NotsoSimple Inheritance Patterns 1 and 2 Remember Genes

Not-so-Simple Inheritance Patterns

#1 and #2 Remember… • Genes are sections of a chromosome that have coded instructions for making proteins. • Alleles are different forms of a gene.

#3 Simple Inheritance • 2 alleles • 2 phenotypes • One allele is dominant • The other allele is recessive • The DOMINANT allele completely masks the recessive allele

Mendel Got Lucky • In many ways Gregor Mendel was quite lucky in discovering his 4 genetic laws. • He happened to use pea plants. • Things in nature aren’t always so simple.

Not-so-Simple Inheritance • 4 Main Types – Codominance – Incomplete Dominance – Multiple Alleles – Polygenic Traits

Codominance #4, 5, & 6 • “Co” means together! • Codominance = two alleles are dominant together. • This produces a third heterozygous phenotype where BOTH traits are Red Cow x White Cow expressed TOGETHER Roan Cow • Ex: Human Blood Type Roan cattle have both –A red and white hairs –B mixed in together! –O – AB

Codominance red x white red & white spotted

#7 Codominance • Two alleles are expressed (multiple alleles) in heterozygous individuals. • Example: blood type 1. type A = IAIA or IAi 2. type B = IBIB or IBi 3. type AB = IAIB 4. type O = ii copyright cmassengale 8

#7 Codominance Problem Example: homozygous male Type B (IBIB) x heterozygous female Type A (IAi) IA i IB I AI B I Bi copyright cmassengale 1/2 = IAIB 1/2 = IBi 9

Another Codominance Problem • Example: male Type O (ii) x female type AB (IAIB) IA IB i I Ai I Bi copyright cmassengale 1/2 = IAi 1/2 = IBi 10

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) copyright cmassengale 11

Codominance • Answer: IA IB i i I AI B ii Parents: genotypes = IAi and IBi phenotypes = A and B copyright cmassengale 12

Incomplete Dominance #8, 9, & 10 • Incomplete Dominance = neither of the two alleles is completely dominant • This produces a third heterozygous phenotype where Amel & Ultra are incompletely the traits are dominant to each other. BLENDED. Amel x Ultramel

Incomplete Dominance red flower x white flower PINK flower

Multiple Alleles #11 & 12 • Any of a set of three or more alleles. • Only two of alleles can be present in a diploid organism. • Examples: – Human Blood Type – Human skin, hair, and eye colors

Polygenic Traits #13 &14 • Result of the interaction of several genes • Human skin, hair, and eye color – Influenced by more than one gene at different locations on the chromosomes • Human Blood Pressure – Not just 1 “blood pressure” gene with several alleles – Caused by several genes that control other traits such as weight, cholesterol level, kidney function, etc… • Human Height – The combined size of all of the body parts from head to foot determines the height of an individual.

Role of Environment #15 • • • Our environment also plays a key role in how traits are expressed. Genes can be turned on/off due to external environmental factors. Examples: – – – Stress Nutrition Chemical exposure Light Temperature

Work on Pages 18 -22 in your packet. Follow directions. BLOOD TYPE Genotypes Can DONATE TO: Can RECEIVE FROM: A IA I A or I ai A or AB A or O B IB I B or I Bi B or AB B or O IA I B AB Anyone (universal recipient) ii Anyone (universal donor) O AB O