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SLSBio11 Genetics MD
SLS Bio 11 Genetics MD
| Term | Definition |
|---|---|
| autosome | a chromosome that is not a sex chromosome. They appear in pairs whose members have the same form but differ from other pairs in a diploid cell, whereas members of an allosome pair may differ from one another and thereby determine sex. |
| codominance | a relationship between two versions of a gene. Individuals receive one version of a gene, called an allele. If the alleles are different, the dominant allele usually will be expressed, while the effect of the other allele, called recessive, is masked. |
| dihybrid | Dihybrid cross is a cross between two pure lines (varieties, strains) that differ in two observed traits. In Mendelian sense, between the alleles of both these loci there is a relationship of complete dominance - recessive. |
| dominant allele | An allele that expresses its phenotypic effect even when heterozygous with a recessive allele; thus if A is dominant over a, then AA and Aa have the same phenotype. |
| genotype | an individual's collection of genes. The term also can refer to the two alleles inherited for a particular gene. The genotype is expressed when the information encoded in the genes' DNA is used to make protein and RNA molecules. |
| heterozygous | refers to a pair of genes where one is dominant and one is recessive — they're different. Like all words with the prefix hetero, this has to do with things that are different — specifically genes. |
| homozygous | If you're homozygous, you've got a pair of matching alleles, which are the two genes that control a particular trait. If both your alleles that determine blood type are O, you're homozygous — and you've got type O blood. |
| monohybrid | a hybrid that is heterozygous with respect to a specified gene. |
| multiple allele | Three or more alternative forms of a gene (alleles) that can occupy the same locus. However, only two of the alleles can be present in a single organism. |
| 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 named after Reginald C. Punnett, The diagram is used by biologists to determine the probability of an offspring having a particular genotype. |
| recessive allele | an allele that produces its characteristic phenotype only when its paired allele is identical |
| sex chromosome | a chromosome involved with determining the sex of an organism, typically one of two kinds. |
| sex-linked trait | A trait associated with a gene that is carried only by the male or female parent. Note : In humans, the gene for colorblindness is carried by the X-chromosome. |
| test cross | a genetic cross between a homozygous recessive individual and a corresponding suspected heterozygote to determine the genotype of the latter. |
| apoptosis | he death of cells that occurs as a normal and controlled part of an organism's growth or development. |
| cell cycle | a series of events that happens in a cell it grows and divides. A cell spends most of its time in interphase, and when it grows, replicates its chromosomes, prepares for cell division. The cell then leaves interphase, undergoes mitosis (cell division) |
| 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. It consists of protein, RNA, and DNA. |
| 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 | two gametes form a diploid zygote with twice this number, two copies of autosomal chromosomes. |
| 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 | is the number of chromosomes in a gamete. Two gametes form a diploid zygote with twice this number, ie one copy of autosomal chromosomes |
| homologous chromosomes | A pair of chromosomes that contain the same gene sequences, each derived from one parent. |
| 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, usually resulting in an abnormal distribution of chromosomes in the daughter nuclei. |
| somatic cell | any cell of a living organism other than the reproductive cells. |
| synapsis | the fusion of chromosome pairs at the start of meiosis. |
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