Bio - Chapter 10: DNA Replication, Transcription, and Translation

Origin of replication

replication begins here

Helicases

Enzymes that untwist the double helix at the replication forks

Single-stranded binding proteins

Stabilize single-stranded DNA

Topoisomerase

Corrects “overwinding” ahead of replication forks by breaking, swiveling, and rejoining DNA strands

Primase

An enzyme that can start an RNA chain from scratch

DNA is always synthesized from

5’ to 3’

DNA polymerases

Enzymes that catalyze the elongation of new DNA at a replication fork

Telomerase

An enzyme that catalyzes the lengthening of telomeres in germ cells

Telomeres

Special nucleotide sequences at the ends of eukaryotic chromosomal DNA molecules

Gene expression

Process where DNA directs protein synthesis

Transcription

Synthesis of RNA using info in DNA

Primary transcript

Initial RNA transcript from any gene prior to processing

Translation

Synthesis of a polypeptide, using info in the mRNA

Template strand

Provides a template for ordering the sequence of complementary nucleotides in an RNA transcript

Non-template strand

Coding strand; same sequence as RNA strand except changes T to U

Triple code

of RNA nucleotides, non-overlapping codons

Codons

3 nucleotide codes

RNA polymerase

Pries DNA strands apart and bonds together RNA nucleotide

Promoter

DNA sequence where RNA polymerase attaches

Transcription unit

The stretch of DNA that is transcribed

3 stages of transcription

Initiation, elongation, termination

Transcription factors

Help bind RNA polymerase to initiate transcription

TATA box

A promoter that is crucial in forming the initiation complex in eukaryotes

5’ cap

The 5’ end receives this modified nucleotide

Poly-A tail

The 3’ end receives this

Introns

Non-coding DNA sequences

Exons

Coding DNA sequences

RNA splicing

Removes introns and joins exons, creating mRNA

Spliceosomes

Consist of a variety of proteins and several small nuclear ribonucleoproteins (snRNPs) that recognize splice sites

Essential amino acids

Not produced by the body

P site

Holds tRNA that carries the growing polypeptide chain

A site

Holds tRNA that carries the next amino acid

E site

The exit site, discharged tRNAs leave the ribosome

Mutation

Any change in the nucleotide sequence of a cell’s DNA

Missense mutations

Involve a single nucleotide and change the amino acid coding

Nonsense mutations

Change an amino acid codon into a stop codon

Silent mutations

Base substitution but does not change the resulting amino acid