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Mendel and the Gene Idea Ch.14 (Many humans traits follow Mendelian…
Mendel and the Gene Idea Ch.14
Mendel used the scientific approach to identify two laws of inheritance
Mendel started breeding garden peas in the abbey garden to study inheritance
chose to work with peas is there is many varieties
one variety purple flowers
another variety white flowers
Heritable feature that varies among individuals such as flower color is called a character
such as purple or white
each variant for a character
called a trait
advantages of using peas
short generation time
large number of offspring from each mating
True breeding
Over generations of of self pollution
Pants had produced only the same variety as the parent plant
ex. a plant w/ purple flowers is true breeding if the seeds produced by self pollination in successive .generations all give rise t pants that also have purple flowers
Probability laws govern Mendelian inheritance
Multiplication rule
states that to determine this probability
Multiply he probability of one event by the porb of the other
Addition rule
The probability that any two or more mutually exclusive event will occur is calculated by adding their individual probabilities
Degrees of Dominance
Complete Dominance
the phenotypes of the heterozygote and the dominant homozygote are indistinguishable
one allele in pair showed over the other
incomplete Dominance
neither allele is dominant
Codominance
two alleles each affect the phenotype in separate ways
Many humans traits follow Mendelian patterns of inheritance
Pedigree
information describing the traits of parents and children across the generations
Behavior of recessive alleles
Carriers
heterozygotes may transmit the recessive allele to their offspring
Fetal testing
amniocentesis
chorionic villus sampling
pleiotropy
one gene affects multiple phenotypic characters
using families history
genetic counseling
helps determines the probability that their children will have genetic disorders
Inheritance patterns are often more complex than predicted by simple Mendelian genetics
Extending Mendelian genetics for two or more genes
Epistasis
phenotypic expression of a gene at once locus alters that of a gene a a second locus
Polygenic Inheritance
Quantitative Characters
human skin color and height are not one of two discrete characters but instead vary in the population in gradations along continuum
Polygenic Inheritance
an addictive effect if two or more genes on a single phenotypic character
many genetic disorders are inherited as simple as recessive traits