Lecture 11

Question 1

What are four major problems of DNA replication?

Answer 1

Replication error, replication fork stalling, supercoiling of genomic DNA, & shortening of genomic DNA

Question 2

Describe the process of initiation of DNA replication

Answer 2

Origin Recognition Complex (ORC) destabilizes replication origin and recruits a replicative helicase complex (MCM) to break apart and separate the strands of DNA. Replication Protein A (RPA) holds the replication bubble open.

Question 3

Which DNA polymerase initiates DNA replication on both sides?

Answer 3

Polymerase alpha-primase

Question 4

Which DNA polymerase replicates the leading strand?

Answer 4

Polymerase epsilon with the help of PCNA as a clamp to hold it to the DNA strand

Question 5

Which DNA polymerase replicates the lagging strand?

Answer 5

Polymerase alpha-primase to Polymerase delta

Question 6

How is the lagging strand replicated?

Answer 6

RNA primers produce Okazaki fragments along the DNA strand. RNase H removes the primers and allows for missing base pairs to be synthesized. FEN1 removes any additional displaced base pairs. DNA ligase fuses the newly formed DNA together

Question 7

How does the DNA correct for mispaired bases?

Answer 7

Exonucleases correct mispaired bases by removing them and replacing them with correct bases

Question 8

What is Meier-Gorlin syndrome?

Answer 8

It is caused by a mutation in one of several genes including ORC1, ORC4, ORC6, CDT1, and CDC6. It causes growth defects before birth that result in underdeveloped parts of the body and even dwarfism (normal intellect, however)

Question 9

Which polymerases proofread replication errors?

Answer 9

Polymerases delta and epsilon

Question 10

What happens during replication fork stalling?

Answer 10

DNA polymerase and helicase decouple from one another, causing helicase to continually open the double stranded DNA without DNA polymerase continually base pairing each strand (results in unpaired DNA)

Question 11

What is ATR?

Answer 11

ATR (ataxia telangiectasia and Rad3-related protein) is a serine/threonine-specific protein kinase that is involved in sensing DNA damage and activating the DNA damage checkpoint, leading to cell cycle arrest

Question 12

What is Seckel syndrome?

Answer 12

Mutations in ATR cause growth defects and mental retardation

Question 13

What do topoisomerases do?

Answer 13

Topoisomerases prevent DNA from supercoiling by nicking and sealing DNA when it begins unwarranted coiling

Question 14

How often do telomeres shorten?

Answer 14

Telomeres shorten with every cell division until they are critically short and trigger a permanent growth arrest called cellular senescence

Question 15

What is idiopathic pulmonary fibrosis?

Answer 15

Pulmonary fibrosis is a disease in which tissue deep in your lungs becomes thick and stiff, or scarred, over time. The formation of scar tissue is called fibrosis

Question 16

What is Aplastic anemia?

Answer 16

A lack of telomerase prevents the proliferation of hematopoietic stem cells. Therefore, an insufficient amount of RBCs, WBCs, or platelets are formed

Question 17

What is Dyskeratosis Congenita (DK)?

Answer 17

Dyskeratosis congenita (DKC), also called Zinsser-Cole-Engman syndrome, is a rare progressive congenital disorder that in some ways resembles premature aging . The disease mainly affects the integumentary system (i.e, the skin, the organ system that protects the body from damage), with a major consequence being anomalies of the bone marrow.