Biology 120 Chapter 13

Front 1

Promoter

Back 1

Is a control sequence for transciption.

Front 2

Transcription Unit

Back 2

Is the section of the gene that is copied into an RNA molecule.

Front 3

Transcription Initiation

Back 3

The molecular machinery that carries out transcription assembles at the promoter and begins synthesiszing an RNA copy of the gene.

Front 4

Transcription Elongation

Back 4

The RNA polymerase moves along the gene extending the RNA chain.

Front 5

Transcription Termination

Back 5

Transciption ends and the RNA molecule (the transcript) and the RNA polymerase are released from the DNA template.

Front 6

RNA Polymerase II

Back 6

The enzyme that transcribes protein-coding genes.

Front 7

TATA Box

Back 7

Is located in the promoter about 30 base pairs upstream of the transcription starting point. It determines where transcription will initiate.

Front 8

Transition Initiation Complex

Back 8

The combination of the transcription factors and RNA Polymerase II.

Front 9

Transcription Factors

Back 9

Bind to the promoter in the area of the TATA box to begin the initiation of transcription.

Front 10

5' Guanine Cap

Back 10

Protects the mRNA from degradation and is the site where ribosomes attach at the start of translation.

Front 11

Polyadenylation Signal

Back 11

Signals the RNA polymerase to strop transcription.

Front 12

Poly (A) Tail

Back 12

Enables the mRNA produced from the pre-mRNA to be translated efficiently and protects it form attack by RNA-digesting enzymes in the cytoplasm.

Front 13

Introns

Back 13

Are non-protein coding sequences that interrupt the protein-coding sequence.

Are transcibed into pre-mRNAs but are removed from pre-mRNAs during processing in the nucleus.

They are about 6 times the length of exons (in humans).

Front 14

Exons

Back 14

The amino-acid coding sequences that are retained in finished mRNAs.

Front 15

mRNA Splicing

Back 15

Occurs in the nucleus.

Removes introns from pre-mRNAs and joins exons together.

Front 16

Splicsosome

Back 16

Where mRNA splicing takes place.

It is a complex formed between the pre-mRNA and a handful of small ribonucleoprotein particles.

Front 17

Ribonucleoprotein Particle

Back 17

Is a complex of RNA and proteins.

Front 18

Small Ribonucleoprotein Particles

Back 18

The ones involved in mRNA splicing are located in the nucleus. Each consists of a relatively short small nuclear RNA (sRNA) bound to a number of proteins. They are known as snRNPs. See page 298 for diagram!!

Front 19

Alternative Splicing

Back 19

Greatly increases the number and variety of proteins encoded in the cell nucleus without increasing the size of the genome.

It causes us to further consider the one gene-one polypeptide hypothesis; for some genes at least, one gene may specify a number of polypeptides, each of which has a related function.

*(Certain exons are also removed with the introns to make different type of muscles).

Front 20

Exon Shuffling

Back 20

A process by which existing protein regions or domains, already selected for due to their useful functions, are mixed into novel combinations to create new proteins.

Front 21

Translation

Back 21

The assembly of amino acids into polypeptides on ribosomes.

Front 22

Transfer RNA (tRNA)

Back 22

Bring the amino acids to the complex/ribosome to be joined, one-by-one, into the polypeptide chain.

Front 23

Anticodon

Back 23

The three-nucleotide segment that base pairs with a codon in mRNAs.

The anticodon and the codon pair in an antiparallel manner (same as the two strand in the DNA helix)!!

Front 24

Wobble Hypothesis

Back 24

Proposed that the complete set of 61 codons can be read by fewer than 61 distinct tRNAs because of the particular pairing properties of the bases in the anticodons.

EX) In many cases, the same tRNA's anticodon can read codons that have either U or C in the third position (UUU or UUC).

Front 25

Aminoacylation or Charging

Back 25

The process of adding an amino acid to a tRNA.

Front 26

Aminoacyl-tRNA

Back 26

Is the finished product of charging, a tRNA linked to its "correct" amino acid. The energy in the aminoacyl-tRNA eventually drives the formation of the peptide bond linking amino acids during translation.

