Mendel’s Laws Law of Dominance: if the two alleles at a locus differ, then one, the dominant allele, determines the organism′s appearance; the other, the recessive allele, has no noticeable effect on the organism′s appearance Law of Segregation: the two alleles for a heritable character separate (segregate) during gamete formation and end up in different gametes Law of Independent Assortment: each pair of alleles segregates independently of other pairs of alleles during gamete formation
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Mendel’s Laws Law of Dominance: if the two alleles at a locus differ, then one, the dominant allele, determines the organism′s appearance; the other, the.
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Mendel’s Laws
Law of Dominance: if the two alleles at a locus differ, then one, the dominant allele, determines the organism′s appearance; the other, the recessive allele, has no noticeable effect on the organism′s appearanceLaw of Segregation: the two alleles for a heritable character separate (segregate) during gamete formation and end up in different gametesLaw of Independent Assortment: each pair of alleles segregates independently of other pairs of alleles during gamete formation
Bell Work In a type of lizard called anoles brown
skin is dominant to the color green diagram how genes would be expressed in a heterozygous individual with the genotype Bb
In the example above what does B stand for?
Other Inheritance Patterns
Incomplete Dominance
The heterozygote has a phenotype that is intermediate between the phenotypes of the two homozygotes.
Example: Petal color in certain flowers.
Incomplete dominance example
Codominance The heterozygote expresses both
traits at the same time. Example: roan coat color in cattle
Red “Roan” White
CWCW x CWCW
CRCW x CRCW
CRCR x CRCW
CRCR x CWCW
CRCW x CWCW
Color BlindTest
Color BlindTest
Sex-Linked Inheritance Genes located on sex chromosomes
produce different patterns in males and females.
Females generally have two alleles for these genes.
Males generally have only one allele.
If a male inherits a sex-linked recessive allele from his mother, the allele will be expressed.
Red/Green Color Blindness
color-blind male x carrier female
Continuous variation Most traits show a range of variation
rather than distinct either/or types This occurs when multiple genes
and environmental factors influence the trait’s expression
Continuous variation is often described with frequency distribution tables.
Example using actual data
Polygenic Inheritance
Many genesinfluence a single trait
Multiple Alleles For many genes, several alleles
exist in the population. This expands the number of
possible genotypes and phenotypes.
Example of Multiple Alleles
Human blood type is determined by three alleles: A, B, & O.
IA & IB are codominant. i is recessive.
Linked Genes Genes located on the
same chromosome tend to be inherited together
Such genes are said to be “linked genes.”
When genes are linked, they do not assort independently.
Segregation Alleles segregate
when homologous chromosomes separate during Meiosis I.