Housekeeping

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Housekeeping

• Genomics reports 11/21
• A week from today
• Next exam 11/26
• A week from next Tuesday
• Need to be stamped for all labs before last week
  of lab!
• Lab assigned problem
• DUE AT BEGINNING OF LAB 12/2-6
• NO ACCEPTIONS!

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Mendels Conclusions
1. We have different alleles for each gene 2. We
have 2 alleles for each gene in our body 3. Some
alleles may be dominant, some recessive 4. Law
of Segregation Our 2 alleles separate during
meiosis 5. Law of independent assortment Allele
s segregate independently during meiosis
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Probability

• We can predict what the chance is of having
  offspring with particular traits based on the
  genotypes of the parents
• MATH
• PUNNETT SQUARE

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Probability

• Rule of multiplication
• The chance of two independent events occurring at
  once
• Rule of addition
• Chance that an event can occur in two or more ways

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Whats the point? Why look at probability/Punnett
squares?
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Heredity isnt always as easy as what Mendel
figured out.
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What happened??
All pink
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• Incomplete dominance

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1. Different kinds of Dominance
Heredity isnt always as easy as what Mendel
figured out.
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1. Different kinds of Dominance

• Complete One allele exhibits phenotype
• Incomplete dominance intermediate phenotype when
  heterozygous
• CoDominance Both alleles are present in the
  phenotype
• Blood types

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What is dominance?

• Alleles are variations in nucleotide sequence
• Alleles dont interact with each other to ensue
  dominance
• Dominance depends on how the alleles are
  expressed
• Dominance does not indicate popularity (or wild
  type)

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Tay Sachs syndrome
TT normal enzyme made
tt die, enzyme produces abnormal proteins
Tt survive, but still produce abnormal proteins
Remember each allele is a sequence of DNA
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Smooth or wrinkled?
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Smooth or Wrinkled?

• R smooth allele
• Enzyme converts sugar to starch
• Seed dries, remains smooth cause of starch
• r wrinkled cell
• Defective enzyme (sugar accumulates)
• Osmosis, water accumulated
• Seed wrinkles

RR smooth
rr wrinkled
Rr Smooth
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Polydactyly

• F polydactyl (more than five fingers)
• f five fingers

What would our (being those people with 5
fingers) genotype be?
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What is dominance?

• Alleles are variations in nucleotide sequence
• Alleles dont interact with each other to ensue
  dominance
• Dominance depends on how the alleles are
  expressed
• Range from dominance to codominance
• Dominance does not indicate popularity (or wild
  type)

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What are some other issues that Mendel didnt see?
Heredity isnt always as easy as what Mendel
figured out.
1. Different kinds of Dominance
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Heredity isnt always as easy as what Mendel
figured out.
1. Different kinds of Dominance
2. Multiple alleles
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Heredity isnt always as easy as what Mendel
figured out.
1. Different kinds of Dominance
2. Multiple alleles
3. Pleiotropy
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Pleiotropy
One gene
trait
trait
trait
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Sickle cell Disease
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Heredity isnt always as easy as what Mendel
figured out.
1. Different kinds of Dominance
2. Multiple alleles
3. Pleiotropy
4. Epistasis
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Epistasis
Gene
One gene affects phenotype of another gene
Gene
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Epistasis
Mouse Coat color
B coat color
B black (dominant)
b brown (recessive)
C Coat pigment
C pigmented (dominant)
c no pigment (recessive)
Lets mate two heterozygotes for both genes
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Heredity isnt always as easy as what Mendel
figured out.
1. Different kinds of Dominance
2. Multiple alleles
3. Pleiotropy
4. Epistasis
5. Polygenic inheritance
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Polygenic inheritance

• 2 genes affect phenotype
• Additive effect
• Traits vary along a continuance
• Skin color, height
• Quantitative characters
• Foot size

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A Dark allele a light allele

B Dark allele b light allele

C Dark allele c light allele
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Heredity isnt always as easy as what Mendel
figured out.
1. Different kinds of Dominance
2. Multiple alleles
3. Pleiotropy
4. Epistasis
5. Polygenic inheritance
6. Environment
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Nature vs. Nurture

• Skin color
• Twins
• Multifactorial characters
• Genetics and nature influence phenotype

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In sum,

• Mendelian genetics is our anchor
• Apply principles to entire organism-HUMANS

1. We have different alleles for each gene 2. We
have 2 alleles for each gene in our body 3. Some
alleles may be dominant, some recessive 4. Law of
Segregation Our 2 alleles separate during
meiosis 5. Law of independent assortment Alleles
segregate independently during meiosis
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Why didnt Mendel study humans?
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Why not humans?

• Only reproduce 1 offspring at a time and not that
  many in our lifetime!
• Cant control who breeds with who
• Have found other means to study human genetics...

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Pedigrees
Diseased

• Study the past mating patterns
• Look at phenotypes in a pedigree

Non-Diseased
Recessive or dominant trait??
Understand the past and predict the future!
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Genetic disorders

• Recessive Inherited diseases
• Dont have a normal protein being made
• Heterozygotes-carriers
• Cystic fibrosis
• Dominant Inherited diseases
• Not many lethal-dominant alleles Why??
• Huntingtons disease
• Multi-factorial diseases
• Polygenic
• Environmental
• Diabetes, Cancer, Mental illness

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Genetic TestingGenetic Counselor

• Determine the risk of disease in your child
• Are you a carrier?
• Detect the genotype of your unborn
• Detect the genotype of your born child
• Ethical considerations