Semester 1, Day 9 Modes of Inheritance

Agenda  Review for Mendelian Genetics Quiz  Turn in Homework (Section 10.1)  Take Mendelian Genetics Quiz  Lecture on Modes of Inheritance  Silent Work/Reading Time  Group Work/Reading Time

Review for Mendelian Genetics  How to determine the probability a child will be male or female  What is the definition of a dominant allele? A recessive allele?  Define genotype, phenotype, heredity, and zygosity  What is the zygosity of the following genotypes: AA, Aa, aa?  Given a genotype (AA, Aa, aa), determine the phenotype.  Know the TITLES and DEFINITIONS of both of Mendel’s Laws  Be able to do a monohybrid Punnett square  Determine which letters to use to represent genotypes  Fill in the Punnett square correctly  Determine probabilities  Be able to do a dihybrid Punnett square  Determine the four possible groups of alleles a person can pass on (FOIL)  Fill in the Punnett square correctly  Determine probabilities

Turn in Homework  Section 10.1  Cornell Notes  Section Assessment: #1-6  Chapter 10 Assessment  2, 3, 7, 8, 11, 12, 14, 16, 17, 20-24

Mendelian Genetics Quiz  Corrections:  #5 – Change (Fill in “orange” or “pink”) to (Fill in “red” or “purple”)  #8.d – Change ‘homozygous recessive black fur’ to ‘homozygous recessive WHITE fur’  #8.f – Change ‘if a cat with homozygous recessive black fur mates’ to ‘if a cat with homozygous recessive WHITE fur mates’.  Reminders:  Take quiz silently  When finished, flip quiz over  Eyes on your own paper

Albinism

Modes of Inheritance  Basic Patterns of Inheritance  Mendelian Genetics  Homozygous Dominant: 2 Dominant Alleles, Shows Dominant Trait  Heterozygous: 1 Dominant Allele, 1 Recessive Allele, Shows Dom. Trait  Homozygous Recessive: 2 Recessive Alleles, Shows Recessive Trait  Recessive Genetic Disorders  Recessive allele codes for disorder  Dominant allele codes for healthy GenotypeZygosityPhenotype AAHomozygous DominantPigmented AaHeterozygousPigmented (Carrier) aaHomozygous RecessiveAlbino A = normal melanin production a = abnormal melanin production

Modes of Inheritance  Basic Patterns of Inheritance: Mendelian Genetics (cont.) Example: Mom and Dad are carriers Heterozygous, carry dominant (healthy) allele & recessive (disorder) allele; only shows dominant trait AAAa aa Aa Female A a Male Child Genotype Probabilities AA = 1 / 4 = 25% (homozygous dominant) Aa = 2 / 4 = 50% (heterozygous) aa = 1 / 4 = 25% (homozygous recessive) Phenotype Probabilities Pigmented (Non-Carrier) = 25% Pigmented (Carrier) = 50% Albino = 25% Carrier!

Huntington’s Disease 

Modes of Inheritance  Basic Patterns of Inheritance: Mendelian Genetics (cont.)  Dominant Genetic Disorders  Dominant allele codes for disorder  Recessive allele codes for healthy Hhhh Hhhh Hh Female h h Male Child H = Huntington’s h = Healthy Genotype Probabilities AA = 0 / 4 = 0% (homozygous dominant) Aa = 2 / 4 = 50% (heterozygous) aa = 2 / 4 = 50% (homozygous recessive) Phenotype Probabilities Huntington’s = 50% Healthy = 50% Carrier!

Modes of Inheritance  Complex Patterns of Inheritance  Incomplete Dominance  Neither allele is fully dominant over the other  Heterozygous condition BLENDS phenotypes Example R = red flower W = white flower Use uppercase for both alleles RR Female W W Male Child Mom is a red snapdragon (RR) Dad is a white snapdragon (WW) Genotype Probabilities RW = 4/4 = 100% Heterozygous RR = 0/4 = 0% Homozygous Dominant WW = 0/4 = 0% Homozygous Dominant Phenotype Probabilities Pink = 100% RW

Modes of Inheritance  Complex Patterns of Inheritance (cont.)  Codominance  Neither allele is fully dominant over the other  Heterozygous condition shows BOTH phenotypes Example B = Black Cat T = Tan Cat Use uppercase for both alleles BB Female T T Male Child Mom is a black cat (BB) Dad is a tan cat (TT) Genotype Probabilities TB = 4/4 = 100% Heterozygous BB = 0/4 = 0% Homozygous Dominant TT = 0/4 = 0% Homozygous Dominant Phenotype Probabilities Tabby (Black & Tan Stripes) = 100%

Modes of Inheritance  Complex Patterns of Inheritance (cont.)  Multiple Alleles  There are more than 2 allele forms for a trait  **Note: However, you still only get one allele copy from each parent for a total of 2 copies per child Example (also shows codominance) I A = blood type A (dominant) I B = blood type B (dominant) i = blood type O (recessive) Codominant Mom is I A i (heterozygous Type A) Dad is I b i (heterozygous Type B) IAIBIAIB IBiIBi IAiIAiii IAIA i Female IBIB i Male Child

Modes of Inheritance  Complex Modes of Inheritance: Multiple Alleles (cont.) GenotypeZygosityPhenotypeProbability IAIBIAIB Heterozygous Type AB (Codominant!) 1 / 4 = 25% IBiIBiHeterozygousType B1 / 4 = 25% IAiIAiHeterozygousType A1 / 4 = 25% ii Homozygous Recessive Type O1 / 4 = 25% IAIBIAIB IBiIBi IAiIAiii IAIA i Female IBIB i Male Child

Modes of Inheritance  Complex Modes of Inheritance: Multiple Alleles (cont.) Example #2 IAIAIAIA IAIBIAIB IAiIAiIBiIBi IAIA IBIB Female IAIA i Male Child Mom = I A I B Dad = I A i GenotypeZygosityPhenotypeProbability IAIAHom. Dom.Type A 2 / 4 = 50% IAiHet.Type A IAIBHet. Type AB (codominant!) 1 / 4 = 25% IBiHet.Type B1 / 4 = 25%

Modes of Inheritance  Complex Patterns of Inheritance (cont.)  Sex-Linked Traits  Traits controlled by genes located on a sex chromosome (X-linked traits more common)  Recall: Female (XX), Male (XY)  X-linked traits expressed in males more b/c they only have one X chromosome  X-linked traits expressed in females less b/c the other X chromosome usually masks (hides) the trait

Red-Green Color Blindness

Modes of Inheritance  Complex Modes of Inheritance: Sex-Linked Traits (cont.) Example X B = normal sight X b = red-green color blind Y = Y chromosome Mom = X B X b Dad = X B Y XBXBXBXB XBXbXBXb XBYXBYXbYXbY XBXB XbXb Female XBXB Y Male Child Genotype Probabilities X B X B = 1 / 4 = 25% X B X b = 1 / 4 = 25% X B Y = 1 / 4 = 25% X b Y = 1 / 4 = 25% Phenotype Probabilities Female & Healthy = 1 / 2 = 50% Female & Carrier = 1 / 2 = 50% Female & Color-Blind = 0 / 2 = 50% Male & Healthy = 1 / 2 = 50% Male & Carrier = 0 / 2 = 0% Male & Color-Blind = 1 / 2 = 50% Why can’t a male be a carrier??

Reading/Work Time  Read Chapter 12  Questions:  12.1 #1-5  12.2 #1-5  12.3 #1-5  Chapter 12 Assessment # 1-18,  First 30 Minutes: Silent Work Time  Remaining Time: Group Work Time (conditional)