A&PII final

  1. Somatic Cells
    Body cells having the diploid number of chromosomes; all cells of the body other than gametes.
  2. Gamete
    Reporductive cells (eggs and sperm) which have a haploid or single set of chromosomes.
  3. Gonad
    Organ in which gametes are formed (ovary and testis in animals; gametophytic organs in plants)
  4. Mitosis
    Regular cell division in which there is an exact quantitative and qualitative replication of each chromosome, one going to each of two daughter cells.
  5. Meiosis
    The type of cell division which occurs during the formation of gametes in which the diploid number of chromosomes found in body cells is reduced to the haploid number (2n to n). In this process each gamete receives one, and only one, member of each homologous pair of chromosomes.
  6. Diploid
    Referring to cells with the double or 2n number of chromosome characteristics of all body or somatic cells except mature gametes.
  7. Haploid
    Referring to cells with a single set, or n number of chromosomes, characteristic of mature gametes.
  8. Chromosome
    A chromatin body found in the nucleus of cells which bears genes arranged in a definite order along its length, and which acts as a unit during mitosis and meiosis.
  9. Sex Chromosome
    A particular chromosome which determines or influences the sex of an individual (in many animals including man: XX=female, XY=male) and bears the sex-linked genes.
  10. Autosomal Chromosome
    Any and all chromosome except the sex chromosome.
  11. Homologous Chromosomes
    Any pair of chromosomes which have the same linear arrangements being derived at fertilization from the egg (maternal chromosomes) and the other from the sperm (paternal chromosome)
  12. Gene
    Defined classically as a hereditary unit, located at a particular position on a particular chromosome.
  13. Alleles
    Two genes with the same or differing genetic effects occupying corresponding locations on the two members of a homologous chromosome pair.
  14. Homozygous
    Referring to both alleles are the same for a trait - homozygous dominant = AA (pure breeding) - homozygous recessive = aa (pure breeding)
  15. Heterozygous
    Referring to one of each allele is present: Aa (Not necessary to say heterozygous "dominant" since in the heterozygous condition the dominant allele will always be expressed.
  16. Hemizygous
    Referring to only one allele present , as in sex-linked inheritance (X - expressed allele, Y - basically only "maleness")
  17. Genotype
    The genetic constitution of an individual (e.g., BB, Bb, or bb)
  18. Phenotype
    The appearance of the individual, irrespective of the actual genetic constitution (e.g., in the case of dominance, BB and Bb would have the same appearance)
  19. Dominant
    A gene which when present is able to suppress the phenotypic expression of its unlike allele (e.g., gen A, B, or, C)
  20. Recessive
    A gene which is unable to express its phenotypic effect in the presence of its dominant allele.
  21. Partial or incomplete dominance
    The absence of dominance; both members of an unlike pair of allelic genes are able to partially express their phenotypic effect in the presence of the other allele.
  22. Lethal
    The expression of a gene which causes death when homozygous.
  23. Test Cross or Back Cross
    The crossing of a phenotypically dominant individual of unknown genotype (Ex. A_B_) to a homozygous recessive individual to determine the genotype of the test animal.
  24. Mutation
    A spontaneous chemical change within a gene that changes the phenotypic effect of the gene in successive generations.
  25. Segregation
    The separation of the members of homologous pairs of chromosomes during meiosis, with the result that each gamete receives one member of each pair of chromosomes.
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A&PII final