Principles of Life, Ch. 10 Reading

Proteins in the ________ that lack signal sequences for destinations within the endomembrane system are usually secreted from the cell via vesicles that fuse with the cell membrane.

RER

Requires a promoter (special region of DNA to which the ________ binds) to tell ________ where to begin and which of the 2 strands to transcribe.

RNA polymerase

When not active in the ________ the ribosome exists as two separate subunits.

translation of mRNA

________ can technically start synthesizing anywhere, but DNA sequences and certain proteins tell ________ where to stand.

RNA

________ occurs when RNA polymerase catalyzes the formatio nof phosphodiester bonds between added nucleotides and the growing RNA chain, releasing pyrophosphate in the process.

Transcription

________ bind by hydrogen bonds and run antiparallel.

Codon & anticodon

________ A change in a genes sequence that changes the amino acid at that site in the encoded protein; usually causes a single amino acid change in the protein, which may or may not cause a change in function.

Missense mutations

________ read the DNA template in the 3 to 5 direction and synthesize the RNA strand in the 5 to 3 direction.

RNA polymerase

Helps export ________ from nucleus, bind proteins, and makes ________ stable.

mRNA

________ interrupt, but do not scramble, the DNA sequence of a gene.

Introns

TRNAs bind to particular ________.

amino acids

________ spliced out of pre- mRNAl 5 cap and 3 poly A tail added to mRNA.

Introns

When a(n) ________ is encoded by four codons, the first two letters are always the same.

amino acid

There is at least 1 specific tRNA molecule for each of the 20 ________.

amino acids

The synthesis of RNA using one strand of DNA as a template

Transcription

The synthesis of a protein (polypeptide); Takes place on ribosomes, using the information encoded in messenger RNA

Translation

The premise that information flows from DNA to RNA to polypeptide (protein)

Central Dogma of Molecular Biology

Most abundant RNA types

mRNA, rRna, and tRNA

Encodes protein information that comes from a template strand of DNA; leaves the nucleous

mRNA

One of the two strands of DNA that for a particular gene specifies the amino acids in a protein; Same base sequence as transcribed RNA but with Ts instead of Us

Coding Strand

The DNA strand that is transcribed to create an RMA transcript; Also refers to a strand of RNA that is used to create a complementary RNA

Template Strand

Several species of RNA that are incorporated into the ribosome; Involved in peptide bond formation

rRNA

A family of folded RNA molecules; each carries a specific amino acid and anticodon that will pair with the complementary codon in mRNA during translation; recognizes which amino acid needs to be added next

tRNA

a protein that binds to RNA polymerase, allowing the complex to bind to and stimulate the transcription of a specific class of genes

Sigma Factors

Proteins that assemble on a eukaryotic chromosome, allowing RNA polymerase II to perform transcription

Transcription Factors

The nucleotide sequences in a gene that directly specify amino acids in a protein

Coding Regions

A portion of a gene within the coding region that is transcribed into pre-mRNA but is spliced out prior to translation

Introns

A portion of a DNA molecule, in eukaryotes, that is present in the mature mRNA and codes for part of a polypeptide

Exons

The initial gene transcript before it is modified to produce functional mRNA; Also known as the primary transcript

Pre-mRNA

introns are removed, and both ends of the pre-mRNA are chemically modified

The primary transcript of a eukaryotic gene is modified in several ways before it leaves the nucleus

The last stage of RNA processing in eukaryotes, in which the transcripts of introns are excised through the action of small nuclear ribonucleoprotein particles (snRNP)

RNA Splicing

Short stretches of DNA that appear, with little variation, in many different genes

Consensus Sequences

A conserved sequence (A followed by several pyrimidines) in the interior of an intron that is used during intron splicing to attach the 5 end of the intron

Branch point

A complex of an enzyme and a small nuclear RNA molecule, functioning in RNA splicing

snRNPs

An RNA-protein complex that splices out introns from eukaryotic pre-mRNAs

Spliceosome

A chemically modified GTP added to the 5 end of mRNA; facilitates binding of mRNA to ribosome and prevents mRNA breakdown

5 Cap

A long sequence of adenine nucleotides (50-250) added after transcription to the 3 end of most eukaryotic cells

Poly A Tail

Three nucleotides in messenger RNA that direct the placement of a particular amino acid into a polypeptide chain

