Molecular genetics

Question 1

What was Griffith’s contribution?

Answer 1

“Transformation” or, a change in genotype and phenotype due to the uptake of external DNA by a cell.
His experiment helped show that DNA is the genetic material

Question 2

What did Hershey and Chase do?

Answer 2

Research that satisfied most scientists that DNA is the genetic material

Worked with a bacteriophage called T2

Question 3

What did Chargaff do?

Answer 3

The DNA composition varies from one species to another.
Amount of G and C nucleotide residues were equal within one species, and the amount of A and T residues were likewise equal.

Question 4

What did Franklin determine?

Answer 4

Was composed of two antiparallel sugar-phosphate backbones, with the nitrogenous bases paired in the molecule’s interior

The nitrogenous bases are paired in specific combinations: adenine with thymine, and cytosine with guanine.

Question 5

What did Watson and Crick determine?

Answer 5

An elegant double-helical model for the structure of DNA., and that purines are paired with pyridamines

Question 6

Adenine and thymine form ___ bonds, cytosine and guanine form _____ bonds

Answer 6

two

three

Question 7

What did Meselson and Stahl determine?

Answer 7

Supported the semiconservative model of DNA replication

Question 8

What does the semiconservative model of DNA replication say?

Answer 8

The parent molecule unwinds, and two new daughter strands are built based on base-pairing rules

Question 9

Where does DNA replication begin?

Answer 9

At an origin of replication

Question 10

What is a replication fork?

Answer 10

A structure that forms within the nucleus during DNA replication. It is created by helicases, which break the hydrogen bonds holding the two DNA strands together. The resulting structure has two branching “prongs”, each one made up of a single strand of DNA.

Question 11

What enzyme adds nucleotides to the 3’ end of a new DNA strand?

Answer 11

DNA polymerase

Question 12

In which direction are nucleic acids built?

Answer 12

Nucleic acids are always built in the 5’ to 3’ direction.

This includes both DNA and RNA.

Question 13

In DNA replication, ______ separates the two DNA strands

Answer 13

Helicase

Question 14

In DNA replication, _________ cuts and rejoins each strand to correct overwinding.

Answer 14

Topoisomerase

Question 15

After topoisomerase cuts the DNA, what happens?

Answer 15

Strands held apart by single-stranded DNA binding proteins.

Question 16

In DNA replication, ____ _______ lays down RNA primer

Answer 16

RNA Primase

Question 17

In DNA replication, first, ____ ____ ____follows RNA primer with DNA, then _______ ______ _______ replaces RNA primer with DNA.

Answer 17

DNA Pol III

DNA Pol I

Question 18

In the last step of DNA replication, ______ joins ends together.

Answer 18

Ligase

Question 19

How are nucleotides added to the RNA primer of the leading strand?

Answer 19

DNA polymerase III can synthesize a complementary strand continuously, following along the replication

Question 20

What synthesizes the lagging stand of DNA?

Answer 20

The lagging strand is synthesized as a series of DNA segments called Okazaki fragments (affectionately known as Okazaki’s little pieces”,) which are then joined together by an enzyme called DNA ligase.

Question 21

Why is the lagging strand harder to lay down?

Answer 21

To elongate the other new strand of DNA, the lagging strand, DNA polymerase III must work in the direction away from the replication fork.

This process must be repeated continuously as the
replication fork uncovers yet more DNA to be copied.

Question 22

DNA ________ proofread newly made DNA

Answer 22

polymerases

Question 23

An enzyme called _______ catalyzes the lengthening of telomeres in germ cells.

Answer 23

telomerase