GLOSSARY OF TERMS

A B C D E F G -H I J K- L M N O P- Q R- S -T U V W X Y Z

A

adenine

One of four bases found in DNA or RNA.

allele

A gene that occupy a given locus. 2) One of two or more different forms of a gene. (i.e. In peas, there is a purple allele and a white allele for flower color).

aqueous

Containing water, such as the aqueous environment of a cell.

B

base

A compound that is capable of accepting a hydrogen ion.

bicyclic

Containing two rings.

C

centrioles

Structures found in animal cells, composed of an array of microtubules around which the mitotic spindle is organized.

chiasma/chiasmata

Location on chromatids where crossing over ocurs.

chromatid

Either of the longitudinal subunits produced by chromosomal replication.

chromosome

A structure composed of DNA and protein that carries the genetic information of an organism.

covalent bond (single)

A bond formed through the sharing of a pair of electrons between two atoms.

cytosine

One of four bases found in DNA or RNA.

cross

A mating. (i.e. The cross between the round pea plant and the wrinkled pea plant resulted in all round progeny). Can also be used as a verb to indicate "to set up a mating." (i.e. Mendel crossed a round pea plant to a wrinkled pea plant and found that all the progeny had round seeds).

D

DNA

Deoxyribonucleic acid, the heritable material found in all cells.

DNA damage repair

Any of several different processes for restoring the correct base(s) of the original DNA molecule of the organism after they have been incorrectly modified or incorporated.

DNA replication

Semi-conservative copying of DNA molecule occurring during interphase of cells.

diploid

An organism with two copies of chromosomes (2n).

dipole

A separation of positive and negative charge.

dominant

Able to produce a phenotype with just one copy of the allele. Compare to recessive. (i.e. Pea plants with one copy of the dominant purple allele will have purple flowers, even if a recessive white allele is also present).

double covalent bond

A covalent bond formed through the sharing of two pairs of electrons between two atoms.

E

egg

Female reproductive cell; female gamete.

electron

Negatively charged subatomic particle.

electron shell

A grouping of electrons in an atom according to energy.

electronegativity

A measure of the electron-attracting power of an atom.

electrostatic interaction

Interaction of two or more charged particles.

F

F1

First filial generation; the progeny of the parental generation. The descendents of the F1 generation are the F2 generation.

F2

Second filial generation; the progeny of the F1 generation.

fertilization

Fusion of egg and sperm to create an embryo, which grows into a new individual.

G

gametes

Haploid (n) reproductive cells such as sperm or egg that unite to form a diploid (2n) zygote. 2) Any reproductive cell, including pollen/sperm and ovule/egg.

gene

A distinct stretch of DNA that is the basic physical and functional unit of heredity.

genetics

The study of traits that can be passed down from parent to offspring; the study of heredity and variation. Usually restricted to traits that are largely due to inherited genes, but it can be difficult to distinguish the role of genes from the role of the environment.

genotype

Actual physical DNA make up of an organism. 2) The genetic constitution of an individual, including alleles carried for a particular trait. Compare to phenotype. (i.e. A pea with a round phenotype could have a genotype of RR or Rr).

genotypic

Pertaining to genotype.

group (periodic table)

A vertical column of elements in the periodic table.

guanine

One of four bases found in DNA or RNA.

H - I - J - K

helix

A corkscrew-shaped object.

heredity

The passing down of traits from parent to offspring. Usually restricted to traits that are largely due to inherited genes, but it can be difficult to distinguish the role of genes from the role of the environment.

heterozygote

An individual that carries two different alleles. Compare to homozygote. (i.e. The heterozygote has the genotype Rr).

heterozygous

Having different alleles for a trait. 2) Carrying two different alleles. Compare to homozygous. (i.e. The heterozygous plant has the genotype Rr).

histone

A small, positively charged protein involved in DNA packaging.

homologous chromosomes (homologs)

Chromosomes that have the same genetic loci and structure and that pair in meiosis I.

homozygote

An individual that carries two copies of the same allele. Compare to heterozygote. (i.e. The dominant homozygote has the genotype RR, while the recessive homozygote has the genotype rr).

homozygous

Having identical alleles for a trait. 2) Carrying two copies of the same allele. Compare to heterozygous. (i.e. A homozygous plant could have the genotype RR or rr).

hybrid

Offspring of parents that differ for at least one trait. (i.e. The Aa hybrid was the result of the cross AA x aa).

