DNA and The Genome

Question 1

STRUCTURE OF DNA

Answer 1

STRUCTURE OF DNA

Question 2

structure of DNA

What shape is DNA?

Answer 2

A double stranded helix

Question 3

Structure of DNA

What are the subunits which make up DNA called?

Answer 3

Nucleotides

Question 4

Structure of DNA

What is each nucleotide composed of?

Answer 4

• Deoxyribose sugar
• Phosphate
• Base

Question 5

Structure of DNA

What is the sugar phosphate backbone formed from?

Answer 5

Deoxyribose sugars and phosphates

Question 6

Structure of DNA

What forms the genetic code?

Answer 6

The base sequence of DNA

Question 7

Structure of DNA

What forms between the bases to create a double stranded molecule?

Answer 7

Hydrogen bonds

Question 8

Structure of DNA

Where is the phosphate located on the strand?

Answer 8

The 5’ end

Question 9

Structure of DNA

Where is the Deoxyribose sugar located on the strand?

Answer 9

The 3’ end

Question 10

Structure of DNA

How do the strands run?

Answer 10

In an anti parallel direction from 5’ to 3’

Question 11

Structure of DNA

What are the four nitrogenous bases?

Answer 11

• Adenine
• Thymine
• Guanine
• Cytosine

Question 12

Structure of DNA

What shape represents the deoxyribose sugar and why?

Answer 12

A pentagon as it contains 5 carbons

Question 13

Structure of DNA

What shape represents the phosphate?

Answer 13

A circle

Question 14

Structure of DNA

Describe the organisation of DNA in a prokaryotic cell.

Answer 14

• Prokaryotes have a single, circular chromosome (usually within the centre known as the nucleoid region), ie, they have no true nucleus/do not have a membrane bound nucleus
• Prokaryotes also contain small circular chromosomes and circular plasmids

Question 15

Structure of DNA

Describe the organisation of DNA in a eukaryotic cell, naming the proteins associated within chromosomes

Answer 15

• Eukaryotic cells contain linear chromosomes within a nucleus tightly coiled around proteins called histones
• They also contain circular chromosomes in the mitochondria and chloroplasts.

Question 16

Structure of DNA

Why is yeast a special example of a eukaryotic cell?

Answer 16

Yeast is described as a special example of a eukaryote as it also contains plasmids.

Question 17

Structure of DNA

Which cell is prokaryotic?

Answer 17

Bacteria cells

Question 18

Structure of DNA

Which cells are eukaryotic?

Answer 18

Animal, plant, fungal and yeast cells

Question 19

REPLICATION OF DNA

Answer 19

REPLICATION OF DNA

Question 20

Replication of DNA

When does DNA replication occur?

Answer 20

Before cell division

Question 21

Replication of DNA

What controls DNA replication?

Answer 21

DNA polymerase

Question 22

Replication of DNA

Why is DNA replication important?

Answer 22

So an exact copy of the genetic material is passed to daughter cells. This also maintains the chromosome compliment (number)

Question 23

Replication of DNA

What does DNA polymerase do?

Answer 23

Adds DNA nucleotides to the 3’ end of the strand using complimentary base pairings

Question 24

Replication of DNA

What is a primer?

Answer 24

A short segment of DNA that acts as the starting point for a new strand that is complimentary to the DNA template and binds to the 3’ end.

Question 25

# Replication of DNA What are the stages of replication?

Answer 25

1. The DNA helix unwinds and unzips as the hydrogen bonds between the bases break, forming two strands 2. A primer attaches to the 3' end 3. The DNA polymerase adds DNA nucleotides to the 3' end 4. The lagging strand is produced in fragments. The fragments are joined together by an enzyme named ligase

Question 26

# Replication of DNA Why is the leading and lagging strand produced?

Answer 26

DNA polymerase can only add DNA nucleotides in one direction (5' => 3')

Question 27

# Replication of DNA What does PCR stand for?

Answer 27

polymerase chain reaction

Question 28

# Replication of DNA What is PCR?

Answer 28

A technique used to amplify DNA outside the body (invitro) using complimentary primers for specific target sequences. Tiny samples of DNA are taken and a vast number of copies are made.

Question 29

# Replication of DNA What are the requirements for PCR?

Answer 29

- target strand of DNA - heat tolerant DNA polymerase - two types of primers - DNA nucleotides

Question 30

# Replication of DNA What are the stages of PCR?

Answer 30

1. The solution is heated to between 92°C - 98°C to separate the DNA strands by breaking the hydrogen bonds between the bases 2. The solution is cooled to between 50°C - 65°C to allow the primers to aneal (bind to) the target sequences of DNA 3. The solution is heated to 70°C - 80°C to allow heat tolerant DNA polymerase to replicate the section of DNA

Question 31

# Replication of DNA Where do primers bind?

Answer 31

To the complementary DNA at the 3' end

Question 32

# Replication of DNA Why is the solution reheated in stage 3?

Answer 32

So it is closer to the optimum temperature for heat tolerant DNA polymerase

Question 33

# Replication of DNA Why is heat tolerant DNA polymerase used?

Answer 33

So it doesn't denature at a high temperature

Question 34

# Replication of DNA What can PCR be used for?

Answer 34

- Solve crimes - Paternity testing - diagnosing - genetic disorders