Chapter 3 Flashcards
(50 cards)
Polymorphic
The presence of several distinct forms of a gene or phenotypic trait within a population.
Alcaptonuria
A recessive enzyme deficiency that results in an accumulation of homogentisic acid, a normal product of the breakdown of phenylalanine and tyrosine. Urine of affected individuals turns dark upon exposure to air.
Antibodies
Proteins manufactured by the body to neutralize or destroy an antigen.
ABO blood-type system
A blood-type system that consists of two basic antigens, A and B. Blood type O is the absence of both antigens.
Multiple alleles
A situation in which a gene has more than two alleles.
Codominant
The situation in which, in the heterozygous condition, both alleles are expressed in the phenotype.
Agglutination
A clumping together of red blood cells in the presence of an antibody.
Rh blood-type system
A blood-type system consisting of two major alleles. A mating between an Rh- mother and an Rh + father may produce the hemolytic disease erythroblastosis fetails in the infant.
Erythroblastosis fetails
A hemolytic disease affecting unborn or newborn infants caused by the destruction of the infants Rh + blood by the mothers anti-Rh antibodies.
Hemolytic disease
Disease involving the destruction of blood cells
Phenylketonuria (PKU)
A genetic disease, inherited as a recessive, brought about by the absence of the enzyme responsible for the conversion of the amino acid phenylalanine to tyrosine; phenylalanine accumulates in the blood and then breaks down into by-products that cause severe mental retardation in addition to other symptoms.
Achondroplastic dwarfism
Form of dwarfism In which the individuals head and trunk are of normal size but the limbs are quite short; inherited as a dominant.
Pedigree
A reconstruction of past mating in a family, expressed as a diagram.
Sex-limited gene
Nonsex- linked allele that is expressed in only one of the sexes.
Phenotypic sex
The sex that a person is judged to be, based in his or her physical appearance. Phenotypic sex may not correspond to chromosomal sex.
Chromosomal sex
The number of X and Y chromosomes a person has. The chromosomal sex of a person with two X chromosomes is a female. The chromosomal sex of a person with one X and one Y chromosome is a male.
Genetic sex
In humans, male sex is determined by the presence of the SRY gene, which is located on the Y chromosome. Persons who lack the Y chromosome, hence the SRY gene, or who possess an abnormal allele of the SRY gene, are genetically female.
Gonad
General term used for an organ that produces sex cells; the ovary and testis.
Hemophilia
A recessive X-linked trait characterized be excessive bleeding due to a faulty clotting mechanism.
Chromosomal aberration
Abnormal chromosome number or chromosome structure.
Nondisjunction
An error of meiosis in which the members of a pair of chromosomes move to the same pole rather than moving to opposite poles.
Down syndrome
Condition characterized by a peculiarity of eyefolds, malformation of the heart and other organs, stubby hands and feet, short stature, and mental retardation; result of extra chromosome 21.
Trisomy
The state of having three of the same chromosome, rather than the normal pair. For example, trisomy 21, or down syndrome, is a tripling of chromosome number 21.
Turner Syndrome
Genetic disease characterized by 45 chromosomes with a sex chromosome count of X-; phenotypically female, but sterile.