hydrogen bond

An intermolecular force of attraction between a highly polar hydrogen to a highly polar lone pair of electrons associated with an F, O, N, or Cl atom.

hydrogen bond acceptor

The atom possessing the lone pair of electrons involved in a hydrogen bond.

hydrogen bond donor

The hydrogen atom involved in a hydrogen bond.

hypothesis

A proposed explanation based on available evidence.

interphase

Interval between nuclear divisions, beginning after cytokinesis and lasting until just before the beginning of prophase in the next round of mitosis.

ion

A charged atom generated when a neutral atom gains or loses one or more electrons.

ionic bond

A bond formed through the transfer of electron(s) from one atom to another and the resulting association of the two atoms through electrostatic interactions.

L

line

A strain of true-breeding plants or animals. (i.e. The poodle that won the dog show was carefully bred from a line of champion poodles).

locus/loci

A position on a chromosome.

M

microtubules

Polymers of tubulin, involved in the segregation of chromosomes during cell division.

mitotic (M) phase

The period in which mitosis, the process of nuclear division, occurs.

mole

A group of approximately 6.02 x 10^23. For example, a dozen eggs = 12 eggs, and a mole of eggs = 6.02*10^23 eggs.

monohybrid

Offspring of parents that differ in a single trait. (i.e. The monohybrids had the genotype Aa). Also used as an adjective to describe something (i.e. an individual or a cross) that differs for only one trait. (i.e. The monohybrid cross of AA x aa produce monohybrid progeny with genotype Aa). Compare to dihybrid and trihybrid.

N

natural selection

The process by which traits that are favorable and heritable becomes increasing in numbers in succeeding generations.

noble gas

Elements belonging to group VIII (8) of the periodic table and possessing completely filled electron shells.

nuclear envelope

Lipid bilayer membrane enclosing the nucleus in eukaryotic cells.

nucleosome

The repeating unit of DNA packaging, containing histones and the DNA wrapped around them.

nucleotide

The repeating unit found in DNA and RNA, consisting of three parts: a phosphate group, a sugar, and a base.

O

offspring

Children; progeny; immediate descendants.

orbital (atomic)

A mathematical function describing the regions of an atom where the probability of finding electrons is high.

ovule

The female reproductive cell (i.e. egg, female gamete) of a plant.

P

period (periodic table)

A horizontal row of elements of the periodic table.

phenotype

Physical and behavioral characteristics of an organism. 2) An individual's observable form. Compare to genotype. (i.e. A pea with a round phenotype could have a genotype of RR or Rr).

phenotypic

Pertaining to phenotype.

ploidy

Chromosome count, 2n if diploid, n if haploid. In humans, 2n = 46 in diploid somatic cells, and n = 23 in haploid germ cells.

polar

Term to describe molecules possessing dipoles, or separation of charges.

polar (covalent) bond

A covalent bond where a separation of charges exists in the bond.

pollen

The male reproductive cell (i.e. sperm, male gamete) of a plant.

polymer

A chain of repeating units.

population

Interbreeding organisms inhabiting a specified area.

predator

An organism that feeds on another living organism (i.e. prey).

progeny

Children; offspring; immediate descendants.

proton

Positively charged subatomic particle.

purine

A double-ringed base, (i.e. adenine or guanine).

pyrimidine

A single-ringed base, (i.e. cytosine, thymine, or uracil).

Q - R

RNA

Ribonucleic acid, a molecule structurally similar to DNA that plays several different roles in the cell.

recessive

Only able to produce a phenotype when no dominant allele is present. Compare to dominant. (i.e. Pea plants with one copy of the dominant purple allele and one copy of the recessive white allele will have purple flowers). Plants with two copies of the white allele will have white flowers.

reciprocal cross

A cross that differs from another cross only in the sex of the parents. (i.e. AA male x aa female is the reciprocal cross to aa male x AA female).

ribose

A sugar molecule that contains five carbons.

S

sexual reproduction

A form of reproduction were a sperm cell and an egg cell are required to produce offspring. Allows offspring to be genetically different from the parents. In contrast to asexual reproduction, where the offspring is genetically identical to the parent (i.e. when part of a plant is broken off to give a new plant).

species

Often referred to as an interbreeding group of organism with a set of unifying characteristics.

T - U - V - W - X - Y - Z