A B C
J K L
Q R S
adenine (A) - a base in DNA and RNA
that always bonds with thymine (T) in DNA, and with uracil (U)
alleles - two different forms or versions of a gene
that occupy corresponding positions on homologous chromosomes.
A person has two alleles of a trait--one from each parent.
amino acids - the basic building blocks of proteins;
there are twenty different types linked together in different
sequences to form different proteins.
anaphase - the third stage of mitosis in which chromatids
move to opposite poles of the cell.
antisense strand - the portion of DNA double helix that
is not transcribed during protein synthesis (as opposed to the
antisense technology - gene silencing or the process
of inactivating a gene.
autosome - any chromosome not involved in sex determination.
Twenty two of the human chromosome pairs are autosomes.
bases - the molecular building blocks
of DNA and RNA: adenine (A), cytosine (C), guanine (G), thymine
(T), and in RNA only, uracil (U). In DNA, A attaches only to
T, and C attaches only to G. In RNA, A attaches only to U, and
C attaches only to G.
base pairs - the pairs of complementary bases that form
the rungs of DNA: adenine (A) pairs with thymine (T), cytosine
(C) pairs with guanine (G).
base sequence - the order of bases in DNA.
biotechnology - the use of biological processes to make
carrier - an individual who is heterozygous
for a recessive trait.
cell - the basic unit of life; the smallest basic part
of every living thing that can function by itself. It is made
of a nucleus surrounded by cytoplasm, organelles (similar to
organs in a body) and proteins. Each cell contains the entire
cell cycle - the time from one cell division to the
next. Varies from minutes to days, but the actual division takes
less than 10% of the cycle.
centromere - the region on a chromosome that ensures
proper pairing of sister chromatids.
chromatin - a complex of protein and DNA that make up
chromosome - a long coiled strand in the nucleus, made
up of DNA and protein. There are 46 human chromosomes, each
containing DNA for hundreds or thousands of individual genes.
chromosome jumping - the process of moving rapidly up
or down a chromosome in search of a particular gene by jumping
over uninformative areas of DNA.
chromosome map - a diagram showing the locations and
relative spacing of genes along a chromosome.
clone - a genetic duplicate.
cloning - the process of producing a genetically identical
group of cells from a single ancestor.
codominant - two genes that are neither dominant or
recessive; neither masks the other, as in the case of red geraniums
crossed with white geraniums yielding pink geraniums.
codon - a special code to make amino acid; a sequence
of three nucleotides.
complementary DNA (cDNA) - a single strand of DNA made
in the lab to complement the bases in a strand of messenger
conserved DNA sequences - sequences that have not changed
controlled breeding - the reproduction of desired characteristics.
crossing-over/recombination - a process of chromsome
exchange during cell division, resulting in new combinations
cytogenics - the study of the genetic implications of
chromosome structure and behavior.
cytoplasm - all the organelles and materials inside
a cell between the cell membrane and the nucleus.
cytosine (C) - a base in DNA that always bonds with
daughter cell - one of two cells resulting
from cell division.
daughter strand - the DNA, or chromosome, strand newly
deletion - the loss of a segment of genetic material.
deoxyribonucleic acid - see DNA
differentiated cells - cells in which some of the DNA
shuts off so that the cells can be different; they make liver
cell, bone cells, etc.
dihybrid cross - the graphing of two or more traits
in a Punnett Square to predict heredity.
diploid - a cell or organism that has two complete sets
of chromosomes, as opposed to haploid, or those with only one
member of each pair of the same chromosomes.
DNA (deoxyribonucleic acid) - a large double-stranded,
spiraling molecule that contains genetic instructions for growth,
development and replication. It is organized into bodies called
chromosomes and found in the cell nucleus.
DNA fingerprinting - the use of fragments of DNA to
identify the unique genetic makeup of an individual. There are
the RFLP method and the PCR method.
DNA replication - the process or copying a DNA molecule
just before cell division.
