Glossary

α

the Greek letter alpha

β

the Greek letter beta

γ

the Greek letter gamma

λ

the Greek letter lambda

σ

the Greek letter sigma

E. coli

the bacterium Escherichia coli

"-ase"

suffix indicating an enzyme

acidic

having the properties of an acid; the opposite of basic

acrosomal cap

tip of sperm cell that contains digestive enzymes for penetrating the egg

adenoma

a tumor (cell mass) of gland cells

aerobic

with oxygen, or requiring it

agar

gel derived from algae

agglutinate

clump together

aggregate

stick together

algorithm

procedure or set of steps

allele

a particular form of a gene

allelic variation

presence of different gene forms (alleles) in a population

allergen

substance that triggers an allergic reaction

allolactose

"other lactose"; a modified form of lactose

amino acid

a building block of protein

amino termini

the ends of a protein chain with a free NH₂ group

amniocentesis

removal of fluid from the amniotic sac surrounding a fetus, for diagnosis

amplify

produce many copies of, multiply

anabolic steroids

hormones used to build muscle mass

anaerobic

without oxygen or not requiring oxygen

androgen

testosterone or other masculinizing hormone

anemia

lack of oxygen-carrying capacity in the blood

aneuploidy

abnormal chromosome numbers

angiogenesis

growth of new blood vessels

anion

negatively charged ion

anneal

join together

anode

positive pole

anterior

front

antibody

immune-system protein that binds to foreign molecules

antidiuretic

a substance that prevents water loss

antigen

a foreign substance that provokes an immune response

antigenicity

ability to provoke an immune response

apoptosis

programmed cell death

Archaea

one of three domains of life, a type of cell without a nucleus

archaeans

members of one of three domains of life, have types of cells without a nucleus

aspirated

removed with a needle and syringe

aspiration

inhalation of fluid or solids into the lungs

association analysis

estimation of the relationship between alleles or geno-types and disease

asymptomatic

without symptoms

ATP

adenosine triphosphate, a high-energy compound used to power cell processes

ATPase

an enzyme that breaks down ATP, releasing energy

attenuation

weaken or dilute

atypical

irregular

autoimmune

reaction of the immune system to the body's own tissues

autoimmunity

immune reaction to the body's own tissues

autosomal

describes a chromosome other than the X and Y sex-determining chromosomes

autosome

a chromosome that is not sex-determining (not X or Y)

axon

the long extension of a nerve cell down which information flows

bacteriophage

virus that infects bacteria

basal

lowest level

base pair

two nucleotides (either DNA or RNA) linked by weak bonds

basic

having the properties of a base; opposite of acidic

benign

type of tumor that does not invade surrounding tissue

binding protein

protein that binds to another molecule, usually either DNA or protein

biodiversity

degree of variety of life

bioinformatics

use of information technology to analyze biological data

biolistic

firing a microscopic pellel into a biological sample (from biological/ballistic)

biopolymers

biological molecules formed from similar smaller molecules, such as DNA or protein

biopsy

removal of tissue sample for diagnosis

biotechnology

production of useful products

bipolar disorder

psychiatric disease characterized by alternating mania and depression

blastocyst

early stage of embryonic development

brackish

a mix of salt water and fresh water

breeding analysis

analysis of the offspring ratios in breeding experiments

buffers

substances that counteract rapid or wide pH changes in a solution

Cajal

Ramon y Cajal, Spanish neuroanatomist

carcinogens

substances that cause cancer

carrier

a person with one copy of a gene for a recessive trait, who therefore does not express the trait

catalyst

substance that speeds a reaction without being consumed (e.g., enzyme)

catalytic

describes a substance that speeds a reaction without being consumed

catalyze

aid in the reaction of

cathode

negative pole

cDNA

complementary DNA

cell cycle

sequence of growth, replication and division that produces new cells

centenarian

person who lives to age 100

centromere

the region of the chromosome linking chromatids

cerebrovascular

related to the blood vessels in the brain

cerebrovascular disease

stroke, aneurysm, or other circulatory disorder affecting the brain

charge density

ratio of net charge on the protein to its molecular mass

chemotaxis

movement of a cell stimulated by a chemical attractant or repellent

chemotherapeutic

use of chemicals to kill cancer cells

chloroplast

the photosynthetic organelle of plants and algae

chondrocyte

a cell that forms cartilage

chromatid

a replicated chromosome before separation from its copy

chromatin

complex of DNA, histones, and other proteins, making up chromosomes

ciliated protozoa

single-celled organism possessing cilia, short hair-like extensions of the cell membrane

