Mastering Bio #4 (TEST 1)

What are the components of a nucleotide?

a sugar, a phosphate group and a nitrogenous base

Which of the following did Watson and Crick already know when they were trying to determine the structure of DNA? The number of _____.

purines is always the same as pyrimidines

What are the chemical components of a DNA molecule?

sugars nitrogenous bases phosphate groups

In the 1950s, when Watson and Crick were working on their model of DNA, which concepts were well accepted by the scientific community? Chromosomes are made up of protein and nucleic acid. Chromosomes are found in the nucleus. Genes are made of DNA. Genes are located on chromosomes.

Chromosomes are made up of protein and nucleic acid. Chromosomes are found in the nucleus. Genes are located on chromosomes.

Early, flawed DNA models proposed by Watson and Crick and by Linus Pauling correctly described which property of DNA? Bases pair with complementary bases. DNA is composed of sugars, phosphates, and bases. Bases face the center of the molecule, with a phosphate backbone on the outside. DNA is a double helix.

DNA is composed of sugars, phosphates, and bases.

In the early 1950s, many researchers were racing to describe the structure of DNA using different approaches. Which of the following statements is true? Jim Watson and Francis Crick built theoretical models, incorporating current knowledge about chemical bonding and X-ray data. Rosalind Franklin and Maurice Wilkins conducted genetic experiments to explore DNA's role in inheritance. Rosalind Franklin and Maurice Wilkins built theoretical models, incorporating current knowledge about chemical bonding and X-ray data. Jim Watson and Francis Crick used X-ray diffraction to understand the structure of DNA.

Jim Watson and Francis Crick built theoretical models, incorporating current knowledge about chemical bonding and X-ray data.

Nucleic acids have a definite polarity, or directionality. Stated another way, one end of the molecule is different from the other end. How are these ends described?

One end has an unlinked 3 carbon; the other end has an unlinked 5 carbon.

Erwin Chargaff observed that the proportions of adenine (A) and thymine (T) bases were always equal, as were the proportion of guanine (G) and cytosine (C). Chargaff's observation suggests which of the following statements?

The data suggest that A would always pair with T and G would always pair with C in a DNA molecule.

What is the structural feature that allows DNA to replicate?

complementary pairing of the nitrogenous bases

Which of the following best describes DNA's secondary structure?

double antiparallel helical strands

In a DNA double helix, what kind of chemical bonds form between the complementary nitrogenous bases?

hydrogen bonds