DNA sequencing - the process of determining the order
of bases in a segment of DNA.
dominant gene - a gene which passes on a certain physical
characteristic, dominating over a recessive gene present on
double helix - a common name for DNA, referring to the
double-stranded, spiraling structure of the molecule.
egg - the female reproductive cell.
electrophoresis - a method of separating large molecules
such as DNA fragments from a mixture of similar molecules.
enzymes - the biological catalysts that speed up a chemical
eugenics - the use of genetic engineering to produce
a superior race.
eukaryotes - all living things whose cells have nuclei
(most living things).
excision - the removal of a DNA fragment from a chromosome.
exon - a gene segments that has instructions for making
a protein, as opposed to introns, which dont have these
founder effect - the change in gene
frequency occurring when a population is based on only a few
fraternal twins - twins resulting from fertilization
of separate eggs; genetically related as siblings.
gametes - the sex cells in human beings--sperm
in men and ova in women. Each gamete cell has 23 chromosomes,
half the number found in other body cells.
gel electrophoresis - see electrophoresis
gene - the unit of heredity in chromosomes; a segment
of double-stranded DNA.
gene cloning - the process of separating a gene and
making identical copies of it.
gene expression - the way information in a gene is changed
to a protein or RNA. The DNA sequence is changed into RNA and
usually (not always) then changed into protein.
gene linkage map - a map of relative positions of genes
on a chromosome. Genes inherited together are close to each
other on the chromosome, and said to be linked. (see gene mapping)
gene locus - the position a gene occupies on a chromosome.
gene mapping - the process of determining the relative
positions of genes on a DNA molecule. (see gene linkage map)
gene pool - the genetic make-up of a specific population.
gene silencing - the process of inactivating a gene
that may cause disease or be defective in another way.
gene splicing - the process of cutting the DNA of a
gene in order to add base pairs.
gene targeting - the process of changing or turning
off a particular gene.
gene therapy - a method of treating a disease by exchanging
the defective gene causing the disease with a healthy one in
geneticist - a scientist who studies genes.
gene transcription - the first step in gene expression
where the genes DNA sequence is copied into messenger
gene translation - the method where transcribed messenger
RNA directs the making of proteins from amino acids.
genetic code - all the genes a living thing has inherited.
They determine appearance, function, growth, behavior, etc.
genetic disease - a disease caused by a genetic mutation.
genetic engineering - the technology used to genetically
manipulate living cells to produce new chemicals or to perform
genetic marker - a landmark that identifies a certain
spot on a chromosome.
genetics - the study of genes and heredity, or how characteristics
are passed from parents to children.
genetic testing or screening - a technique used to find
out whether a person or organism has a particular gene.
genome - all the genetic information necessary to build
a living organism. It is species-specific.
genotype - all the traits, dominant and recessive, that
an organism inherits. This is different from the phenotype,
or acquired observable traits.
germ cells - the cells that give rise to sperm or egg.
germplasm - the protoplasm of germ cells containing
guanine (G) - a base in DNA and RNA that always bonds
with cytosine (C).
haploid - cells that have a single set
of chromosomes, or half the full set of genetic material, as
opposed to diploids. Sperm and egg cells are haploid.
Hardy-Weinberg principle - states that the allele frequency
for dominant and recessive alleles remains the same over the
generations in a particular population as long as certain conditions
helix - spiral in form.
heredity - all of the traits passed on to children by
parents (plant or animal) or the process of transferring these
heteromorphic chromosome pairs - chromosomes that visibly
differ, like X and Y.
heterosis/hybrid vigor - the superiority of hybrids.
heterozygous - refers to having dissimilar alleles of
one or more genes, as opposed to homozygous.
homologous recombination - the process of replacing
one DNA segment with a similar sequence.
homozygous - refers to having an identical pair of alleles,
one from each parent, as opposed to heterozygous.
