DNA Structure and Replication

Question 1

Who discovered the Transforming Principle and when?

Answer 1

Frederick Griffith in 1928.

Question 2

What is DNA replication?

Answer 2

Process of creating an exact copy of a molecule of DNA.

Question 3

What does semi-conservative replication mean?

Answer 3

Each new molecule of DNA contains one strand of the original complementary DNA and one new strand.

Question 4

What happens during termination in DNA replication?

Answer 4

Completion of new DNA.

Question 5

What catalyzes the formation of new DNA molecules during replication?

Answer 5

DNA polymerase

It plays a crucial role in synthesizing new DNA strands.

Question 6

What happened when heat-killed pathogenic bacteria were treated with a DNA-destroying enzyme?

Answer 6

Transformation did not occur.

Question 7

What happens to the DNA strands after they are newly formed?

Answer 7

They rewind automatically into their chemically stable helix structure

This is a natural process following replication.

Question 8

What is a primer in DNA replication?

Answer 8

A short strand of RNA that is complementary to a DNA template and serves as a starting point for the attachment of new nucleotides.

Question 9

What are the four bases found in DNA nucleotides?

Answer 9

• Adenine (A)
• Guanine (G)
• Cytosine (C)
• Thymine (T)

Question 10

What is found in a single-stranded form at the replication fork?

Answer 10

Only a very short region of DNA

This region is crucial for the replication process.

Question 11

What is a nucleic acid?

Answer 11

Weakly acidic phosphorus-containing substance that can be isolated from the nuclei of white blood cells

Nucleic acids include DNA and RNA.

Question 12

When was the Human Genome Project completed?

Answer 12

2003

It was a monumental effort to sequence the entire human genome.

Question 13

What is the replication machine?

Answer 13

A complex involving dozens of different enzymes and proteins that work together in the process of DNA replication.

Question 14

Define DNA polymerase.

Answer 14

An enzyme that uses the parent strands as a template to add nucleotides to make complementary strands.

Question 15

What was the first entire genome to be sequenced?

Answer 15

The virus 0X174 in 1977

This marked a significant milestone in genomics.

Question 16

What is the process of identifying the precise nucleotide sequence of a DNA fragment called?

Answer 16

DNA Sequencing

DNA sequencing has become routine with advancements in technology.

Question 17

What occurs during termination of DNA replication?

Answer 17

The completion of new DNA strands and the dismantling of the replication machine

This marks the end of the replication process.

Question 18

What are helicases?

Answer 18

Enzymes that cleave and unravel short segments of DNA just ahead of the replicating fork during DNA replication.

Question 19

Define gene.

Answer 19

A specific sequence of DNA that encodes a protein, tRNA, rRNA molecule or regulates the transcription of such a sequence.

Question 20

What is a genome?

Answer 20

The sum of all the DNA carried in an organism’s cells, including genes and regions of non-coding DNA.

Question 21

What is DNA made up of?

Answer 21

Two strands of nucleotides bound together to form a double helix

Each strand has a backbone made of sugar and phosphate molecules.

Question 22

What did Phoebus Levene isolate in the early 1900s?

Answer 22

DNA and RNA

He also showed that chromosomes are made up of a combination of DNA and proteins.

Question 23

What did Watson and Crick publish in 1953?

Answer 23

A paper describing the molecular structure of DNA

This research identified DNA as the material of heredity.

Question 24

What is the significance of the Human Genome Project?

Answer 24

It determined the sequence of the three billion base pairs making up the human genome

This has important applications in medicine and other sciences.

Question 25

What are the three key differences between RNA and DNA?

Answer 25

* Sugar component of RNA is ribose rather than deoxyribose * RNA does not have thymine (T), it has uracil (U) instead * RNA remains single-stranded

Question 26

How does replication occur on the leading and lagging strands?

Answer 26

In slightly different ways ## Footnote This difference is essential for the efficiency of DNA replication.

Question 27

What happened when heat-killed pathogenic bacteria were treated with a protein-destroying enzyme?

Answer 27

Transformation still occurred.

Question 28

Which bases are complementary in DNA?

Answer 28

* Adenine (A) and Thymine (T) * Cytosine (C) and Guanine (G) ## Footnote This base pairing is essential for DNA replication.

Question 29

What holds the two strands of DNA together?

Answer 29

Hydrogen bonds between pairs of complementary bases ## Footnote The nitrogenous bases project out from the backbone.

Question 30

What is a nucleotide?

Answer 30

Units making up nucleic acids such as DNA and RNA, composed of a five-carbon sugar, a phosphate group, and one of five nitrogen-containing bases.

Question 31

What did Rosalind Franklin contribute to the understanding of DNA?

Answer 31

Provided crucial information about the molecular structure of DNA using X-ray photography.

Question 32

What are complementary base pairs in DNA?

Answer 32

Hydrogen-bonded pairs of adenine and thymine and cytosine and guanine.

Question 33

What did Griffith discover about dead pathogenic bacteria?

Answer 33

They passed on their disease-causing properties to live, non-pathogenic bacteria.

Question 34

What are Okazaki fragments?

Answer 34

Short nucleotide fragments synthesized during DNA replication of the lagging strand.

Question 35

Define Ribonucleic Acid (RNA)

Answer 35

A nucleic acid that plays a role in gene expression and protein synthesis, shares similar structure with DNA ## Footnote RNA is single-stranded and contains uracil instead of thymine.

Question 36

What is the Transforming Principle?

Answer 36

The ability of dead pathogenic bacteria to pass on their disease-causing properties to live, non-pathogenic bacteria.

Question 37

What does antiparallel mean in the context of DNA?

Answer 37

Describes the property by which the 5’ to 3’ phosphate bridges run in opposite directions on each strand of nucleotides.

Question 38

What is the double helix structure of DNA?

Answer 38

A threadlike molecule made up of two long strands of nucleotides bound together in a spiral shape.

Question 39

What is the role of DNA ligase?

Answer 39

Enzyme that splices together Okazaki fragments during DNA replication on the lagging strand.

Question 40

What did Hershey and Chase demonstrate in 1952?

Answer 40

Genes are made of DNA using radioactive labelling.

Question 41

What is Chargaff's Rule?

Answer 41

In any sample of DNA, the amount of adenine is always approximately equal to the amount of thymine, and the amount of cytosine is always approximately equal to the amount of guanine.

Question 42

What is a replication bubble?

Answer 42

Oval-shaped unwound area within a DNA molecule that is being replicated.

Question 43

Define Deoxyribonucleic Acid (DNA)

Answer 43

Nucleic acid molecule that governs the process of heredity in all plant and animal cells ## Footnote DNA is often referred to as the genetic material.