Ch. 14: Human HeredityCh. 14: Human HeredityEssential questions:Essential questions:How is blood type inherited?How is blood type inherited?What is a What is a sex-linked trait?sex-linked trait?

– Why are sex-linked disorders more Why are sex-linked disorders more common in males?common in males?

What is What is non-disjunctionnon-disjunction, and what , and what problems it can cause?problems it can cause?

Chapter 14–1: Human HeredityChapter 14–1: Human Heredity

Human ChromosomesHuman Chromosomes– karyotype – picture of chromosomes karyotype – picture of chromosomes

arranged in pairsarranged in pairs

– sex chromosomes – XX or XYsex chromosomes – XX or XY– Autosomal chromosomes – non-sex Autosomal chromosomes – non-sex

chromosomeschromosomes

Human traitsHuman traits– Most traits polygenic – many genes Most traits polygenic – many genes

control traitscontrol traits– many traits influenced by environmentmany traits influenced by environment

Ex: height & nutritionEx: height & nutrition

Human GenesHuman Genes– Blood Group GenesBlood Group Genes

Rh group – single gene with 2 alleles ( + is Rh group – single gene with 2 alleles ( + is dominant, - is recess.)dominant, - is recess.)

ABO groupABO group– 3 alleles I3 alleles IA A IIB B ii

first 2 are codominantfirst 2 are codominant IIAAIIBB = type AB = type AB IIAAIIA A or Ior IA A i = type Ai = type A IIBBIIBB or I or IB B i = type Bi = type B ii = type Oii = type O

14–214–2 Human Human ChromosomesChromosomes

Sex-linked genesSex-linked genes– many sex-linked genes found on X many sex-linked genes found on X

chromosomechromosome– males have only 1 X, so all x-linked males have only 1 X, so all x-linked

alleles are expressedalleles are expressed ColorblindnessColorblindness HemophiliaHemophilia

Chromosomal disordersChromosomal disorders– nondisjunction – error in meiosis – nondisjunction – error in meiosis –

homologous chromosomes fail to homologous chromosomes fail to separate – abnormal numbers of separate – abnormal numbers of chromos. end up in gameteschromos. end up in gametes Down Syndrome – 3 copies of #21 Down Syndrome – 3 copies of #21

chromosome (chromosome (““trisomytrisomy””))

Sex Chromosome DisordersSex Chromosome Disorders– TurnerTurner’’s syndrome – XOs syndrome – XO– KlinefelterKlinefelter’’s syndrome - XXYs syndrome - XXY