2B1 Molecular Biology Fundamentals

Question 1

What is the central dogma of biology?

Answer 1

The flow of genetic information from DNA to RNA to protein.

It demonstrates how DNA information leads to protein synthesis, emphasizing unidirectional flow.

Question 2

What analogy helps understand the central dogma?

Answer 2

Baking a cake, where DNA is the recipe, RNA is the copy of the picture, and protein is the 3D cake.

Question 3

Who proposed the central dogma theory?

Answer 3

James Watson and Francis Crick

This was in 1957.

Question 4

What did Crick propose in his paper on the central dogma theory?

Answer 4

DNA is copied to RNA, which requires an intermediate (later identified as tRNA) to create proteins.

Question 5

What evidence led to the expansion of the central dogma theory?

Answer 5

Discovery of reverse transcriptase by Howard Temin and David Baltimore in 1970.

Question 6

What is reverse transcriptase and its significance?

Answer 6

It’s an enzyme that creates DNA from RNA, crucial in viral replication, including HIV.

Reverse transcriptase is also used in techniques like RT-PCR (Reverse Transcription Polymerase Chain Reaction), which is widely used in molecular biology and diagnostics.

Question 7

What were the three original processes in the central dogma?

Answer 7

1. DNA replication from DNA
2. Transcription of DNA to RNA
3. Translation of RNA to protein

Question 8

Describe simply how DNA replication occurs?

Answer 8

DNA polymerase (enzyme) reads DNA and synthesizes a complementary strand of nucleotides.

Question 9

What does transcription involve?

Answer 9

DNA is copied to RNA by RNA polymerase.

Question 10

What is translation in the context of the central dogma?

Answer 10

RNA is read by ribosomes to synthesize proteins.

Question 11

Compare the structure RNA to DNA?

Answer 11

• RNA is single-stranded, DNA is double stranded.
• RNA uses ribose sugar, DNA uses deoxyribose sugar.
• RNA contains uracil instead of thymine.

Question 12

How did Watson and Crick describe DNA replication?

Answer 12

That it involves creating more copies using nucleotides A, G, C, and T.

Question 13

Where does transcription occur in cells?

Answer 13

Nucleus

Question 14

What is the role of ribosomes in the synthesis of proteins?

Answer 14

They translate RNA into proteins in the cytoplasm.

Question 15

What does the central dogma propose about protein synthesis and DNA shape?

Answer 15

Proteins cannot be used to synthesize DNA, suggesting unidirectional flow.

Question 16

Which 3 additional steps did the expanded central dogma include?

Answer 16

• RNA replication from RNA.
• DNA replication from RNA through reverse transcription.
• Direct translation of DNA to protein.

Question 17

Describe another way that information is coded in the genome, other than direct coding sequences of DNA.

Answer 17

Non-coding RNA plays a role in gene regulation, protein functionality, and information transfer.

Question 18

What is DNA responsible for in cells?

Answer 18

Carrying genetic information.

Question 19

Where is DNA found in cells?

Answer 19

In the nucleus, condensed into chromatin.

Question 20

Define a gene.

Answer 20

Genes are units of inheritance grouped within DNA.

Question 21

What is the function of a gene?

Answer 21

By being expressed into proteins, vital for cellular functions and observable traits.

Question 22

Describe the structure of DNA.

Answer 22

• A double stranded, double-helical structure.
• Made of nucleotides containing deoxyribose sugar, phosphate group, and nitrogenous base.
• The two strands twisted around each other.

Question 23

What are the two types of nitrogenous bases in DNA?

Answer 23

• Purines (adenine and guanine)
• Pyrimidines (thymine and cytosine)

Question 24

Describe how nitrogenous bases complementary base pair in DNA.

Answer 24

• Adenine pairs with thymine (2 hydrogen bonds)
• Cytosine pairs with guanine (3 hydrogen bonds)

Question 25

What is **DNA replication**, and how does it occur?

Answer 25

* It's the process of producing two identical copies of DNA. * It involves unzipping the DNA double helix, synthesis of new DNA strands, and bonding them together.

Question 26

What **enzymes** are involved in DNA replication?

Answer 26

* Helicase * DNA polymerase * RNA primase * DNA ligase

Question 27

What is meant by the '**leading strand**' of DNA and how is it synthesized?

Answer 27

Runs in the **3'-5' direction** and is **synthesized continuously** by DNA polymerase.

Question 28

What is the **lagging strand**, and how is it synthesized?

Answer 28

Runs in the **5'-3' direction** and is **synthesized discontinuously** in **Okazaki fragments**.

Question 29

Define **DNA sequencing**.

Answer 29

A molecular genetic technology revealing the base pairing content of DNA, used in research and diagnostics.

Question 30

Who developed the first DNA sequencing method, and what was it called?

Answer 30

Frederick Sanger developed the chain termination method or Sanger sequencing.

Question 31

What has replaced the Sanger sequencing in modern laboratories and why?

Answer 31

Next-generation sequencing methods due to increased efficiency and reduced costs.

Question 32

What is the human genome project, and when was it completed?

Answer 32

It was a project to sequence the entire human genome completed in 2003, revealing the sequence of bases in human DNA.

Question 33

How long would the stretched DNA of a single cell be, and what compacts it?

Answer 33

Approximately 2 meters long. ## Footnote Compaction is done by proteins called histones.

Question 34

Which 3 scientists contributed to the discovery of DNA's double helical structure?

Answer 34

* Rosalind Franklin * James Watson * Francis Crick ## Footnote They discovered the structure using using X-ray diffraction.

Question 35

What percentage of DNA comprises genes?

Answer 35

Only about 1%.

Question 36

What are the non-coding segments called?

Answer 36

Introns

Question 37

What are exons in DNA?

Answer 37

Coding segments responsible for the synthesis of proteins during gene expression.

Question 38

What is the function of DNA polymerase in DNA replication?

Answer 38

Adds complementary nucleotides to the newly forming DNA strand during replication, ensuring accurate copying of the DNA template.

Question 39

What is the significance of semi-conservative DNA replication?

Answer 39

Ensures that each newly formed DNA molecule contains one original (parental) strand and one newly synthesized (daughter) strand, maintaining genetic fidelity.

Question 40

What is the role of histones in DNA compaction?

Answer 40

These are proteins that DNA wraps around to form nucleosomes, promoting compaction and organization of DNA into chromatin, allowing it to fit within the cell nucleus. ## Footnote Histones also play a role in regulating gene expression by controlling access to the DNA.

Question 41

How does DNA sequencing contribute to research and diagnostics?

Answer 41

Provides valuable information about the genetic makeup of organisms, aiding in understanding genetic diseases, evolutionary relationships, and personalized medicine.

Question 42

What are the main stages of the cell cycle?

Answer 42

1. Interphase (G1, S, and G2 phases) 2. Mitosis (or M phase)

Question 43

What is the difference between the composition of the sugar ribose and that of deoxyribose?

Answer 43

Ribose has an extra hydroxyl (OH) group attached to one of its carbon atoms.

Question 44

Describe what happens during **interphase**.

Answer 44

It's the phase where the cell grows, replicates its DNA, and prepares for cell division.

Question 45

At what stage of the cell cycle does DNA replication occur?

Answer 45

S stage.

Question 46

Why is the cell cycle important?

Answer 46

* It is essential for growth, development, and repair of organisms. * It ensures accurate duplication and distribution of genetic material to daughter cells.