Front 27

Aminoacyl-tRNA Synthetases

Back 27

Is a collection of different enzymes that catalyzes aminoacylation.

Front 28

Ribosomes

Back 28

Are ribonucleoprotein particles that carry out protein synthesis by translating mRNA into chains of amino acids.

Front 29

A Site (Aminoacyl Site)

Back 29

Where the incoming aminoacyl-tRNA (carrying the next amino acid to be added to the polypeptide chain) binds to the mRNA.

Front 30

P Site (Peptidyl Site)

Back 30

Where the tRNA carrying the growing polypeptide chain is bound.

Front 31

E Site (Exit Site)

Back 31

Where an exciting tRNA binds as it leaves the ribosome.

Front 32

Translation Initiation

Back 32

The translation components assemble on the start codon of the mRNA.

Front 33

Translation Elongation

Back 33

The assembled complex reads the string of codons in the mRNA one at a time while joining the specified amino acids into the polypeptide.

Front 34

Translation Termination

Back 34

Completes the translation process when the complex disassembles after the last amino acid of hte polypeptide specified by the mRNA has been added to the polypeptide.

Front 35

Ribosome Binding Site

Back 35

A short, specific RNA sequence.

Front 36

Reading Frame

Back 36

The series of codons for the polypeptide encoded by the mRNA.

Front 37

Peptidyl-tRNA

Back 37

tRNA linked to a growing polypeptide chain containing two or more amino acids.

Front 38

Elongation Factor (EF)

Back 38

The protein that facilitates the binding of the appropriate aminoacyl-tRNA to the codon in the A site of the ribosome. Another EF is used when the ribosome translocates along the mRNA to the next codon. This proteins are bound to the aminoacyl-tRNA and are released once its job is completed.

Front 39

Peptidyl Transferase

Back 39

Catalyzes the formation of the peptide bond between the C-terminal end of the growing polypeptide on the P site tRNA and hte amino acid on the A site tRNA.

Front 40

Release Factor (RF)

(also called the termination factor)

Back 40

Binds in the A site and causes the ribosome to disassemble into its subunits.

It is a protein.

Front 41

Polysome

Back 41

The entire structure of an mRNA molecule and the multiple ribosomes attached to it.

Front 42

Chaperones or Chaperonins

Back 42

Assist many proteins in the folding process by combining with the folding protein, promoting correct 3-D structures and inhibiting incorrect ones.

Front 43

Cotranslational Import

Back 43

When the signal sequence/signal peptide (a short segment of amino acids near the N-terminal end) is recognized by a signal recognition particle that initiates a series of steps that ultimately result in the polypeptide entering the lumen (interior) of the rough ER.

Front 44

Post-Translational Import

Back 44

When proteins are sorted to the nucleus, mitochondria, chloroplasts, and micro-bodies after they have been made on free ribosomes in the cytosol.

Proteins that go to the mitochondria, chloroplasts and micro-bodies have short amino acid sequences called transit sequences at their N-terminal ends.

Proteins that go to the nucleus have short amino acid sequences called nuclear localization signals.

Front 45

Mutations

Back 45

Changes in the sequence of bases in the genetic material.

Front 46

Base-Pair Substitution Mutations

Back 46

Involve a change of one particular base to another in teh genetic material. This will cause a change in a base in a codon in mRNA.

Front 47

Missense Mutation

Back 47

Alters the codon to specify a different amino acid (resulting in a different amino acid sequence).

EX) sickle cell disease is due to a missense mutation

Front 48

Nonsence Mutation

Back 48

Changes a sense (amino-acid coding) codon to a nonsense (termination) codon in the mRNA. Results in a premature "stop" and a shorter-than-normal polypeptide.

Front 49

Silent Mutation

Back 49

A base-pair substitution mutation that does not alter the amino acid specified by the gene because the changed codon specifies the same amino acid as in the normal polypeptide.

Front 50

Frameshift Mutation

Back 50

When a single base pair is deleted or inserted in teh coding region of a gene (causing the reading frame of the resulting mRNA to be altered). The resulting polypeptide is usually non-functional.