Agenda

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Agenda

• Concept Map
• Lecture Mendelian genetics and blood typing
• Binomial Expansion
• Learning Outcome I can apply the laws of
  probability to solve Mendelian genetics
  problems.  I can describe the inheritance of
  blood type. I can explain inheritance patterns
  aside from those predicted by simple Mendelian
  genetics.

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Mendel and the Gene Idea

• Particulate Hypothesis- parents pass on discrete
  heritable units, called genes, that retain their
  separate identities in offspring.

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Fig. 14-3
EXPERIMENT
P Generation (true-breeding parents)
?
Purple flowers
White flowers
F1 Generation (hybrids)
All plants had purple flowers
F2 Generation
224 white-flowered plants
705 purple-flowered plants
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Mendels Model

• Alternative versions of genes account for
  variations in inherited characters. These
  alternative versions of a gene are called
  alleles.
• For each character, an organism inherits two
  alleles, one from each parent.
• If the two alleles at a locus differ, then one,
  the dominant allele, determines the organisms
  appearance the other, the recessive allele, has
  no noticeable effect on the organisms
  appearance.
• Law of Segregation- the two alleles for a
  heritable character separate (segregate) during
  gamete formation and end up in different gametes.

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Fig. 14-4
Allele for purple flowers
Homologous pair of chromosomes
Locus for flower-color gene
Allele for white flowers
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Monohybrid Cross

• A brown dog is homozygous for the gene that
  controls coat color. The brown dog is mated with
  an albino (all white) dog. The dogs have many
  puppies. All of the puppies have brown coat
  color.
• Draw a punnett square for this cross and give the
  expected genotypic and phenotypic outcomes.
• What are the dominant and recessive alleles?
  Provide symbols for both alleles.
• P.283 genetic tips

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Mendels Terminology

• Genotype- the genetic makeup
• Phenotype- the appearance of observable traits
• Monohybrid Cross- of a single character
• Dihybrid Cross- with two characters
• Law of Independent Assortment- each pair of
  alleles segregates independently of each other
  pair of alleles during gamete formation. (This
  applies only to genes located on different,
  non-homologous chromosomes).

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Dihybrid Cross

• About 70 of Americans perceive a bitter taste
  from the chemical phenylthiocarbamide (PTC). The
  ability to taste this chemical results from a
  dominant allele (T) and not being able to taste
  PTC is the result of having two recessive alleles
  (t).
• Albinism is also a single locus trait with normal
  pigment being dominant (A) and the lack of
  pigment being recessive (a). A normally pigmented
  woman who is heterozygous for PTC tasting, has a
  father who is homozygous for both albinism and
  PTC tasting. She marries a heterozygous, normally
  pigmented man who is a taster but who has a
  mother that does not taste PTC
• Give the phenotypic and genotypic ratios of the
  offspring.
• .

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Dihybrid Cross

• A blue-eyed, left-handed woman marries a
  brown-eyed, right handed man who is heterozygous
  for both traits. Blue eyes and left-handedness
  are recessive.
• Give the phenotypic and genotypic ratios of the
  offspring

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The Laws of Probability

• The Multiplication Rule- used to determine the
  probability that two or more independent events
  will occur together in some specific combination.
  
• Multiply the probability of one event by the
  probability of the other event.
• The Addition Rule- used to determine the
  probability that any one of two or more mutually
  exclusive events will occur.
• Calculated by adding their individual
  probabilities.

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Degrees of Dominance

• Complete Dominance- the phenotypes of the
  heterozygote and the dominant homozygote are
  indistinguishable.
• Incomplete Dominance- neither allele is
  completely dominant and the F1 hybrids have a
  phenotype somewhere between those of the two
  parental varieties.
• Codominance- the two alleles both affect the
  phenotype in separate, distinguishable ways.

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Fig. 14-10-3
P Generation
Red
White
CRCR
CWCW
Gametes
CR
CW
Pink
F1 Generation
CRCW
1/2
1/2
CR
CW
Gametes
Sperm
1/2
1/2
CR
CW
F2 Generation
1/2
CR
CRCW
CRCR
Eggs
1/2
CW
CRCW
CWCW
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Additional Inheritance Patterns

• Multiple Alleles- most genes exist in populations
  in more than two allelic forms.
• Pleiotropy- multiple phenotypic effects
  (exhibited by most genes).
• Epistasis- a gene at one locus alters the
  phenotypic expression of a gene at a second
  locus.
• Polygenic Inheritance- an additive effect of two
  or more genes on a single phenotypic character,
  which produces quantitative characters that exist
  on a continuum.
• Environmental Effect- Epigenetics

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Fig. 14-11
IA
A
IB
B
i
none
(a) The three alleles for the ABO blood groups
and their associated carbohydrates
IAIA or IA i
A
B
IBIB or IB i
AB
IAIB
ii
O
(b) Blood group genotypes and phenotypes
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Blood Problem

• Identification bracelets were accidentally
  removed from three newborn babies. Blood typings
  were taken to help in the identification
  procedures. The blood types for the babies and
  their parents were Baby 1- type A, Baby 2- type
  O, Baby 3- type AB
• Mr. Black type A Mrs. Black type B
• Mr. Green type AB Mrs. Green type O
• Mr. White type O Mrs. White type O
• Which baby could belong to Mr. and Mrs. Black?
• Which baby could belong to Mr. and Mrs. Green?
• Which baby could belong to Mr. and Mrs. White?

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Exit Slip

• If a man with type AB blood marries a woman with
  type O blood, what blood types would you expect
  in their children. (Popcorn)
• Homework
• Read chapter 14 RG. 
• Binomial expansion problems.

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Fig. 14-15b
1st generation (grandparents)
Ww
Ww
ww
ww
2nd generation (parents, aunts, and uncles)
Ww
Ww
ww
ww
ww
Ww
3rd generation (two sisters)
ww
WW
or
Ww
Widows peak
No widows peak
(a) Is a widows peak a dominant or recessive
trait?
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You Try It!

• Jane and Joe Smith have dimples, their daughter,
  Clarissa, does not. Joes dad has dimples, but
  his mother and his sister do not. Janes dad,
  Mr. Renaldo her brother, Jorge and her sister,
  Emily, do not have dimples, but her mother does.

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Recessively Inherited Disorders show up only in
individuals homozygous for the allele
Parents
Normal
Normal
Aa
Aa
?
A
a
Aa
AA
A
Normal (carrier)
Normal
Aa
aa
Normal (carrier)
a
Albino
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Dominantly Inherited DisordersDominant alleles
that cause a lethal disease are rare and arise by
mutations.
Parents
?
Dwarf
Normal
Dd
dd
d
D
Dd
dd
d
Normal
Dwarf
dd
Dd
d
Normal
Dwarf
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Genetic Testing and Counseling

• Tests for identifying carriers
• Fetal testing
• Amniocentesis
• Chorionic villus sampling (CVS)
• Ultrasound
• Fetoscopy
• Newborn screening