chapter 9 fundamentalsofgenetics revised by: r. leblanc biology 1/12

Chapter 9Chapter 9

FundamentalsFundamentals

OfOf

GeneticsGenetics

Revised by: R. LeBlanc

Biology

1/’12

Section 1 Mendel’s Legacy

Chapter 9 Chapter 9 ObjectivesObjectives DescribeDescribe how Mendel was able to control how his how Mendel was able to control how his

pea plants were pollinated.pea plants were pollinated.

DescribeDescribe the steps in Mendel’s experiments on the steps in Mendel’s experiments on true-breeding garden peas.true-breeding garden peas.

DistinguishDistinguish between dominant and recessive between dominant and recessive traits.traits.

StateState two laws of heredity that were developed two laws of heredity that were developed from Mendel’s work.from Mendel’s work.

DescribeDescribe how Mendel’s results can be explained how Mendel’s results can be explained by scientific knowledge of genes and by scientific knowledge of genes and chromosomes.chromosomes.

Mendel's LegacyMendel's Legacy

What is genetics?What is genetics? The field of biology devoted to

understanding how characteristics are transmitted from parents to offspring

Section 1

Introduction to Mendel's Introduction to Mendel's LegacyLegacy

How does this alligator How does this alligator differ from other differ from other alligators? (Notes: This is alligators? (Notes: This is NOTNOT an albino and an albino and NOTNOT a a different species, but it different species, but it just has different traits just has different traits (genetic condition)(genetic condition) which which are rare.)are rare.)

White and brown are White and brown are contrasting traitscontrasting traits of skin of skin color.color.

What are other What are other characteristics that are characteristics that are examples of contrasting examples of contrasting traits?traits?

Did you write down: Did you write down: color, color, height, texture, etcheight, texture, etc

Section 1

Note: Skin color and eye color are genetically controlled characteristics of alligators. Skin traits: white & brown;

eye color traits: blue & brown


List 5 characteristics that are passed on List 5 characteristics that are passed on in families:in families:

Did you list: eye color, hair color, Did you list: eye color, hair color, etc ??etc ??

Name one characteristic that may also Name one characteristic that may also be inherited but that is also influenced be inherited but that is also influenced by behavior or environment:by behavior or environment:

Muscle size, body weight, having a Muscle size, body weight, having a suntan, height.suntan, height.

Section 1

Mendel’s Mendel’s ExperimentExperiment Observe the Observe the

pea plants in pea plants in the given the given image.image.

List the List the noticeable noticeable characteristics characteristics of the pea of the pea plants:plants: See the next slideSee the next slide

Mendel’s 7 Mendel’s 7 Characteristics:Characteristics:

Seed shapeSeed shape Seed colorSeed color Flower colorFlower color Flower Flower

positionposition Pod color Pod color Pod shapePod shape Plant heightPlant height


““Father of Genetics” – 1800’s Father of Genetics” – 1800’s Carried out the first experiments on heredity using pea Carried out the first experiments on heredity using pea

plants.plants. Carefully controlled his experiments, studying only one Carefully controlled his experiments, studying only one

trait at a time and analyzed data mathematically. trait at a time and analyzed data mathematically. Was the first to succeed in predicting how traits are Was the first to succeed in predicting how traits are

transferred from generation to generation.transferred from generation to generation. HeredityHeredity-Passing on of characteristics from parent to -Passing on of characteristics from parent to

offspring.offspring. GeneticsGenetics-- Branch of biology that studies inherited traits. Branch of biology that studies inherited traits.

Plant reproductive termsPlant reproductive terms

GAMETESGAMETES - Male or - Male or Female sex cell. In plants, Female sex cell. In plants, pollen (male)pollen (male) and and ovule ovule (female).(female).

FERTILIZATIONFERTILIZATION- Fusion of - Fusion of the male and female the male and female gametes within the gametes within the flower.flower.

POLLINATIONPOLLINATION - Transfer of - Transfer of pollen from the anther to pollen from the anther to the pistil, usually by wind, the pistil, usually by wind, water, or insects. water, or insects.

CROSS-POLLINATIONCROSS-POLLINATION - - Transfer of pollen from Transfer of pollen from one flower (tall) to one flower (tall) to another flower (short)another flower (short)

Plant Reproductive Plant Reproductive OrgansOrgans

Mendel’s ExperimentMendel’s Experiment

MendelMendel’’s Experimentss Experiments

Mendel bred plants for several Mendel bred plants for several generations that were true-generations that were true-breeding for specific traits and breeding for specific traits and called these thecalled these the P generation. P generation.

Offspring of the P generation were Offspring of the P generation were called thecalled the FF11 generation. generation.

Offspring of the FOffspring of the F11 generation were generation were called thecalled the FF22 generation. generation.

Three Steps of Mendel’s Three Steps of Mendel’s ExperimentsExperiments

MendelMendel’’s Results and s Results and ConclusionsConclusions

Recessive and Dominant TraitsRecessive and Dominant Traits– Mendel concluded that inherited Mendel concluded that inherited

characteristics are controlled by characteristics are controlled by factors that occur in pairs. factors that occur in pairs.

– In his experiments on pea plants, In his experiments on pea plants, one factor in a pair masked the one factor in a pair masked the other. The trait that masked the other. The trait that masked the other was called theother was called the dominant dominant trait. The trait that was masked trait. The trait that was masked was called thewas called the recessiverecessive trait.trait.

