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