Chapter 14 - Mendel Flashcards
The mating, or crossing, of two true-breeding varieties in genetics
Hybridization
An observable hereditary feature that may vary among individuals
Character
The true-breeding (homozygous) parent individuals from which F1 hybrid offspring are derived in studies of inheritance (P stands for parental)
P generation
The first filial, hybrid (heterozygous) offspring arising from a parental cross
F1 generation
The offspring resulting from interbreeding (or self-pollination) of the hybrid F1 generation
F2 generation
Any of the alternative versions of a gene that may produce distinguishable phenotypic effects
Allele
An allele that is fully expressed in the phenotype of a heterozygote, determines the organism’s appearance
Dominant allele
An allele whose phenotypic effect is not observed in a heterozygote
Recessive allele
Mendel’s first law, states 2 alleles in a pair segregate into different gametes during gamete formation
Law of Segregation
A diagram used in the study of inheritance to show the predicted genotypic results of random fertilization in genetic crosses between individuals of known genotype
Punnett square
Having two identical alleles for a given gene
Homozygous
Having two different alleles for a given gene
Heterozygous
The observable physical and physiological traits of an organism which are determined by its genetic makeup
Phenotype
The genetic makeup, or set of alleles, of an organism
Genotype
Breeding an organism of unknown genotype with a homozygous recessive individual to determine the unknown genotype; the ratio of phenotypes in the offspring reveals the unknown genotype
Testcross
An organism that is heterozygous with respect to a single gene of interest; all offspring from a cross between parents homozygous for different alleles are this; for example, parents of genotypes AA and aa produce a genotype Aa
Monohybrids
A cross between 2 organisms that are heterozygous for the character being followed (or the self-pollination of a heterozygous plant).
Monohybrid cross
An organism that is heterozygous with respect to 2 genes of interest; all the offspring from a cross between parents doubly homozygous for different alleles are this; for example, parents of genotypes AABB and aabb produce a genotype AaBb.
Dihybrids
A cross between 2 organisms that are each heterozygous for both of the characters being followed (or the self-pollination of a plant that is heterozygous for both characters)
Dihybrid cross
Mendel’s 2nd law, states each pair of alleles segregates independently of each other pair during gamete formation; applies when genes for 2 characters are located on different pairs of homologs or when they are far enough apart on the same chromosome to behave as though they are on different chromosomes
Law of Independent Assortment
A rule of probability stating that the probability of 2 or more independent events occurring together can be determined by multiplying their individual probabilities
Multiplication rule
A rule of probability stating that the probability of any one of two or more mutually exclusive events occurring can be determined by adding their individual probabilities
Addition rule
The situation in which the phenotypes of the heterozygote and dominant homozygote are indistinguishable
Complete dominance
The situation in which the phenotypes of heterozygotes is intermediate between the phenotype of individuals homozygous for either allele
Incomplete dominance
The situation in which the phenotypes of both alleles are exhibited in the heterozygote because both alleles affect the phenotype in separate distinguishable ways
Codominance
A human genetic disease caused by a recessive allele for a dysfunctional enzyme, leading to accumulation of certain lipids in the brain; seizures, blindness, and degeneration of motor and mental skills usually manifest a few months after birth, followed by death in a few years
Tay-Sachs Disease
Ability of a single gene to have multiple effects
Pleiotropy
A type of gene interaction in which the phenotypic expression of one gene alters that of another independently inherited gene
Epistasis
Heritable features that vary continuously over a range rather than in an either-or fashion
Quantitative characters
An additive effect of two or more genes on a single phenotypic character
Polygenic inheritance
A diagram of a family tree with conventional symbols showing the occurrence of heritable characters in parents and offspring over multiple generations
Pedigree
An individual who is heterozygous at a given genetic locus for a recessively inherited disorder. The heterozygote is usually phenotypically normal for the disorder but can pass on the recessive allele to the offspring
Carriers
A human genetic disorder caused by a recessive allele for a chloride channel protein; characterized by excessive secretion of mucus and consequent vulnerability to infection; fatal if untreated
Cystic Fibrosis
A recessively inherited human blood disorder in which a single nucleotide change in the gene causes hemoglobin to aggregate, changing RBC shape and causing multiple symptoms in afflicted individuals
Sickle-Cell Disease
A human genetic disorder caused by a dominant allele, characterized by uncontrollable body movements and degeneration of the nervous system; usually fatal 10-20 years after onset of symptoms
Huntington’s Disease
A technique used for prenatal diagnosis in which amniotic fluid is obtained from aspiration of a needle inserted into the uterus; fluid is analyzed to detect certain genetic and congenital defects in the fetus
Amniocentesis
Technique for prenatal diagnosis in which a small sample of the fetal portion of the placenta is removed for analysis to detect certain genetic and congenital defects in the fetus
Chorionic Villus Sampling (CVS)