circadian

relating to day or day length

cleavage

hydrolysis

cleave

split

clinical trials

tests performed on human subjects

codon

a sequence of three mRNA nucleotides coding for one amino acid

Cold War

prolonged U.S.-Soviet rivalry following World War II

colectomy

colon removal

colon crypts

part of the large intestine

complementary

matching opposite, like hand and glove

conformation

three-dimensional shape

congenital

from birth

conjugation

a type of DNA exchange between bacteria

cryo-electron microscope

electron microscope that integrates multiple images to form a three-dimensional model of the sample

cryopreservation

use of very cold temperatures to preserve a sample

cultivars

plant varieties resulting from selective breeding

cytochemist

chemist specializing in cellular chemistry

cytochemistry

cellular chemistry

cytogenetics

study of chromosome structure and behavior

cytologist

a scientist who studies cells

cytokine

immune system signaling molecule

cytokinesis

division of the cell's cytoplasm

cytology

the study of cells

cytoplasm

the material in a cell, excluding the nucleus

cytosol

fluid portion of a cell, not including the organelles

de novo

entirely new

deleterious

harmful

dementia

neurological illness characterized by impaired thought or awareness

demography

aspects of population structure, including size, age distribution, growth, and other factors

denature

destroy the structure of

deoxynucleotide

building block of DNA

dimerize

linkage of two subunits

dimorphism

two forms

diploid

possessing pairs of chromosomes, one member of each pair derived from each parent

disaccharide

two sugar molecules linked together

dizygotic

fraternal or nonidentical

DNA

deoxyribonucleic acid

domains

regions

dominant

controlling the phenotype when one allele is present

dopamine

brain signaling chemical

dosage compensation

equalizing of expression level of X-chromosome genes between males and females, by silencing one X chromosome in females or amplifying expression in males

ecosystem

an ecological community and its environment

ectopic expression

expression of a gene in the wrong cells or tissues

electrical gradient

chemiosmotic gradient

electrophoresis

technique for separation of molecules based on size and charge

eluting

exiting

embryogenesis

development of the embryo from a fertilized egg

endangered

in danger of extinction throughout all or a significant portion of a species' range

endogenous

derived from inside the organism

endometriosis

disorder of the endometrium, the lining of the uterus

endometrium

uterine lining

endonuclease

enzyme that cuts DNA or RNA within the chain

endoplasmic reticulum

network of membranes within the cell

endoscope

tool used to see within the body

endoscopic

describes procedure wherein a tool is used to see within the body

endosymbiosis

symbiosis in which one partner lives within the other

enzyme

a protein that controls a reaction in a cell

epidemiologic

the spread of diseases in a population

epidemiologists

people who study the incidence and spread of diseases in a population

epidemiology

study of incidence and spread of diseases in a population

epididymis

tube above the testes for storage and maturation of sperm

epigenetic

not involving DNA sequence change

epistasis

suppression of a characteristic of one gene by the action of another gene

epithelial cells

one of four tissue types found in the body, characterized by thin sheets and usually serving a protective or secretory function

Escherichia coli

common bacterium of the human gut, used in research as a model organism

estrogen

female horomone

et al.

"and others"

ethicists

a person who writes and speaks about ethical issues

etiology

causation of disease, or the study of causation

eubacteria

one of three domains of life, comprising most groups previously classified as bacteria

eugenics

movement to "improve" the gene pool by selective breeding

eukaryote

organism with cells possessing a nucleus

eukaryotic

describing an organism that has cells containing nuclei

ex vivo

outside a living organism

excise

remove; cut out

excision

removal

exogenous

from outside

exon

coding region of genes

exonuclease

enzyme that cuts DNA or RNA at the end of a strand

expression analysis

whole-cell analysis of gene expression (use of a gene to create its RNA or protein product)

fallopian tubes

tubes through which eggs pass to the uterus

fermentation

biochemical process of sugar breakdown without oxygen

fibroblast

undifferentiated cell normally giving rise to connective tissue cells

fluorophore

fluorescent molecule

forensic

related to legal proceedings

founder

population

fractionated

purified by separation based on chemical or physical properties

fraternal twins

dizygotic twins who share 50 percent of their genetic material

frontal lobe

one part of the forward section of the brain, responsible for planning, abstraction, and aspects of personality

