Pathology

Front 1

agenesis

Back 1

failure of an organ or part to develop or grow

Front 2

albinism

Back 2

congenital, partial, or total absence of pigment of hair, skin, and eyes

Front 3

aplasia

Back 3

failure of an organ or part to develop normally

Front 4

allele

Back 4

one of a series of alternate forms of a gene at the same locus. Ex. A, B, and O are alleles for the blood group gene. A person with blood type AB has the A allele on one chromosome and the B allele at the same locus on the homologous chromosome

Front 5

atresia

Back 5

congenital absences or closure of a normal body opening or tubular structure

Front 6

autosome

Back 6

a chromosome that is not a sex chromosome

Front 7

carrier

Back 7

an individual possessing a mutant gene or chromosomal rearrangement which usually is not clinically apparent and which may be passed on to his/her offspring

Front 8

chromosome

Back 8

the structural elements in the cell nucleus composed of DNA and proteins which contain the genes

Front 9

congenital

Back 9

present at birth

Front 10

consanguinity

Back 10

refers to a mating between individuals of common ancestry

Front 11

consult and consultant

Back 11

the individual who seeks counseling. On the pedigree it is marked by an arrow

Front 12

division failures

Back 12

a failure of tissue to separate into parts which results in anomaly

Front 13

dominant

Back 13

a gene (allele) which is expressed clinically in the heterozygous state. In a dominant disorder the mutant allele overshadows the normal allele

Front 14

dysplasia

Back 14

abnormal development of tissue

Front 15

dysraphic anomalies

Back 15

failure of a raphe formation or failure of fusion of parts that normally fuse

Front 16

ectopic

Back 16

in an abnormal position

Front 17

expressivity

Back 17

the extent to which a gene is clinically expressed in an individual. Variable expressivity refers to the variation in severity produced by the same gene in different individuals

Front 18

gamete

Back 18

the germ cells, egg, and sperm

Front 19

genotype

Back 19

the genetic composition of an individual

Front 20

heterotopic

Back 20

development of normal tissue, organ, or part in an abnormal location

Front 21

heterozygote

Back 21

an individual who has two different alleles at a given locus on a pair of homologous chromosomes

Front 22

homologous chromosome

Back 22

a pair of chromosomes, one from each parent carrying the genes for the same traits. When looking at a karyotype, the members of a homologous pair look alike

Front 23

hypoplasia

Back 23

underdevelopment of a tissue, organ, or body

Front 24

index case

Back 24

the affected individual who brings the family to the attention of the geneticist. Also known as the proband or propositus/proposita

Front 25

homozygote

Back 25

an individual who has two identical alleles at a given locus

Front 26

involution failures

Back 26

failure of the normal involution of congenital tissue which results in anomaly

Front 27

karyotype

Back 27

the picture of the chromosomes arranged in a standard order

Front 28

linkage

Back 28

when genes for different traits are located in close proximity on the same chromosome

Front 29

locus

Back 29

the position or place that a gene occupies on a chromosome

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monosomy

Back 30

when one chromosome of one pair is missing

Front 31

mosaic

Back 31

an individual who has two or more cell lines which differ from each other in chromosome number or morphology

Front 32

multifactorial

Back 32

the interaction of many genes and the environment

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mutagen

Back 33

an environmental agent, either physical, chemical, or biological, capable of inducing mutation

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mutation

Back 34

a heritable change in a gene

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nondisjunction

Back 35

failure of paired chromosomes to separate during cell division

Front 36

pedigree

Back 36

a graphic picture using symbols that represent an individual's family tree

Front 37

penetrance

Back 37

frequency with which individuals carrying a given gene will show the clinical manifestations associated with that gene

Front 38

phenotype

Back 38

the observable characteristics of an individual

Front 39

recessive

Back 39

a gene (allele) which is expressed clinically in the homozygous state. In a recessive disorder, both genes at a given locus must be abnormal to manifest the condition

Front 40

syndrome

Back 40

a collection or pattern of physical findings that occur together and have the same etiology

Front 41

sex chromosome

Back 41

the x and y chromosomes which normally are responsible for sex determination

Front 42

teratogen

Back 42

an environmental agent capable of causing malformation(s)

Front 43

translocation

Back 43

a rearrangement occurring when a piece of one chromosome is broken off and joined to another chromosome. An individual with a balanced translocation has the normal amount of genetic material, but it is rearranged and thus gametes could be produced which contain an unbalanced translocation

Front 44

trisomy

Back 44

the presence of three homologous chromosomes rather then the normal two

Front 45

x-linked

Back 45

a gene located on an x-chromosome (formerly known as sex-linked)

Front 46

zygote

Back 46

a fertilized egg