Genetics 210 (Exam 3)

Major groove

The larger of the two grooves in the DNA double helix

Minor groove

The smaller of the two grooves in the DNA double helix

DNA supercoiling

The formation of additional coils in DNA due to twisting forces

Intergenic region

DNA between genes

Microdomain

A loop of DNA that is found in a bacterial chromosome and is typically 10 kbp in length

Protein-coding gene

Transcribes into mRNA

Structural gene

A gene that codes for a product, such as an enzyme, protein, or RNA, rather than serving as a regulator

Topoismerase

Relaxes the DNA from supercoiled nature

Retrotransposition

An element's RNA is used as a template to synthesize DNA molecules, which are inserted into new chromosomal sites

Retrotransposon

A transposable element that uses reverse transcriptase to transpose through an RNA intermediate.

Transposable elements

Genetic element that has the ability to move (transpose) from one site on a chromosome to another.

Transposase

Enzyme which recognizes host DNA and cuts and glues transposons in and out of genome

30-nm fiber

nucleosome units organized into a more compact structure that is 30 nm in diameter

Constitutive heterochromatin

Chromosomal regions that remain condensed in heterochromatin at most times in all cells

Euchromatin

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

Loop domain

A segment of chromosomal DNA that is anchored by proteins, so it forms a loop

DNA helicase

An enzyme that unwinds the DNA double helix during DNA replication

DNA ligase

An enzyme that eventually joins the sugar-phosphate backbones of the Okazaki fragments

DNA polymerase I, III

An enzyme that catalyzes the elongation of new DNA at a replication fork by the addition of nucleotides to the existing chain.

Lagging strand

The strand in replication that is copied 3' to 5' as Okazaki fragments and then joined up.

Leading strand

The new continuous complementary DNA strand synthesized along the template strand in the mandatory 5' to 3' direction.

Okazaki fragment

Short segment of DNA synthesized discontinuously in small segments in the 3' to 5' direction by DNA polymerase

Primase

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

Primer

A short segment of DNA that acts as the starting point for a new strand

Replication fork

A Y-shaped region on a replicating DNA molecule where new strands are growing.

Replisome

Group of proteins needed for DNA synthesis

Semiconservative

Method of replication that implies that each new strand of DNA is half original and half new

Topoisomerase II

An enzyme that breaks a DNA double helix, rotates the ends, and seals the break.

DNA pol. a

works with primase to make DNA primers required to initiate DNA synthesis

DNA pol. δ

lagging strand synthesis

DNA pol. ε

leading strand synthesis

Flap endonuclease

Removes RNA primers in eukaryotes

Telomere

Repetitive DNA at the end of a eukaryotic chromosome

Branch migration

The lateral movement of a Holliday junction

Heteroduplex

A double-stranded region of DNA that contains one or more base mismatches

Holliday junction

Cross-shaped structure that forms during the process of genetic recombination

Homologous recombination

Exchange of genetic information between homologous DNA molecules.

Holoenzyme

Enzyme with its cofactor

Promoter

Specific region of a gene where RNA polymerase can bind and begin transcription

Regulatory sequence

The part of a gene that determines the timing, amount, and location of protein production

rho-dependent termination

rho protein recognizes specific DNA sequences and causes a pause in the RNA polymerase

rho-independent termination

Hairpin structure formed by inverted repeats, followed by a string of uracils

RNA polymerase

Enzyme that links together the growing chain of RNA nucleotides during transcription using a DNA strand as a template

Sigma subunit

Directs enzyme to the promoter

Alternative splicing

Post-translational RNA modification process in which some exons are removed or joined in various combinations.

Exon

Expressed sequence of DNA; codes for a protein

Intron

Sequence of DNA that is not involved in coding for a protein

General transcription factors

A set of proteins that bind to the promoter of a gene whose combined action is necessary for transcription.

Spliceosome

A complex of enzymes that serves to splice out the introns of a pre-mRNA transcript

TATA box

A promoter DNA sequence crucial in forming the transcription initiation complex.

Anticodon

A group of three bases on a tRNA molecule that are complementary to an mRNA codon

Elongation factor

One of multiple proteins that facilitates the lengthening of a polypeptide during protein synthesis.

Initiation factor

A protein that binds to mRNA to initiate translation

P site

Holds the tRNA carrying the growing polypeptide chain

A site

where tRNA enters

E site

The exit site, where discharged tRNAs leave the ribosome

Primary structure

sequence of amino acids

Quaternary structure

Results from two or more polypeptide subunits.

Secondary structure

Either an alpha helix or beta pleated sheet.

Tertiary structure

Results from interactions between side chains.