Pop QuizPop Quiz

1.1.Define the term Trait. What is an Define the term Trait. What is an example?example?

2.2.Who is the Father of Genetics?Who is the Father of Genetics?

3.3.What is the principle of dominance?What is the principle of dominance?

4.4.What are gametes? Provide an What are gametes? Provide an exampleexample

5.5.What do we call the offspring What do we call the offspring between parents with different between parents with different traits?traits?

Chapter 10: Sexual Chapter 10: Sexual Reproduction & GeneticsReproduction & Genetics

10-2: Mendelian Genetics & Punnett 10-2: Mendelian Genetics & Punnett SquaresSquares

•Students know how to predict the probable outcome of phenotypes in a genetic cross from the genotypes of the parents and mode of inheritance (autosomal or X-linked, dominant or recessive). b. Students know the genetic basis for Mendel’s laws of segregation and independent assortment.

•Students know how to predict possible combinations of alleles in a zygote from the genetic makeup of the parents.

VocabularyVocabulary

•ProbabilityProbability

•Punnett squarePunnett square

•HomozygousHomozygous

•HeterozygousHeterozygous

•PhenotypePhenotype

•GenotypeGenotype

Genetics and ProbabilityGenetics and Probability

•The likelihood that a particular The likelihood that a particular event will occur is called event will occur is called probabilityprobability..

•The principles of probability can be The principles of probability can be used to predict the outcomes of used to predict the outcomes of genetic crosses.genetic crosses.

Punnett SquaresPunnett Squares

•The gene combinations that The gene combinations that might result from a genetic cross might result from a genetic cross can be determined by drawing a can be determined by drawing a diagram known as a Punnett diagram known as a Punnett square.square.

•Punnett squares can be used to Punnett squares can be used to predict and compare the genetic predict and compare the genetic variations that will result from a variations that will result from a cross.cross.

• A capital letter A capital letter represents the represents the dominantdominant allele for tall.allele for tall.

• A lowercase A lowercase letter letter represents the represents the recessiverecessive allele for short.allele for short.

• In this example, In this example,

• TT = tall = tall

• tt = short = short

• Gametes Gametes produced by produced by each Feach F11 parent are parent are shown along shown along the top and the top and left side.left side.

• Possible Possible gene gene combinations combinations for the Ffor the F22 offspring offspring appear in the appear in the four boxes.four boxes.

•Organisms that have two Organisms that have two identical alleles for a particular identical alleles for a particular trait are said to be trait are said to be homozygous.homozygous. (TT or tt) (TT or tt)

•Organisms that have two Organisms that have two different alleles for the same different alleles for the same trait are trait are heterozygousheterozygous. (Tt). (Tt)

•All of the tall plants have the All of the tall plants have the same same phenotypephenotype, or physical , or physical characteristics. characteristics.

•The tall plants do not have the The tall plants do not have the same same genotypegenotype, or genetic , or genetic makeup.makeup.

•One third of the tall plants are One third of the tall plants are TTTT, , while two-thirds of the tall plants while two-thirds of the tall plants are are Tt.Tt.

Phenotype vs. GenotypePhenotype vs. Genotype

• The plants have The plants have different different genotypes (genotypes (TT TT and and TtTt), but they ), but they have the same have the same phenotype (tall).phenotype (tall).

TTHomozygous

TtHeterozygous

• One fourth (1/4) of One fourth (1/4) of the Fthe F22 plants have plants have two alleles for two alleles for tallness (tallness (TTTT).).

• 1/2 have one allele 1/2 have one allele for tall (for tall (TT), and one ), and one for short (for short (t).t).

• One fourth (1/4) of One fourth (1/4) of the Fthe F22 have two alleles for have two alleles for short short (tt).(tt).

•Because the allele for tallness (Because the allele for tallness (TT) is ) is dominant over the allele for dominant over the allele for shortness (t), 3/4 of the Fshortness (t), 3/4 of the F22 plants plants should be tall.should be tall.

•The ratio of tall plants (The ratio of tall plants (TTTT or or TtTt) to ) to short short (tt)(tt) plants is 3:1. plants is 3:1.

•vi.vi. The predicted ratio showed up in The predicted ratio showed up in Mendel’s experiments indicating Mendel’s experiments indicating that that segregationsegregation did occur. did occur.

Probabilities Predict AveragesProbabilities Predict Averages•Probabilities predict the average Probabilities predict the average

outcome of a large number of events.outcome of a large number of events.

•Probability cannot predict the precise Probability cannot predict the precise outcome of an individual event.outcome of an individual event.

• In genetics, the larger the number of In genetics, the larger the number of offspring, the closer the resulting offspring, the closer the resulting numbers will get to expected values.numbers will get to expected values.