HeredityHeredityWhy do you look like you Why do you look like you

look? What made you look? What made you the way you are?the way you are?

All of your genetic information is contained on your CHROMOSOME

S!!GENES are on your chromosomes!!DNA is found on your

genes!!

Cats – 38Cats – 38

23 from mom

Human body cells

Each pair has a number from 1-23.

Chromosome 1 from dad/mom have similar

genetic information.This is also true for the other

22 pairs.

Different organisms contain different numbers of chromosomes!!

Dogs - 78

46 chromosomes 23 pair of

chromosomes

23 from dad

These chromosome pairs are calledThese chromosome pairs are called

Genes that Genes that determine a determine a

specific trait are specific trait are found in the same found in the same

location on that location on that pair of pair of

chromosomeschromosomes

Example: the gene that

determines ear shape is located

in same place on 2 homologous chromosomes.

HOMOLOGOUS CHROMOSOMES

Actual (expression)Physical appearance.

Genotype determines Phenotype.

Those homologous chromosomes carry the genes that make

you—YOU!!Those two make up yourGENOTYP

E Genes passed to offspring.

PHENOTYPE

Dominant and Recessive AllelesDominant and Recessive AllelesMany traits are Many traits are controlled by a controlled by a single gene. single gene.

Ex.- 1 gene = Earlobes Ex.- 1 gene = Earlobes attachedattached

1 gene = Earlobes 1 gene = Earlobes freefreeDifferent forms of same gene

are called

Alleles will be either: Dominant = Stronger TraitRecessive = Weaker Trait

Look at the table to the right for examples of human traits.

TraitTraitTrait Trait MadeMade ByByDominaDominantnt AlleleAllele

Trait Trait MadeMade ByBy RecessiRecessiveve AlleleAllele

HairHairType Type

Curly Curly ororWavyWavy

StraightStraight

Hair Hair ColorColor

DarkDark LightLight

EarlobeEarlobe FreeFree AttacheAttachedd

DimplesDimples PresentPresent Not Not PresentPresent

ALLELES

Identifying Genotypes and Identifying Genotypes and PhenotypesPhenotypes

Genotype trait is written asGenotype trait is written as2 letters.2 letters.

The allele that causes free earlobesis dominant over the allele for

attached earlobes.So F is used for free earlobe gene.

What do you think is used for attached earlobe gene?

Lowercase f

Dominant Allele-- Capital

LetterRecessive Allele-- Lowercase

Letter

More on Genotypes and More on Genotypes and PhenotypesPhenotypes

Offspring receive 2 copies of Offspring receive 2 copies of each gene-1 from each each gene-1 from each parent.parent.

3 possible genotypes : FF, ff, or Ff.FF and ff = HomozygousFf = Heterozygous

“Homo” means “the same.”Homozygous genotype – Made up of 2 dominant or 2 recessive alleles.Ex.- FF or ff

“Hetero” means “different.”Heterozygous genotype – Made upof 1 dominant and 1 recessive allele.

Do your ears hang low?Do your ears hang low?

If an organism inherits a If an organism inherits a dominant allele, the dominant allele, the dominant trait is dominant trait is expressed.expressed.Allele for free earlobes = dominant.

So, how would we write the genotype?

___________________________FF and Ff

How then would we write thegenotype for attached earlobes?

___________________________ff

Let’s Stop and Answer Some QuestionsLet’s Stop and Answer Some Questions1. What do living things inherit and from where?1. What do living things inherit and from where?2. What are some things you can inherit from mom/dad?2. What are some things you can inherit from mom/dad?3. What are genes?3. What are genes?4. What else do genes do? Give some examples.4. What else do genes do? Give some examples.5. What do the terms genotype and phenotype mean?5. What do the terms genotype and phenotype mean?6. Genotype determines ___________________.6. Genotype determines ___________________.7. Where are genes located?7. Where are genes located?8. What is the job of chromosomes?8. What is the job of chromosomes?9. One chromosome contains many different _____________.9. One chromosome contains many different _____________.10. How many chromosomes do we receive from mom/dad? For a 10. How many chromosomes do we receive from mom/dad? For a

total of?total of?11. How many pairs of chromosomes does each human cell have?11. How many pairs of chromosomes does each human cell have?12. Describe how the chromosome pairs are numbered and how the 12. Describe how the chromosome pairs are numbered and how the

genetic information is arranged.genetic information is arranged.13. What are homologous chromosomes?13. What are homologous chromosomes?14. What are alleles?14. What are alleles?15. What is meant by the terms dominant and recessive?15. What is meant by the terms dominant and recessive?16. Give some dominant and recessive traits.16. Give some dominant and recessive traits.17. How do you distinguish between dominant and recessive traits 17. How do you distinguish between dominant and recessive traits

when written?when written?

Using Punnett SquaresUsing Punnett Squares

Used to predict results of Used to predict results of genetic genetic

crosses.crosses.

Cross – Mating of 2 parent organisms

Punnett Squares are used to calculateprobability of genotypes/phenotypesin offspring.

Let’s make a Punnett Square with the Let’s make a Punnett Square with the information below.information below.Task – Predict outcome of Task – Predict outcome of

crossing tall pea plant crossing tall pea plant with short pea plant.with short pea plant.First, I must know the genotype of each parent plant.

There are 3 possible genotypes : TT, Tt, and ttGenotype of pure tall plant : TT <---- It has 2 dominant alleles Genotype of pure short plant : tt <--- It has 2 recessive alleles.

To make a Punnett Square, 1st separate the parent alleles.Place 1 pair across top of square, and other pair down the left side.

t t

T

T

Tt Tt

Tt Tt

Genotype - GenesDominant Gene always 1st in genotype

t t

T

T

tall tall

tall tall

Phenotypes - physical

Let’s consider a cross between 2 plants with Let’s consider a cross between 2 plants with heterozygous genotypes : Tt x Ttheterozygous genotypes : Tt x Tt

TT t

T

t

TT Tt

Tt tt

Tall Tall

Tall Short

How many possible genotypes here? 3: TT, Tt, ttHow many phenotypes? Tall , Short

Probability oftall plants?3 out of 4,or 75%.

Probability ofshort plants?1 out of 4,or 25%.

We’re done! Let’s answer some questions.We’re done! Let’s answer some questions.Discussion QuestionDiscussion Question

Suppose you crossed a pea plant that has round seeds (R) with a pea plant that has wrinkled seeds (r). If 50 percent of the offspring have round seeds and 50 percent of the offspring have wrinkled seeds, what are the genotypes of the parent plants? Make a Punnett Square to help you answer the question.

1. 2 different forms of the same gene are called A. phenotypes. C. dominant traitsB. genotypes. D. alleles 2. An organism’s expressed traits make up itsA. recessive traits C. phenotypeB. genotype D. alleles

3. A pea plant that is homozygous dominant for seed color is crossed with a pea plant that ishomozygous recessive for seed color. Since yellow is the dominant color, the letters Y and yrepresent the genes for seed color. What cross represents these 2 plants?A. Yy x Yy C. YY x yyB. YY x Yy D. Yy x yy4. You meet a person and notice that she has dimples. What can you say for sure about the phenotypes of her parents?A. At least 1 of her parents has dimples. C. Neither parent has dimples.B. Both of her parents have dimples. D. 1 of her parents does not have dimples.