Human Genome Project - a large project to map and sequence
all DNA in human chromosomes.
hybrid - a plant or animal that results from two different
breeds or varieties of parents; carries two different genes
for a characteristic.
hybridization - the cross-fertilization or breeding
of plants and animals to get the best.
hybrid vigor/heterosis - the superiority of hybrids.
identical twins - the offspring resulting
from a fertilized egg splitting into two separate embryos.
inbreeding - the crossing of two closely related beings.
inbreeding depression - the decrease in health or fertility
because of inbreeding.
interphase - the period of cell growth between divisions.
introns - DNA sequences without instructions for making
protein that come between those sequences with instructions
for making protein (exons). Introns are not in messenger RNA,
and it is not known what they are for.
inversion - a mutation occurring where a segment of
DNA flips upside down in a sequence, but remains in place.
karyotype - a photograph of a cells
chromosomes, arranged in order from largest to smallest.
linkage - the tendency of genes on the
same chromosome to be associated in inheritance.
linkage group (linked genes) - genes found near each
other on a chromosome.
locus - the position of a particular gene on a chromosome.
mass selection - large-scale controlled
maternal inheritance - the inheritance of a trait from
the female gamete.
meiosis - the process of cell division, where the number
of chromosomes is reduced by half, then the new cells divide
again by mitosis. Results in four daughter cells.
messenger RNA (mRNA) - a single strand of RNA that directs
metaphase - the second stage of mitosis during which
the chromatid pairs align at the cells equator.
mitochondria - the part of a cell that turns food into
energy for chemical reactions, movement, and growth.
mitosis - cell division resulting in daughter (new)
cells that are genetically identical to each other and to the
parent; the chromosomes are divided before the cell divides.
molecular genetics - the study of molecules of DNA in
order to identify the form and function of the genes in them.
monohybrid cross - the graphing of only one trait in
a Punnett Square, used for predicting heredity.
mRNA - see messenger RNA.
multifactorial trait - a trait that is determined by
heredity and environment.
mutagens - substances which increase the likelihood
mutation - a permanent change in a DNA sequence that
can be passed on. It can be a change in genetic information,
addition of information, or deletion of information.
natural selection - the process by which
only the organisms better adapted to the environment survive
nuclear transfer technology - the process of taking
the nucleus with the DNA from one cell and putting it into another.
nucleotide - the building block of DNA (rungs on the
ladder of the DNA double helix) made up of four
molecules that occur in pairs--adenine (A) with thymine (T),
and cytosine (C) with guanine (G). Thousands of nucleotides
are linked to form a DNA or RNA molecule.
nucleus - the center part of the cell. It contains 6
feet of DNA in 23 pairs of chromosomes and is the largest part
of the cell. Living things are divided into eukaryotes (whose
cells have nuclei) and prokaryotes (whose cells have no nuclei).
oligonucleotide - a short string of
nucleotides; a single-stranded segment of DNA. Used as a probe
to find matching sequence of DNA or RNA.
organelle - an organized structure within a cell, with
a specific function.
outcrossing - an inbreed crossed with a less related.
ovule - the structure in a seed plant that develops
into a seed after fertilization.
ovum - the human female reproductive cell.
parent cell - the original cell before
paternal inheritance - the inheritance of a trait from
the male gamete.
PCR (polymerase chain reaction) - a process developed
in mid-1980s to make a large number of copies of a DNA
sequence from very little DNA. It is used in forensics when
little DNA is available for testing.
pedigree - a diagram representing family relationships
peptide - two or more amino acids linked together.
phenotype - all the observable traits a person inherits,
as opposed to the genome, or all the traits inherited.
plasma membrane - the fatty layer surrounding the molecules
of a cell.
plasmids - the rings of DNA in bacteria.
pollen - the grains that contain the male reproductive
cells of a seed plant.
pollination - the transfer of pollen in a flower from
the stamen to the pistil (male to female).
polymerase chain reaction - see PCR.
polymorphisms - the differences in DNA sequences that
occur naturally. They are used as genetic markers because researchers
can use them to tell apart DNA from different sources.
polyploidy - cells that have extra chromosomes.
population - all the members of a species that live
in a particular location.
population genetics - the study of how genetic principles
apply to entire generations.
