DNA replication

Question 1

Why is DNA replication so important to the growth and development of a multi-cellular organism?

Answer 1

• DNA is important in the function of cells - codes for proteins and traits
• during cell division, some DNA should also go into the ‘daughter cell’
• Genetic continuity

Question 2

Where does DNA replication occur?

Answer 2

In Eukaryotic cell, it occurs in the nucleus. It starts at the “origin” (part identified by certain DNA sequences)

Question 3

When does DNA replication happen?

Answer 3

During Interphase (…)

Question 4

Who helps with the process of DNA replication?

Answer 4

Enzymes

Question 5

The 1st step for DNA Replication: __________ (also, where?)

Answer 5

• The DNA helix is unraveled
• Helicase breaks the H bonds - creates a replication fork

Extra enzymes:

• SSB prevents h-bond formation - ammealing
• Gyrose - prevents tension

Question 6

Which Enzyme unwinds the two strands of DNA? And How?

Answer 6

Helicase (the unzipping enzyme);

It breaks through the Hydrogen Bonds that hold DNA bases together

Question 7

What is the second step of DNA replication?

Answer 7

binding of RNA Primase to the strand

Question 8

What is RNA Pirmase and what does it do?

Answer 8

An enzyme that synthesizes short RNA sequences called primers.

During DNA replication, an RNA primer serves as a starting point for DNA polymerase, which builds complementary DNA.

Question 9

What is the third step of DNA replication?

Answer 9

When DNA polymerase replicates molecules to build a new strand of DNA

Question 10

When DNA polymerase builds a new strand in 5’ to 3’ direction, what does it mean for the old, template strand? (in terms of direction)

Answer 10

This means that it moves along the old, template strand in the 3’ to 5’ direction.

Question 11

Which one is the leading strand? (in terms of carbon)

Answer 11

The old strand is the one that goes in 3’ to 5’ direction (as the helicase opens up the DNA)

DNA polymerase builds in the 5’ to 3’ direction.

Question 12

DNA replication only occurs in the __________ (carbon) direction

Answer 12

5’ to 3’ direction

Question 13

Which one is the lagging strand?

Answer 13

the 5’ to 3’ (in the direction the helicase opens up the DNA: reading from the bottom)

Question 14

What happens on the lagging strand?

Answer 14

Primers have to keep being placed in order for DNA polymerase to build. Since polymerase can only build in the 5’ to 3’ direction, fragments are formed

Question 15

What is the name of the fragments formed on the lagging strand?

Answer 15

Okazaki Fragments

Question 16

What is the fourth step of DNA replication?

Answer 16

Primers (on the lagging strand) have to get replaced with DNA bases (the were removed). The gaps on the Okazaki fragments are sealed together.

Question 17

What is Ligase and it’s purpose?

Answer 17

Ligase “glues” the gaps between the Okzaki Fragments, sealing them together

Question 18

What are the replicated DNA molecules called/the type of DNA replication? (And Why?)

Answer 18

Semi-conservative.

The two copies of DNA strand each contain one old original strand, and one newly made strand.

Question 19

What happends when DNA polymerase matches incorrect bases?

Answer 19

Results in an incorrectly coded gene, which ultimately ends up in an incorrect protein, or no protein.

Question 20

What enzyme is the “proofread” during DNA replication?

Answer 20

DNA Polymerase

Question 21

What is the part called, where the Helicase breaks apart the hydrogen bonds and turns one strand, into two?

Answer 21

Replication Fork

Question 22

Draw the steps of DNA replication, including the beginning, the replication on leading and lagging strands.

Answer 22

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