Alternate Patterns of Inheritance Genetics Part 2 3

Alternate Patterns of Inheritance (Genetics Part 2) – 3 rd Quarter

Review: Mendelian Genetics • Gregor Mendel “Father of modern genetics ” – He crossed pea plants with different characteristics (traits) Gregor mendel

Phenotype = physical appearance of the allele for a specific trait (purple/white flower for flower color trait) Genotype = genetic makeup the alleles that represent the phenotype (one dominant, one recessive; or 2 dominant alleles and 2 recessives)

Complete dominance • A kind of dominance pattern where the dominant allele completely masks the effect of the recessive allele in heterozygous condition PP = purple pp = white tschwartz Pp = purple

Alternate Patterns of Inheritance EXCEPTIONS TO MENDEL’S RULES! (NON-MENDELIAN GENETICS)

Incomplete Dominance • The dominant allele cannot totally hide the recessive, resulting in a blended heterozygote. (3 rd phenotype/look shows up !) *Snapdragons

Co-Dominance • 2 equally dominant alleles expressed at the same time (“co” - together) “Roan” fur coloring on cows/horses – 2 separate colors show up equally (red/white)

Co-Dominance Example: The ABO blood type in humans • The alleles for A and B blood types are codominant and both are expressed in the phenotype AB Blood Types is Codominant = BOTH show up equally

Multiple Alleles • A pattern when 2 or more allele options exist for a single trait. Example: ABO blood type in humans – the alleles for A and for B are both dominant over O

Polygenic Inheritance • Creates multiple variations of phenotypes (looks) Example: Human skin colors Figure 9. 15

Q. Q. 1/11/19 Which of the blood types in the ABO system may safely be given to a person with AB blood? a) O or AB only b) B or AB only c) A or B only d) A, B, AB, or O

Q. Q. 1/11/19 Which of the blood types in the ABO system may safely be given to a person with AB blood? a) O or AB only b) B or AB only c) A or B only d) A, B, AB, or O (AB blood = universal receiver!)

Co-Dominance Example: The ABO blood type in humans • The alleles for A and B blood types are codominant and both are expressed in the phenotype AB Blood Types is Codominant = BOTH show up equally

Sex- Linked Traits • Sex linkage is the phenotypic expression of an allele related to the chromosomal sex of the individual (male or females)

Sex Linked – Most sex-linked human disorders are due to recessive alleles and are mostly seen in males Examples: Hemophilia, Color Blindness, and Duchenne Muscular Dystrophy Queen victoria Albert Alice Louis Alexandra Figure 9. 24 A Figure 9. 24 B Czar Nicholas II of Russia Alexis

Another Sex Linked trait! – Linked to Y chromosome (only males) Example: Hypertrichosis Pinnae Auris (aka HAIRY EARS!!!)

Environmental conditions can affect phenotypes! Example: soil p. H affects the color of hydrangea flowers –

Pedigrees- Genetic traits in humans can be tracked through family Dd Joshua Lambert D? John Eddy Dd Abigail Linnell dd Jonathan Lambert D? Abigail Lambert D? Hepzibah Daggett Dd Elizabeth Eddy Male Female Mating Dd Dd dd Dd Dd Dd dd Female Male Deaf Hearing Figure 9. 8 B Offspring

• Recessive Disorders - Most human genetic disorders are recessive Parents Normal Dd × Normal Dd Sperm D d D Offsprin g Dd Normal (carrier) Eggs d Figure 9. 9 A DD Normal Dd Normal (carrier) dd Deaf

• Dominant Disorders - Some human genetic disorders are dominant Parents Dwarf Dd Normal dd Sperm Achondroplasia – cause of dwarfism D d Offspring × Dd Dwarf d dd Normal Eggs d Figure 9. 9 B Dd Dwarf dd Normal

Let’s Practice! 1. 2. Complex patterns of inheritance worksheet Pedigree worksheet

1) There is a DIFFERENCE between sex CHROMOSOME and sex CELL! Human SOMATIC cell (type? From male or female ? Why 2 pairs? ? ? ) Human GAMETE cell (type? From sperm/ovum? Why 1 of each? )