Learning Targets Please write down at the top of your notes: Explain Mendel’s experiments and data, including the Law of Segregation. Explain how there can be many forms of a one gene and how genes influence the development of traits.  Describe the purpose of monohybrid crosses, and use them as tools to calculate inheritance probabilities.

Mendelian genetics

18 Things You Should Know About Genetics genetics video

Gregor Mendel: Hereditary Genetics  Gregor Mendel: Hereditary Genetics Garden peas are: Self-pollinating Easy to experimentally cross-pollinate Clear traits—pure purple, pure white, etc. Trait: any single feature of an organism

What Mendel Discovered!  What Mendel Discovered! P Generation (“Parent”) F1 Generation (“First Filial”) (Kids) Whoa! F2 Generation (“Second Filial”) (Grandkids)

Did You Catch That? Where did that short plant (trait) come from? Was it hiding?

Recessive Traits “Hide” Behind Dominant Traits  Recessive Traits “Hide” Behind Dominant Traits Sexual Organisms have two of each trait (homologous pairs) One of each pair is passed on to offspring by each parent.

Recessive Traits “Hide” Behind Dominant Traits  Recessive Traits “Hide” Behind Dominant Traits Different forms of the same trait are called alleles PLANT HEIGHT What TRAIT is being studied in this experiment? “Tall” … and … What are the TWO ALLELES (forms) of the trait being studied? “Short”

Other Traits That Mendel Studied (Which word below is a synonym for “allele”?) ALLELES ALLELES

Try one What trait is being studied? What’s the dominant allele of the trait? What’s the recessive allele of the trait?

WHY? Note the Percentages In P Gen: ____% Tall, ____% Short 50:50 WHY? 100:0 ~75:25 In P Gen: ____% Tall, ____% Short In F1 Gen: ____% Tall, ____% Short In F2 Gen: ____% Tall, ____% Short 50 50 100 ~75 ~25

 Mendel proposed that “Factors” segregate (separate) from pairs to be passed on to offspring, one from each parent! (Sounds familiar?)

Why does this sound familiar? During what process does this occur? Think – Pair -Share Why does this sound familiar? During what process does this occur? Turn to your shoulder partner and discuss what you think the process is. 3 groups will be asked to share.

(Sounds familiar?) (Sounds familiar?)

Homologous chromosomes split up in anaphase I so that only one allele of each trait gets passed on in your gametes!

The pair of alleles you have (for any trait) is called your GENOTYPE  The pair of alleles you have (for any trait) is called your GENOTYPE Example Trait: Nose Shape (Let us pretend that round nose is dominant to pointy nose) (usually, letters are used to represent alleles, upper case for dominant) N n Alleles: ___ (dominant), ___ (recessive) Genotypes: ____, ____, ____ NN Nn nn “Homozygous Dominant” “Homozygous Recessive” “Heterozygous”

The pair of alleles you have (for any trait) is called your GENOTYPE Again! NN Nn nn Genotypes: ____, ____, ____ This genotype is described as __________________________ This genotype is described as _____________ This genotype is described as __________________________ “Homozygous Dominant” (Purebred) “Heterozygous” (hybrid or carrier) “Homozygous Recessive” (Purebred)

How Did You Get Your Genotypes? One from Mom One from Dad  Each set of alleles is a homologous pair, one from Mom and one from Dad!

What is this person’s genotype? This is called your PHENOTYPE (an expressed feature you can see!)  N N ________________ Homozygous Dominant What kind of nose do they have? Round? Or Pointy?

What is this person’s genotype? Remember: Dominant overshadows recessive! N n ________________ Heterozygous What is this person’s PHENOTYPE? Round? Or Pointy?

What is this person’s genotype? Recessive alleles show only if no dominant is present! n n ________________ Homozygous Recessive What is this person’s phenotype? Round? Or Pointy?

Gregor Mendel Research and Principles Mendel Video Mendel’s Principles Principles of Segregation States that every individual possesses a pair of alleles for any particular trait and that each parent passes a randomly selected copy (allele) of only one of these to its offspring. The offspring then receives its own pair of alleles for that trait. (Factors for a particular trait occur in pairs.) Principle of Independent Assortment States that genes for different traits can segregate independently during the formation of gametes. (Factors segregate randomly during anaphase I of meiosis.) Principles of Dominance States that some alleles are dominant and others are recessive. (Dominant factors mask recessive ones.)

Another Example: What’s the TRAIT? What are the ALLELES? Which is dominant? PP pp Pp

Remember: Only one of each allele is passed on from each parent! Pp Rr What is Mom’s genotype? What is Dad’s genotype? GERM CELL  Heterozygous Ova (either) Heterozygous Pp GERM CELL Sperm (either) 

Let’s Look At the Offspring Probabilities Ova (either) What if this egg meets this sperm? What if this egg meets this sperm? What if this egg meets this sperm? Sperm (either) What if this egg meets this sperm? What if this egg meets this sperm?

This Is Called A Punnett Square  Punnett squares allow us to predict probabilities about offspring

What percentages does this Punnett square predict? How many Purple? ______ 75% (3/4) How many White? ______ 25% 25% 25% (1/4) How many homozygous dominant? ___ 25% (1/4) How many heterozygous? ______ 25% 25% 50% (2/4) How many homozygous recessive? ___ 25% (1/4)

What is the probability that this couple will have a baby with the “a” disease? Healthy allelle = A Disease allele = a 25% (1/4)

A CARRIER is a heterozygote (he or she can “pass on” the trait) What is the probability that this couple will have a baby who is a CARRIER for the “a” disease? Healthy allelle = A Disease allele = a 50% (2/4) A CARRIER is a heterozygote (he or she can “pass on” the trait) 

 Your Turn! (For disease “a”): What if a homozygous dominant man marries a carrier woman? AA Aa Offspring Genotype: - HD (AA) = ___% - Het (Aa)= ___% - HR (aa)= ___% ____ X ____ Dad Mom 50 A a 50 A AA Aa Offspring Phenotype: - Healthy* = ___% - Disease = ___% - *(Healthy) Carrier = _____% 100 A AA Aa 50

 One More Time! (For disease “a”): What if a carrier man marries a woman with the disease? Aa aa ____ X ____ Offspring Genotype: - HD (AA) = ___% - Het (Aa)= ___% - HR (aa)= ___% Dad Mom a a 50 50 A Aa Aa Offspring Phenotype: - Healthy* = ___% - Disease = ___% - *(Healthy) Carrier = _____% 50 50 a aa aa 50

WHY! NOW YOU KNOW Note the Percentages 50:50 NOW YOU KNOW WHY! 100:0 ~75:25 In P Gen: ____% Tall, ____% Short In F1 Gen: ____% Tall, ____% Short In F2 Gen: ____% Tall, ____% Short 50 50 100 ~75 ~25