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Human Genetics. Multiple Alleles. There are more than two possible genes that can be inherited for a trait. Examples Flower color Blood type. Sex-linked Traits. Trait for which the gene is located on one of the sex chromosomes. X H X H ~ female, normal

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multiple alleles
Multiple Alleles
  • There are more than two possible genes that can be inherited for a trait.
  • Examples
    • Flower color
    • Blood type
sex linked traits
Sex-linked Traits
  • Trait for which the gene is located on one of the sex chromosomes.

XHXH ~ female, normal

XHXh ~ female, normal carrier

XhXh ~ female, hemophiliac

XHY ~ male, normal

XhY ~ male, hemophiliac

  • A family tree that shows how a particular trait is passed from parents to offspring.
  • Be able to read and interpret
pedigree of a sex linked trait
Pedigree of a Sex-linked Trait

Colorblindness is sex-linked.

Blue box is colorblind

White box is normal vision with two normal genes.

Half blue/half white is a carrier with normal vision, but one abnormal gene.

  • Process in which cells undergoing mitosis are crushed, and their chromosomes paired up. This can reveal abnormalities as seen below.

Female – 2 X chromosomes

  • The failure of chromosomes to separate during anaphase I or II of meiosis.
  • Can result in too many chromosomes (Down Syndrome) or not enough (Turner Syndrome)
autosomal dominant diseases
Autosomal Dominant Diseases
  • If the abnormal gene is present, the person has the disease
    • Huntington’s Disease
huntington s disease
Huntington’s Disease
  • Chromosome 4
  • HH or Hh
  • Nerve cells degenerate
  • Symptoms include: mood swings, irritability, loss of memory, and uncontrolled movements
  • People of western European descent
autosomal recessive disease
Autosomal Recessive disease
  • Must have 2 abnormal forms of the gene for the disease to be present
    • Cystic Fibrosis
    • Tay Sachs
    • PKU (Phenylketonuria)
    • Sickle Cell Anemia
cystic fibrosis
Cystic Fibrosis
  • Chromosome 7
  • cc
  • Causes think, sticky mucus to build up in the lungs, digestive tract, and other areas of the body
  • Mainly Caucasians
tay sachs
Tay Sachs
  • Chromosome 15
  • tt
  • Causes a buildup of a chemical on the nerve cells
  • Babies lose or fail to gain motor and mental skills
  • Paralysis usually occurs
  • Death at an early age
  • Jews of eastern European descent and French-Canadians
  • Chromosome 12
  • pp
  • Born without the ability to break down phenylalanine
  • Smaller than normal head, epilepsy, and mental retardation may occur when undiagnosed
  • Caucasians and east Asians
sickle cell anemia
Sickle Cell Anemia
  • Chromosome 11
  • ss
  • Red blood cells form an abnormal crescent shape
  • Pain; spleen, lung, and heart damage, and anemia
  • People of African


sex linked diseases
Sex-linked Diseases
  • Gene for the disease is carried on the sex-chromosome
    • Colorblindness
    • Hemophilia
  • Carried on the X chromosome
  • XbXb or XbY
  • Cannot distinguish between colors
  • Affects all races and ethnic groups
  • Carried on the X chromosome
  • XhXh or XhY
  • Blood does not clot well because missing the gene that codes for a blood clotting protein
  • Affects all races and ethnic groups
chromosomal aneuploidy diseases
Chromosomal Aneuploidy Diseases
  • A disease caused by an abnormal number of chromosomes
    • Down Syndrome
    • Turner’s syndrome
    • Kleinfelter’s syndrome
    • XYY Male
down s syndrome
Down’s Syndrome
  • Autosomalanueploidy
  • Trisomy (three chromosomes at 21)
  • Mental retardation, upward slant to the eyes, decreased muscle tone, and a variation of other symptoms
turner s syndrome
Turner’s Syndrome
  • Sex chromosome anueploidy
  • Monosomy
  • Alters development in females; shorter than average, infertile, extra skin on the neck, skeletal abnormalities, heart defects, and kidney problems
kleinfelter s syndrome
Kleinfelter’s Syndrome
  • Sex chromosome anueploidy
  • Trisomy (XXY)
  • Armpit and facial hair, enlarged breasts, tall stature, and abnormal body proportions
  • Increased possibility of learning disorders
xyy male
XYY Male
  • Sex chromosome anueploidy
  • Trisomy (XYY)
  • Increased risk of learning disabilities, delayed speech and language skills