BIO 151 14.5-.6

What is the name of the subunit that acts as the sliding clamp, which keeps the replicating enzyme complex attached to the template in eukaryotic cells.

DNA polymerase II

Which of the following facilities the reversal of damage to out hereditary material before a permanent mutation can occur?

DNA repair systems

The two main eukaryotic DNA polymerase that extends DNA are

Delta, epsilon

Based on replication proteins, DNA replication in archaea is most similar to that of...

Eukaryotes

Which types of cells have more than one origin of replication

Eukaryotes

In a aging cell, the activity of telomerase would be

Low

The level of telomerase stays high in _____, despite their age.

Lymphocytes

_____ repair is responsible for removing bases that were incorrectly incorporated into DNA during replication.

Mismatch

What type of repair mechanism is responsible for removing bases that were incorrectly inserted into DNA during replication?

Mismatch repair

Agents that cause mutation are known as

Mutagens

Radiation, UV light, x-rays, and chemicals in the environment can cause mutations in DNA and are therefore referred to as

Mutagens

The two general categories of DNA repair are

Nonspecific Specific

Damage caused by UV light leading to thymine diners is corrected during photo repair by the enzyme

Photolyase

The enzyme ___ can repair UV damage by binding to a thymine dimmer and cleaving it, therefore restoring two thymine.

Photolyase

Which of the following enzymes involved in DNA replication are found in all three types of cells (bacterial, archaeal, and eukaryotic)?

Sliding Clamp Clamp loader Primase Polymerases Helicase

Which enzyme prevents chromosomal shortening by attaching a repeat sequence to the ends of chromosomes?

Telomerase

Short, repeated sequences of DNA are characteristic of

Telomeres

Which of the following are short repeats of DNA on the ends of eukaryotic chromosomes?

Telomeres

____ are short protective repeats of DNA on the ends on eukaryotic chromosomes which are generated by the enzyme _____.

Telomeres Telomerase

If normal fibroblast cells are grown in cell culture and the enzyme telomerase is introduced in them.

The cells show an increased lifespan

DNA repair mechanisms have likely evolved because

There is no way for cells to avoid exposure to mutagens

Why do eukaryotic cells have multiple origins of replication?

To ensure timely replication of multiple, relatively large chromosomes.

Which E. Coli genes encode the proteins required to preform excision repair?

UvrA,uvrB, and uvrC

The amount of the enzyme ___ declines within cells as they age.

telomerase

What is the name of the regions at the ends of the eukaryotic chromosomes?

telomeres

cancer cells contain

Higher levels of telomerase than normal, non cancer cells.

What is the function of the UrvABC complex in exclusion repair in E. Coli?

It binds to the damaged DNA and removes damaged DNA by cleaving a single strand on each side

The function of telomeres is to

Protect the ends of chromosomes

____ repair systems target a single kind of lesion in DNA and repair only the damage, while ____ repair systems use a single mechanism to repair multiple kinds of lesions in DNA.

Specific Nonspecific

The enzyme ___ contains a small internal piece of RNA, which is used as a template to extend the end of a linear DNA molecule.

Telomeres

The problems in replicating the ends of linear chromosomes are caused by (choose all that apply)

The directionality of polymerases The need of a primer

Which origins are more sequence-specific?

Οri/C

List several differences in prokaryotic and eukaryotic replication.

* structure of chromosome (linear vs circular) * number of origins of replication * complexity of enzymology

Order the steps in excision repair from first to last, starting at the top.

1. Recognition of damage 2. Removal of the damaged region 3. Resynthesis using the information on the un damaged strand as a template

Match the types of repair mechanism with how they work : 1.Specific 2. Nonspecific

1.Target a single kind of lesion in DNA and repair the damage 2. Repair multiple kinds of lesions in DNA, using a single mechanism

Telomerase uses which of the following as a template

A short internal RNA

What is a thymine dimer?

A site where two adjacent thymine bases become covalently cross-linked to each other.

How are the origins of replication adjusted in eukaryotic cells, so that early in the embryonic development of eukaryotic organisms of DNA can be replicated faster?

Cells can increase the number of origins used in early development.

Telomeres are related to

cellular aging

DNA replication in eukaryotic cells is complicated by the fact that eukaryotic cells have

linear chromosomes

In order for mismatch repair to occur in a bacterial cell, the enzyme machinery must be able to

Distinguish between the template strand and a newly synthesize strand.

Cells have several non-specific repair pathways. Indicate which of the following are two general categories of repair mechanism:

Error-free Error-prone

In E. Coli, the SOS response is part of the

Error-prone repair mechanism

The type of primase is a combination of RNA polymerase and DNA polymerase that makes short RNA primers and then extends them with DNA to produce the final primer:

Eukaryotic

In which type of repair mechanism a damaged region of DNA is removed and then replaced by DNA synthesis

Excision repair

In order for mismatch repair ro occur in a bacterial cell, the enzyme machinery must be able to distinguish between the template strand and a newly synthesized strand. How is that activated?

For a short period of time after replication, the sequence GATC is methylated at the A only on the template strand.

On this strand, the removal of the last primer leaves a gap that cannot be primed at the ends of the chromosome.

Lagging