3-4

Proteins

Polypeptides made from amino acids.

Amino acids

Building blocks of proteins linked by peptide bonds.

Gene expression

Process where DNA directs protein synthesis.

Transcription

Synthesis of RNA using DNA information.

Translation

Synthesis of polypeptides from RNA information.

Nucleus

Cell organelle where transcription occurs.

Ribosome

Site where translation occurs.

Messenger RNA (mRNA)

Carries genetic information from DNA to ribosomes.

Transfer RNA (tRNA)

Brings specific amino acids to ribosomes during translation.

Ribosomal RNA (rRNA)

Forms ribosomes and links amino acids.

Template strand

DNA strand used for RNA synthesis.

Codon

Three-nucleotide sequence on mRNA coding for amino acids.

Triplet code

Groups of three nucleotides in DNA coding for amino acids.

64 codons

Total combinations of codons in genetic code.

61 coding codons

Codons that specify amino acids.

3 stop codons

Codons that signal termination of translation.

Reading frame

Correct grouping of codons during translation.

Initiation

First step of transcription where RNA polymerase binds.

Elongation

RNA polymerase synthesizes mRNA strand.

Termination

End of transcription when RNA polymerase detaches.

Promoter region

DNA sequence where RNA polymerase binds to start transcription.

TATA box

Eukaryotic promoter region aiding RNA polymerase binding.

Polyadenylation signal

Sequence signaling termination in eukaryotic transcription.

5' cap

Modified guanine nucleotide added to mRNA's 5' end.

Poly-A tail

Adenine nucleotides added to mRNA's 3' end.

RNA splicing

Removal of introns and joining of exons in mRNA.

Introns

Non-coding sequences removed during RNA splicing.

Exons

Coding sequences retained in mature mRNA.

Alternative splicing

Single gene coding for multiple polypeptides.

mRNA modifications

Changes to pre-mRNA before translation.

Cytoplasm

Location where mature mRNA is translated.

RNA polymerase

Enzyme that synthesizes RNA from DNA template.

Transcription factors

Proteins aiding RNA polymerase binding in eukaryotes.

Anticodon

tRNA sequence complementary to mRNA codon.

Base pairing

A=U, C=G in RNA transcription.

Cysteine (Cys)

Amino acid coded by specific mRNA codon.

Serine (Ser)

Amino acid produced during translation from mRNA.

Mature mRNA

Processed mRNA ready for translation.

RNA nucleotides

Building blocks of RNA, paired during transcription.

Translation

Synthesis of polypeptides from mRNA information.

Ribosome

Site where translation occurs; composed of subunits.

tRNA

Transfer RNA that carries amino acids to ribosomes.

Anticodon

tRNA region complementary to mRNA codon.

Aminoacyl-tRNA synthetase

Enzyme attaching amino acids to tRNA.

Charged tRNA

tRNA carrying an amino acid for translation.

mRNA

Messenger RNA that codes for amino acids.

Initiation

First stage of translation; starts with AUG codon.

Elongation

Second stage; amino acids are added to polypeptide.

Termination

Final stage; stop codon signals polypeptide release.

Codon

Three-nucleotide sequence on mRNA coding for amino acid.

Stop codon

Signals termination; does not code for amino acids.

Peptide bond

Bond formed between amino acids during elongation.

Translocation

Movement of tRNA from A site to P site.

Ribosomal subunits

Small and large parts of ribosomes; differ in size.

Prokaryotic ribosome

30s small subunit and 40s large subunit.

Eukaryotic ribosome

40s small subunit and 60s large subunit.

A site

Amino acid site; holds next tRNA.

P site

Polypeptide site; holds growing polypeptide chain.

E site

Exit site for tRNA after amino acid transfer.

Codon recognition

tRNA anticodon pairs with mRNA codon in A site.

Peptide bond formation

Links amino acids during elongation.

Common ancestry

All organisms share the same genetic code.

Primary structure

Linear chain of amino acids in a protein.

Secondary structure

Coils and folds formed by hydrogen bonds.

Tertiary structure

Overall 3D shape due to side chain interactions.

Quaternary structure

Interaction of multiple polypeptide chains.

Chaperone proteins

Assist in correct folding of polypeptides.

Retroviruses

Viruses like HIV that reverse genetic information flow.

Reverse transcriptase

Enzyme converting RNA to DNA in retroviruses.

Functional protein

Active protein resulting from correct translation and folding.