What is translation?

The biological polymerization of amino acids into polypeptide chains (AKA: turning AAs into proteins)

What does translation require?

Amino acids, mRNA, ribosomes, tRNA

What reads the mRNA?

ribosomes

What are ribosomes made of?

ribosomal proteins and ribosomal RNAs

large & small subunits

Where is 16sRNA found in and what can it do?

-found in bacteria

provides species-specific sequences

What can microbiome analysis do for us?

-Identify which microorganisms allow a better fermentation process to have high performance cows.

-Increase profitability and value of our products.

What is tRNA and what is it made of?

an adaptor molecule that’s made of 3 consecutive ribonucleotides that are compliment to a codon

What is an anticodon?

Another region of the tRNA is covalently bound to the codon’s corresponding AA

transcribed from DNA

What is the name of the tRNA structure

cloverleaf

What is aminoacylation

process of charging a tRNA

What is aminoacyl tRNA synthetase

Enzyme that catalyzes aminoacylation

there are 20, one for each amino acid

What is needed to initiate translation

Small and large ribosomal subunits, mRNA molecule, GTP, charged initiator tRNA, Mg2+, initiation factors

What is the order of the phases for initiation of translation

Aminoacyl (A)

Peptidyl (P)

Exit (E)

What is the Shine-Dalgarno sequence

AGGAGG

comes before the start codon in bacteria

Base-pairs with region on 16S rRNA of 30S small subunit, facilitating initiation

What is an initiation complex

Small ribosomal subunit + initiation factors + mRNA at codon AUG

Combines with large ribosomal subunit

What forms during elongation?

the P and A site

What is the role of 23S rRNA

Catalyzes peptide bond formation between amino acid on tRNA at A site and growing peptide chain bound to tRNA in P site

What is peptidyl transferase

initially believed to be catalytic enzyme for reactions. It is in fact the catalytic activity of 23S rRNA

What are GTP-dependent release factors

Stimulates hydrolysis of polypeptide from peptidyl tRNA—released from translation complex

What are polysomes/polyribosomes

an mRNA molecule with several ribosomes translating at once

What makes ribosomes in eukaryotes different from prokaryotes

are larger and live longer

Where does transcription occur?

in the nucleus

What two modifications occur in transcription

5′ end of mRNA capped with 7-methylguanosine

Poly-A tail added at 3′ end of mRNA

What needs to happen for mRNA to mature

intron splicing

Where does translation occur

in the cytoplasm

What is the Kozak sequence

considered to increase efficiency of translation by interacting with initiator tRNA

What do eukaryotes need more of for translation compared to prokaryotes?

needs more factors for initiation, elongation, and termination than in bacteria

Where are ribosomes found in eukaryotes

attached to the ER

How does the closed loop translation happen

mRNA forms a loop that closes where the cap and tail are

poly-A-binding proteins bind to the cap-binding protein to form a loop

What is alkaptonuria

When an individual cannot metabolize alkapton

What is phenylketonuria

When an individual is unable to convert phenylalanine to tyrosine

-Phenylalanine hydroxylase is inactive in affected individuals

What happens when phenylalanine reaches high levels?

Phenylalanine enters cerebrospinal fluid and results in mental retardation

What is a precursor to protein

polypeptides

Amino acids assembled on and released from ribosomes as polypeptides

What makes up an amino acid

Carboxyl group

Amino group

R (radical) group

What are the three types of AA?

nonpolar, polar, and positive/negative charged

What is a peptide bond

A dehydration reaction that facilitates a bond between carboxyl group of one amino acid and amino group of another

What are the four levels of protein structures

Primary: Sequence of amino acids

Secondary: α-helix and β-pleated sheets

Tertiary: Three-dimensional conformation

Quaternary: Composed of more than one polypeptide chains

What is needed for proteins to be functional?

Posttranslational modifications

What are some examples of posttranslational modifications

N-terminus amino acid removed or modified

Individual amino acid residues modified

Carbohydrate side chains are sometimes attached

Polypeptide chains may be trimmed

Signal sequences are removed

Polypeptide chains often complexed with metals

Is protein folding considered random?

no

What does protein folding depend on?

chaperone molecules

What two diseases happen due to misfolded proteins

Scrapie and Bovine Spongiform Encephalopathy (BSE/mad cow disease)

What are clinical signs of scrapie and BSE

tremors, loss of coordination, death, weight loss, biting of limbs

What is the role of hemoglobin and myoglobin

they transport oxygen

What is the role of collagen and keratin

Structural proteins associated with skin, connective tissue, and hair

What are actin and myosin

Contractile proteins found in muscle tissue

What is tubulin

Basis of microtubule function in mitotic and meiotic spindle fibers

What are immunoglobulins

Function in immune system of vertebrates

What are histones

bind to DNA in eukaryotes

What is the role of transcription factors

regulate gene expression

What are enzymes

Specialize in catalyzing chemical reactions