Chapter 14 Mendel and the Gene Idea
Concept 14.1 Mendel used the scientific approach to identify two laws of inheritance
concept 14.2 probability laws govern mendelian inheritance
Concept 14.3 inheritance patterns are often more complex than predicted by simple mendelian genetics
concept 14.4 many human traits follow mendelian patterns of inheritance
Character- A heritable feature that varies among individuals
Trait- each variant for a character
true breeding- over many generations of self pollination these plants had produced only the same variety as the parent plant
hybridization- of two true breeding species
P generation- parental generation
F1 generation- first filial generation
F2 generation- second filial generation
Mendel's model
Alleles- alternative versions of genes
dominant allele- determines the organisms appearance
recessive allele- has no noticeable effect on organism's appearance
law of segregation- two alleles for a heritable character segregates during gamete formation and end up in different gametes
punnett square- diagrammatic device for predicting the allele composition of offsrping from a cross between individuals of known genetic makeup
useful genetic vocabulary
homozygote- a pair of identical alleles
heterozygote- has two different alleles
homozygous- for that gene
heterozygous- for that gene
phenotype- observable traits
genotype- genetic makeup
test cross- it can reveal the genotype of that organism
Law of Independent Assortment
monohybrids- they were heterozygous for ONE particular character being followed in the cross
dihybrids- individuals heterozygous for the TWO characters being followed in the cross
monohybrid cross- refer to cross between such heterzygotes
dihybrid cross- figure 14.8 pg 276
law of independent assortment- two or more genes assort independently that is each pair of alleles segregates independently of any other pair of alleles during gamete formation
multiplication rule- that to determine this probability we multiply the probability of one event by the probability of the other event
addition rule- probability that any one of two or more mutually exclusive events will occur is calculated by adding their individual probabilities
degrees of dominance
complete dominance- dominant allele
incomplete dominance- neither allele is completely dominant
codominance- two allele each effect the phenotype in separate, distinguishable ways
Tay-Sachs disease- inherited disorder by humans, brain cells in a child cannot metabolize certain lipids because a crucial enzyme does not work properly
pleiotropy- have multiple phenotypic effects
epistasis- the phenotype expression of a gene at one locus alters that of a gene of the second locus
polygenic inheritance- an addictive effect of two or more genes on a single phenotypic character
quantitative characters- vary in the population in gradations along a continuum
nature and nurture: the environmental impact on phenotype
multifactorial- many factors both genetic and environmental, collectively influence phenotype
pedigree- traits of parents and children across the generations
cystic fibrosis- most common lethal disease in the US
sickle-cell disease- most common inherited disorder among people of african descent
huntington's disease- degenerative disease of the nervous system
fetal testing
aminocentesis- which can be performed starting at the 15th week of pregnancy, to test for Tay-sachs
chorionic villus sampling (CVS)- physician inserts a narrow tube through the cervix into the uterus and suctions out a tiny sample of tissue from the placenta