Molecular Biology Chapter 16 Vocabulary

Front 1

DNA Replication

Back 1

The process by which a DNA molecule is copied; also called DNA synthesis.

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Transformation

Back 2

(1) The conversion of a normal animal cell to a cancerous cell. (2) A change in genotype and phenotype due to the assimilation of external DNA by a cell. When the external DNA is from a member of a different species, transformation results in horizontal gene transfer.

Front 3

Bacteriophage

Back 3

A virus that infects bacteria; also called a phage.

Front 4

Phages

Back 4

A virus that infects bacteria; also called a bacteriophage.

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Virus

Back 5

An infectious particle incapable of replication outside the cell, consisting of an RNA or DNA genome surrounded by a protein coat (capsid) and, for some viruses, a membranous envelope.

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Double Helix

Back 6

The form of native DNA, referring to its two adjacent antiparallel polynucleotide strands wound around an imaginary axis into a spiral shape.

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Antiparallel

Back 7

Referring to the arrangement of the sugar-phosphate backbones in a DNA double helix (they run opposite 5’ → 3’ directions).

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Semiconservative Model

Back 8

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.

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Origins of Replication

Back 9

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

Front 10

Replication Fork

Back 10

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

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Helicases

Back 11

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

Front 12

Single Strand Binding Proteins

Back 12

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.

Front 13

Topoisomerase

Back 13

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

Front 14

Primer

Back 14

A short stretch of RNA with a free 3’ end, bound by complementary base paring to the template strand and elongated with DNA nucleotides during DNA replication.

Front 15

Primase

Back 15

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

Front 16

DNA Polymerases

Back 16

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.

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Leading Strand

Back 17

The new complementary DNA strand synthesized continuously along the template strand toward the replication fork in the mandatory 5’→ 3’ direction.

Front 18

Lagging Strand

Back 18

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

Front 19

Okazaki Fragments

Back 19

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.

Front 20

DNA Ligase

Back 20

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).

Front 21

Mismatch Repair

Back 21

The cellular process that uses specific enzymes to remove and replace incorrectly paired nucleotides.

Front 22

Nuclease

Back 22

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.

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Nucleotide Excision Repair

Back 23

A repair system that removes and then correctly replaces a damaged segment of DNA using the undamaged strand as a guide.

Front 24

Telomere

Back 24

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

Front 25

Telomerase

Back 25

An enzyme that catalyzes the lengthening of telomeres in eukaryotic germ cells.

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Histones

Back 26

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.

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Nucleosome

Back 27

The basic, beadlike 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.

Front 28

Nucleoid

Back 28

A non-membrane bounded region in a prokaryotic cell where the DNA is concentrated.

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Chromatin

Back 29

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

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Heterochromatin

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Eukaryotic chromatin that remains highly compacted during interphase and is generally not transcribed.

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Euchromatin

Back 31

The less condensed form of eukaryotic chromatin that is available for transcription.