AP BIO Cummaltive Unit 3 (6) - 4

double helix

the twisted-ladder shape of DNA

antiparallel

the structure of the DNA double helix, where the two complementary strands run in opposite directions.

semiconservative

when a DNA double helix is copied, each of the two resulting DNA molecules is an exact hybrid: it consists of one original (parent) strand and one newly synthesized complementary strand. *

replication fork

Y-shaped structure formed during initiation of replication

DNA polymerase

the primary enzyme responsible for synthesizing new DNA during replication.

DNA replication

the semiconservative process where a cell copies its DNA before division

phage

a type of virus that exclusively infects and replicates inside bacteria

helicase

during replication, this enzyme helps to open up the DNA helix by breaking the hydrogen bonds

primase

enzyme that synthesizes the RNA primer; the primer is needed for DNA pol to start synthesis of a new DNA strand

origin of replication

the specific sequence of DNA where duplication begins

leading strand

strand that is synthesized continuously in the 5'-3' direction which is synthesized in the direction of the replication fork

lagging strand

during replication, the strand that is replicated in short fragments and away from the replication fork

transcription

process through which messenger RNA forms on a template of DNA

translation

process through which RNA directs the formation of protein

messenger RNA (mRNA)

RNA that carries information from DNA to ribosomes during protein synthesis

codon

three consecutive nucleotides in mRNA that specify the insertion of an amino acid or the release of a polypeptide chain during translation

RNA polymerase

the primary enzyme responsible for transcription *

TATA box

conserved promoter sequence in eukaryotes and prokaryotes that helps to establish the initiation site for transcription

transcription factor

protein that binds to the DNA at the promoter or enhancer region and that influences transcription of a gene

5' cap

a methylated guanosine triphosphate (GTP) molecule that is attached to the 5' end of a messenger RNA to protect the end from degradation

poly-A tail

a series of adenine nucleotides that are attached to the 3' end of an mRNA to protect the end from degradation

intron

non–protein-coding intervening sequences that are spliced from mRNA during processing

exon

sequence present in protein-coding mRNA after completion of pre-mRNA splicing

RNA splicing

a post-transcriptional process in eukaryotic cells where non-coding sequences (introns) are removed from pre-mRNA, and the remaining coding sequences (exons) are joined together to form mature mRNA. *

transfer RNA (tRNA)

RNA that carries activated amino acids to the site of protein synthesis on the ribosome

anticodon

three-nucleotide sequence in a tRNA molecule that corresponds to an mRNA codon

operon

collection of genes involved in a pathway that are transcribed together as a single mRNA in prokaryotic cells

repressor

protein that binds to the operator of prokaryotic genes to prevent transcription

differentiation

the process by which unspecialized stem cells become specialized in their structure and function *

cytoplasmic determinants

maternal substances (such as mRNA and proteins) stored in the unfertilized egg.

proto-oncogene

normal gene that when mutated becomes an oncogene

oncogene

mutated version of a normal gene involved in the positive regulation of the cell cycle

tumor suppressor gene

segment of DNA that codes for regulator proteins that prevent the cell from undergoing uncontrolled division

virus

a submicroscopic, non-living infectious agent that acts as an obligate intracellular parasite

capsid

protein coating of the viral core

lytic cycle

type of virus replication in which virions are released through lysis, or bursting, of the cell

lysogenic cycle

type of virus replication in which the viral genome is incorporated into the genome of the host cell

retrovirus

virus with an RNA genome that must be reverse transcribed into DNA before being incorporated into the host cell genome

Signal transduction pathways

the series of molecular steps by which a cell converts an extracellular signal (like a hormone) into a specific cellular response. *

hormone

chemical signaling molecule, usually protein or steroid, secreted by endocrine cells that act to control or regulate specific physiological processes

G protein coupled receptors

the largest and most diverse group of membrane receptors in eukaryotic cells.

receptor tyrosine kinases

membrane receptors that attach phosphates to the amino acid tyrosine *

ligand gated ion channels

a membrane receptor protein that opens or closes in response to the binding of a specific chemical messenger (a ligand). It acts as both a receptor for reception and a "gate" to let ions (like \(Na^{+}\) or \(Ca^{2+}\)) diffuse across the cell membrane. *

phosphorylation cascades

a chain reaction where one enzyme adds a phosphate group to the next, which then activates the next, and so on. *

cyclic AMP (cAMP)

second messenger that is derived from ATP

second messengers

small, non-protein molecule that propagates a signal within the cell after activation of a receptor causes its release

apoptosis

programmed cell death

adenylyl cyclase

an enzyme anchored in the cell membrane that converts ATP into cyclic AMP (cAMP)

genome

total genetic information of a cell or organism

chromosome

structure within the nucleus that is made up of chromatin that contains DNA, the hereditary material

chromatin

protein-DNA complex that serves as the building material of chromosomes

gamete

haploid reproductive cell or sex cell (sperm, pollen grain, or egg)

somatic cell

all the cells of a multicellular organism except the gametes or reproductive cells

sister chromatids

two identical copies of the same chromosome, joined together by a specialized region called the centromere. *

centromere

region at which sister chromatids are bound together; a constricted area in condensed chromosomes

mitosis

(also, karyokinesis) period of the cell cycle during which the duplicated chromosomes are separated into identical nuclei; includes prophase, prometaphase, metaphase, anaphase, and telophase

cytokinesis

division of the cytoplasm following mitosis that forms two daughter cells.

interphase

period of the cell cycle leading up to mitosis; includes G1, S, and G2 phases (the interim period between two consecutive cell divisions

G₁ phase

(also, first gap) first phase of interphase centered on cell growth during mitosis

S phase

second, or synthesis, stage of interphase during which DNA replication occurs

G₂ phase

(also, second gap) third phase of interphase during which the cell undergoes final preparations for mitosis

M phase

the final, active division stage of the eukaryotic cell cycle. *

mitotic spindle

apparatus composed of microtubules that orchestrates the movement of chromosomes during mitosis

centrosome

region in animal cells made of two centrioles

metaphase plate

equatorial plane midway between the two poles of a cell where the chromosomes align during metaphase

Clevage

cytokinesis in animal cells or the rapid cell divisions of early embryonic development.

cell plate

structure formed during plant cell cytokinesis by Golgi vesicles, forming a temporary structure (phragmoplast) and fusing at the metaphase plate; ultimately leads to the formation of cell walls that separate the two daughter cells

binary fission

prokaryotic cell division process

cyclin

one of a group of proteins that act in conjunction with cyclin-dependent kinases to help regulate the cell cycle by phosphorylating key proteins; the concentrations of cyclins fluctuate throughout the cell cycle

cyclin-dependent kinase

one of a group of protein kinases that helps to regulate the cell cycle when bound to cyclin; it functions to phosphorylate other proteins that are either activated or inactivated by phosphorylation