Codons

The set of instructions, in the form of nucleotide triplets, that translates a linear sequence of nucleotides in mRNA into a linear sequence of amino acids in a protein

Genetic Code

A sequence of three nucleotides in an mRNA that encodes a particular amino acid

Sense Codons

The mRNA triplet (AUG) that acts as a signal for the beginning of translation at the ribosome

Start Codon

An organism engineered to contain, and usually express, a gene from another organism

Transgenic organisms

When a DNA substitution alters the codon but does not alter the encoded amino acid; occur because of the degeneracy of the genetic code

Synonymous mutations

A change from a sense codon to a stop (nonsense) codon, causing a premature termination of translation and a shortened protein; usually also loss of function

Nonsense mutations

A change from a stop codon to a sense codon, causing additional amino acids to be added to the end of the protein; effects depend on how many amino acids are added to the end of the protein and how important that part of the protein is to function

Loss-of-stop mutations

The addition or deletion of a single or two adjacent nucleotides in a genes sequence; Results in the misreading of mRNA during translation and the production of a nonfunctional protein

Frame-shift mutations

The three nucleotides in transfer RNA that pair with a complementary triplet (a codon) in messenger RNA

Anticodon

certain bases in the third position of the anticodon are able to pair with more than just their normal partner

Wobble

highly specific enzymes that only bind to one amino acid and one corresponding tRNA, binds using energy

tRNA synthetases

initiation, elongation, termination

Three steps of translation

In protein translation, a combination of a small ribosomal subunit, an mRNA molecule, and the tRNA charged with the first amino acid coded for by the mRNA; formed at the onset of translation

Initiation Complex

The proteins involved in helping to assemble the translation initiation complex

Initiation factors

An RNA molecule with catalyctic activity

Ribozyme

The sequence within a protein that directs the protein to a particular organelle

Signal Sequence

Cutting a polypeptide chain; large polyproteins cannot function unless cut

Proteolysis

Addition of carbohydrates to proteins to form glycoproteins; helps direct some proteins to lysosomes, or help for conformation/regcognition functions at the cell surface

Glycosylation

the additon of phosphate groups to proteins, catalyzed by protein kinases; helps with cell signaling

Phosphorylation

• Used Neurospora (bread mold) to test hypothesis that
specific gene expression → specific enzyme activity.

• All alleles are expressed as phenotypes.

• Wild-type strains have all enzymes to catalyze chemical reactions to make cell constituents.

• They treated wild type Neurospora with mutagens and isolated mutant strains that needed specific nutrient supplements to grow

• For each mutant strain, the addition of just
one compound supported growth.

• Results suggested that each mutation caused a defect in only one enzyme in a metabolic pathway.

Beadle and Tatum

Translation in these species happens because the nuclear envelope separates transcription & translation.

DNA in nucleus, site of
transcription

Ribosomes in cytoplasm (ER), site of translation

mRNA is the intermediate messenger

Eukaryotes

Translation occurs on growing mRNA for these species.

Prokaryotes

RNA polymerases can only add new nucleotides to the __________ of a growing strand.

3'

Transcription factors only occur in...

Eukaryotes

The template of DNA is TGACT. What is the mRNA (with start location)?

5' ACUGA

The mRNA is the same as the ______ end of _______, just replace T with U.

5', non-template DNA

This is added to the 5' end of pre-mRNA. Protects mRNA from being degraded and facilitates mRNA binding to the ribosome.

G cap

Added to the 3' end while processing ends of eukayotic pre-mRNA. May assist in export from nucleus.

Poly A tail

Start codon that initiaties translation.

AUG

Initiation signal for translation is near which end of mRNA?

5'

Stop codons that stop translation and polypeptide is released.

UAA, UAG, UGA

mRNA consists of...

5' cap, Start codon, exons, stop codon, poly a tail

Name for the start codon (AUG)

Methionine

The DNA template for arginine is 3' GCC 5' what is the codon within mRNA?

5' CGG 3'

The DNA template for arginine is 3' GCC 5' what is the anticodon on the tRNA?

3' GCC 5'

Three tRNA binding sites on the large subunit of the ribosome.

A site, P site, E site

During elongation, charged tRNAs enter the _______ site, large subunit acts as peptidyl transferase.

A

During termination, the stop codon enters the _________ site.

Termination

The bond is broken between the tRNA and its amino acid at the _______ site.

P

When the first tRNA has released its methionine, it moves to the ______ site and dissociates from the ribosome.

E