14.1 Human Heredity

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14.1 Human Heredity

• Notes Karyotypes, inheritance patterns,
  sex-linked, pedigrees

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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 persons nucleus
• Called a KARYOTYPE
• Diploid chromosomes are grouped in pairs,
  arranged by decreasing size

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Types of Chromosomes

• Sex Chromosomes

• Autosomal Chromosomes

• 44 of 46
• Body chromosomes
• Determines everything else, basically
• Majority of your traits are in autosomal
  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

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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

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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

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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

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Blood Groups
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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.

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• 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

Sex-Linked
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Human Pedigrees

• Show how traits flow through families
• Help determine the pattern in which traits are
  inherited (recessive, dominant, sex-linked)

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Pedigree Analysis

• Does the grandmother or grandfather show the
  white forelock trait?
• How many daughters they have ______
• How many sons they have _______
• How many of their children married ______
• _____ of 3 children inherited the trait
• Grandfathers genotype must be ________
• Son ________, and wife _________

Grandfather
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1
2
2
Hh
Hh
Hh