gamete

reproductive cell, such as sperm or egg

gastrulation

embryonic stage at which primitive gut is formed

gel electrophoresis

technique for separation of molecules based on size and charge

gene expression

use of a gene to create the corresponding protein

genetic code

the relationship between RNA nucleotide triplets and the amino acids they cause to be added to a growing protein chain

genetic drift

evolutionary mechanism, involving random change in gene frequencies

genetic predisposition

increased risk of developing diseases

genome

the total genetic material in a cell or organism

genomics

the study of gene sequences

genotype

set of genes present

geothermal

related to heat sources within Earth

germ cell

cell creating eggs or sperm

germ-line

cells giving rise to eggs or sperm

gigabase

one billion bases (of DNA)

glucose

sugar

glycolipid

molecule composed of sugar and fatty acid

glycolysis

the breakdown of the six-carbon carbohydrates glucose and fructose

glycoprotein

protein to which sugars are attached

Golgi network

system in the cell for modifying, sorting, and delivering proteins

gonads

testes or ovaries

gradient

a difference in concentration between two regions

Gram negative bacteria

bacteria that do not take up Gram stain, due to membrane structure

Gram positive

able to take up Gram stain, used to classify bacteria

gynecomastia

excessive breast development in males

haploid

possessing only one copy of each chromosome

haplotype

set of alleles or markers on a short chromosome segment

hematopoiesis

formation of the blood

hematopoietic

blood-forming

heme

iron-containing nitrogenous compound found in hemoglobin

hemolysis

breakdown of the blood cells

hemolytic anemia

blood disorder characterized by destruction of red blood cells

hemophiliacs

a person with hemophilia, a disorder of blood clotting

herbivore

plant eater

heritability

proportion of variability due to genes; ability to be inherited

heritability estimates

how much of what is observed is due to genetic factors

heritable

genetic

heterochromatin

condensed portion of chromosomes

heterozygote

an individual whose genetic information contains two different forms (alleles) of a particular gene

heterozygous

characterized by possession of two different forms (alleles) of a particular gene

high-throughput

rapid, with the capacity to analyze many samples in a short time

histological

related to tissues

histology

study of tissues

histone

protein around which DNA winds in the chromosome

homeostasis

maintenance of steady state within a living organism

homologous

carrying similar genes

homologues

chromosomes with corresponding genes that pair and exchange segments in meiosis

homozygote

an individual whose genetic information contains two identical copies of a particular gene

homozygous

containing two identical copies of a particular gene

hormones

molecules released by one cell to influence another

hybrid

combination of two different types

hybridization (molecular)

base-pairing among DNAs or RNAs of different origins

hybridize

to combine two different species

hydrogen bond

weak bond between the H of one molecule or group and a nitrogen or oxygen of another

hydrolysis

splitting with water

hydrophilic

"water-loving"

hydrophobic

"water hating," such as oils

hydrophobic interaction

attraction between portions of a molecule (especially a protein) based on mutual repulsion of water

hydroxyl group

chemical group consisting of-OH

hyperplastic cell

cell that is growing at an increased rate compared to normal cells, but is not yet cancerous

hypogonadism

underdeveloped testes or ovaries

hypothalamus

brain region that coordinates hormone and nervous systems

hypothesis

testable statement

identical twins

monozygotic twins who share 100 percent of their genetic material

immunogenicity

likelihood of triggering an immune system defense

immunosuppression

suppression of immune system function

immunosuppressive

describes an agent able to suppress immune system function

in vitro

"in glass"; in lab apparatus, rather than within a living organism

in vivo

"in life"; in a living organism, rather than in a laboratory apparatus

incubating

heating to optimal temperature for growth

informed consent

knowledge of risks involved

insecticide

substance that kills insects

interphase

the time period between cell divisions

intra-strand

within a strand

intravenous

into a vein

intron

untranslated portion of a gene that interrupts coding regions

karyotype

the set of chromosomes in a cell, or a standard picture of the chromosomes

kilobases

units of measure of the length of a nucleicacid chain; one kilo-base is equal to 1,000 base pairs

