GENETICS
GERM CELL
determine whether particular genetic de-
fects are present in an individual's
DNA
.
Genetic probes are mainly used in ante-
natal diagnosis of
genetic disorders
,
and
in investigating whether people with a
family history of a genetic disorder carry
the defective gene themselves.
genetics
The study of
inheritance
,
the
chemical basis by which characteristics
are determined, and the causes of the
similarities and differences among indi-
viduals of a species or between different
species. Branches of human genetics
include population genetics, which stu-
dies the relative frequency of various
genes
in different races; molecular gen-
etics,
which is concerned with the
structure,
function,
and
copying
of
DNA
; and clinical genetics, which is
concerned with the study and preven-
tion of
genetic disorders
.
genital herpes
See
herpes, genital
.
genitalia
The reproductive organs, esp-
ecially those that are external. The male
genitalia include the
penis
,
testes
(in the
scrotum
),
prostate gland
,
seminal vesi-
cles
, and associated ducts, such as the
epididymis
and
vas deferens
. The female
genitalia include the
ovaries
,
fallopian
tubes
,
uterus
,
vagina
,
clitoris
,
vulva
, and
Bartholin's glands
.
genitalia, ambiguous
A group of con-
ditions in which the external sex organs
are not clearly male or female, or in
which they appear to be those of the
opposite chromosomal sex. This may
result from an abnormality of the
sex
chromosomes
or a
hormonal disorder
(see
hermaphroditism
;
sex determin-
ation; adrenal hyperplasia, congenital
).
genital ulcer
An eroded area of skin on
the
genitalia
. The most common cause
is a
sexually transmitted infection
, partic-
ularly
syphilis
and genital herpes (see
herpes, genital
).
Chancroid
and
granu-
loma inguinale
are tropical bacterial
infections that cause genital ulcers.
Lymphogranuloma venereum
is a viral
infection producing genital blisters.
Beh-
get's syndrome
is a rare condition that
causes tender, recurrent ulcers in the
mouth and on the genitals. Cancer of
the penis or vulva may first appear as a
painless ulcer with raised edges.
genital warts
See
warts, genital
.
genito-urinary medicine
The branch
of medicine concerned with
sexually
transmitted infections
.
genome, human
The complete set of
human genetic material. The human
genome consists of 23
chromosomes
,
which, together, contain about 30,000
genes. All body cells contain
2
sets of
the 23 chromosomes, one set inherited
from the father and the other from the
mother. An international research pro-
gramme, the Human Genome Project,
was launched in 1990 with the aim of
identifying all the human genes. The
first rough draft of the project was pub-
lished in
2000
.
gentamicin
An
antibacterial drug
given
by injection to treat serious infections
such as
meningitis
and
septicaemia
.
Gentamicin can damage the kidneys or
inner ear if the dosage is not carefully
controlled. The drug is also used in eye
and ear drops but is unlikely to cause
serious side effects with this use.
gentian violet
A purple dye used to
make
bacteria
visible under a micro-
scope. It was also used as an
antiseptic
.
genu valgum
The medical term for
knock-knee
.
genu varum
See
bow leg
.
geriatric medicine
The medical spe-
cialty concerned with care of the elderly.
Elderly people require specialist medical
treatment because they respond differ-
ently from younger people to illness
and its treatment. Physical and mental
decline due to
aging
can mean that ill-
nesses are more severe in older people.
Because the liver becomes less efficient
with age, drug dosages for elderly peo-
ple need to be carefully controlled to
avoid dangerous side effects. Geriatri-
cians also help older people to cope
with everyday life following illness or
injury. (See also
rehabilitation
.)
germ
The popular term used to des-
cribe any microorganisms that cause
disease, such as
viruses
and
bacteria
.
(See also
germ cells
.)
German measles
The common name
for the viral infection
rubella
.
germ cell
An embryonic
cell
with the
potential to develop into a
sperma-
tozoon
or
ovum
,
which, on maturity, are
called
gametes
.
The term also describes
G
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