Exam IV Flashcards
A heritable feature that varies among individuals (such as flower color)
Character
Each variant for a character, such as purple or white color for flowers is called a
trait
plants that produce offspring of the same variety when they self-pollinate
true-breeding
In a typical experiment, Mendel mated two contrasting, true-breeding varieties, a process called
hybridization
The true-breeding parents are called the
P generation
The hybrid offspring of the P generation are called the
F1 generation
When F1individuals self-pollinate or cross-pollinate with other F1hybrids, the ___ is produced
F2 generation
alternative versions of a gene are called
alleles
Each gene resides at a specific ___ on a specific chromosome
locus
if the two alleles at a locus differ, then one, the _______, determines the organism’s appearance
dominant allele
the ____, has no noticeable effect on appearance
recessive allele
the law of segregation:
the two alleles for a heritable character separate (segregate) during gamete formation and end up in different gametes
Possible combinations of sperm and egg can be shown using a ______
Punnett square
An organism with two identical alleles for a gene is called a
homozygote (PP, or pp).
An organism with two different alleles for a gene is a ____
heterozygote (Pp)
we distinguish between an organism’s ___, or physical appearance, and its ___, or genetic makeup
phenotype, genotype
To determine the genotype we can carry out a _____: breeding the mystery individual with a homozygous recessive individual
testcross
The F1offspring produced in this cross were ____, meaning that they were heterozygous for one character
monohybrids
A cross between such heterozygotes is called a
monohybrid cross
Crossing two true-breeding parents differing in two characters produces ___ in the F1 generation
dihybrids
a ____, a cross between F1 dihybrids, can determine whether two characters are transmitted to offspring together as a unit or independently
dihybrid cross
each pair of alleles segregates independently of any other pair of alleles during gamete formation
Law of Independent Assortment
The _____ states that the probability that two or more independent events will occur together is the product of their individual probabilities
multiplication rule
The ______ states that the probability that any one of two or more mutually exclusive events will occur is calculated by adding together their individual probabilities
addition rule
occurs when phenotypes of the heterozygote and dominant homozygote are identical
Complete dominance
the phenotype of F1hybrids is somewhere between the phenotypes of the two parental varieties
Incomplete dominance
two dominant alleles affect the phenotype in separate, distinguishable ways
Codominance
Tay-Sachs disease
a fatal inherited disorder; a dysfunctional enzyme causes an accumulation of lipids in the brain
Most genes have multiple phenotypic effects, a property called ____
pleiotropy
In ____, expression of a gene at one locus alters the phenotypic expression of a gene at a second locus
epistasis
Quantitative characters
those that vary in the population along a continuum
Quantitative variation usually indicates ____, an additive effect of two or more genes on a single phenotype
polygenic inheritance
Traits that depend on multiple genes combined with environmental influences are called
multifactorial
a family tree that describes the inheritance of a trait across generations
pedigree
____ are heterozygous individuals who carry the recessive allele but are phenotypically normal
carriers
Cystic fibrosis
the most common lethal genetic disease in the United States, striking one out of every 2,500 people of European descent
Sickle-cell disease
- It is caused by the substitution of a single amino acid in the hemoglobin protein in red blood cells
- In homozygous individuals, all hemoglobin is abnormal (sickle-cell)
Huntington’s disease
- a degenerative disease of the nervous system
- The disease has no obvious phenotypic effects until the individual is about 35 to 40 years of age
In _____, the liquid that bathes the fetus is removed and tested for certain genetic disorders
amniocentesis
In ______, a sample of the placenta is removed and tested
chorionic villus sampling (CVS)
Around 1902, Sutton and Boveri and others independently noted these parallels and began to develop the
chromosome theory of inheritance
Traits alternative to the wild type are called
mutant phenotypes
A gene that is located on either sex chromosome is called a
sex-linked gene
Genes on the X chromosome are called _____; the human X chromosome contains about 1,100 genes
X-linked genes
Some disorders caused by recessive alleles on the X chromosome in humans:
–Color blindness (mostly X-linked)
–Duchennemuscular dystrophy
–Hemophilia
The inactive X condenses into a
Barr body
Genes that are located on the same chromosome tend to be inherited together and are called
linked genes
the production of offspring with combinations of traits differing from either parent
genetic recombination
Offspring with a phenotype matching one of the parental (P) phenotypes are called
parental types
Offspring with non-parental phenotypes (new combinations of traits) are called
recombinant types, or recombinants
an ordered list of the genetic loci along a particular chromosome
genetic map
a genetic map of a chromosome based on recombination frequencies
linkage map
Distances between genes can be expressed as _____; one map unit represents a 1% recombination frequency
map units
In _______, pairs of homologous chromosomes do not separate normally during meiosis
nondisjunction
____ results from the fertilization of gametes in which nondisjunction occurred
Aneuploidy
A _____ zygote has only one copy of a particular chromosome
monosomic
A____ zygote has three copies of a particular chromosome
trisomic
_____ is a condition in which an organism has more than two complete sets of chromosomes
Polyploidy
•Polyploidy is common in plants, but not animals
•Polyploids are more normal in appearance than aneuploids
removes a chromosomal fragment
deletion
repeats a segment
duplication
reverses orientation of a segment within a chromosome
inversion
moves a segment from one chromosome to another
Translocation
is an aneuploid condition that results from three copies of chromosome 21
Down syndrome
For a few mammalian traits, the phenotype depends on which parent passed along the alleles for those traits. Such variation in phenotype is called ______
genomic imprinting
