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14.1 Human Heredity Notes: Karyotypes, inheritance patterns, sexlinked, pedigrees Studying human heredity • To understand human genetics, we look at the ENTIRE set of genetic information in a person • Called a GENOME • Scientists look at a picture of every chromosome, taken from a person’s nucleus • Called a KARYOTYPE • Diploid chromosomes are grouped in pairs, arranged by decreasing size Types of Chromosomes Sex Chromosomes • 2 of 46 in human genome • Determine sex of individual • Females have X X, males have X Y • All female eggs have 1 X • 50% of male sperm have 1 X, and 50% have 1 Y • This is what makes having a boy versus having a girl, 50/50 probability Autosomal Chromosomes • 44 of 46 • “Body” chromosomes • Determines everything else, basically • Majority of your traits are in autosomal chromosomes Genes on Sex Chromosomes • 1200 genes are on the X chromosome • 140 genes are on the Y, most of which deal with male sex determination and sperm development Dominant & Recessive Alleles • Humans, like pea plants, also follow “normal” dominant or recessive patterns • Ex: Skin and hair color (darker colors are more dominant than lighter colors) • Recessive – red hair (2 recessive alleles) • Ex: Rhesus (Rh) factor- protein found in blood • Rh+ is dominant, Rh- is recessive Codominant & Multiple Alleles • • • • • Many alleles show codominant inheritance Ex: blood type: IA , IB , i Type A – produces antigen A Type B – produces antigen B Type AB – produces both antigens (CODOMINANT) • Type i (O) – produces no antigens Blood Groups: Sex-Linked Inheritance • Genes found on X or Y chromosome show “sex-linked” inheritance patterns • Genes on Y are ONLY found in males • Genes on X are found in males/females, but show different patterns… hmm……. • For females to show recessive traits from X chromosome, BOTH chromosomes need to carry the recessive alleles • If one X has a recessive, and one X has dominant, the trait will not appear • Males only have 1 X, so if they inherit a recessive trait on it, they MUST show that trait since nothing can cover it up Human Pedigrees • Show how traits flow through families • Help determine the pattern in which traits are inherited (recessive, dominant, sex-linked) Pedigree Analysis • Does the grandmother or grandfather show the white forelock trait? Grandfather 2 • How many daughters they have ______ 1 • How many sons they have _______ 2 • How many of their children married ______ 2 • _____ of 3 children inherited the trait • Grandfather’s genotype must be ________ Hh Hh Hh • Son = ________, and wife = _________