Bellringer 11/5/13Bellringer 11/5/13

What is the relationship What is the relationship between DNA and the way you between DNA and the way you look?look?

Topic: Introduction into Topic: Introduction into

geneticsgenetics

EQ: What is EQ: What is genetics?genetics?

The nucleus of a cell contains The nucleus of a cell contains genetic materialgenetic material

DNADNA chromosomes chromosomes genes -> genes -> Alleles Alleles

www.kent.edu/projects/cell/page7.htm

Genetic Material Genetic Material

Who was Gregor Mendel Who was Gregor Mendel and what is genetics?and what is genetics?

Gregor Mendel was an Gregor Mendel was an Austrian monk in the Austrian monk in the mid-nineteenth century.mid-nineteenth century.

He carried out the first He carried out the first important studies of important studies of heredityheredity by using by using pea pea plants.plants.

GeneticsGenetics is the branch is the branch of biology that studies of biology that studies heredity.heredity.

InheritanceInheritance

Occurs when traits are Occurs when traits are passed down from passed down from parent to child.parent to child.

TraitsTraits

The different versions The different versions of a characteristicof a characteristic

Example: blue, green, Example: blue, green, and brown eyesand brown eyes

What is heredity?What is heredity?

HeredityHeredity is the passing on of characteristics is the passing on of characteristics from parents to offspring.from parents to offspring.

The characteristics that are passed down are The characteristics that are passed down are called called traitstraits..

Gregor Mendel’s Monohybrid Cross Gregor Mendel’s Monohybrid Cross (p.156 in science book)(p.156 in science book)

1st Generation= Tall Peas X short Peas

2nd Generation= All tall Peas

3rd Generation= ¾ produced tall peas (75%), ¼ produced short peas (25%)

A monohybrid cross is when you cross two plants that differ only by one trait.

The Rule of Unit FactorsThe Rule of Unit Factors After seeing what happened Mendel concluded that After seeing what happened Mendel concluded that

there are there are twotwo factors that control each trait. factors that control each trait. We now know that these factors are called We now know that these factors are called genesgenes..

Each gene has different forms that are called Each gene has different forms that are called allelesalleles. . One allele is inherited from each of the parents.One allele is inherited from each of the parents.

Genes and AllelesGenes and Alleles Each chromosome Each chromosome

has information has information about thousands of about thousands of traitstraits

Gene- section on Gene- section on chromosome that has chromosome that has information for one information for one traittrait

See page 174

GenesGenes

Genes are short Genes are short sections of sections of chromosomeschromosomes

http://www.accessexcellence.org

What are Genes?What are Genes?

Factors that are passed from one generation Factors that are passed from one generation to the next… to the next…

Genes come in different forms called Genes come in different forms called allelesalleles: : ex: tall and short ex: tall and short

Some are seen and some are notSome are seen and some are not

Genes come in pairsGenes come in pairs Since Since

chromosomes chromosomes come in pairs (one come in pairs (one from mom, one from mom, one from dad) from dad)

Genes come in Genes come in pairspairs

http://anthro.palomar.edu/biobasis/images/karyotype_male.gif

The Rule of DominanceThe Rule of Dominance When the offspring inherit two different alleles When the offspring inherit two different alleles

for one trait, the trait that is expressed is said to for one trait, the trait that is expressed is said to be be dominantdominant while the other is while the other is recessiverecessive..

In Mendel’s pea plants that had one allele for In Mendel’s pea plants that had one allele for tall and one allele for short, the peas were tall and one allele for short, the peas were talltall because tall is the dominant trait.because tall is the dominant trait.

Recessive Dominant

GenesGenes Dominant: those traits that are seenDominant: those traits that are seen Recessive: those traits that are not Recessive: those traits that are not

seenseen

Thus came the Thus came the principle of principle of dominance: dominance: some are dominant some are dominant and others are recessiveand others are recessive

Recessive allele

Recessive allele

Talk about dominant genes!!!

Martin SheenCharlie Sheen

Emilio Estevez Kirk Douglas Michael

Kirk

ActivityActivity

Cut out figure 3 pg. 166Cut out figure 3 pg. 166 Answer the Visual Check #7. Be sure to use Answer the Visual Check #7. Be sure to use

the terms dominant and recessive in your the terms dominant and recessive in your answer.answer.

Genotypes and PhenotypesGenotypes and Phenotypes A A GenotypeGenotype is a specific combination of alleles.is a specific combination of alleles.

A A PhenotypePhenotype is the visual trait that is expressed. is the visual trait that is expressed.

Possible Generation= TT Tt Tt tt

Possible Genotypes= TT Tt Tt tt

Possible Phenotypes= Tall, Tall, Tall, short

Tall Allele short Allele

Homozygous and HeterozygousHomozygous and Heterozygous An organism is An organism is homozygoushomozygous d dominantominant for a trait if both of the alleles carry the for a trait if both of the alleles carry the

dominant gene.dominant gene.

An organism is said to be An organism is said to be homozygous recessivehomozygous recessive for a trait if the alleles both carry for a trait if the alleles both carry the recessive gene.the recessive gene.

An organism is An organism is heterozygousheterozygous for a trait if the two alleles are different.for a trait if the two alleles are different.rr = Homozygous recessive (pure)

RR = Homozygous dominant (pure)

Rr = Heterozygous (Hybrid)

1st Generation= Tt X Tt

TTTT TtTt

TtTt tttt

T t

T

t

2nd Generation= TT, Tt, Tt, tt Genotype Ratio = 25% homozygous tall, 50% heterozygous tall, 25% homozygous short

Phenotype Ratio =

3 Tall, 1 short

Using Alleles in Mendel’s ExperimentUsing Alleles in Mendel’s Experiment

TtTt TtTt

TtTt TtTt

P1 Generation= TT X tt

Punnett Square – a tool used to visualize all the

possible combinations of alleles from the parents

t t

T

T

Tall Allele Short Allele

Genotype Ratio = 100% Tt (heterozygous Tall)

Phenotype Ratio = 100% Tall0% short

Pea Plant TraitsPea Plant Traits