Biol 190 Lec 19

Sequence of nucleotides within a chromosome that provides the instructions for RNA synthesis and eventually a functional protein; macromolecule: nucleic acid

All of the genes within the body

One of the separated parental strands (AKA OG strand); 3' to 5'

The process by which information encoded in DNA directs the synthesis of proteins

Yes, but polypeptides of the same family

-Bacteria: DNA transcribed in cytoplasm->mRNA is translated into polypeptide (in cytoplasm)

-Eukaryote: DNA transcribed in nucleus-> Pre-mRNA undergoes RNA processing-> mRNA comes out of the nucleus into cytoplasm-> ribosomes will convert mRNA into a polypeptide (translation)

Uracil, single-stranded, ribose sugar

No

1. Protection: there is only one copy of each gene in the entire cell

2. Amplification: transcription of one gene can make many RNAs

3. Control: adds another level of control over expression of protein product

Results: mRNA (mature RNA); Location: Leaves nucleus through nuclear pore

Results: Proteins; Location: Cytoplasm

Both use DNA template strands

Replication: turns DNA into more DNA; Gene expression: -DNA->mRNA; only one strand of the DNA template is used (template strand)

Non-template (coding) strand

the RNA copy of a gene used in the cell to produce a polypeptide (protein); same sequence of the non-template strand except T is replaced by U; antiparallel

99; does not make proteins

1

A sequence before a gene (sequence upstream of a gene); signifies the presence of a gene

No

1. Positions RNA polymerase

2. Identifies template strand (promoter reads the template strand)

Transcription factors (proteins) sit at a promoter (every gene has its own combo of transcription factors); correct combo of transcription factors allows RNA polymerase to sit on the promoter

1. Initiation

2. Elongation

3. Termination

Initiation:

-requires the right combination of transcription factors on promoter

-RNA polymerase binds the promoter

1. Begins unwinding the DNA strands

2. Begins synthesizing mRNA at the start point

No, by itself it can catalyze the formation of RNA using a template

Elongation:

-only one mRNA strand is made by RNA polymerase

-DNA template strand is read and complementary mRNA is made from a 5' to 3' direction

-RNA polymerase rewinds the DNA behind it

No

Termination: RNA polymerase "falls off" the template strand where the RNA polymerase/DNA interaction is unstable (where a signal signifies the end of the gene)

-Bacteria: termination signal

-Eukaryotes: polyadenylation signal (AAUAAA)

RNA processing:

-modification of mRNA ends

-RNA splicing

No, RNA splicing makes one gene equal more than one protein

-5' cap: 5' end receives a modified nucleotide (guanine)

-poly-A tail on the 3' end: a lot of adenines on 3' end

-Aid the export of mRNA to cytoplasm

-Protect mRNA from degradation

-Help ribosomes attach to the 5' end during translation

DNAses (enzymes like DNA) & RNAses would live and destroy single-stranded nucleic acids

Coding and noncoding segments

Noncoding regions (does not provide instructions for proteins)

Expressed, translated sequences (coding regions)

Removes introns and joins exons, creating an mRNA molecule with a continuous coding sequence

A snRNP (small nuclear ribonucleoprotein) at each junction generates a spliceosome (complex of RNA and enzymatic proteins) from accessory factors to join two exons together by splicing out introns

Consumed by DNAses to become nucleotides again

An intron for one mRNA can be an exon for another mRNA

Exons from the same gene are joined in different combinations, leading to different mRNA transcripts; creates protein diversity

Yes, the different exons of one gene can form different domains in a new protein

Discrete regions called domains

Spliced out-> the absence of an entire (internal) region from a protein

1. RNA is single-strand-> form hydrogen bonds with its bases to DNA, proteins or other RNAs

2. Forms a 3D structure because of its ability to base pair with itself (w/ hydrogen bonds)

3. Acts as an enzyme (ribozymes) b/c of its varied structure and functional groups

An RNA enzyme; RNA catalyst (i.e. proteins are not the only catalyst)

Some are

1. mRNA

2. Amino acids

3. tRNA

4. Ribosome

mRNA: the "blueprint" intermediate; every three RNA nucleotides represent one codon

Three nucleotides that codes for one amino acid in a polypeptide (not considered a protein yet); 3 nucleotides-> 1 codon-> 1 amino acid

No

Amino acid: multiple codons can encode the same amino acid (redundancy); no ambiguity (e.g. UCU is Serine and cannot represent another amino acid)

Wobble: the only position that can change without making a different amino acid

1; Methionine (AUG)

3

20

tRNA: a 4 cloverleaf (arms) structure with codon/anticodon interactions are held together by H+ bonds; function: carry amino acid needed for translation; an amino acid covalently binds to its 3' end by the enzyme: aminoacyl-tRNA synthetase

20 for each of the 20 amino acids

Two parts in its active site:

1. For amino acids

2. For tRNA; needs ATP to bind the amino acid to tRNA

tRNA becomes charged (due to the charged carboxyl group of the amino acid attaching to the tRNA)

Complementary bases form hydrogen bonds between the antiparallel anticodon (tRNA: 3'->5') and codon (mRNA: 5'->3') stabilizing the interaction

Codon/anticodon

Coding strand: codon; Template strand: anticodon

Ribosome: composed of two rRNA (small and large) subunits and proteins; site of translation where mRNA, tRNA, and rRNA are present

Has three locations: E, P, A

-A site: first site; aminoacyl-tRNA binding site (charged tRNA sits here)

-P site: peptidyl-tRNA binding site; a different tRNA w/ a growing polypeptide chain linked to it

-E site: exit site; a third tRNA w/ nothing on it

Has the mRNA binding site

A correct match between a tRNA and an amino acid (mRNA codon), done by the enzyme aminoacyl-tRNA synthetase

GTP

1. Initiation

2. Elongation

3. Termination

Initiation:

1. The small ribosomal submit binds the mRNA first (at the cap) and scans along until it finds the start codon, AUG (codes for methionine attached to the initiator tRNA)

2. The large ribosomal subunit attaches to begin translation (requires energy)

1. tRNA + methionine

2. Small ribosomal subunit

3. Both bound to mRNA

Elongation: Large subunit catalyzes 2 reactions:

1. Breaks the bond between the growing polypeptide chain and the tRNA (at the P site)

2. Catalyzes formation of peptide bond between Met and the next aa; every aa needs 2 GTP

Termination:

1. Ribosome reaches a stop codon on mRNA

2. Release factor (protein) promotes hydrolysis

3. All components dissociate

1. The first few amino acids are a signal peptide that tell the cell where to go with the polypeptide

2. Signal-recognition particle (SRP) binds to the signal peptide to take it to the lumen of the Rough ER

3. SRP binds to receptor protein at the Rough ER

4. SRP detaches, synthesis resumes

5. Enzyme cuts off signal peptide

6. Polypeptide folds into final confirmation

Enzyme assistants:

1. Proteolysis (polypeptide cuts into thirds, each piece acts as a protein)

2. Phosphorylation

3. Glycosylation (adds sugar)

-all takes place in the golgi apparatus

Overlapping of the two processes/occur at the same time

P: Yes, both occurs in cytoplasm; E: No, transcription (nucleus) and translation (cytoplasm) occur in different places

Can couple transcription and translation (multiple ribosomes can translate a single mRNA simultaneously, forming a polyribosome); do not need to process mRNA