AP Bio Unit 6 Vocabulary

Helicase

Protein that separates the two strands of parental DNA, starting at the point of origin (creates replication forks).

Single-strand binding protein

Protein that binds to and stabilizes single-stranded DNA until nucleotides become attached to the template.

Topoisomerase

Relieves the strain ahead of replication forks by breaking, swiveling, and rejoining DNA strands in front of the helicase.

Primase

Synthesizes an RNA primer at the 5’ end of the leading strand and further up at the lagging strand to create the starting point for an Okazaki fragment.

DNA Polymerase III

Uses parental DNA as a template to synthesize new DNA by adding nucleotides to their corresponding match from the template DNA strand or RNA primer.

DNA Polymerase I

Removes RNA nucleotides of primer from the 3’ end and replaces them with DNA nucleotides.

DNA Ligase

Joins okazaki fragments of lagging strand; on the leading strand, forms covalent bonds between adjacent nucleotides in one strand of DNA. Needed to join the Okazaki fragments together.

Purines

Adenine and Guanine, have two rings in their bases

Pyrimidines

Cytosine, Uracil, Thymine, have one ring in their bases.

Protein Synthesis

The process by which information stored in DNA is used to create proteins.

mRNA

RNA sequence of a DNA segment that specifies a polypeptides amino acid sequence (segments code for amino acids)

tRNA

Transfer RNA, transfers amino acids to the ribosome, dictated by the mRNA sequence.

rRNA

Ribosomal RNA, structural components of ribosome subunits (makes up a part of the ribosome)

Regulatory RNA

Controls gene expression by blocking transcription (stops making proteins when proteins are not needed/in excess).

RNA Polymerase

Enzyme that catalyzes the 5’ → 3’ synthesis of an RNA strand from a single DNA strand. (does not require a primer, unlike DNA polymerase).

Prokaryotic RNA Processing

RNA can be synthesized into proteins (transcription + translation) at once, since the DNA is free-floating in the cytoplasm, no nucleus .

Post-transcriptional modifications

Processes done to RNA transcripts before being shipped out of the nucleus to the ribosome.

Poly-Adenylation Tail

Modification, chain of Adenine residues added to the 3’ end of the transcript. Helps transport the mRNA out of the nucleus, prevents degradation/shortening, similar to telomeres.

5’ Capping

A modified nucleotide (GTP cap) is added to the 5’ end of the mRNA. Similar in function to the poly A tail, prevents degradation from digestive enzymes(?)

Exon splicing

Segments of the transcript (introns) are removed, remaining segments (exons) are spliced together to produce a matured transcript.

Introns

Interspersed sequences of nucleotides that do not code for functional parts of a polypeptide. They must be removed before the transcript can undergo protein synthesis.

Spliceosomes

Proteins and small RNAs, able to recognize the intron/exons and excise introns from the pre-mRNA.