CHAPTER 12 VOCABULARY Mendel and Heredity:
CLASSICAL GENETICS-the study of the inheritance of traits and their patterns
MODERN GENETICS - the study of the biochemical basis of inheritance
HEREDITY is the passing of traits from parents to offspring
GENETICS is the study of how traits are inherited through the action of alleles
GREGOR MENDEL – “Father of Genetics,” responsible for laws governing the inheritance of traits
SEXUAL REPRODUCTION The production of new organism by combing DNA
Plants normally reproduce 2 ways
SELF POLLINATION-pollen from one plant fertilizes ova of same plant
CROSS POLLINATION-pollen from one plant fertilizes another
SELECTIVE BREEDING- The practice of human intervention in creating specific breeds
PURE BREED or TRUE BREEDING STRAIN
– organism that ALWAYS produces offspring of the same type when bred with a member of its “breed.”
SPECIES –organisms that are so similar that they can reproduce VIABLE offspring
HYBRID – the mix of two true breeding strains- extreme examples include ligers or mules
CHARACTER– An identifiable feature of an organism, like flower color or height
TRAITS– any specific characteristic that can be passed from parents to offspring
EXPRESSION – refers to traits that are observed,
HEREDITY– the passing of traits from parents to offspring
DOMINANT– is always expressed; masks a recessive trait
RECESSIVE– can only be expressed if there are no dominant alleles present
ALLELE– one form (dominant or recessive) of a gene
GAMETE- Sex cells (have ONE form of a gene on their chromosomes)
SOMATIC or Body cells have TWO alleles for a single gene
DOMINANT alleles are represented by a capital letter, are expressed in both Homo and heterozygote
RECESSIVE alleles are represented by a lower case letter, only expressed in homozygote
HOMOZYGOUS- two copies of the same allele
BB (homozygous dominant)
bb (homozygous recessive)
HETEROZYGOUS,
Bb Organism with two different alleles
GENOTYPE: the alleles present in the organism, BB, Bb, or bb (THE TYPE OF GENES)
PHENOTYPE: the expression of the genes; observed traits (THE TYPE OF TRAITS)
GENETIC CROSSES- Mating trials between organisms
MONOHYBRID CROSS: cross involving ONE trait, e.g., eye color
DIHYBRID CROSS: cross involving TWO traits, e.g., eye color and hair color
PUNNETT SQUARE – Model to determine offspring’s genotype and phenotype
PARENTAL GENERATION (P1 0r Po) = the parental generation in a breeding experiment
FIRST FILIAL GENERATION (F1) = the first generation of offspring in a breeding experiment
SECOND FILIAL GENERATION (F2) = the second generation of offspring in a breeding experiment
MENDELS LAW OF RANDOM SEGREGATION
Each pair of alleles segregates independently during gamete formation in 50/50 proportions
MENDELS LAW OF INDEPENDENT ASSORTMENT
Traits are not connected in any way to each other, ie pea color and pod color aren’t connected
Mendel is a little wrong on this one
GENETIC CROSS FORMULA –determines the number of possible genotypes in a genetic cross
Formula: 2n (n = # of heterozygotes)
TEST CROSS – Cross that allows you to deduce Parental Genotype by Breeding a dominant with a recessive
ALTERNATIVE MODES OF INHERITANCE – the dominant recessive pattern is not the only way genes are expressed
INCOMPLETE DOMINANCE - Heterozygotes have BLENDED TRAITS their appearance is in between the phenotypes of the two parental
varieties.
CODOMINANCE- BOTH ALLELES are expressed in heterozygote BOTH TRAITS are observed
SEX LINKED TRAITS - Traits (genes) located on the sex chromosomes, Many sex-linked traits carried on X chromosome