Incomplete Dominance Codominance Sexlinked and Polygenic Inheritance Incomplete
- Slides: 16
Incomplete Dominance, Codominance, Sexlinked and Polygenic Inheritance
Incomplete Dominance • Offspring have an appearance somewhat in between the phenotypes of the two parents – “Mixed” – Blended R R W RW RW F 1 generation W RW RW All Rr = pink (heterozygous pink)
Incomplete Dominance • Incomplete dominance occurs when two or more alleles influence the phenotype • Neither allele is completely dominant over the other
Incomplete Dominance
Codominance • BOTH alleles are expressed equally in heterozygous individuals • Neither allele is dominant over the other – Example: blood type • Determined by whether or not you have A or B proteins • IA = A protein • IB = B protein • I = no protein • Another example Is the speckled chicken
Codominance
Codominance Problem • Example: homozygous male Type B (IBIB) • x heterozygous female Type A (IAi) IB IB IA I AI B i I Bi 1/2 = IAIB 1/2 = IBi
Another Codominance Problem Example: male Type O (ii) x female type AB (IAIB) IA IB i I Ai I Bi 1/2 = IAi 1/2 = IBi
Codominance • Question: If a boy has a blood type O and his sister has blood type AB, what are the genotypes and phenotypes of their parents? boy - type O (ii) X girl - type AB (IAIB)
Codominance • Answer: IA IB i i I AI B ii Parents: genotypes = IAi and IBi phenotypes = A and B
Sex-linked Traits • Traits (genes) located on the sex chromosomes • Sex chromosomes are X and Y – XX genotype for females – XY genotype for males • Many sex-linked traits carried on X chromosome
Sex – Linked Traits • Example: Colorblindness – If the mother carries the colorblindness gene on her X chromosome, her son could get it. – As long as one X chromosome X y is ok, a female will not c. X c y X X C express the trait X X XX Xy
Sex-linked Traits Example: Colorblindness Sex Chromosomes Colorblindness XX chromosome - female Xy chromosome - male
Polygenic Inheritance • Inheritance pattern controlled by two or more genes • Genes can be on the same chromosome or on different chromosomes • Genotypes are written as AA, Aa, or aa except you will have three or more genes each with a dominant and recessive trait • Skin color is influenced by the additive effects of melanin by three to six genes. Eye color is also a result of melanin added from multiple genes.
Polygenic Inheritance a pedigree
Polygenic Inheritance of Skin Color Gametes ABC ABc ABC AABBCc Ab. C Abc a. BC AABb. Cc Aa. BBCC a. Bc Ab. C Abc a. BC AAbbcc aa. BBCc a. Bc ab. C abc aa. Bbcc The table shows typical ranges of skin color combinations. Other polygenic influenced conditions include Spina bifida and Cleft palate. ab. C abc
- Codominance and incomplete dominance
- Codominance punnett square
- Incomplete dominance flower
- Co dominance
- Linked genes and unlinked genes
- Polygenic inheritance
- Polygenic inheritance
- What is incomplete dominance simple definition
- Sexlinked inheritance
- The difference between dominance and codominance
- Incomplete dominance example flowers
- Complete dominance pattern of inheritance
- Complete dominance pattern of inheritance
- Heterozygous type a blood
- Incomplete vs codominance
- Polygenic trait graph
- Codominance simple definition