Question | Answer |
Allele | one of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome. |
autosome | any chromosome that is not a sex chromosome. |
codominance | Incomplete dominance is a form of intermediate inheritance in which one allele for a specific trait is not completely expressed over its paired allele |
dihybrid | a hybrid that is heterozygous for alleles of two different genes |
dominant allele | an allele that can take over a recessive allele |
genotype | the genetic constitution of an individual organism. Often contrasted with phenotype. |
heterozygous | an individual having two different alleles of a particular gene or genes, and so giving rise to varying offspring |
homozygous | an individual having two identical alleles of a particular gene or genes and so breeding true for the corresponding characteristic |
monohybrid | a hybrid that is heterozygous with respect to a specified gene. |
multiple allele | an allele of a genetic locus having more than two allelic forms within a population |
phenotype | the set of observable characteristics of an individual resulting from the interaction of its genotype with the environment. |
punnet square | a diagram that is used to predict an outcome of a particular cross or breeding experiment |
recessive allele | one allele masks the contribution of a second allele at the same locus |
sex chromosome | a chromosome involved with determining the sex of an organism, typically one of two kinds |
sex-linked trait | are those found on either the X or Y chromosomes and include hemophilia and fragile X syndrome. |
test cross | test-cross-a cross between an organism whose genotype for a certain trait is unknown and an organism |
apoptosis | the death of cells that occurs as a normal and controlled part of an organism's growth or development |
cell cycle | the life cycle of a dividing cell |
centriole | a minute cylindrical organelle near the nucleus in animal cells, occurring in pairs and involved in the development of spindle fibers in cell division. |
centromere | the point on a chromosome by which it is attached to a spindle fiber during cell division. |
chromatin | the material of which the chromosomes of organisms other than bacteria (i.e., eukaryotes) are composed |
chromosome | a threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes. |
crossing-over | the exchange of genes between homologous chromosomes, resulting in a mixture of parental characteristics in offspring. |
cytokinesis | the cytoplasmic division of a cell at the end of mitosis or meiosis, bringing about the separation into two daughter cells. |
diploid (2n) chromosome number | |
gamete | a mature haploid male or female germ cell that is able to unite with another of the opposite sex in sexual reproduction to form a zygote. |
haploid (n) chromosome number | |
homologous chromosomes | are chromosome pairs, one from each parent, that are similar in length, gene position, and centromere location. |
meiosis | a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell, as in the production of gametes and plant spores |
mitosis | a type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus, typical of ordinary tissue growth |
nondisjunction | the failure of one or more pairs of homologous chromosomes or sister chromatids to separate normally during nuclear division |
somatic cell | any cell of a living organism other than the reproductive cells. |
synapsis | the fusion of chromosome pairs at the start of meiosis. |