General Biology Chapter 14

General Biology
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Advantages of pea plants for genetic study
Many VarietiesMating can be controlledEach flower has sperm-producing(stamen) organs and egg producing organ (carpel)
plants that produce offspring of the samevariety when they self-pollinate
Mendel mated twocontrasting, true-breeding varieties, a processcalled________
The true-breeding parents are the_________
P generation
The hybrid offspring of the P generation are calledthe_____________
F1 generation
When F1 individuals self-pollinate or crosspollinatewith other F1 hybrids, the ____________is produced
F2 generation
alternative versions of genes
Each gene resides at a specific ______ on aspecific chromosome
the two alleles for a heritable character separate(segregate) during gamete formation and end upin different gametes
Law of segregation
a diagram for predicting the results of a genetic cross between individuals of known genetic makeup
Punnett Spuare
An organism with two identical alleles for acharacter is said to be________ for the gene controlling that character
An organism that has two different alleles for agene is said to be __________ for the genecontrolling that character
____________ are not true-breeding
physical appearance
Genetic Makeup
GenotypeIn the example of flower color in pea plants, PPand Pp plants have the same phenotype (purple)but different genotypes
How can we tell the genotype of an individual withthe dominant phenotype?
TestcrossThe answer is to carry out a testcross: breedingthe mystery individual with a homozygousrecessive individual If any offspring display the recessive phenotype,the mystery parent must be heterozygous
individuals that are heterozygous for one character
Crossing two true-breeding parents differing in twocharacters produces __________
a cross between F1 dihybrids
Dihybrid cross
states that each pair of alleles segregates independently of each other pair of alleles during gamete formation
Law of independent assortment
Mendel’s laws of segregation and independentassortment reflect the rules of _______
The _____________ states that the probabilitythat two or more independent events will occurtogether is the product of their individualprobabilities
multiplication rule
Probability in an F1 monohybrid cross can bedetermined using__________
the multiplication rule
The ___________ states that the probability thatany one of two or more exclusive events willoccur is calculated by adding together theirindividual probabilities
addition rule
The___________ can be used to figure out theprobability that an F2 plant from a monohybridcross will be heterozygous rather thanhomozygous
rule of addition
A dihybrid or other multicharacter cross isequivalent to two or more independent____________ occurring simultaneously
monohybrid crosses
In calculating the chances for various genotypes,each character is considered separately, andthen the individual probabilities are________
Inheritance of characters by a single gene maydeviate from simple Mendelian patterns in the which situations?
– When alleles are not completely dominant orrecessive– When a gene has more than two alleles– When a gene produces multiple phenotypes
___________occurs when phenotypesof the heterozygote and dominant homozygote areidentical
Complete dominance
___________the phenotype of F1hybrids is somewhere between the phenotypes ofthe two parental varieties
incomplete dominance
In _____________, two dominant alleles affect thephenotype in separate, distinguishable ways
________ are simply variations in a gene’snucleotide sequence
For any character, dominance/recessivenessrelationships of alleles depend on the level atwhich we examine the ____________
a dysfunctional enzyme causes an accumulation of lipids in the brain
Tay-Sachs disease
Most ______exist in populations in more than twoallelic forms
Most genes have multiple phenotypic effects, aproperty called______
PleiotropyFor example, pleiotropic alleles are responsible forthe multiple symptoms of certain hereditarydiseases, such as cystic fibrosis and sickle-celldisease
in ______________a gene at one locus alters thephenotypic expression of a gene at a secondlocus
_______________are those that vary in thepopulation along a continuum
quantitative characters
Quantitative variation usually indicates ___________, an additive effect of two or moregenes on a single phenotype
polygenic inheritanceSkin color in humans is an example of polygenicinheritance
The ______________ is the phenotypic rangeof a genotype influenced by the environment
norm of reactionFor example, hydrangea flowers of the samegenotype range from blue-violet to pink,depending on soil acidity
Norms of reaction are generally broadest forpolygenic characters, such characters are called ________ because genetic and environmental factorscollectively influence phenotype
An organism’s phenotype includes:
Physical appearanceInternal anatomyPhysiologybehavior
Why aren't humans good subjects for geneticresearch?
– Generation time is too long– Parents produce relatively few offspring– Breeding experiments are unacceptable
Inheritance patterns of particular traits can betraced and described using _______________
Many genetic disorders are inherited in a __________ manner
___________are heterozygous individuals whocarry the recessive allele but are phenotypicallynormal
Recessively inherited disorders show up only inindividuals ____________ for the allele
_______________ (i.e., matingsbetween close relatives) increase the chanceof mating between two carriers of the samerare allele
Consanguineous mating
____________ is the most common lethalgenetic disease in the United States
Cystic Fibrosis
The disease is caused by the substitution of asingle amino acid in the hemoglobin protein inred blood cells
Sickle-cell disease
Dominant alleles that cause a lethal diseaseare rare and arise by __________
In _________________, a sampleof the placenta is removed and tested
chorionic villus sampling (CVS)
In _____________, the liquid that bathes thefetus is removed and tested

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