BIOLOGY CH 5 Flashcards
The place where helicase begins to unwind is a specific sequence of nucleotides on the chromosome called the __________ .
Origin of replication (ORI)
A chromosome would get tangled and eventually break, except that enzymes called ___________ cut one or both strands and unwrap the helix, releasing the excess tension created by the helicases.
Topoisomerase
An ______ primer must be synthesized for each template strand because DNA polymerase cannot start a new DNA chain from scratch.
RNA
RNA primer is synthesized by a set of proteins called the ____________, of which the central component is an ____________ called ____________.
RNA primer is synthesized by a set of proteins called the primase, of which the central component is an RNA polymerase called primase.
DNA polymerase reads the template strand in which direction?
From 3’ to 5’
DNA polymerase elongates a daughter strand by adding dNTPs to its _____ end.
3’
DNA pol is part of a large complex of proteins called the ________________ .
Replisome
The prokaryotic replisome contains __ components and the eukaryotic replisome contains __ components. Additional complexity in the eukaryotic system is required because replication machinery must also ___________ .
13 components prokaryotes; 27 components eukaryotes; unwind DNA from histone proteins
T/F: DNA pol checks each new nucleotide to make sure it forms a correct base-pair
True
The driving force for the polymerization reaction of DNA synthesis is?
The removal and hydrolysis of pyrophosphate (P2O7) from each new dNTP added to the chain
Eventually all RNA primers are replaced by DNA, and the fragments are joined by an enzyme called ____________ .
DNA ligase
T/F: Eukaryotes have several different DNA polymerase enzymes?
True
T/F: In eukaryotic replication, each chromosome has one ORI?
False, each chromosome has several
T/F: In prokaryotic replication, the one chromosome only has one origin?
True
_____________ are disposable repeats at the end of chromosomes. They are consumed and shorten during cell division.
Telomeres
When ________ becomes too short, they reach a critical length where the chromosome can no longer replicate.
Telomeres
What is the Hayflick limit?
The number of times a normal human cell type can divide until telomere length stops cell division
__________ is an enzyme that adds repetitive nucleotide sequences to the ends of chromsomes and therefore lengthens _________ .
Telomerase; telomeres
______________ can express telomerase, which can help the cells immortalize.
Cancer cells
What does it mean when a cell enters a ‘senescent state?’
Where they are alive but not dividing
What are 3 things a cell can do when their telomeres become too short?
- Active DNA repair pathways
- Enter a senescent state
- Apoptosis
What are germline mutations?
Mutations that can be passed onto offspring, since they occur in the germ cells (which give rise to gametes).
What do germ cells give rise to?
Gametes
T/F: Somatic mutations cannot pass onto offspring?
True
