The Human Genome Ch. 14

Human Chromosomes Karyotype = how chromosomes are arranged in pairs Humans have 46 chromosomes or 23 pairs The 23 rd pair are the sex chromosomes – XY = male – XX = female The other 22 pair are called autosomes

Human Traits Pedigrees are a chart that shows the relationships within a family as it relates to a certain trait Circle = female Square = male

Autosomal Disorders Caused by – Recessive alleles Cystic fibrosis – Dominant alleles Achondroplasia – Codominant alleles Sickle cell disease

Sex-linked Genes Colorblindness Hemophilia Duchene Muscular Dystrophy Males have just 1 X chromosome – so all sex linked alleles are expressed in males even if they are recessive

Chromosomal Disorders Nondisjunction = chromosomes don’t separate correctly Down syndrome – 3 copies of the 21 st chromosome