Human Heredity

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Human Heredity

• Who and What and Why of Humans?

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New Flash..   It has been discovered that
having a glowing red nose is a recessive
sex-linked trait in Reindeer.. AND.the strange
ability to fly is also a recessive autosomal
trait..   Deep within the Taiga, two adult
consenting Reindeer mate the male is homozygous
recessive and thus has the ability to fly. But
has a normal black nose The female is a sex
linked carrier for red glowing nosebut her
phenotype is black nose.and she is heterozygous
for flying ability.thus cannot fly   Can these
two Reindeer create Rudolph?? What about
Rudolpha?? SHOW YOUR WORK.. Key, parents,
gametes, Punnett square, results.
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Dominant Genes in Humans

• Simple Dominant Traits (A)
• -Huntingtons disorder
• Free hanging earlobes dominant
• Polydactyly (more than five digits) dominant
• -Right handed over left handed

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Huntingtons Disease Dominant GeneA lethal
disease caused by A rare dominant gene.

• Nervous system degenerates.
• Uncontrolled, jerky movements
• No treatment -
• Onset occurs in the thirties so they could have
  passed it on to their children-
• 1 in 10,000

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Recessive Genes in Humans (a)

• Cystic Fibrosis - the most common lethal genetic
  disorder among white Americans.
• 1 in 25 white Americans carries it. (Aa)
• The mucus in the lungs is particularly thick.
• Breathing is difficult because mucus collects in
  the lungs.

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Recessive Genes in Humans (b)

• Sickle-cell anemia - most common recessive gene
  found in African Americans.
• 1 in 500 African Americans is a carrier (Bb)
• Red blood cells are sickle shaped.
• The red cells cannot carry oxygen as well when
  sickled.
• Cells can clog the blood vessels.
• Does decrease the chances of malaria infection

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Recessive Genes in Humans (f)

• Tay-Sachs Disease - is a disease to the central
  nervous system.
• Occurs in the Jewish population. (Ff)
• Lipids ( fat ) are broken down by an enzyme.
• People with Tay-Sachs do not produce this enzyme.
• Lipids (fats) build up in the brain .
• And results are a loss of movement, blindness and
  mental deterioration.
• Death occurs before the age of five. ( ff )

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Multiple Alleles ( A, B , O)

• Blood Groups - blood types are determined by
  three different alleles- A, B, O
• The Blood gene (I) has three different alleles
• A A blood - A surface molecule
• B B blood - B surface molecule
• O O blood - no surface molecule - recessive

Both codominant
Phenotype
Genotype
Genotype
Phenotype
IA IA IAi
A Blood
IA IB
AB Blood
IB IB I B i
B Blood
i i
O Blood
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Polygenic Traits

• There are thousands of traits in humans in where
  many genes ( polygenic ) combine to form one
  trait.
• As many as 12 or more genes acting together to
  produce..
• Eye color
• hair color
• skin color
• Foot size

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Sex-Linked Traits

• Males are XY
• Females are XX
• The Y chromosome does not have the genes to mask
  the genes that are on the X chromosome
• Examples are
• Red Green Color Blindness
• Hemophilia

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Red - Green Color Blindness

• People with red-green color blindness can not see
  the difference between these two colors

Female Carrier
XR
Xr
XR
XR XR
XR Xr
Male Normal
Y
Xr Y
XR Y
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Hemophilia

• Hemophilia is a sex-linked disease in which a
  person is unable to clot their blood when they
  cut or bruise themselves.
• The family of Queen Victoria is best known for
  this disease.

Female Carrier
Xh
XH
XH XH
XH Xh
XH
Female Normal
Female Carrier
Male Normal
Y
XH Y
Xh Y
Male Normal
Male Hemophiliac
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What determines the sex of the offspring???

• The 23rd pair of chromosomes are called the sex
  chromosomes.
• In the male , they are X and Y
• In the female they are X and X
• X Y
• X
• X

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Mistakes in Meiosis

• In meiosis there is a chance that some pairs of
  chromosomes will not split.
• This causes the chance of Trisomy
• ( 3 chromosomes of a certain chromosome )
• Karyotype is a picture of all the chromosomes.
• It is determined by Amniocentesis, a sample of
  amniotic fluid from the uterus

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Nondisjunction

• The failure of a chromosome pair to separate
  during meiosis.
• Downs Syndrome is a disorder where no separation
  of the pair chromosome 21.
• This causes the sperm or egg to carry 24
  chromosomes.
• Occurs in a higher amount to mothers over 40
• Also called
• Trisomy 21

3 chromosome 21s