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Chapter 12-15
Biology Key Terms
| Term | Definition |
|---|---|
| Gonads | Sex organs: ovaries in females, testes in males. |
| Autosomes | Paired chromosomes present in both males and females; all chromosomes except the X and Y chromosomes. |
| Sex Chromosomes | Paired chromosomes that differ between males and females, XX in females, XY in male. |
| X-Linked Trait | A phenotype determined by an allele on an X chromosome. |
| Pedigree | A visual representation of the occurrence of phenotype across generations. |
| Y-Chromosome Analysis | Comparing sequences on the Y chromosomes to examine paternity and paternal ancestry. |
| Incomplete Dominance | A form of inheritance in which heterozygotes have a phenotype that is intermediate between homozygous dominant and homozygous recessive. |
| Codominance | A form of inheritance in which both alleles contribute equally to the phenotype. |
| Continuous Variation | Variation in a population showing an unbroken range of phenotypes rather than discrete categories. |
| Polygenic Trait | A trait whose phenotype is determined by the interaction among alleles of more than one gene. |
| Multifactorial Inheritance | An interaction between genes and the environment that contributes to a phenotype or trait. |
| Aneuploidy | An abnormal number of one or more chromosomes (either extra or missing copies). |
| Nondisjunction | The failure of chromosomes to separate accurately during cell division; nondisjunction in meiosis leads to aneuploidy gametes. |
| Trisomy 21 | Carrying an extra copy of chromosome 21; also known as Down syndrome. |
| Amniocentesis | A procedure that removes fluid surrounding the fetus to obtain and analyze fetal cells to diagnose genetic disorders. |
| Karyotype | The chromosomal makeup of cells. Karyotype analysis can be used to detect trisomy 21 prenatally. |
| Stem Cells | Immature cells that can divide and differentiate into specialized cell types. |
| Tissue | An organized group of different cell types that work together to carry out a particular function. |
| Adult (Somatic) Stem Cells | Stem cells located in tissues that help maintain and regenerate those tissues. |
| Cellular Differentiation | The process by which a cell specializes to carry out a specific role. |
| Differential Gene Expression | The process by which genes are "turned on," or expressed, in different cell types. |
| Multipotent | Describes a cell with the ability to differentiate into a limited number of cell types in the body. |
| Embryonic Stem Cells | Stem cells that make up an early embryo and which can differentiate into nearly every cell type in the body. |
| Blastocyst | The stage of embryonic development in which the embryo is a hollow ball of cells. Researchers can derive embryonic stem cell lines during the blastocyst stage. |
| Pluripotent | Describes a cell with the ability to differentiate into nearly any cell type in the body. |
| Totipotent | Describes a cell with the ability to differentiate into any cell type in the body. |
| Induced Pluripotent Stem Cell | A pluripotent stem cell that was generated by manipulation of a differentiated somatic cell. |
| Antibiotics | Chemicals that either kill bacteria or slow their growth by interfering with the function of essential bacterial cell structures. |
| Binary Fission | A type of asexual reproduction in which one parental cell divides into two. |
| Population | A group of organisms of the same species living together in the same geographic area. |
| Evolution | Change in allele frequencies in a population over time. |
| Fitness | The relative ability of an organism to survive and reproduce in a particular environment. |
| Natural Selection | Differential survival and reproduction of individuals in response to environmental pressure that leads to change in allele frequencies in a population over time. |
| Adaptation | The process by which populations become better suited to their environment as a result of natural selection. |
| Directional Selection | A type of natural selection in which organisms with phenotypes at one end of a spectrum are favored by the environment. |
| Stabilizing Selection | A type of natural selection in which organisms near the middle of the phenotypic range of variation are favored by the environment. |
| Diversifying Selection | A type of natural selection in which organisms with phenotypes at both extremes of the phenotypic range are favored by the environment. |
| Population Genetics | The study of the genetic makeup of populations and how the genetic composition of a population changes. |
| Gene Pool | The total collection of alleles in a population. |
| Allele Frequency | The relative proportion of an allele in a population. |
| Nonadaptive Evolution | Any change in allele frequency that does not by itself lead a population to become more adapted to its environment; the causes of nonadaptive evolution are mutation, genetic drift, and gene flow. |
| Genetic Drift | Random changes in the allele frequencies of a population between generations; genetic drift tends to have more dramatic effects in smaller populations than in larger ones. |
| Founder Effect | A type of genetic drift in which a small number of individuals leaves one population and establishes a new population; by chance, the newly established population may have lower genetic diversity than the original population. |
| Bottleneck | A type of genetic drift that occurs when a population is suddenly reduced to a small number of individuals, and alleles are lost from the population as a result. |
| Gene Flow | The movement of alleles from one population to another, which may increase the genetic diversity of a population. |
| Inbreeding | Mating between closely related individuals. Inbreeding does not change the allele frequency within a population, but it does increase the proportion of homozygous individuals to heterozygotes. |
| Inbreeding Depression | The negative reproductive consequences for a population associated with having a high frequency of homozygous individuals possessing harmful recessive alleles. |
| Hardy-Weinberg Equilibrium | The principle that, in a nonevolving population, both allele and genotype frequencies remain constant from one generation to the next. |
| Hardy-Weinberg Equation | A mathematical formula that calculates the frequency of genotypes and phenotypes one would expect to find in a nonevolving population. |
| Biological Species Concept | The definition of a species as a population whose members can interbreed to produce fertile offspring. |
| Reproductive Isolation | Mechanisms that prevent mating (and therefor gene flow) between members of different species. |
| Speciation | The genetic divergence of populations, leading over time to reproductive isolation and the formation of new species. |
Created by:
tblackdog
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