kilodalton

a unit of molecular weight, equal to the weight of 1000 hydrogen atoms

kinase

an enzyme that adds a phosphate group to another molecule, usually a protein

knocking out

deleting of a gene or obstructing gene expression

laparoscope

surgical instrument that is inserted through a very small incision, usually guided by some type of imaging technique

latent

present or potential, but not apparent

lesion

damage

ligand

a molecule that binds to a receptor or other molecule

ligase

enzyme that repairs breaks in DNA

ligate

join together

linkage analysis

examination of co-inheritance of disease and DNA markers, used to locate disease genes

lipid

fat or wax-like molecule, insoluble in water

loci/locus

site(s) on a chromosome

longitudinally

lengthwise

lumen

the space within the tubes of the endoplasmic reticulum

lymphocytes

white blood cells

lyse

break apart

lysis

breakage

macromolecular

describes a large molecule, one composed of many similar parts

macromolecule

large molecule such as a protein, a carbohydrate, or a nucleic acid

macrophage

immune system cell that consumes foreign material and cellular debris

malignancy

cancerous tissue

malignant

cancerous; invasive tumor

media

(bacteria) nutrient source

meiosis

cell division that forms eggs or sperm

melanocytes

pigmented cells

meta-analysis

analysis of combined results from multiple clinical trials

metabolism

chemical reactions within a cell

metabolite

molecule involved in a metabolic pathway

metaphase

stage in mitosis at which chromosomes are aligned along the cell equator

metastasis

breaking away of cancerous cells from the initial tumor

metastatic

cancerous cells broken away from the initial tumor

methylate

add a methyl group to

methylated

a methyl group, CH₃, added

methylation

addition of a methyl group, CH₃

microcephaly

reduced head size

microliters

one thousandth of a milliliter

micrometer

1/1000 meter

microsatellites

small repetitive DNA elements dispersed throughout the genome

microtubule

protein strands within the cell, part of the cytoskeleton

miscegenation

racial mixing

mitochondria

energy-producing cell organelle

mitogen

a substance that stimulates mitosis

mitosis

separation of replicated chromosomes

molecular hybridization

base-pairing among DNAs or RNAs of different origins

molecular systematics

the analysis of DNA and other molecules to determine evolutionary relationships

monoclonal antibodies

immune system proteins derived from a single B cell

monomer

"single part"; monomers are joined to form a polymer

monosomy

gamete that is missing a chromosome

monozygotic

genetically identical

morphologically

related to shape and form

morphology

related to shape and form

mRNA

messenger RNA

mucoid

having the properties of mucous

mucosa

outer covering designed to secrete mucus, often found lining cavities and internal surfaces

mucous membranes

nasal passages, gut lining, and other moist surfaces lining the body

multimer

composed of many similar parts

multinucleate

having many nuclei within a single cell membrane

mutagen

any substance or agent capable of causing a change in the structure of DNA

mutagenesis

creation of mutations

mutation

change in DNA sequence

nanometer

10^-9(exp) meters; one billionth of a meter

nascent

early-stage

necrosis

cell death from injury or disease

nematode

worm of the Nematoda phylum, many of which are parasitic

neonatal

newborn

neoplasms

new growths

neuroimaging

techniques for making images of the brain

neurological

related to brain function or disease

neuron

nerve cell

neurotransmitter

molecule released by one neuron to stimulate or inhibit a neuron or other cell

non-polar

without charge separation; not soluble in water

normal distribution

distribution of data that graphs as a bell-shaped curve

Northern blot

a technique for separating RNA molecules by electrophoresis and then identifying a target fragment with a DNA probe

Northern blotting

separating RNA molecules by electrophoresis and then identifying a target fragment with a DNA probe

nuclear DNA

DNA contained in the cell nucleus on one of the 46 human chromosomes; distinct from DNA in the mitochondria

nuclear membrane

membrane surrounding the nucleus

nuclease

enzyme that cuts DNA or RNA

nucleic acid

DNA or RNA

nucleoid

region of the bacterial cell in which DNA is located

nucleolus

portion of the nucleus in which ribosomes are made

nucleoplasm

material in the nucleus

nucleoside

building block of DNA or RNA, composed of a base and a sugar

nucleoside triphosphate

building block of DNA or RNA, composed of a base and a sugar linked to three phosphates

