Heredity Misconceptio

nsHaving misconceptions is actually a good thing – it means that you’ve been thinking! However, it’s time to unlearn a few things …

Misconception 1: Genes code for traits

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

Misconception 2: Genetics Determine Who I Am

ACTUALLY …Remember GATTACA!Genes code for proteinsEnvironment, choices have huge effects!

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

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.

Misconception 5: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?

Misconception 6:Dominant Alleles Are

BetterMost genetic diseases tend to be

recessiveWhy 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

Misconception 7: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

Misconception 8: 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 (next slide)

What Actually HappensSome 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 ifOne set of instructions produces enough proteins to have the trait

I.e. if you are heterozygous you have the trait

A trait is recessive ifOne 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

Ex: flower color is “new” color. Heterozygous (Red allele & white allele) = Pink

Co-DominanceMultiple 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 dominance…just FYI. Blood type has 2 types of inheritance!

Male v. FemaleMales XYFemales XX

What This Means

Males have only one copy of genes on the X chromosome

Females have two X chromosomes

For Your Future Trivia Needs

XY system is only really in mammals

Some other fascinating sex determination systems

Birds and Some ReptilesZW system – females are ZW, males are ZZ

Kind of similar to our system, except roles are reversed

The egg determines the sex

In BeesMales 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!

https://www.youtube.com/watch?v=wG9qpZ89qzc