View
226
Download
3
Category
Tags:
Preview:
Citation preview
ObserviObserving ng
PatternPatterns s in in
InheriteInherited Traitsd TraitsChapter 7Chapter 7
Skin ColorSkin Color
Terms Used in Modern Terms Used in Modern GeneticsGenetics
Heredity- Heredity- characteristics passing from characteristics passing from parents to offspring through genesparents to offspring through genes
GenesGenes Each gene has a specific Each gene has a specific locuslocus on a on a
chromosomechromosome Heterozygous (Aa or Bb)Heterozygous (Aa or Bb) Homomzygous (AA or BB)Homomzygous (AA or BB)
Gregor Mendel
GeneticsGenetics
An allele is An allele is dominantdominant if its effect if its effect masks the effect of a masks the effect of a recessiverecessive allele paired with itallele paired with it
Mendel’s Law of Mendel’s Law of SegregationSegregation
Only one of the Only one of the 2 alleles gets 2 alleles gets put into each put into each gametegamete
Fig. 11-5, p. 172
homozygous dominant parent
homozygous recessive parent
(chromosomes duplicated before
meiosis)
meiosis I
meiosis II
(gametes) (gametes)
fertilization produces heterozygous offspring
Segregation of Alleles at Segregation of Alleles at a Gene Locusa Gene Locus
genotype
phenotype
Construction of a Construction of a Punnett SquarePunnett Square
Punnett squarePunnett square
Dihybrid CrossDihybrid Cross
2 loci 2 loci
AABBAABB x x aabbaabb FF22 phenotype ratio is 9:3:3:1 phenotype ratio is 9:3:3:1
Mendel’s Law Mendel’s Law of Independent of Independent
AssortmentAssortment Mendel’s law ofMendel’s law of independent independent
assortmentassortment One trait does not influence the One trait does not influence the
inheritance of the otherinheritance of the other Exception: linked genesException: linked genes
Fig. 11-9a, p. 175
parent plant homozygous for purple
flowers and long
stems
parent plant homozygous
for white flowers and short stems
AABB aabb
AB x ab
Fig. 11-9b, p. 175
What gametes will they form?
AaBb AaBb AaBb
F1 generation
Fig. 11-9c, p. 175
AB Ab aB ab
AB AABB AABb AaBB AaBb
Ab AABb AAbb AaBb Aabb
aB AaBB AaBb aaBB aaBb
ab AaBb Aabb aaBb aabb
D Out of 16 possible genetic outcomes of this dihybrid cross, 9 will result in plants that are purple-flowered and tall; 3, purple-flowered and short; 3, white-flowered and tall; and 1, white-flowered and short. The ratio of phenotypes of this dihybrid cross is 9:3:3:1.
CodominanceCodominance Two nonidentical alleles of a gene are Two nonidentical alleles of a gene are
both fully expressed in heterozygotes, both fully expressed in heterozygotes, so neither is dominant or recessiveso neither is dominant or recessive
Multiple allele systemsMultiple allele systems
Incomplete DominanceIncomplete Dominance One allele is not fully dominant over its One allele is not fully dominant over its
partnerpartner
EpistasisEpistasis
EpistasisEpistasis Two or more gene products influence a Two or more gene products influence a
traittrait Typically, one gene product suppresses Typically, one gene product suppresses
the effect of anotherthe effect of another
Epistasis in Coat ColorsEpistasis in Coat Colors
PleiotropyPleiotropy
PleiotropyPleiotropy One gene One gene
product product influences two or influences two or more traitsmore traits
Example:Example: Marfan Marfan syndromesyndrome
Genes and the Genes and the EnvironmentEnvironment
Expression of some genes is affected Expression of some genes is affected by environmental factors such as by environmental factors such as temperature, altitude, or chemical temperature, altitude, or chemical exposureexposure
Recommended