Question 1

Which experiment provided the first direct evidence that DNA is the genetic material responsible for transformation in bacteria?

Accepted Answer

Griffith's experiment with Streptococcus pneumoniae

Question 2

In the Hershey–Chase experiment, which radioactive isotope was used to label DNA, and what was the key finding?

Accepted Answer

Radioactive phosphorus ($$^{32}P$$); DNA was found in the pellet, indicating it entered the bacterial cell

Question 3

According to Chargaff’s rules, if a DNA sample contains 30% adenine, what percentage of guanine would you expect?

Accepted Answer

20%

Question 4

Which structural feature of DNA did Rosalind Franklin’s X-ray diffraction photo reveal?

Accepted Answer

The double-helical structure and uniform width of DNA

Question 5

Why does pairing a purine with a pyrimidine in the DNA double helix result in a uniform width?

Accepted Answer

Purine-purine pairs are too wide, pyrimidine-pyrimidine pairs are too narrow, but purine-pyrimidine pairs fit the X-ray data

Question 6

Which equation correctly represents the relationship between base pairs in DNA according to Chargaff’s rules?

Accepted Answer

$$A = T$$ and $$G = C$$

Question 7

During DNA replication, which enzyme is responsible for relieving the strain caused by unwinding the double helix?

Accepted Answer

Topoisomerase

Question 8

What is the function of single-strand binding proteins during DNA replication?

Accepted Answer

They bind to and stabilize single-stranded DNA

Question 9

Which direction does DNA polymerase add nucleotides to a growing DNA strand?

Accepted Answer

5′ → 3′

Question 10

What is the role of DNA ligase in DNA replication?

Accepted Answer

It joins Okazaki fragments on the lagging strand

Question 11

Which model of DNA replication was supported by the Meselson–Stahl experiment?

Accepted Answer

Semiconservative model

Question 12

Why do eukaryotic chromosomes have telomeres?

Accepted Answer

To postpone the erosion of genes near the ends of DNA molecules

Question 13

Which enzyme catalyzes the lengthening of telomeres in germ cells?

Accepted Answer

Telomerase

Question 14

What is the evolutionary significance of mutations in DNA?

Accepted Answer

They are the source of genetic variation upon which natural selection operates

Question 15

Which process is illustrated by the equation $$	ext{dATP} ightarrow 	ext{DNA} + 2	ext{PP}_i$$ during DNA replication?

Accepted Answer

Addition of a nucleotide to a growing DNA strand via dehydration reaction

Question 16

What is the main difference between euchromatin and heterochromatin?

Accepted Answer

Euchromatin is loosely packed and accessible for gene expression, while heterochromatin is highly condensed and less accessible

Question 17

Which protein is responsible for the main level of DNA packing in interphase chromatin?

Accepted Answer

Histones

Question 18

What is a nucleosome?

Accepted Answer

A segment of DNA wound twice around a core of eight histones

Question 19

Which repair mechanism involves a nuclease cutting out and replacing damaged stretches of DNA?

Accepted Answer

Nucleotide excision repair

Question 20

If a mutation occurs in a gene coding for a DNA repair enzyme, what is a likely consequence?

Accepted Answer

Higher rates of permanent mutations and possible genetic diseases

Chapter 16: The Molecular Basis of Inheritance – DNA Structure, Replication, and Chromosome Organization

Guida di studio - Domande di pratica