Heredity Misconceptions

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Heredity Misconceptions

• Having misconceptions is actually a good thing
  it means that youve been thinking!
• However, its time to unlearn a few things ?

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Misconception 1 Genes code for traits

• ACTUALLY Genes are instructions for building
  proteins, which have major affects on traits.

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Misconception 2 Genetics Determine Who I Am

• ACTUALLY
• Remember GATTACA!
• Genes code for proteins
• Environment, choices have huge effects!

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Misconception 3 Most Traits Are Controlled by a
Single Gene

• ACTUALLY multiple proteins can affect this
  phenotype
• E.g. eye color is controlled by at least 2 genes
  and is probably affected by many more

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Misconception 4 There are only 2 alleles for
each gene, dominant and recessive

• There can be many different alleles for each gene
• E.g. blood type, there is the IA allele, IB
  allele and i allele.

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Misconception 5Dominant Alleles Are More Common

• Not true at all
• Examples 6 fingers, a certain type of dwarfism,
  Huntingtons Disease,
• Why might a dominant trait be really rare?

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Misconception 6Dominant Alleles Are Better

• Most genetic diseases tend to be recessive
• Why would dominant lethal diseases tend to
  disappear rather quickly?
• But in general a trait being dominant DOES NOT in
  any way mean it is better

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Misconception 7There is a Gene for Diseases

• Diseases are mostly the result of mutated alleles
  for necessary genes
• Thus the person does not produce a necessary
  protein, or produces a deformed protein

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Misconception 8 Dominant Alleles Shut Off
Recessive Alleles

• The alleles are on separate chromosomes and do
  not interact with each other at all
• Im going to talk about what REALLY happens for
  your own piece of mind/knowledge/trivia not for
  the quizzes (next slide)

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What Actually Happens

• Some alleles are instructions for producing
  functional proteins
• The other alleles produce no protein at all or a
  protein that does not function at all

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A trait is dominant if

• One set of instructions produces enough proteins
  to have the trait
• I.e. if you are heterozygous you have the trait

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A trait is recessive if

• One set of instructions is not enough to cause
  the trait
• I.e. if you are heterozygous you will not have
  the trait

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Incomplete Dominance

• Heterozygotes produce fewer proteins, so they
  have an intermediate phenotype
• Ex flower color is new color. Heterozygous
  (Red allele white allele) Pink

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Co-Dominance

• Multiple alleles produce functional proteins
  pretty equally
• Ex Black chicken (BB) and white chicken (WW)
  heterozygous (BW) is a speckled black and white
  chicken
• Also blood type! AB blood both proteins show up
  on the blood cell. O is simple dominancejust
  FYI. Blood type has 2 types of inheritance!

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Male v. Female

• Males XY
• Females XX

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What This Means

• Males have only one copy of genes on the X
  chromosome
• Females have two X chromosomes

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For Your Future Trivia Needs

• XY system is only really in mammals
• Some other fascinating sex determination systems

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Birds and Some Reptiles

• ZW system females are ZW, males are ZZ
• Kind of similar to our system, except roles are
  reversed
• The egg determines the sex

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In Bees

• Males have half as many chromosomes
• If egg is fertilized, it becomes a female, if it
  is not fertilized it grows into a male

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In Some Reptiles (alligators)

• Temperature the egg is incubated at determines
  sex
• Temperature seems to turn on or off certain
  enzymes

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In Some Fish (clownfish)

• The largest member of a school becomes the
  reproductive female
• The next in line is the reproductive male
• All others are non-reproductive

When Nemos mother died he would have become a
man because his dad would have become a woman
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Parthenogenesis (asexual)

• Some animals lay eggs that require no
  fertilization
• Interestingly in these snakes individuals still
  mate with each other, even though there is no
  exchange of DNA, before laying eggs

Not really having sex, just dancing
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Hermaphroditic Snails and Slugs

• Have male and female anatomies
• But reproduce with others, not with themselves
• This video will blow your mind!

https//www.youtube.com/watch?vwG9qpZ89qzc