BIO 1305 Chapter 16: The Molecular Basis of Inheritance

DNA and protein

The two macromolecules debated by early scientists for their role in genetic material.

Federick Griffith

Scientist whose research led to the discovery of the genetic role of DNA.

Transformation

A change in genotype and phenotype due to assimilation of foreign DNA.

S strain, R strain

In Griffith's experiments, the information specifying virulence passed from the dead ____________ cells into the live __________ cells in a process called transformation.

Oswald Avery, Maclyn McCarty, and Colin MacLeod

Scientists who identified the transforming substance as DNA.

RNase, DNase, Protease

Avery, McCarty, and MacLeod's experiments used _____________, _______________, and ______________ to treat the Type S heat-killed and filtered.

DNAse

In Avery, McCarty, and MacLeod's experiments, only ________________ treated filtrate prevented transformation.

bacteriophages

More evidence for DNA as the genetic material came from studies of viruses that infect bacteria called ______________________.

Virus

DNA (sometimes RNA) enclosed by a protective coat made of protein.

Alfred Hershey and Martha Chase

Scientists that designed an experiment with E. coli to show that only the DNA (not the protein) enters the cell during infection, and that the injected DNA of the phage provides the genetic information.

Erwin Chargaff

Reported that DNA base composition varies from one species to the next. He also determined that the amount of adenine = amount of thymine, and that the amount of cytosine = amount of guanine.

Rosalind Franklin

Performed X-ray diffraction studies to identify the 3-D structure of DNA and discovered that DNA is helical.

James Watson and Francis Crick

Deduced the double helix structure of DNA using evidence from Chargaff, Franklin, and others.

antiparallel

Watson built a model in which the backbones of DNA were _________________.

Phosphate group

Bound to the 5'-carbon of sugar and gives DNA a negative charge.

phosphodiester bonds

Nucleotides are joined together by _________________________.

5'

Beginning of the DNA strands.

3'

End of the DNA strands.

sugar-phosphate backbone

The secondary structure of DNA contains a ______________________ joined by phosphodiester bonds.

hydrogen bonds

Nitrogenous base pairs are held togather by _______________________.

copying mechanism

Watson and Crick noted that the specific base pairing suggested a possible __________________ for genetic material.

DNA replication

The copying of DNA.

template

Since the two strands of DNA are complementary, each strand acts as a __________________ for building a new strand in replication.

Semiconservative model

Watson and Crick's replication model that predicts that when a double helix replicates, each daughter molecule will have one old strand (derived or "conserved" from the parent molecule) and one newly made strand.

Origin of replication

Where DNA replication begins.

replication bubble

At the origin of replication, DNA strands are separated to create a ___________________, which creates an entry point for DNA replication proteins.

Helicase

Enzyme that unwinds the double helix and allows for bases to be read.

Single-strand binding proteins

Bind to and stabilize single-stranded DNA and prevent secondary structure formation and reannealing.

Topoisomerase (DNA gyrase)

Relieves torsional stress caused by unwinding the DNA helix.

DNA polymerase

Builds new DNA strands (polymers); only adds nucleotides to the 3' end.

primer

All DNA polymerases require a _____________ to which they add nucleotides.

Primase

An enzyme that synthesizes the primer.

replication fork

DNA polymerases catalyze the synthesis of new DNA at a _____________________.

Nucleoside triphosphate

Each nucleotide that is added to a growing DNA strand.

dATP

Supplies adenine to DNA and is similar to the ATP of energy metabolism.

sugars

The difference in dATP and ATP is in their ______________ (one has deoxyribose and the other has ribose).

3' end

DNA polymerases add nucleotides to the _____________ end of a growing strand.

5' to 3'

New DNA strands only elongate in the ______________ direction.

leading strand

Along one template strand, DNA polymerase synthesizes a __________________ continuously, moving toward the replication fork.

lagging strand

To elongate the new strand, called the ________________, which is synthesized in segments, DNA polymerase must work in the direction away from the replication fork.

DNA ligase

Enzyme that joins DNA fragments together.

Proofreading

DNA polymerase I from the 3' to 5' exonuclease activity removes the incorrectly paired nucleotide.

Mismatch repair

Repair enzymes remove and replace incorrectly paired nucleotides to correct errors after replication is complete.

Nucleotide excision repair

Process where nuclease cuts out and replaces damaged stretches of DNA.

Mutations

The source of genetic variation upon which natural selection operates and are ultimately responsible for the appearance of new species.

repeated rounds of replication

Produce shorter DNA molecules with uneven ends.

Telomeres

Special nucleotide sequences at the ends of eukaryotic chromosomes that help solve the end replication problem by postponing the erosion of genes near the ends of DNA molecules.

Telomerase

Lengthens telomeres, active in germline cells, inactive in most of our cells.

shortening of telomeres

The ____________________ might protect cells from cancerous growth by limiting the number of cell divisions.

Bacterial chromosome

A double-stranded circular DNA molecule associated with a small amount of protein.

Eukaryotic chromosomes

Have linear DNA molecules associated with a large amount of protein.

supercoiled

In a bacterium, the DNA is "_______________" and found in a region of the cell called the nucleoid.

chromatid

In the eukaryotic cell, DNA is precisely combined with proteins in a complex called ______________.

histones

Proteins responsible for the main level of DNA packing in interphase chromatin.

Nucleosome

Bead-like structure composed of DNA wound twice around a core of eight histones, two each of the four main histone types.

Histone tail

The amino end of each histone that extends outward from the nucleosome and is involved in regulation of gene expression.

Euchromatin

Loosely packed chromatin.

Heterochromatin

During interphase, a few regions of chromatin (centromeres and telomeres) are highly condensed into __________________.

dense packing

The __________________ of heterochromatin makes it difficult for the cell to express genetic information coded into these regions.

chemical modifications

Histones can undergo _________________ that result in changes in chromatid condensation.