Teacher's Vocabulary #2

abortion	Premature, spontaneous or induced expulsion of the embryo or fetus from uterus.
aneuploidy	Having one extra or one less chromosome relative to the parental chromosome number.
autosome	Any chromosome of a type that is the same in males and females of the species.
crossing over	At prophase I of meiosis, an interaction in which non-sister chromatids of a pair of homologous chromosomes break at corresponding sites and exchange segments; genetic recombination is the result.
deletion	At cytological level, loss of a segment from a chromosome. At molecular level, loss of one to a few base pairs from a DNA molecule.
disease	Outcome of infection when defenses aren't mobilized fast enough and a pathogen's activities interfere with normal body functions.
double-blind study	Different investigators independently collect, then compare data.
duplication	Gene sequence repeated several to many hundreds or thousands of times. Even normal chromosomes have such sequences.
genetic abnormality	A rare or less common version of a heritable trait.
genetic disorder	Any inherited condition that causes mild to severe medical problems.
genetic recombination	Result of any process that puts new genetic information into a DNA molecule (e.g., by crossing over).
homologous chromosome	Of cells with a diploid chromosome number, one of a pair of chromosomes identical in size, shape, and gene sequence, and that interact at meiosis. Nonidentical sex chromosomes (e.g., X and Y) also interact as homologues during meiosis.
in-vitro fertilization	Conception outside the body (''in glass'' petri dishes or test tubes).
independent assortment	Mendelian theory that by the end of meiosis, each pair of homologous chromosomes (and linked genes on each one) are sorted before shipment to gametes independently of how the other pairs were sorted. Later modified to account for the disruptive effect of crossing over on linkages.
inversion	Part of a chromosome that became oriented in reverse, with no molecular loss.
karyotype	Preparation of metaphase chromosomes sorted by length, centromere location, other defining features.
linkage group	All genes on a chromosome.
mosaicism	Cells of same type express genes differently, so phenotypic differences emerge in same type of tissue. E.g., occurs by X chromosome inactivation in female mammals; also by nondisjunction in any cell after fertilization (only descendants of altered cell inherit the abnormal chromosome number).
Non-disjunction	Failure of sister chromatids or a pair of homologous chromosomes to separate during meiosis or mitosis. Daughter cells end up with too many or too few chromosomes.
polyploidy	Having three or more of each type of chromosome in the nucleus of a eukaryotic cell at interphase.
reciprocal cross	A paired cross. In the first cross, one parent displays the trait of interest. In the second, the other parent displays it.
sex chromosome	A chromosome with genes that affect sexual traits. Depending on the species, somatic cells have one or two sex chromosomes of the same or different type (e.g., in mammals, XX females, XY males).
syndrome	A set of symptoms that may not individually be a telling clue but collectively characterize a genetic disorder or disease.
translocation	Of cells, movement of a stretch of DNA to a new chromosomal location with no molecular loss. Of vascular plants, distribution of organic compounds by way of phloem.
X chromosome	A type of sex chromosome. An XX mammalian embryo becomes female; an XY pairing causes it to develop into a male.
Y chromosome	A type of sex chromosome. An XX mammalian embryo becomes female; an XY pairing causes it to develop into a male.

Vocabulary # 1

Alelle:One of a number of different forms of a gene.

Codominance:Refers to a relationship between two alleles of a gene. 

Dihibrid cross:Is a cross between F₁ offspring (first generation offspring) of two individuals that differ in two traits of particular interest.

Epitasis:Interaction among the products of two or more gene pairs.

F1:The offspring of an initial genetic cross.

F2:The offspring of parents who are the first filial generation from a genetic cross.

Gene:Unit of information for a heritable trait, passed from parents to offspring.

Genotype:Genetic makeup of an organism; a single gene pair or the sum total of an individual's genes.

Heterozygous:Having a pair of nonidentical alleles at a gene locus (that is, on a pair of homologous chromosomes).

Homozygous dominant:Having a pair of dominant alleles at a gene locus (on a pair of homologous chromosomes).

Homozygous recessive:Having a pair of recessive alleles at a gene locus (on a pair of homologous chromosomes).

Hybrid offspring:Of a genetic cross, offspring having a pair of nonidentical alleles for a trait.

Incomplete dominance:Condition in which one allele of a pair is not fully dominant.

Independent assortment :Mendelian theory that by the end of meiosis, each pair of homologous chromosomes (and linked genes on each one) are sorted before shipment to gametes independently of how the other pairs were sorted. Later modified to account for the disruptive effect of crossing over on linkages.

Monohybrid cross:Intercross between two F₁ heterozygotes that are identical for one gene locus.

Multiple allele system:Three or more slightly different molecular forms of a gene that occur among individuals of a population.

Phenotype:Observable trait or traits of an individual that arise from gene interactions and gene-environment interactions.

Pleiotropy:Positive or negative effects on two or more traits owing to expression of alleles at a single gene locus.

Probability:The chance that each outcome of a given event will occur is proportional to the number of ways the outcome can be reached.

Punnett-square method:Construction of a simple diagram as a way to predict probable outcomes of a genetic cross.

Segregation:Mendelian theory. Separation of alleles during gamete formation.

Test cross:Experimental cross to determine whether an individual of unknown genotype that shows dominance for a trait is either homozygous dominant or heterozygous.

True-breeding lineage:Of sexually reproducing species, a lineage in which only one version of a trait appears over the generations in all parents and their offspring.