mendel’s laws law of dominance: if the two alleles at a locus differ, then one, the dominant...

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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 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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Page 1: 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

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

Page 2: 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

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?

Page 3: 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

Other Inheritance Patterns

Page 4: 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

Incomplete Dominance

The heterozygote has a phenotype that is intermediate between the phenotypes of the two homozygotes.

Example: Petal color in certain flowers.

Page 5: 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

Incomplete dominance example

Page 6: 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

Codominance The heterozygote expresses both

traits at the same time. Example: roan coat color in cattle

Red “Roan” White

Page 7: 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

CWCW x CWCW

Page 8: 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

CRCW x CRCW

Page 9: 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

CRCR x CRCW

Page 10: 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

CRCR x CWCW

Page 11: 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

CRCW x CWCW

Page 12: 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

Color BlindTest

Page 13: 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

Color BlindTest

Page 14: 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

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.

Page 15: 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

Red/Green Color Blindness

Page 16: 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

color-blind male x carrier female

Page 17: 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

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.

Page 18: 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

Example using actual data

Page 19: 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

Page 20: 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

Polygenic Inheritance

Many genesinfluence a single trait

Page 21: 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

Multiple Alleles For many genes, several alleles

exist in the population. This expands the number of

possible genotypes and phenotypes.

Page 22: 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

Example of Multiple Alleles

Human blood type is determined by three alleles: A, B, & O.

IA & IB are codominant. i is recessive.

Page 23: 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

Page 24: 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

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.

Page 25: 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

Segregation Alleles segregate

when homologous chromosomes separate during Meiosis I.

Page 26: 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

IndependentAssortment

Not all traits are simply inherited by dominant and recessive alleles (Mendelian Genetics). In some traits, neither allele is dominant or many alleles

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