Complex Patterns of Inheritance

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Complex Patterns of Inheritance
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Incomplete Dominance

• The phenotype of the heterozygote is intermediate
  between those of the two homozygotes
• Neither allele of the pair is completely dominant

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Incomplete Dominance
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Incomplete Dominance
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Incomplete Dominance
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Codominance

• Both alleles are expressed equally
• The phenotypes of both homozygote parent
  organisms are expressed in the offspring

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Codominance

• What do you get when you cross a black chicken
  with a white chicken?

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Sex - linked traits

• Determined by genes located on the sex
  chromosomes
• X chromosome is larger carries more genes than
  the Y chromosome
• Genes carried on the X chromosome are called
  X-linked genes while genes carried on the Y
  chromosome are called Y-linked genes

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Sex linked

• Most X-linked alleles have no homologous
  counterpart on the Y chromosome (XRY)
• Males 1-X chromosome, recessive allele on X
  chromosome will ALWAYS be expressed (XrY)
• In females, it takes 2 recessive alleles (one on
  each X chromosome) to be expressed (XrXr)
• A female who has one recessive allele is said to
  be a carrier (XRXr)

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Sex linked

• The genes for many of the undesirable sex linked
  traits are recessive and thus are rare but when
  they do occur, they occur more commonly in males
• Common sex linked traits are hemophilia
  (bleeding disorder -lack clotting factor),
  defective tooth enamel, and colorblindness

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Sex linked problemswww.biology.arizona.edu/mendel
ian_genetics/problem_sets/sex_linked_inheritance/0
6Q.html

• A. 100B. 25C. 50D. 75E. 0

• In a cross between a white-eyed (XrXr) female
  fruit fly and red-eyed male (XRY), what percent
  of the female offspring will have white eyes?
  (White eyes are X-linked, recessive)
• E. 0

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Red Green Colorblindness

• A human female "carrier" who is heterozygous for
  the recessive, sex-linked trait causing red-green
  color blindness (or alternatively, hemophilia),
  marries a normal male. What proportion of their
  male progeny will have red-green color blindness
  (or alternatively, will be hemophiliac)?
• C. 50

• A. 100
• B. 75
• C. 50
• D. 25
• E. 0

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Hemophilia

• A.half of daughters are normal and half of sons
  are hemophilic.
• B.all sons are normal and all daughters are
  carriers.
• C.half of sons are normal and half are
  hemophilic all daughters are carriers.
• D.all daughters are normal and all sons are
  carriers.
• E.half of daughters are hemophilic and half of
  daughters are carriers all sons are normal.

• Hemophilia in humans is due to an X-chromosome
  mutation. What will be the results of mating
  between a normal (non-carrier) female and a
  hemophilac male?
• B.all sons are normal and all daughters are
  carriers.

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Sex Influenced Traits

• Traits that are expressed differently in males
  and females
• Male and female with the same genotype express
  different phenotypes
• Usually due to hormone levels
• Ex. Pattern baldness Males express baldness
  while females do not due to higher testosterone
  levels in males

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Traits Controlled by Multiple Alleles

• Multiple Allele Traits
• Traits controlled by three or more alleles of the
  same gene that code for a single trait
• Ex. Blood is controlled by three alleles
• IA, IB i

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Multiple Alleles - Blood

• Your blood type consists of 2 of the three
  alleles
• IAIB are codominant and both are dominant to the
  i allele

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Multiple Alleles Vocab

• Plasma-the fluid part of the blood, mostly water
  and nutrients (55)
• RBC (red blood cells) transports oxygen/carbon
  dioxide produced in red bone marrow (ribs,
  humerus, femur, sternum, long bones (44) no
  nuclei
• WBC (white blood cells)-defend the body against
  disease (contain nuclei)
• Platelets- cell fragments that help clot blood
• Serum-plasma without clotting proteins

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Blood Facts

• Life span of a RBC is
• 120 days (liver destroys
• Most common blood type
• O
• Rarest blood type
• AB-
• RH factor
• 85 , 15 -

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Blood Type Problemshttp//www.biology.arizona.edu
/Human_Bio/problem_sets/blood_types/01q.html

• A.Possible
• B.Not possible

• Could a man with type B blood and a woman with
  type AB produce a child with type O blood?" I
  think not, because type O is recessive, and the
  B's seem to be dominant. My cousin thinks yes.
  Thank you for your help. -- Vicki

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Blood Type Problem

• What if the mother is type O and the father is
  A-? What would the offspring's blood type be?
  --Mark

• The offspring could be
• A.A, or O
• B.A-, or O-
• C.A, A-, O, or O-
• D.A, or O-

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Blood Type Problem

• I am trying to figure out what blood type the
  father of my son could have since my son and I
  are both type A. Also, my brother is type 0 and
  my mom is A. We can't find anything that
  explains how this can be. Could you please
  help??? --From a concerned Mom

• The father could be
• A.A, AB, B, or O
• B.Either A or B
• C.Either A or O

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More Blood Vocab

• Agglutinate- clumping of red blood cells due to
  antigen/antibody reactions
• Agglutinin-antibodies (proteins that defend
  against foreign particles)
• Agglutinogen-antigens, identifying proteins found
  on the surface of an organism

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RH Factor

• 1900 Landsteiner discovers ABO blood groups
• 1940 Landsteiner and Wiener discover Rh factor
  in blood types
• Rh involves 45 different antigens on the RBC
• Named after the rhesus monkeys that were
  initially used in research for the antiserum

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• Incompatability occurs when mom is Rh- (dd) and
  dad is Rh( DD, Dd)
• Usually only occurs during the second pregnancy,
  because in the first pregnancy the mom has not
  built up antibodies against the Rh factor
• 1/1000 babies are born with Rh incompatability
• Europeans are 13 more at risk with 6 having
  complications

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At birth, placenta ruptures occur, causing the
mixture of mother/fetus blood and thus the
development of Rh antibodies by mom

• The first child is not at risk but subsequent
  births are at risk (Rh child)
• Mother will be given a drug called Rho-GAM (anti
  Rh antibody drug)at 28 weeks of pregnancy and 72
  hours after birth

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Erythroblastosis fetalis

• May occur when mom is Rh- and baby is Rh
• Result can be life-threatening anemia because of
  a lack of oxygen in the blood. 
• The baby also usually is jaundiced, fevered,
  quite swollen, and has an enlarged liver and
  spleen.   
• Treatment is immediate massive transfusions of
  Rh blood into the baby with the simultaneous
  draining of the existing blood to flush out Rh
  antibodies.  This is usually done immediately
  following birth, but it can be done to a fetus
  prior to birth.

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