AP Biology: Chapter 16 Vocab - Molecular Basis of Inheritence

Avery, Macleod, McCarty

Proved that DNA is the hereditary material

Bacterial Transformation

A bacterial cell takes up DNA from the environment and incorporates some of the information into its own

(a change in genotype and phenotype due to the assimilation of external DNA by a cell)

Bacteriophage

A virus that infects bacteria; also called a phage

Chargaff's Rules

(1) DNA base composition varies between species, and (2) for each species, the percentages of A and T bases are roughly equal, as are those of G and C bases

Chromatin

The complex of DNA and proteins that makes up eukaryotic chromosomes. When the cell is not dividing, this exists in its dispersed form, as a mass of very long, thin fibers that are not visible with a light microscope

DNA ligase

A linking enzyme essential for DNA replication; catalyzes the covalent bonding of the 3′ end of one DNA fragment (such as an Okazaki fragment) to the 5′ end of another DNA fragment (such as a growing DNA chain)

DNA polymerase

An enzyme that catalyzes the elongation of new DNA (for example, at a replication fork) by the addition of nucleotides to the 3′ end of an existing chain. There are several different DNA polymerases; DNA polymerase III and DNA polymerase I play major roles in DNA replication in E. coli

(Rosalind) Franklin

Woman who generated x-ray images of DNA, she povided Watson and Crick with key data about DNA She discovered the density of DNA and, more importantly, established that the molecule existed in a helical conformation

(Frederick) Griffith

Conducted an experiment suggesting that bacteria are capable of transferring genetic information through a process known as transformation

Helicase

An enzyme that untwists the double helix of DNA at replication forks, separating the two strands and making them available as template strands

(Alfred) Hershey & (Martha) Chase

Demonstrated that DNA was transferred from bacteriophages to bacteria, a discovery that confirmed DNA as the bearer of genetic information

Histones

A small protein with a high proportion of positively charged amino acids that binds to the negatively charged DNA and plays a key role in chromatin structure

Lagging Strand

A discontinuously synthesized DNA strand that elongates by means of Okazaki fragments, each synthesized in a 5′ ® 3′ direction away from the replication fork

Leading Strand

The new complementary DNA strand synthesized continuously along the template strand toward the replication fork in the mandatory 5′ ® 3′ direction

Nuclease

An enzyme that cuts DNA or RNA, either removing one or a few bases or hydrolyzing the DNA or RNA completely into its component nucleotides

Nucleosomes

The basic, bead-like unit of DNA packing in eukaryotes, consisting of a segment of DNA wound around a protein core composed of two copies of each of four types of histone

Okazaki fragments

A short segment of DNA synthesized away from the replication fork on a template strand during DNA replication. Many such segments are joined together to make up the lagging strand of newly synthesized DNA

Origin of replication

Site where the replication of a DNA molecule begins, consisting of a specific sequence of nucleotides

Primase

An enzyme that joins RNA nucleotides to make a primer during DNA replication, using the parental DNA strand as a template

Primer

A short polynucleotide with a free 3′ end, bound by complementary base pairing to the template strand and elongated with DNA nucleotides during DNA replication

Purines

One of two types of nitrogenous bases found in nucleotides, characterized by a six-membered ring fused to a five-membered ring. Adenine (A) and guanine (G) are examples

Pyrimidines

One of two types of nitrogenous bases found in nucleotides, characterized by a six-membered ring. Cytosine (C), thymine (T), and uracil (U) are examples

Replication fork

A Y-shaped region on a replicating DNA molecule where the parental strands are being unwound and new strands are being synthesized

Semiconservative model

Type of DNA replication in which the replicated double helix consists of one old strand, derived from the parental molecule, and one newly made strand

Single-strand binding protein

A protein that binds to the unpaired DNA strands during DNA replication, stabilizing them and holding them apart while they serve as templates for the synthesis of complementary strands of DNA

Telomerase

An enzyme that adds nucleotides to telomeres, especially in cancer cells

Telomeres

The tandemly repetitive DNA at the end of a eukaryotic chromosome's DNA molecule. They protect the organism's genes from being eroded during successive rounds of replication

Topoisomerase

A protein that breaks, swivels, and rejoins DNA strands. During DNA replication, this helps to relieve strain in the double helix ahead of the replication fork

Watson & Crick

Deduced that DNA is a double helix and built a structural model