Intro to DNA II

Question 1

What joins the base pairs across DNA molecules

Answer 1

Hydrogen bonds join base pairs across the centre of the DNA molecule

Question 2

How many hydrogen bonds between G-C basepair

Answer 2

G-C base pair has 3 hydrogen bonds

Question 3

How many hydrogen bonds between A- T basepair

Answer 3

A-T base pair has 2 hydrogen bonds

Question 4

How many hydrogen bonds between A- U basepair

Answer 4

A-U basepair has 2 hydrogen bonds

Question 5

Which base pair if the strongerst

Answer 5

G-C base pair has it has 3 hydrogen bonds compared to 2

Question 6

What is the distance between the H bonds in Base pairs (2)

Answer 6

Between C=O and N-H is 2.9 A
Between N- H and C=N-c is 3.0 A

Question 7

What does it mean when DNA strands are complementary and anti-parallel

Answer 7

3 Prime head binds to the opposing complementary strand, the 5 Prime head of the molecule.
Therefore despite both base pairs having identical DNA sequences, they are bound to each other in opposite directions

Question 8

In what direction does the coding strand run

Answer 8

Coding strand runs from 5’ to 3’

Question 9

In what direction does the complementary strand run

Answer 9

Complementary strand runs from 3’ to 5’

Question 10

At what part of the cell cycle is DNA replicated

Answer 10

DNA is replicated during the S phase of the cell cycle

Question 11

What direction is chain growth

Answer 11

Chain growth is directional, from 5’ to 3’

Question 12

What is a stepwise Reaction

Answer 12

a stepwise reaction is a chemical reaction with one or more reaction intermediates.

Question 13

What are the three stages of DNA replication?

Answer 13

1. Initiation
2. Elongation
3. Termination

Question 14

What is the difference in chromosomes between Eukaryotes and Prokaryotes

Answer 14

Chromosomes are linear (and larger) in Eukaryotes

Question 15

What is a leading strand?

Answer 15

The leading strand is a single DNA strand that, during DNA replication, is replicated in the 3’ – 5’ direction
(same direction as the replication fork).

Question 16

What is the Laging strand?

Answer 16

The lagging strand is a single DNA strand that, during DNA replication, is replicated in the 5′ – 3′ direction
(opposite direction to the replication fork).

Question 17

Eukaryotic DNA replication - initiation

Answer 17

Kickstarted by primase (enzyme) – a short RNA primer is made

This permits DNA polymerase binds at the 3’ end of a strand within the origin

Question 18

Eukaryotic DNA replication - elongation

Answer 18

As elongation proceeds, a second DNA polymerase binds to the 3’ end of the lagging strand

The lagging strand is copied in a series of short fragments called Okazaki fragments

This occurs because the DNA is still being unwound as the lagging strand is copied

Multiple different DNA polymerases have to bind in sequence to make these small copies - CALLED OKAZAKI Fragments.

DNA ligase stitches the Okazaki fragments together

The newly formed DNA is wound up into a helix

Question 19

Eukaryotic DNA replication - termination

Answer 19

Eventually, two replication bubbles meet

DNA ligase joins together the different fragments

Two new strands of DNA have been produced

Question 20

What is the structure of an Unreplicated Chromosome

Answer 20

2 Arms

Question 21

What is the structure of a replicated chromosome

Answer 21

4 Arms, Two sister chromatids attached in the middle by a Centromere

Question 22

What does one chromosome equal to

Answer 22

One chromosome = One DNA molecule

Question 23

How many Chromosomes and BP’s in a nucleus

Answer 23

46 chromosomes (22 autosome pairs + 2 sex chromosomes),
containing about 3 billion base pairs (bp) of DNA in total.

Question 24

Structure and components of nucleic acid

Answer 24

Nucleic acids are polynucleotides—
long chainlike molecules composed of a series of nearly identical building blocks called nucleotides.
Each nucleotide consists of a nitrogen-containing aromatic base
attached to a pentose (five-carbon) sugar, which is in turn attached to a phosphate group.

Question 24

Structure and components of nucleic acid

Answer 24

Nucleic acids are polynucleotides—
long chainlike molecules composed of a series of nearly identical building blocks called nucleotides.
Each nucleotide consists of a nitrogen-containing aromatic base
attached to a pentose (five-carbon) sugar, which is in turn attached to a phosphate group.

Question 25

What is the primary structure of DNA

Answer 25

The sequence of nucleotides that make up a molecule of DNA is referred to as its primary structure

Question 26

What is the secondary structure of DNA

Answer 26

The two strands of a DNA molecule run in an antiparallel fashion so that the 5’ end of one strand is the 3’ end of the other.
This base pairing of nucleotides between the two strands of a single DNA molecule is called DNA’s secondary structure.

Question 27

What is the Tertiary structure of DNA

Answer 27

The tertiary structure is the three-dimensional geometrical formation of the nucleotides and can include
B-DNA, A-DNA, and Z-DNA which are determined by the base pair geometry.
(The double helix)

Question 28

What is the quaternary Structure of DNA

Answer 28

DNA quaternary structure is used to refer to the binding of DNA to histones to form nucleosomes,
and then their organisation into higher-order chromatin fibres.

Question 29

What is semi-conservative replication

Answer 29

Double-stranded molecules of nucleic acid separate into two single strands each of which serves as a template for the formation of a complementary strand that together with the template forms a complete molecule.
(Semiconservative replication describes the mechanism of DNA replication in all known cells. )