Separates the DNA strands to allow for DNA replication

Also known as gyrase. Cuts both strands of the DNA molecule just upstream of the replication fork, lets the DNA untwist, and seals the strands back together again. This relieves tension from the separating strands and prevents damage to the DNA.

Single-strand binding protein

Binds to the separated strands of DNA during replication to stabilize them and prevent them binding back together.

Lays down a short primer of RNA bases on a bare strand of DNA. This gives the DNA polymerase a place to start replicating.

Main enzyme that replicates DNA. Extends primers laid down by primase & builds a new DNA strand complimentary to existing template strand. Like all DNA polymerases, it only copies in the 5’ – 3’ direction & cannot copy a bare strand but can extend primer

Removes RNA bases laid down as primers and replaces them with DNA bases. Begins after rest of DNA is copied, extending DNA strand just upstream of primer. Can't catalyze last bond between the final nucleotide it lays down & next nucleotide w/o ligase

Enzyme catalyzes binding of two adjacent DNA nucleotides to each other. It doesn't copy DNA, but seals nicks in DNA strands & repairs breaks in DNA molecules. Active in DNA replication, in general repair of DNA molecules, and is widely used in lab work.

Responsible for transcription. Binds to promoter region , separates DNA strands (only short distance at time) & synthesizes RNA strand using DNA strand as template. Like DNA polymerases, can only copy in 5’ – 3’ direction; but can copy from bare DNA

A region just upstream of a gene where the RNA polymerase binds. Different genes have different promoters, and this allows them to have different regulatory mechanisms.

A protein that binds to a DNA strand to regulate transcription. Transcription factors can initiate or prevent the transcription of a gene into mRNA.

Found in prokaryotes. A set of related genes (often encoding enzymes in the same pathway) that share a common regulatory mechanism.

A relatively short piece of newly replicated DNA on the lagging strand. These short fragments are necessitated by the fact that polymerases only copy in the 5’ – 3’ direction.

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Bio 121 Genetics pt2

Genetics terms for Bio 121 pt 2

Term	Definition
Helicase	Separates the DNA strands to allow for DNA replication
Topoisomerase	Also known as gyrase. Cuts both strands of the DNA molecule just upstream of the replication fork, lets the DNA untwist, and seals the strands back together again. This relieves tension from the separating strands and prevents damage to the DNA.
Single-strand binding protein	Binds to the separated strands of DNA during replication to stabilize them and prevent them binding back together.
Primase	Lays down a short primer of RNA bases on a bare strand of DNA. This gives the DNA polymerase a place to start replicating.
DNA polymerase III	Main enzyme that replicates DNA. Extends primers laid down by primase & builds a new DNA strand complimentary to existing template strand. Like all DNA polymerases, it only copies in the 5’ – 3’ direction & cannot copy a bare strand but can extend primer
DNA polymerase I	Removes RNA bases laid down as primers and replaces them with DNA bases. Begins after rest of DNA is copied, extending DNA strand just upstream of primer. Can't catalyze last bond between the final nucleotide it lays down & next nucleotide w/o ligase
DNA ligase	Enzyme catalyzes binding of two adjacent DNA nucleotides to each other. It doesn't copy DNA, but seals nicks in DNA strands & repairs breaks in DNA molecules. Active in DNA replication, in general repair of DNA molecules, and is widely used in lab work.
RNA polymerase	Responsible for transcription. Binds to promoter region , separates DNA strands (only short distance at time) & synthesizes RNA strand using DNA strand as template. Like DNA polymerases, can only copy in 5’ – 3’ direction; but can copy from bare DNA
Promoter	A region just upstream of a gene where the RNA polymerase binds. Different genes have different promoters, and this allows them to have different regulatory mechanisms.
Transcription factor	A protein that binds to a DNA strand to regulate transcription. Transcription factors can initiate or prevent the transcription of a gene into mRNA.
Operon	Found in prokaryotes. A set of related genes (often encoding enzymes in the same pathway) that share a common regulatory mechanism.
Okazaki fragment	A relatively short piece of newly replicated DNA on the lagging strand. These short fragments are necessitated by the fact that polymerases only copy in the 5’ – 3’ direction.

Created by: naomicreer

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