ALL KEY TERMS FOR BIO FINAL - WEST

Chargaff's rule

The observation that in DNA, the amount of adenine equals thymine and the amount of guanine equals cytosine.

Antiparallel

The orientation of the two strands of a DNA double helix, where they run in opposite directions (5' to 3' and 3' to 5').

Semiconservative replication

The mechanism of DNA replication where each daughter molecule consists of one original parental strand and one newly synthesized strand.

Okazaki fragments

Short, newly synthesized DNA fragments that are formed on the lagging strand during DNA replication.

Telomerase

An enzyme that adds nucleotide sequences to the ends of chromosomes to prevent the loss of genetic information during replication.

PCR (polymerase chain reaction)

A laboratory technique used to amplify specific segments of DNA through repeated cycles of denaturation, annealing, and extension.

Frameshift mutation

A genetic mutation caused by an insertion or deletion of nucleotides that shifts the reading frame of the genetic sequence.

Transcription

The process by which the information in a strand of DNA is copied into a new molecule of messenger RNA (mRNA).

Operon

A cluster of genes under the control of a single promoter, commonly found in prokaryotes.

Splicing

The process in eukaryotic cells where introns are removed from pre-mRNA and exons are joined together.

Translation

The process by which ribosomes synthesize proteins based on the sequence of codons in mRNA.

Wobble hypothesis

The flexibility in base pairing between the third base of a codon and the corresponding base of a tRNA anticodon.

Epigenetics

The study of heritable changes in gene expression that do not involve alterations to the underlying DNA sequence.

Barr body

The inactive X chromosome in a female somatic cell, appearing as a condensed mass of chromatin.

Lytic cycle

A viral reproductive cycle that results in the destruction of the host cell and the release of new viral particles.

Hardy-Weinberg equilibrium

A principle stating that allele and genotype frequencies in a population will remain constant from generation to generation in the absence of evolutionary influences.

Natural selection

The process whereby organisms better adapted to their environment tend to survive and produce more offspring.

Allopatric speciation

Speciation that occurs when biological populations of the same species become isolated due to geographic barriers.

Fixed action pattern (FAP)

A sequence of unlearned, innate behaviors that is essentially unchangeable and, once initiated, usually carried to completion.

Hamilton's rule

A formula (rB > C) predicting that altruistic behavior will evolve if the benefit to the recipient multiplied by the coefficient of relatedness exceeds the cost to the actor.

Trophic cascade

An ecological phenomenon where the addition or removal of top predators causes reciprocal changes in the relative populations of predator and prey through a food chain.

Keystone species

A species on which other species in an ecosystem largely depend, such that if it were removed, the ecosystem would change drastically.

Carrying capacity (K)

The maximum population size of a species that an environment can sustain indefinitely given the available resources.

nucleotide

the basic building block of DNA and RNA

consists of a sugar, phosphate group, and nitrogenous base

Chargaff's rule

A = T and C = G in DNA

base pairing rule that ensures complementarity

complementary base pairing

A pairs with T and C pairs with G in DNA

rules for matching DNA strands

antiparallel

DNA strands run in opposite directions (5'→3' and 3'→5')

5' end

end of DNA/RNA strand with a phosphate group

3' end

end of DNA/RNA strand with a hydroxyl group

phosphate group

component of nucleotide backbone that links sugars

hydroxyl group (-OH)

group at 3' end used for DNA/RNA extension

melting temperature (Tm)

temperature at which DNA strands separate

higher GC = higher Tm

GC content

percentage of guanine and cytosine bases in DNA

AT content

percentage of adenine and thymine bases in DNA

DNA replication

process of copying DNA into two identical strands

Meselson-Stahl experiment

experiment proving semiconservative DNA replication

semiconservative replication

each new DNA has one old and one new strand

conservative replication

old DNA remains intact and new DNA is separate (incorrect model)

dispersive replication

old and new DNA mixed in both strands (incorrect model)

helicase

unwinds DNA double helix

single-stranded binding protein (SSB)

prevents DNA strands from rejoining

primase

makes RNA primer for DNA replication

RNA primer

short RNA segment that starts DNA synthesis

DNA polymerase III

main enzyme that adds nucleotides during replication

DNA polymerase I

replaces RNA primers with DNA

sliding clamp

holds DNA polymerase in place on DNA

replication fork

Y-shaped region where DNA is unwound

leading strand

DNA strand synthesized continuously

lagging strand

DNA strand synthesized in fragments

Okazaki fragments

short DNA fragments on lagging strand

telomere

repetitive DNA at chromosome ends

telomerase

enzyme that extends telomeres

prevents shortening

mismatch repair

fixes incorrect base pairing after replication

excision repair

removes damaged DNA and replaces it

PCR (polymerase chain reaction)

method to amplify DNA

Taq polymerase

heat-stable DNA polymerase used in PCR

dNTPs

nucleotides used for DNA synthesis

denaturation

separating DNA strands using heat

annealing

primers bind to DNA template

extension

DNA polymerase builds new strand

mutation

change in DNA sequence

nucleotide-level mutation

change affecting one or few bases

chromosome-level mutation

change affecting large DNA segments

point mutation

single base substitution

substitution

replacing one base with another

insertion

adding extra nucleotide(s)

deletion

removing nucleotide(s)

frameshift mutation

insertion/deletion that shifts reading frame

silent mutation

mutation with no amino acid change

missense mutation

mutation that changes amino acid

nonsense mutation

mutation creating premature stop codon

transition

purine↔purine or pyrimidine↔pyrimidine change

transversion

purine↔pyrimidine change

chromosomal deletion

large DNA segment lost

duplication

segment of chromosome repeated

inversion

segment reversed in orientation

translocation

segment moved to another chromosome

spontaneous mutation

mutation from natural DNA errors

induced mutation

mutation caused by mutagens

mutagen

agent that increases mutation rate

tautomer

temporary altered base form causing mispairing

somatic mutation

mutation in body cells (not inherited)

germ-line mutation

mutation in gametes (heritable)

heritable mutation

mutation passed to offspring

transcription

DNA → RNA synthesis

RNA polymerase

enzyme that makes RNA

promoter

DNA region where transcription starts

coding strand

DNA strand matching RNA sequence

template strand

DNA strand used to make RNA

elongation

growth of RNA strand

initiation

start of transcription

termination

end of transcription

hairpin loop

RNA structure that stops transcription

rho factor

protein that terminates transcription in bacteria

rho-dependent termination

termination using rho protein