Chapter 14 Flashcards
describe the “blending” hypothesis
the genetic material from two parents blends into the offspring, like blue and yellow paint blend to make green
describe the “particulate hypothesis
the idea that parents pass on discrete heritable units (genes)
sperm producing organs of plants
stamens
egg producing organs of plants
carpels
what is a true-breeding plant
one that produces identical copies when self-pollinating (homozygous)
what is hybridization
the process of mating contrasting, true-breeding plants
what generation are the true breeding plants
P
what generation are they hybrids produced by the true breeding cross
F1
what generation are the offspring of the self-pollinated F1 individuals
F2
what term did Mendel use for “gene”
heritable factor
alternate versions of a gene are called _____
alleles
where do genes reside
at a specific locus on a specific chromosome
what are the four related concepts that Mendel used to explain his findings
alternate versions of genes account for genetic variation, for each character an organism inherits two alleles (one from each parent), if the alleles at a locus differ the dominant one with affect the phenotype, two alleles for a gene sperate during gamete formation and end up in different gametes (law of segregation)
describe the law of segregation
during gamete formation, the sperm or egg cell receives only one of the two alleles that were present in the original somatic cell, this is linked to the distribution of homologous chromosomes in meiosis
describe the difference between a phenotype and a genotype
a phenotype is the physical appearance of expression of a trait, while a genotype is the genetic make up
what is a testcross
this is the process of breeding an organism that portrays a dominant phenotype with one that is homozygous recessive for the purpose of discovering the genotype of the parent
what is a monohybrid cross
a cross between organisms that are heterozygous for one trait
what is a dihybrid cross and what is it used for
a cross between organisms that are heterozygous for two traits, used to determine whether traits are inherited together or separate
describe the law of independent assortment
each pair of alleles segregates independently of each pair of alleles during gamete formation (applies to genes on different, nonhomologous chromosomes)
what genes tend to be inherited together
those near each other on the same chromosome
give three examples of when inheritance of characters by a single gene may deviate from simple mendelian patterns
when alleles are not completely dominant or recessive, when a gene has more than two alleles, when a gene produces multiple alleles
what is complete dominance
when phenotypes of the heterozygote and dominant homozygote are identical
what is incomplete dominance
when the phenotype of F1 hybrids is somewhere between the phenotypes of the two parental varieties
describe the different levels of dominance shown in Tay-Sachs disease
organismal level it is recessive, at the biochemical level it is incompletely dominant as the enzyme activity is between infected and normal, at the molecular level it is codominant, as equal numbers of normal and dysfunctional enzyme are produced
what is it called when a gene has multiple phenotypic effects
pleiotropy
what is an example of pleiotropy
the various symptoms caused by hereditary diseases
what is it called when a gene at one locus alters the phenotypic expression of a gene at a second locus
epistasis
what is a common example of epistasis
coat color in animals, one gene controls the color, and the other determines whether the pigment is deposited into the hair
what are quantitative characters
those that vary in the population along a continuum
what is an additive effect of two or more genes on a single phenotype
polygenic inheritance
common example of polygenic inheritance
skin color
what is the phenotypic range of a genotype influenced by the environment
norm of reaction
what type of characters are most affected by norms of reaction
polygenic characters
what are characters called that are influenced by genetic and environmental factors
multifactorial characters
what makes up an organisms phenotype
physical appearance, internal anatomy, physiology, and behavior
this is the most common lethal genetic disease in the united states
cystic fibrosis
what causes sickle-cell disease
the substitution of a single amino acid in the hemoglobin protein in red blood cells
this is when the liquid that bathes the fetus is removed and tested
amniocentesis
this is when a sample of the placenta is removed and tested
chorionic villus sampling
