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AP Bio Review #4
Heredity
| Term | Definition |
|---|---|
| heredity | The transmission of characteristics from parent to offspring. |
| genetics | The branch of biology that deals with heredity, especially the mechanisms of hereditary transmission and the variation of inherited characteristics among similar or related organisms. |
| gene | discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA, in some viruses). |
| asexual reproduction | A type of reproduction involving only one parent that produces genetically identical offspring by budding or by the division of a single cell or the entire organism into two or more parts. |
| clone | 1) A lineage of genetically identical individuals or cells. (2) In popular usage, a single individual organism that is genetically identical to another individual |
| sexual reproduction | A type of reproduction in which two parents give rise to offspring that have unique combinations of genes inherited from the gametes of the two parents. |
| karyotype | A method of organizing the chromosomes of a cell in relation to number, size, and type |
| homologus chromosomes | Chromosome pairs of the same length, centromere position, and staining pattern that possess genes for the same characters at corresponding loci. One homologous chromosome is inherited from the organism's father, the other from the mother. |
| sex chromosomes | The pair of chromosomes responsible for determining the sex of an individual. |
| autosome | chromosome that is not directly involved in determining sex, as opposed to the sex chromosomes |
| haploid | cell containing only one set of chromosomes |
| fertilization | The union of haploid gametes to produce a diploid zygote |
| syngamy | The process of cellular union during fertilization |
| zygote | The diploid product of the union of haploid gametes in conception; a fertilized egg |
| diploid cells | A cell containing two sets of chromosomes (2n), one set inherited from each parent |
| meiosis | A two-stage type of cell division in sexually reproducing organisms that results in gametes with half the chromosome number of the original cell. |
| alternation of generations | A life cycle in which there is both a multicellular diploid form, the sporophyte, and a multicellular haploid form, the gametophyte; characteristic of plants. |
| sporophyte | The multicellular diploid form in organisms undergoing alternation of generations that results from a union of gametes and that meiotically produces haploid spores that grow into the gametophyte generation. |
| spores | In the life cycle of a plant or alga undergoing alternation of generations, a meiotically produced haploid cell that divides mitotically, generating a multicellular individual, the gametophyte, without fusing with another cell. |
| gametophyte | The multicellular haploid form in organisms undergoing alternation of generations, which mitotically produces haploid gametes that unite and grow into the sporophyte generation |
| meiosis I | chromosomes in a diploid cell resegregate, producing four haploid daughter cells. It is this step in meiosis that generates genetic diversity |
| meiosis II | Meiosis II is similar to mitosis. However, there is no "S" phase. The chromatids of each chromosome are no longer identical because of recombination. Meiosis II separates the chromatids producing two daughter cells each with 23 chromosomes (haploid), and |
| synapsis | The pairing of replicated homologous chromosomes during prophase I of meiosis |
| tetrad | In genetics, a pair of homologous chromosomes that have replicated and come together in prophase I of meiosis; consists of four chromatids. |
| chiasmata | (plural) The X-shaped, microscopically visible region representing homologous chromatids that have exchanged genetic material through crossing over during meiosis |
| chiasma | (singular) The X-shaped, microscopically visible region representing homologous chromatids that have exchanged genetic material through crossing over during meiosis |
| crossing over | The reciprocal exchange of genetic material between nonsister chromatids during synapsis of meiosis I. |
| monohybrid cross | A breeding experiment that uses parental varieties differing in a single character |
| P generation | parent generation |
| F1 generation | The first filial or hybrid offspring in a genetic cross-fertilization |
| F2 generation | Offspring resulting from interbreeding of the hybrid F1 generation |
| alleles | An alternative form of a gene |
| dominant alleles | In a heterozygote, the allele that is fully expressed in the phenotype |
| recessive alleles | in a heterozygote, the allele that is completely masked in the phenotype |
| law of segregation | Mendel's first law, stating that allele pairs separate during gamete formation, and then randomly re-form pairs during the fusion of gametes at fertilization. |
| homozygous | A diploid organism that carries identical alleles at one or more genetic loci |
| heterozygous | A diploid organism that carries two different alleles at one or more genetic loci |
| phenotype | The physical and physiological traits of an organism |
| genotype | genetic makeup of an organism |
| dihybrid cross | breeding experiment in which parental varieties differing in two traits are mated |
| law of independent assortment | Mendel's second law, stating that each allele pair segregates independently during gamete formation; applies when genes for two traits are located on different pairs of homologous chromosomes |
| incomplete dominance | A type of inheritance in which F1 hybrids have an appearance that is intermediate between the phenotypes of the parental varieties. |
| complete dominance | The type of inheritance in which both heterozygotes and dominant homozygotes have the same phenotype. |
| codominance | A phenotypic situation in which both alleles are expressed in the heterozygote. |
| multiple alleles | Any of a set of three or more alleles, or alternative states of a gene, only two of which can be present in a diploid organism. |
| pleiotropy | The ability of a single gene to have multiple effects |
| epistasis | A phenomenon in which one gene alters the expression of another gene that is independently inherited |
| polygenic inheritance | An additive effect of two or more gene loci on a single phenotypic character |
| wild type | An individual with the normal phenotype. |
| sex-linked gene | Genes located on one sex chromosome but not the other |
| linked genes | Genes that are located on the same chromosome. |
| genetic recombination | The general term for the production of offspring that combine traits of the two parents |
| translocation | An aberration in chromosome structure resulting from an error in meiosis or from mutagens; attachment of a chromosomal fragment to a nonhomologous chromosome. |
| recombination | The formation of new gene combinations; in eukaryotes, may be accomplished by new associations of chromosomes produced during sexual reproduction or crossing over; in prokaryotes, may be accomplished through transformation, conjugation, or transduction |
| linkage map | A genetic map based on the frequencies of recombination between markers during crossing over of homologous chromosomes. The greater the frequency of recombination between two genetic markers, the farther apart they are assumed to be. |
| nondisjunction | An accident of meiosis or mitosis, in which both members of a pair of homologous chromosomes or both sister chromatids fail to move apart properly. |
| deletion | (1) A deficiency in a chromosome resulting from the loss of a fragment through breakage. (2) A mutational loss of a nucleotide from a gene. |
| duplication | An aberration in chromosome structure resulting from an error in meiosis or mutagens; duplication of a portion of a chromosome resulting from fusion with a fragment from a homologous chromosome. |
| inversion | An aberration in chromosome structure resulting from an error in meiosis or from mutagens; reattachment in a reverse orientation of a chromosomal fragment to the chromosome from which the fragment originated. |
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kgillette