AP Biology Unit 6 Topic 3: Transcription

Flashcards covering key vocabulary; terms and definitions related to transcription, RNA processing, and translation.

Gene Expression

The process by which DNA directs the synthesis of proteins.

Proteins

Polypeptides made of amino acids

Transcription

The synthesis of RNA using information from DNA, occurring in the nucleus.

Translation

The synthesis of a polypeptide using information from RNA, occurring at the ribosome.

Messenger RNA (mRNA)

RNA synthesized during transcription that carries information from DNA at the nucleus to ribosomes in the cytoplasm.

Transfer RNA (tRNA)

RNA molecules that carry specific amino acids and can attach to mRNA via their anticodon.

Ribosomal RNA (rRNA)

RNA that helps form ribosomes and links amino acids together.

DNA sequence

Read in groups of three called the triplet code

Codon

A nucleotide sequence on mRNA read in groups of three, coding for amino acids.

Template Strand

The DNA strand used as a template for creating mRNA during transcription.

mRNA molecules formed are

Anti parallel and complementary to the DNA nucleotides

Codons

64 different codon combinations

61 code for amino acids

3 are stop codons

Redundancy

More than one codon codes for each amino acid

Initiation (Transcription)

The first step in transcription where RNA polymerase attaches to the promoter region of DNA. Does not need primer to attach. Promoter regions are upstream of the desired gene to transcribe

Initiation in Eukaryotes

Promoter region is called TATA box

Needs transcription factors to bind

Initiation in Prolaryotes

RNA polymerase can bind directly to promoter

Elongation (Transcription)

RNA polymerase opens the DNA triplet code of the template strand

Moves in the 3’ to 5’ direction

mRNA transcript elongates 5’ to 3’

RNA polymerase moves downstream

Only opens small sections of DNA at a time

Pairs complementary RNA nucleotides

The growing mRNA strand peels away from the DNA template strand

DNA double helix reforms

Termination (Transcription)

The final step in transcription when RNA polymerase detaches from DNA and releases the mRNA transcript.

Termination in Eukaryotes

RNA polymerase transcribes a sequence of DNA called the polyadenylation Signal sequence

Codes for polyadenylation signal (AAUAAA)

Releases pre mRNA from the DNA

Must undergo modifications before translation

Termination in prokaryotes

Transcription proceeds through a termination sequence

Causes a termination signal

RNA polymerase detaches

mRNA transcript is released and goes to translation

mRNA doesn’t need modifications

Pre-mRNA Modifications

Modifications that must occur to eukaryotic pre-mRNA before it can be translated, including 5' cap, poly-A tail, and RNA splicing.

RNA splicing

Sections of the pre mRNA called interns are removed and then exons are joined together

Introns

Intervening sequence do not code for amino acids

Exons

Expressed sections code for amino acids

Alternative Splicing

A process allowing a single gene to code for multiple proteins by rearranging exons and removing introns.

Amino Acid

The building blocks of proteins, coded for by codons in mRNA.