Erwin Chargaff’s work on the composition of nucleic acids began in 1944. His findings, which later became known as Chargaff’s rules, detail the specific pairings that occur in double-stranded DNA molecules.
According to one of Chargaff’s rules, a section of DNA molecule that contains 50 base pairs and has 15 adenine bases must also contain —
{silence}Option A.{silence}
15 guanine bases
{silence}Option Be.{silence}
15 cytosine bases
{silence}Option C.{silence}
15 thymine bases
{silence}Option D.{silence}
15 uracil bases
Option C. 15 thymine bases
Some cells can die as a result of external agents such as poison or trauma. However, most cells die through a process known as apoptosis, or programmed cell death.
What is a likely consequence of a mutation that prevents apoptosis?
{silence}Option A.{silence}
A tumor
{silence}Option Be.{silence}
A loss of amino acids
{silence}Option C.{silence}
A lack of cell division
{silence}Option D.{silence}
A reduction in chromosome number
Option A. A tumor
Erwin Chargaff examined DNA samples from different organisms to study base pairing. Some data from DNA samples are shown.
Organism Adenine Guanine Cytosine Thymine
Sea urchin 32.8% 17.7% 17.3% 32.1%
Salmon 29.7% 20.8% 20.4% 29.1%
Wheat 28.1% 21.8% 22.7% 27.4%
Which conclusion is supported by the data in the table?
{silence}Option A.{silence}
Each organism contains more cytosine than any other base.
{silence}Option Be.{silence}
The three organisms have the same sequence of nucleotides.
{silence}Option C.{silence}
All three organisms contain the same types of nitrogen bases.
{silence}Option D.{silence}
The presence of each base is dependent on the size of the organism.