nucleosome

chromosome structural unit, consisting of DNA wrapped around histone proteins

nucleotide

a building block of RNA or DNA

ocular

related to the eye

oncogene

gene that causes cancer

oncogenesis

the formation of cancerous tumors

oocyte

egg cell

open reading frame

DNA sequence that can be translated into mRNA; from start sequence to stop sequence

opiate

opium, morphine, and related compounds

organelle

membrane-bound cell compartment

organic

composed of carbon, or derived from living organisms; also, a type of agriculture stressing soil fertility and avoidance of synthetic pesticides and fertilizers

osmotic

related to differences in concentrations of dissolved substances across a permeable membrane

ossification

bone formation

osteoarthritis

a degenerative disease causing inflammation of the joints

osteoporosis

thinning of the bone structure

outcrossing

fertilizing between two different plants

oviduct

a tube that carries the eggs

ovulation

release of eggs from the ovaries

ovules

eggs

ovum

egg

oxidation

chemical process involving reaction with oxygen, or loss of electrons

oxidized

reacted with oxygen

pandemic

disease spread throughout an entire population

parasites

organisms that live in, with, or on another organism

pathogen

disease-causing organism

pathogenesis

pathway leading to disease

pathogenic

disease-causing

pathogenicity

ability to cause disease

pathological

altered or changed by disease

pathology

disease process

pathophysiology

disease process

patient advocate

a person who safeguards patient rights or advances patient interests

PCR

polymerase chain reaction, used to amplify DNA

pedigrees

sets of related individuals, or the graphic representation of their relationships

peptide

amino acid chain

peptide bond

bond between two amino acids

percutaneous

through the skin

phagocytic

cell-eating

phenotype

observable characteristics of an organism

phenotypic

related to the observable characteristics of an organism

pheromone

molecule released by one organism to influence another organ-ism's behavior

phosphate group

PO₄ group, whose presence or absence often regulates protein action

phosphodiester bond

the link between two nucleotides in DNA or RNA

phosphorylating

addition of phosphate group (PO₄)

phosphorylation

addition of the phosphate group PO₄^3-

phylogenetic

related to the evolutionary development of a species

phylogeneticists

scientists who study the evolutionary development of a species

phylogeny

the evolutionary development of a species

plasma membrane

outer membrane of the cell

plasmid

a small ring of DNA found in many bacteria

plastid

plant cell organelle, including the chloroplast

pleiotropy

genetic phenomenon in which alteration of one gene leads to many phenotypic effects

point mutation

gain, loss, or change of one to several nucleotides in DNA

polar

partially charged, and usually soluble in water

pollen

male plant sexual organ

polymer

molecule composed of many similar parts

polymerase

enzyme complex that synthesizes DNA or RNA from individual nucleotides

polymerization

linking together of similar parts to form a polymer

polymerize

to link together similar parts to form a polymer

polymers

molecules composed of many similar parts

polymorphic

occurring in several forms

polymorphism

DNA sequence variant

polypeptide

chain of amino acids

polyploidy

presence of multiple copies of the normal chromosome set

population studies

collection and analysis of data from large numbers of people in a population, possibly including related individuals

positional cloning

the use of polymorphic genetic markers ever closer to the unknown gene to track its inheritance in CF families

posterior

rear

prebiotic

before the origin of life

precursor

a substance from which another is made

prevalence

frequency of a disease or condition in a population

primary sequence

the sequence of amino acids in a protein; also called primary structure

primate

the animal order including humans, apes, and monkeys

primer

short nucleotide sequence that helps begin DNA replication

primordial soup

hypothesized prebiotic environment rich in life's building blocks

probe

molecule used to locate another molecule

procarcinogen

substance that can be converted into a carcinogen, or cancer-causing substance

procreation

reproduction

progeny

offspring

prokaryote

a single-celled organism without a nucleus

promoter

DNA sequence to which RNA polymerase binds to begin transcription

promutagen

substance that, when altered, can cause mutations

pronuclei

egg and sperm nuclei before they fuse during fertilization

proprietary

exclusively owned; private

proteomic

derived from the study of the full range of proteins expressed by a living cell

proteomics

the study of the full range of proteins expressed by a living cell

protists

single-celled organisms with cell nuclei

protocol

laboratory procedure

protonated

possessing excess H⁺ ions; acidic

pyrophosphate

free phosphate group in solution

quiescent

non-dividing

radiation

high energy particles or waves capable of damaging DNA, including X rays and gamma rays

