Chapter 14: Genes Flashcards
Character
A heritable feature that varies among individuals in a population such as hair color
Trait
A variant for a character such as the actual color of hair a person has
P generation
A true beeding parental generation such as purple color flowers
F1 generation
Hybrid offspring of a parental generation
F2 generation
Generation of offspring that result from the F1 generation
Alleles
Alternate versions of a gene such as purple and white petal colors in pea plants
Law of segregation
Two alleles for a heritable chracter segregate during gamete formation and end up in different gametes
An egg or sperm gets only one of the two alleles that are present in the diploid cells of the organism making the gamete
Phenotype vs. genotype
A phenotype describes an organism’s appearance or observable traits
A genotype is an organism’s genetic makeup
Testcross
The breeding of an organism with an unknown genotype with a recessive homozygote to reveal the gentype of the unknown organism
Monohybrids
The F1 progeny of crosses of true-breeding parents that are all heterozygous for one particular character that is being followed in the cross
Monohybrid cross
A cross between F1 monohybrid heterozygotes
Dihybrids
The F1 hybrids of individuals heterozygous for two characters being followed in a cross
Dihybrid cross
A cross between F1 dihybrid heterozygotes
Law of independent assortment
Two or more genes will assort independently during gamete formation; each pair of alleles segregates independently of any other pair of alleles
Only applies to genes located on different chromosomes or that are very far apart on the same chromosome
Multiplication rule
The probability that one event and another event will occur such as two coins landing on heads
Probability of one event is multiplied by the probability of the other event
Addition rule
The probability that one event or another mutually exclusice event will occur such as rolling a 1 or a 2 on a six-sided dice
Probability of one event is added to the probability of the other event
Incomplete dominance
When neither allele is completely dominant and F1 hybrids have an intermediate phenotype
Codominance
The two alleles each affect the pheotype in seperate, distinguishable ways
AB blood pheotypes are not all one or the other but express both antigens
Tay-Sachs disease
An inherited disorder in humans where brain cells cannot metabolize certain lipids due to a deficiency in a crucial enzyme
An individual who is heterozygous for the disease will have impaired enzyme function but does not exhibit any significant deficits
Pleiotropy
A property of genes in which they exert phenotypic effects on multiple characters rather than only influencing one
Epistasis
The phenotypic expression of a gene at one locus alters that of a gene at a second locus
Polygenic inheritance
An additive effect of two or more genes on a single pheotypic character such as height or skin color
Usually the result of quantitative characters- characters that do not exist as two discrete varieties but instead present as gradiations along a continuum in a population
Pedigree
A family tree describing the a trait across generations from information in an individuals family tree
Recessively inherited disorders
Albinism
Tay-Sachs disease- highest incidence among Ashkenazic Jews
Sickle-cell disease- most common recessively inherited disorder
Cystic fibrosis- chloride ion transport channels in the plasma membrane are absent or defective which leads to elevated intracellular chloride levels which causes excessive water uptake
Consanguineous matings
Consanguineous matings (i.e., matings between close relatives) increase the chance of mating between two carriers of the same rare allele
Dominantly inherited disorders
Achondroplasia- a form of dwarfism
Huntington’s disease- fatal neurodegenerative disease that doesn’t cause phenotypic effects until an individual is 35-45 years old
Fetal testing
Amniocentesis
Chorionic villus sampling (CVS)- a sample of the placenta is removed and tested
