Chapter 9 Key terms& study guide

  1. Codominance
    The expression of two different alleles of gene in a heterozygote
  2. Hemophilia
    A human genetic disease caused by a sex-linked recessive alele and charachterized by excessive bleeding following injury
  3. Red-green colorblindness
    • A category of common sex-linked human disorders involving several genes
    • on the X chromosome and characterized by a malfunction of light
    • sensitive cells in the eyes; affects mostly males but also homozygous
    • females
  4. Carrier
    An individual who is heterozygous for a recessively inherited disorder and who therefore does not show symptoms of that disorder
  5. Recessive allele
    In heterozygotes, the allele that has no noticeable effect on the phenotype
  6. testcross
    • The mating between an individial of unknown genotype for a particular
    • character and an individual that is homozygous recessive for that same
    • character
  7. Monohybrid cross
    A mating of individuals differing at one genetic locus
  8. Heredity
    The transmission of traits from one generation to the next
  9. Hypercholesterolemia
    An inherited human disease characterized by an excessively high level of cholesterol in the blood
  10. Chromosome theory of inheritance
    A basic principle in biology stating that genes are located on chromosomes and that the behavior of chromosomes during meiosis accounts for inheritance patterns
  11. F2generation
    The offspring of the F1 generation. F2 stands for second filial
  12. Law of independant assortment
    A general rule of inheritance, first proposed by Gregor Mendel, that states that when gametes form during meiosis, each pair of alleles for a particular character segregate (seperate) independantly of each other pair
  13. Genotype
    The genetic makeup of an organism
  14. Dihybrid cross
    A mating of individuals differing at two genetic loci
  15. Punnett square
    A diagram used in the study of inheritance to show the results of random fertilization
  16. inbreeding
    The mating of close relatives
  17. Sex-linked gene
    A gene located on a sex chromosome
  18. Linkage map
    A map of a chromosome showing the relative positions of genes
  19. Phenotype
    The expressed traits of an organism
  20. Polygenetic inheritance
    The additive effect of two or more genes on a single phenotypic characteristic
  21. Alleles
    An alternative version of a gene
  22. Genetics
    The scientific study of heredity
  23. Trait
    a variant of a character found within a population, such as purple flowers in pea plants
  24. achondroplast
    A form of homan dwarfism caused by a single dominant allele. the homozygous condition is lethal
  25. Homozygous
    Having two identical alleles for a given gene
  26. Hybrids
    The offspring of parents of two different species or two different varieties of one species; the offspring of two parents that differ in one or more inherited traits; an individual that is heterozygous for one or more pairs of genes
  27. True-breeding
    • Referring to organisms for which sexual reproduction produces offspring
    • with inherited traits identical to those of the parents. The organisms
    • are homozygous for the characteristics under consideration
  28. P generation
    The parent individuals from which offspring are derived in studies of inheritance. P stands for parental
  29. Locus
    The particular site where a gene s found on a chromosome. homologous chromosomes have corresponding gene loci
  30. heterozygous
    Having two different allele for a given
  31. ABO
    Genetically determined classes of human blood that are based on the presence or absence of carbohydrates A and B on the surface of red blood cells. The ABO blood group phenotypes, also called blood types are A, B, AB, and O
  32. Rules of mutiplication
    A rule stating that the probability of a compound event is the product of the seperate probabilites of the independent events
  33. Pedigree
    A family tree representing the occurance of heritable traits in parents and offspring across a number of generations
  34. Recombination frequency
    With respect to two given genes, the number of recombinant progeny from a mating divided by the total number of progeny/ Recombinant progeny can carry combinations of alleles different from that seen in either of the parents as a result of independent assortment of chromosomes and crossing over.
  35. Sickle-Cell Disease
    A genetic disorder in which the red blood cells have abnormal hemoglobin molecules and take on an abnormal shape
  36. Huntingtons disease
    A human genetic disease caused by a dominant allele; characterized by uncontrollable body movements and degeneration of the nervous system; usually fatal 10 to 20 years after the onset of symptoms
  37. incomplete dominance
    a type of inheritance in which the phenotpe of a heterozygote (Aa) is intermediate between the phenotypes of the two types of homozygotes (AA and aa)
  38. Dominant Allele
    In a heterozygote, the allele that determines the phenotype with respect to a particular gene
  39. Law of Segregation
    a general rule of inheritance, first proposed by Gregor Mendel. the states that two alleles in a pair segregate (separate) into different gametes during meiosis
  40. Character
    A heritable feature that varies among individuals within a population, such as flower color in pea plants
  41. F1 generation
    The offspring of two parental (p. generation) individuals. F1 stands for first filial
  42. wild-type trait
    The trait most commonly found in nature
  43. Pleiotropy
    the control of more than one phenotypic character by a single gene
  44. linked genes`
    Genes located close enough together on a chromosome that they are usually inherited together
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Chapter 9 Key terms& study guide
key terms and study guide chapter 9