Chapter 17: Gene Expression: From Gene To Protein

Front 1

Gene Expression

Back 1

The process by which DNA directs the synthesis of proteins. (or in some cases, just RNA's)

Front 2

Transcription

Back 2

Synthesis of RNA using information in the DNA.

Front 3

Messenger RNA (mRNA)

Back 3

Carries a genetic message from the DNA to the protein-synthesizing machinery of the cell.

Front 4

Translation

Back 4

Synthesis of a polypeptide using information in the mRNA. During this stage the cell must translate the nucleotide sequence into an amino acid sequence of a polypeptide.

Front 5

Ribosomes

Back 5

Site of translation. Molecular complexes that facilitate the orderly linking of amino acids into polypeptide chains.

Front 6

Primary Transcript

Back 6

The initial RNA transcript from any gene, including those specifying RNA that is not translated into protein.

Front 7

Triplet Code

Back 7

The genetic instructions for a polypeptide chain are written in the DNA as a series of nonoverlapping, three-nucleotide words that are translated into a chain if amino acids.

Front 8

Template Strand

Back 8

Provides the pattern or template for the sequence of nucleotides in an RNA transcript.

Front 9

Codons

Back 9

mRNA nucleotide triplets. Written in the 5' to 3' direction.

Front 10

Reading Frame

Back 10

Our ability to extract the intended message from a written language depends on reading the symbols in the correct groupings or reading frames.

Front 11

RNA Polymerase

Back 11

An enzyme which pries the two strands of DNA apart and joins together RNA nucleotides complementary to the end template strand, thus elongating the RNA polynucleotide .

Front 12

Transcription Unit

Back 12

The stretch of DNA downstream from the promoter that is transcribed into an RNA molecule.

Front 13

Start Point

Back 13

The nucleotide where RNA synthesis actually begins. Typically extends several dozen or more nucleotide pairs upstream from the start point.

Front 14

Transcription Factors

Back 14

In eukaryotes a collection of proteins which mediate the binding of RNA polymerase abd the initiation of transcription.

Front 15

Transcription Initiation Complex

Back 15

The whole complex of transcription factors and RNA polymerase II buns to the promoter.

Front 16

TATA Box

Back 16

Crucial promoter DNA sequence in forming the initiation complex at a eukaryotic promoter.

Front 17

RNA Processing

Back 17

Both ends of the primary transcript are alerted. In most cases certain interior sections of the RNA molecule are cut out and the remaining parts spliced together. This products a ready mRNA ready for translation.

Front 18

RNA Splicing

Back 18

The removal of large portions of the RNA molecule that is initially synthesized.

Front 19

Introns

Back 19

The noncoding segments of nucleic acid that lie between coding regions.

Front 20

Exons

Back 20

The other regions are exons because they are expressed usually being translated into amino acid sequences.

Front 21

Spliceosome

Back 21

Large complex made of proteins and small RNA's. Binds to several short nucleotide sequences along an intron, including key sequences at each end. Catalyze the splicing reaction.

Front 22

Ribozymes

Back 22

RNA molecules that function as enzymes.

Front 23

Alternative RNA Splicing

Back 23

A consequence of the presence of introns in genes is that a single gene can encode more than one kind of polypeptide. A process where many Bind to the unpaired DNA strands, keeping them from repairing. Genes are known to give rise to two or more different polypeptides, depending on which segments ARE treated as exons during RNA processing.

Front 24

Domains

Back 24

Structural and functional regions of proteins.

Front 25

Transfer RNA (tRNA)

Back 25

A cell must read a generic message to build a polypeptide. Originally a series of codons, the tRNA translates the codons. Transfers amino acids from the cytoplasmic pool of amino acids to a growing polypeptide in a ribosome

Front 26

Anticodon

Back 26

The particular nucleotide triplet that base pairs to a specific mRNA codon.

Front 27

Aminoacyl-tRNA Synthestases

Back 27

The family of enzymes which correctly match up tRNA and amino acid.

Front 28

Wobble

Back 28

The flexible base pairing at the end of an anticodon.

Front 29

Ribosomal RNA's (rRNA)

Back 29

A ribosome consists of a large subunit and a small subunit each made of proteins and rRNAs.

Front 30

P-Site

Back 30

Peptide-tRNA binding site. Holds the tRNA carrying the growing polypeptide chain.

Front 31

A Site

Back 31

Aminoacyl-tRNA binding site. Holds the tRNA carrying the next amino acid to be added to the chain.

Front 32

E Site

Back 32

Exit site. Discharged tRNA's leave the ribosome.

Front 33

Signal Peptide

Back 33

The polypeptides odd protein destined for the endomembrane system are marked by this. Targets the protein to the ER .

Front 34

Signal- Recognition Particle (SRP)

Back 34

The signal peptide, a sequence of about 20 amino acids at or near the leading end (N-terminus) of the polypeptide, is recognized as it emerges from the ribosome by a protein-RNA complex called a SRP.

Front 35

Polyribosome (Polysomes)

Back 35

Strings of ribosomes. Enable a cell to make copies of a polypeptide quickly.

Front 36

Mutations

Back 36

Changes responsible for the huge diversity of genes found among organisms. Responsible for new genes.

Front 37

Point Mutations

Back 37

Changes in a single nucleotide pair of a gene.

Front 38

Nucleotide-Pair Substitution

Back 38

The replacement of one nucleotide and its partner with another pair of nucleotides.

Front 39

Silent Mutation

Back 39

Has no observable effect on the phenotype. (Can occur outside genes)

Front 40

Missense Mutations

Back 40

Substitutions that change one amino acid to another one.

Front 41

Nonsense Mutation

Back 41

Causes translation to be terminated prematurely; the resulting polypeptide encoded by the normal gene. Most lead to nonfunctional Proteins.

Front 42

Frameshift Genes

Back 42

Occurs whenever the number of nucleotides inserted or deleted is not a multiple of three. Makes the protein almost certain to be nonfunctional.

Front 43

Mutagens

Back 43

A number of physical and chemical agents which interact with DNA in ways that cause mutations.

Front 44

Steps of Transcription

Back 44

1) Chromatin unwinds from associated histones.
2) Activator proteins bind to enhancer sequences.
3) DNA bending proteins bring activator proteins to the promoter.
4) Activator proteins interact with other transcription factors.
5) RNA polymerase II joins other proteins, making the transcription initiation complex.
6) The DNA strands unwinds, exposing 10-20 bases.
7) RNA polymerase II reads the DNA and it begins making single stranded RNA 5' to 3'.
8) RNA polymerase moves past an AAUAAA signal.
9) The pre-mRNA molecules is cut off downstream from the AAUAA signal.
10) Activator positions recognized the promoter region and the TATAA box.

Front 45

Steps of Translation:

Back 45

1) Mature mRNA leaves the nucleus.
2) The small ribosomal subunit binds to the mRNA.
3) The large and small subunits fall off the mRNA, and release the peptide.
4) The small subunit finds the start codon and the initiator tRNA binds to it.
5) The large ribosomal subunit binds to complete ribosome.
6) The next codon use recognized by an incoming tRNA to the A site.
7) A peptide bond is formed between the 2 amino acids.
8) The ribosome moves down the mRNA by one codon.
9) The empty trends leaves through the E Site.
10) The ribosomes comes to a stop codon: AUU, AGU, AUG.
11) A release factor binds to the A site.
12) A water molecule is added to the peptide chain, releasing it from the ribosome.