Q: If the DNA of E. coli is 1.36 mm long, and the distance between two base pairs is $$0.34 \times 10$$^{-9}$$ m, calculate the approximate number of base pairs in E. coli DNA.

$$4 \times 10^6$ (since 1.36$$ \times $$10^{-3}$$ \div 0.34 \times $$10^{-9} = 4$$ \times $$10^6)$$

Question 1

Which experimental evidence first confirmed the semiconservative model of DNA replication as depicted in the Watson-Crick model?

Accepted Answer

The Meselson-Stahl experiment using isotopes of nitrogen

Question 2

In the semiconservative model of DNA replication, what is the composition of the two daughter DNA molecules after one round of replication?

Accepted Answer

Each contains one parental and one newly synthesized strand

Question 3

If the DNA of E. coli is 1.36 mm long, and the distance between two base pairs is $$0.34 	imes 10$$^{-9}$$ m, calculate the approximate number of base pairs in E. coli DNA.

Accepted Answer

$$4 	imes 10^6$ (since 1.36$$ 	imes $$10^{-3}$$ \div 0.34 	imes $$10^{-9} = 4$$ 	imes $$10^6)$$

Question 4

Which of the following statements about the structure of DNA is correct?

Accepted Answer

The backbone is formed by sugar and phosphate groups

Question 5

What is the main reason DNA is more stable than RNA as a genetic material?

Accepted Answer

DNA is double-stranded and lacks a 2'-OH group

Question 6

Which enzyme is responsible for joining Okazaki fragments during DNA replication?

Accepted Answer

DNA ligase

Question 7

During transcription in eukaryotes, what is the fate of introns in the primary transcript?

Accepted Answer

They are spliced out and not present in mature mRNA

Question 8

Which of the following is a property of the genetic code?

Accepted Answer

The code is nearly universal

Question 9

A point mutation in the gene for the beta-globin chain changes a single base pair, resulting in sickle cell anemia. What type of mutation is this?

Accepted Answer

Missense mutation

Question 10

Which of the following best describes the function of tRNA during translation?

Accepted Answer

It brings amino acids to the ribosome and matches them to the mRNA codon

Question 11

In the lac operon, what is the role of the repressor protein encoded by the i gene?

Accepted Answer

It binds to the operator and prevents transcription in the absence of lactose

Question 12

Which of the following is NOT a goal of the Human Genome Project?

Accepted Answer

Increase the mutation rate in humans

Question 13

What is the main principle behind DNA fingerprinting?

Accepted Answer

Polymorphism in repetitive DNA sequences such as VNTRs

Question 14

Which of the following statements about chromatin structure is correct?

Accepted Answer

Nucleosomes are the repeating units of chromatin

Question 15

Which of the following is a function of ribosomes during translation?

Accepted Answer

They provide a platform for peptide bond formation

Question 16

Which of the following is true regarding the directionality of DNA polymerase activity during replication?

Accepted Answer

It synthesizes DNA in the 5' to 3' direction

Question 17

Which of the following is a consequence of a frameshift mutation?

Accepted Answer

The reading frame is altered, changing all downstream amino acids

Question 18

Which of the following is a property of satellite DNA used in DNA fingerprinting?

Accepted Answer

It shows high degree of polymorphism

Question 19

Which of the following best describes the role of the promoter in a transcription unit?

Accepted Answer

It provides the binding site for RNA polymerase to initiate transcription

Question 20

Which of the following is a reason why both DNA and RNA can serve as genetic material, but DNA is preferred for long-term storage?

Accepted Answer

DNA is more stable chemically and structurally

Molecular Basis of Inheritance: DNA Structure, Replication, and Gene Expression

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