positional cloning - the process of finding the gene
for a specific trait by comparing the DNA of people with the
trait to the DNA of relatives without the trait.
principle of segregation - the principle, first noted
by Gregor Mendel, that explains why children dont always
directly inherit their parents characteristics.
probe - a radioactive DNA or RNA molecule used in DNA-RNA
or DNA-DNA hybridization trials.
prokaryotes - the living things whose cells do not have
nuclei; includes only single-celled bacteria.
propagation - the multiplication of plants.
promoter - a segment of DNA that acts as controlling
element in expression of a gene. Marks the place of the beginning
of gene transcription.
prophase - the first stage of mitosis or meiosis.
protein - a molecule made up of amino acids linked together.
They are the bodys workhorses whose function can be as
enzymes, structural components, or signaling molecules.
Punnett Square - a chart that shows all possible genetic
outcomes of a mating.
recessive gene - a gene which is hidden
by a dominant gene; it must be present on both chromosomes in
a pair (one from the father, one from the mother) to show outward
signs of the characteristic.
recombinant DNA - the new DNA resulting from combining
two or more types of DNA.
recombinant DNA technology - the technique for cutting
apart, splicing together and producing pieces of DNA from different
recombination/crossing-over - a process of chromosome
exchange during cell division, resulting in new combinations
restriction enzyme - an enzyme capable of cutting DNA
retrovirus - a cancer-causing virus that transforms
cells by altering the function of host-cell genes or by carrying
cancer-causing genes from one host to another.
ribosome - the small cellular structure where RNA translates
the genetic code into proteins.
RFLP (restriction fragment length polymorphism) - considered
to be the most accurate DNA test; it takes several weeks to
complete, and is becoming more frequently used in forensics
RNA (ribonucleic acid) - single-stranded nucleic acid
(similar to double-stranded DNA) containing the bases adenine
(A), cytosine (C), guanine (G), and uracil (U). The different
forms include messenger RNA (mRNA), transfer RNA (tRNA), and
ribosomal RNA (rRNA), which are all part of making protein.
sense strand - the portion of the DNA
double helix that is transcribed during protein synthesis (as
opposed to the antisense strand).
sex chromosome - the X or Y chromosome, which determines
sex. Females have two X chromosomes in each cell, and males
have an X and a Y.
sex-influenced trait - a trait whose expression depends
on the sex of the individual organism.
sex-limited trait - a trait expressed in one sex and
not in the other.
sex-linked trait - a trait whose gene is located on
or linked to the X chromosome.
single-stranded DNA - the result of genes being changed
or copied before a cell division; half of the normal two strands
that form the double helix.
somatic cell - any cell in the body other than the sex
species - a group of closely related organisms capable
of mating and producing fertile offspring.
sperm - the male reproductive cells.
stamen - the male part of a plant, which produces pollen.
telephase - the fourth stage of mitosis
where chromosomes uncoil and new nuclear membranes form.
thymine (T) - a base in DNA that always bonds with adenine
transcription - the process by which DNA passes genetic
information to RNA. The first step in producing proteins.
transfer RNA (tRNA) - a class of RNA that carries amino
acids into ribosomes and bonds with mRNA for protein production.
transformation - a process by which some bacteria can
absorb DNA from their surroundings.
transgenic - organisms with inserted genes.
translation - process by which RNA makes proteins.
translocation - a mutation in which a chromosomal piece
becomes attached to another chromosome.
uracil (U) - a base in RNA that bonds
only with adenine (A).
vector - a DNA molecule into which a
gene or DNA segment is inserted by recombinant DNA techniques;
a cloning vehicle.
virus - an infectious parasite.
wildtype - the most common phenotype
or genotype in a population.
X chromosome - one of the chromosomes
that determines sex. Females have two X chromosomes in each
somatic cell, and males have one X and one Y chromosome..
Y chromosome - one of the chromosomes
that determines sex. Males carry one X chromosome and one Y
chromosome in each somatic cell.
zygote - the new cell formed when the
male sperm unites with a female egg.