Agenda  Check in HW- have it on desk  Heredity misconceptions  Whiteboard out HW  Heredity Practice  HW: Finish GATTACA reflection?

Heredity Misconceptions Unlearn these things

Genes code for traits  Genes are instructions for building proteins, which have major affects on traits

Genetics Determine Who I Am  Remember GATTACA!  Genes code for proteins  Environment, choices have huge effects!

Most Traits Are Controlled by a Single Gene  E.g. eye color is controlled by at least 2 genes and is probably affected by many more  Because multiple proteins can affect this phenotype

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 I A allele, I B allele and i allele.

Dominant Alleles Are More Common  Not true at all  Examples: 6 fingers, a certain type of dwarfism, Huntington’s Disease,  Why might a dominant trait be really rare?

Dominant 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

There 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

Dominant Alleles Shut Off Recessive Alleles  The alleles are on separate chromosomes and do not interact with each other at all  I’m going to talk about what REALLY happens for your own piece of mind/knowledge/trivia – not for the quizzes

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

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

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

Incomplete Dominance  Heterozygotes produce fewer proteins, so they have an intermediate phenotype

Co-Dominance  Multiple alleles produce functional proteins

Male v. Female  Males XY  Females XX

What This Means  Males have only one copy of genes on the X chromosome  Females have two

For Your Future Trivia Needs  XY system is only really in mammals  Some other fascinating sex determination systems

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

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

In Some Reptiles (alligators)  Temperature the egg is incubated at determines sex  Temperature seems to turn on or off certain enzymes

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 Nemo’s mother died he would have become a man… because his dad would have become a woman…

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

Hermaphroditic Snails and Slugs  Have male and female anatomies  But reproduce with others, not with themselves  This video will blow your mind! G9qpZ89qzc

Whiteboarding – 5 minutes to have explanation ready  Aces – 5a  2s – 2  3s – 3  4s – 4  5s – 5b  6s – 6  7s - 7

DO NOT DOODLE WITH THE MARKERS No more warnings, instant detention