recessive

requiring the presence of two alleles to control the phenotype

recombinant DNA

DNA formed by combining segments of DNA, usually from different types of organisms

recombining

exchanging genetic material

replication

duplication of DNA

restriction enzyme

an enzyme that cuts DNA at a particular sequence

retina

light-sensitive layer at the rear of the eye

retroviruses

RNA-containing viruses whose genomes are copied into DNA by the enzyme reverse transcriptase

reverse transcriptase

enzyme that copies RNA into DNA

ribonuclease

enzyme that cuts RNA

ribosome

protein-RNA complex at which protein synthesis occurs

ribozyme

RNA-based catalyst

RNA

ribonucleic acid

RNA polymerase

enzyme complex that creates RNA from DNA template

RNA triplets

sets of three nucleotides

salinity

of, or relating to, salt

sarcoma

a type of malignant (cancerous) tumor

scanning electron microscope

microscope that produces images with depth by bouncing electrons off the surface of the sample

sclerae

the "whites" of the eye

scrapie

prion disease of sheep and goats

segregation analysis

statistical test to determine pattern of inheritance for a trait

senescence

a state in a cell in which it will not divide again, even in the presence of growth factors

senile plaques

disease

serum (pl. sera)

fluid portion of the blood

sexual orientation

attraction to one sex or the other

somatic

nonreproductive; not an egg or sperm

Southern blot

a technique for separating DNA fragments by electrophoresis and then identifying a target fragment with a DNA probe

Southern blotting

separating DNA fragments by electrophoresis and then identifying a target fragment with a DNA probe

speciation

the creation of new species

spindle

football-shaped structure that separates chromosomes in mitosis

spindle fiber

protein chains that separate chromosomes during mitosis

spliceosome

RNA-protein complex that removes introns from RNA transcripts

spontaneous

non-inherited

sporadic

caused by new mutations

stem cell

cell capable of differentiating into multiple other cell types

stigma

female plant sexual organ

stop codon

RNA triplet that halts protein synthesis

striatum

part of the midbrain

subcutaneous

under the skin

sugar

glucose

supercoiling

coiling of the helix

symbiont

organism that has a close relationship (symbiosis) with another

symbiosis

a close relationship between two species in which at least one benefits

symbiotic

describes a close relationship between two species in which at least one benefits

synthesis

creation

taxon/taxa

level(s) of classification, such as kingdom or phylum

taxonomical

derived from the science that identifies and classifies plants and animals

taxonomist

a scientist who identifies and classifies organisms

telomere

chromosome tip

template

a master copy

tenets

generally accepted beliefs

terabyte

a trillion bytes of data

teratogenic

causing birth defects

teratogens

substances that cause birth defects

thermodynamics

process of energy transfers during reactions, or the study of these processes

threatened

likely to become an endangered species

topological

describes spatial relations, or the study of these relations

topology

spatial relations, or the study of these relations

toxicological

related to poisons and their effects

transcript

RNA copy of a gene

transcription

messenger RNA formation from a DNA sequence

transcription factor

protein that increases the rate of transcription of a gene

transduction

conversion of a signal of one type into another type

transgene

gene introduced into an organism

transgenics

transfer of genes from one organism into another

translation

synthesis of protein using mRNA code

translocation

movement of chromosome segment from one chromosome to another

transposable genetic element

DNA sequence that can be copied and moved in the genome

transposon

genetic element that moves within the genome

trilaminar

three-layer

triploid

possessing three sets of chromosomes

trisomics

mutants with one extra chromosome

trisomy

presence of three, instead of two, copies of a particular chromosome

tumor

mass of undifferentiated cells; may become cancerous

tumor suppressor genes

cell growths

tumors

masses of undifferentiated cells; may become cancerous

vaccine

protective antibodies

vacuole

cell structure used for storage or related functions

van der Waal's forces

weak attraction between two different molecules

vector

carrier

vesicle

membrane-bound sac

virion

virus particle

wet lab

laboratory devoted to experiments using solutions, cell cultures, and other "wet" substances

wild-type

most common form of a trait in a population

Wilm's tumor

a cancerous cell mass of the kidney

X ray crystallography

use of X rays to determine the structure of a molecule

xenobiotic

foreign biological molecule, especially a harmful one

zygote

fertilized egg