Chapter 14 Flashcards
“Blending” hypothesis
The idea that genetic material contributed by the two parents mixes
“Particulate” hypothesis
The gene idea.
Character
A heritable feature that varies among individuals, such as flower color.
Trait
Each variant for a character
Stamens
Pollen-producing organs
Carpel
An egg-bearing organ
True-breeding
Referring to organisms that produce offspring of the same variety over many generations of self-pollination.
Hybridization
Mating, or crossing, of two true-breeding varieties
P generation
Parental generation
F1 generation
First filial generation
F2 generation
Second filial generation
Alleles
Alternative versions of a gene
Locus
The location of a gene in a chromosome
For each character, an organism inherits two copies (that is, two alleles) of a gene, one from each parent.
True
Dominant allele
Determines the organism’s appearance.
Law of segregation
States that the two alleles for a heritable character segregate (separate from each other) during gamete formation and end up in different gametes.
Homozygous
An organism that has a pair of identical alleles for a character
Heterozygous
An organism that has two different alleles for a gene
Phenotype
Observable traits
Genotype
Genetic makeup
Testcross
Breeding an organism of unknown genotype with a recessive homozygote
Mendel derived the law of segregation from experiments in which he followed only a single character, such as flower color.
True
Monohybrid
An organism that is heterozygous with respect to a single gene of interest.
Monohybrid cross
A cross between two organisms that are heterozygous for the character being followed.
Mendel identified the law of independent assortment by following two characters at the same time, such as seed color and seed shape.
True
Dihybrids
Individuals heterozygous for the two characters being followed in the cross.
Dihybrid cross
A cross between F1 dihybrids
Law of independent assortment
States that two or more genes assort independently— that is, each pair of alleles segregates independently of each other pair of alleles— during gamete formation.
Incomplete dominance
Neither allele is completely dominant, and the F1 hybrids have a phenotype somewhere between those of the two parental varieties.
Codominance
The two alleles each affect the phenotype in separate, distinguishable ways.
Pleiotropy
The property of genes having multiple phenotypic effects.
Epistasis
The phenotypic expression of a gene at one locus alters that of a gene at a second locus.
Quantitative character
A heritable feature that varies continuously over a range rather than in an either-or fashion
Polygenic inheritance
An additive effect of two or more genes on a single phenotypic character.
A genotype generally is not associated with a rigidly defined phenotype, but rather with a range of phenotypic possibilities due to environmental influences.
True
Multifactorial
Many factors, both genetic and environmental, collectively influence phenotype.
Carriers
Heterozygotes; they may transmit the recessive allele to their offspring.
The probability of passing on recessive traits increases greatly if the man and woman are close relatives.
True
The most common lethal genetic disease in the United States is ________, which strikes one out of every 2,500 people of European descent but is much rarer in other groups.
Cystic fibrosis
The most common inherited disorder among people of African descent is __________, which affects one out of 400 African—Americans.
Sickle-cell disease
Sickle cell is caused by…
The substitution of a single amino acid in the hemoglobin protein of red blood cells.
Achondroplasia is a trait for which the recessive allele is much more prevalent than the corresponding dominant allele.
True
Dominant alleles that cause a lethal disease are much less common than recessive alleles that have lethal effects.
True
Huntington’s disease is caused by a lethal dominant allele that has no obvious phenotypic effect until the individual is about 35 to 45 years old.
Heart disease, diabetes, cancer, alcoholism, certain mental illnesses such as schizophrenia and bipolar disorder, and many other diseases are multifactorial.
True
Amniocentesis
Technique used to help determine whether the developing fetus has Tay-Sachs disease.
Chorionic villus sampling (CVS)
Technique where a sample of placenta is used to detect genetic disorders.
CVS is faster than amniocentesis and can be performed earlier.
True
Ultrasound
Technique where reflected sound waves are used to produce an image of the fetus by a simple noninvasive procedure.
Fetoscopy
Technique where a needle-thin tube containing a viewing scope and fiber optics is inserted into the uterus.
