InheritanceHow Traits are Passed On

Have your coloring picture out, analysis & your DNA origami

We’ll be hanging our DNA up!Remember to know your

vocabulary…make flashcards, etc.

Hanging our DNA!You will be tying your DNA to the person

sitting next to you & then hanging over the lights.

1. Hole punch at the end.2. cut 70 cm of thread3. tie 1 DNA to either end of the thread4. hang DNA on the light above your desk by

CAREFULLY standing on your stool and having 1 DNA on either side of the light.

* this process will take a little time and will continue throughout the class until everyone is done

Introduction to heredity presentation

Complete dominance punnet squares

We’ll watch a crash course to get an over view of genetics. You can also read about it in your book or many websites. You can also watch the crash course over and over

It’s gonna be a lot and we’ll watch it again at then end of the unit!

http://www.youtube.com/watch?v=CBezq1fFUEA

ChromosomesHumans have 46 chromosomes

23 from mom & 23 from dad which are called homologus pairs.

Each codes for hundreds to thousands of genes

GeneA gene is a

segment of DNA that codes for one protein

That protein can determine what trait we express (i.e. the protein for brown pigments can give us brown eyes)

Inherited TraitsHomologous pairs code for

the same genes, though they may have slightly different versions (i.e. one codes for brown eyes, one for green eyes)

Different versions of the gene are called alleles EX: brown eye allele

For every gene we have 2 alleles, which may be different or the same

Homologous

You have 2 alleles for every gene type because you have 23 homologus pairs one from mom & one from dad!

Each parent gave you a random set of ½ of their homologous chromosomes, these homologous chromosomes have same types of genes BUT can have different alleles.

So, you look a bit like each parent but not exactly like either because you are a mix of both of their genes.

VocabularyHomozygous – to have 2

identical allelesHeterozygous – to have 2

different alleles

Homozygous Heterozygous

So you have 2 alleles. Which determines what you look like??

It depends. This is where genetics gets really complicated

We’ll start with the easiest…Complete Dominance!

Medelian genetics and humans?TRUE MendelianWet (dominant) or

dry (recessive) earwax

Ability to taste phenylthiocarbamide (dominant)

Albinism (recessive)Brachydactyly (short

ness of fingers and toes)

Once THOUGHT to be…

Eye colorHair colorMorton's toeTongue rollingWidow's peak (allele)Detached (dominant)

or attached (recessive) earlobes

Hitchhiker's thumb (recessive)

True Mendelian traits are RARE in humans.

Also pretty rare in general.We will look at these more complex

inheritance traits in the next few days

First we’ll master complete dominance! AKA Menden traits.

Complete DominanceOne allele, the dominant one,

completely “hides” the effects of the recessive allele (or rather the recessive just doesn’t make a protein). You either express it (you have the trait) or you don’t.

You express the dominant trait if you have 1 or 2 dominant alleles. Either Homozygous DOMINANT (AA) OR Heterozygous (Aa)

Only see recessive trait if have both recessive alleles Homozygouus RECESSIVE (aa)

What is the dominant trait in the picture?

Yellow seeds.

A heterozygote is a CARRIER of the recessive trait and can pass that recessive allele to their offspring.

The Punnett SquareWe can use the symbols we have learned

and the idea of segregation to predict the outcomes of a cross between 2 individuals.

The Punnett square is a shorthand way of finding the expected proportions of possible genotype and phenotype in the offspring of a cross.If you know the genotypes of the parents, you can use the Punnett square to predict the genotypes and phenotypes of the offspring.

BEWARE! The Punnett square does not give you ACTUAL results – it is a statistical prediction of what you could EXPECT from a given cross.

Human TraitsRaise your hand if you have…DimplesFree earlobesHand clasping with left on topMid-digital hair

Punnett SquareShow the possible

alleles each parent could give.

This example shows an Aa (heterozygous) person mating with an aa (homozygous recessive individual)

Parent 1

Pare

nt

2

Start monohybrid crossesMono=1 so we are looking at 1 trait with

complete dominance (the simplest ones that are pretty rare and Mendel was sort of lucky sort of just looked at the ones that were “working” the way he wanted- or he just picked the ones that were working out the “right” way.)

Start the worksheet with the possible crosses (do the vocab at home) so you are sure on how to do punnet sq before you leave today.