Biology 1305 Chapter 16 (Experiments)

Who proposed the double-helical structure of DNA?

James Watson and Francis Crick in April 1953.

What is the genetic material in cells?

DNA (deoxyribonucleic acid).

What are chromosomes made of?

DNA and proteins.

What phenomenon did Frederick Griffith discover?

Transformation, a change in genotype and phenotype due to assimilation of foreign DNA.

What did Oswald Avery, Maclyn McCarty, and Colin MacLeod identify as the transforming substance?

DNA.

What is the role of bacteriophages in genetic research?

Bacteriophages are used as tools to study molecular genetics.

What did Hershey and Chase demonstrate in their 1952 experiment?

They showed that DNA is the genetic material of the T2 phage.

What are the components of a nucleotide?

A nitrogenous base, a sugar, and a phosphate group.

What did Chargaff's rules state about DNA base composition?

Amount of adenine = amount of thymine; amount of cytosine = amount of guanine.

What technique did Rosalind Franklin use to study DNA structure?

X-ray crystallography.

What did Watson and Crick deduce about the structure of DNA?

DNA is a double helix with two antiparallel strands.

What is the significance of base pairing in DNA?

Adenine pairs with thymine and guanine pairs with cytosine, ensuring uniform width.

What is the directionality of DNA strands?

DNA strands have directionality from 5' to 3'.

What is the role of DNA polymerase III?

It catalyzes the synthesis of new DNA strands.

What does helicase do during DNA replication?

It unwinds the double-stranded DNA into single strands.

What is the function of DNA ligase?

It joins Okazaki fragments together during DNA replication.

What does primase do?

It synthesizes RNA primers for starting points of DNA replication.

What is the role of telomerase?

It replicates the ends of linear chromosomes to maintain their length.

What is the function of topoisomerase?

It relieves the stress of the DNA double helix being unwound during replication.

What is transformation in the context of genetics?

The process by which a cell takes up foreign DNA and incorporates it into its own genome.

How did Chargaff's findings contribute to the understanding of DNA structure?

They provided evidence for the base pairing rules that led to the double helix model.

What is the diameter of the DNA helix as discovered by Franklin?

2 nm.

What is the significance of the 3.4 nm measurement in DNA?

It indicates the distance for one complete turn of the DNA helix.

What did Watson and Crick's model of DNA reveal about the arrangement of nitrogenous bases?

The bases are paired in the interior of the helix, contributing to the molecule's stability.

What is the primary role of DNA in heredity?

To store and transmit genetic information.

What is the main challenge biologists faced in the early 20th century regarding inheritance?

Identifying the molecules responsible for heredity.