Chapter 9

MendelMendel’’s Conclusionss Conclusions

Section 1 Mendel’s Legacy

MendelMendel’’s Results and s Results and ConclusionsConclusions

The Law of SegregationThe Law of Segregation– TheThe law of segregationlaw of segregation states that a pair of states that a pair of

factors is segregated, or separated, during factors is segregated, or separated, during the formation of gametes. the formation of gametes.

The Law of Independent AssortmentThe Law of Independent Assortment– TheThe law of independent assortmentlaw of independent assortment states states

that factors for individual characteristics are that factors for individual characteristics are distributed to gametes independent of one distributed to gametes independent of one another. another.

– The law of independent assortment is The law of independent assortment is observed only for genes that are located on observed only for genes that are located on separate chromosomes or are far apart on separate chromosomes or are far apart on the same chromosome.the same chromosome.

Support for MendelSupport for Mendel’’s s ConclusionsConclusions

We now know that the factors that We now know that the factors that Mendel studied areMendel studied are allelesalleles, or , or alternative forms of a gene.alternative forms of a gene.

One allele for each trait is passed One allele for each trait is passed from each parent to the offspring.from each parent to the offspring.

Section 2 Genetic CrossesSection 2 Genetic CrossesChapter 9ObjectiveObjectivess DifferentiateDifferentiate between the genotype and the phenotype between the genotype and the phenotype

of an organism.of an organism.

ExplainExplain how probability is used to predict the results of how probability is used to predict the results of genetic crosses.genetic crosses.

UseUse a Punnett square to predict the results of a Punnett square to predict the results of monohybrid and dihybrid genetic crosses.monohybrid and dihybrid genetic crosses.

ExplainExplain how a testcross is used to show the genotype of how a testcross is used to show the genotype of an individual whose phenotype expresses the dominant an individual whose phenotype expresses the dominant trait.trait.

DifferentiateDifferentiate a monohybrid cross from a dihybrid cross.a monohybrid cross from a dihybrid cross.

Chapter 9

Calculating ProbabilityCalculating Probability

Section 2 Genetic Crosses

Chapter 9

Punnett Square Method for Punnett Square Method for Solving Genetics ProblemsSolving Genetics Problems


A Cross Between One Pair of Contrasting TraitsA Cross Between One Pair of Contrasting Traits

Punnett SquarePunnett Square - Prediction of offspring (F1) using - Prediction of offspring (F1) using genotypes from parents (P)genotypes from parents (P)

Using the letters Using the letters T= tallT= tall and and t= shortt= short show a cross show a cross between a between a homozygous dominanthomozygous dominant and and homozygous homozygous recessiverecessive plant. plant.

Example #1:Example #1:

t

t

T T

TTttTTtt

TTtt TTtt

The letters T and t represent alleles

(characteristics of various traits)

Monohybrid CrossMonohybrid Cross•Genotype Ratio:Genotype Ratio: This ratio list the number of off-spring with the 3 This ratio list the number of off-spring with the 3 possible allele combinations:possible allele combinations:

Homozygous Dominate : Heterozygous : Homozygous RecessiveHomozygous Dominate : Heterozygous : Homozygous Recessive

(PURE DOMINANT : MiXeD DoMiNaNt : pure recessive)(PURE DOMINANT : MiXeD DoMiNaNt : pure recessive)

•Phenotype Ratio:Phenotype Ratio: This ratio list the number of off-spring with This ratio list the number of off-spring with physical trait characteristics:physical trait characteristics:

Example: # of Tall : # of shortExample: # of Tall : # of short

•What would be the Genotype and Phenotype ratios for Example #1?What would be the Genotype and Phenotype ratios for Example #1?

Genotype Ratio 0 : 4 : 0 (Pure tall / mixed tall / short)Genotype Ratio 0 : 4 : 0 (Pure tall / mixed tall / short)

Phenotype Ratio 4 : 0 (Tall / short)Phenotype Ratio 4 : 0 (Tall / short)

Ex. 2 - Monohybrid CrossEx. 2 - Monohybrid Cross

Show a cross between two heterozygous Show a cross between two heterozygous tall plants. Complete the Punnett square tall plants. Complete the Punnett square below and give the phenotypic and below and give the phenotypic and genotypic ratios for the possible genotypic ratios for the possible offspring!offspring!

T

t

T t

TTtt

TTttTTTT

tttt

Phenotype ratio 3:1 (Tall to short)

Genotype ratio1:2:1

(Homozygous Dominant to Heterozygous to

Homozygous recessive)

Section 2 Genetic CrossesChapter 9

Predicting Results of Monohybrid Predicting Results of Monohybrid CrossesCrosses

A A testcrosstestcross, , in which an in which an individual of unknown genotype individual of unknown genotype is crossed with a homozygous is crossed with a homozygous recessive individual, can be recessive individual, can be used to determine the used to determine the genotype of an individual genotype of an individual whose phenotype expresses whose phenotype expresses the dominant trait.the dominant trait.

Chapter 9TestcrossTestcross


Law of Independent Law of Independent AssortmentAssortment

Traits are inherited independently of each Traits are inherited independently of each other.other.

To determine which trait a parent will To determine which trait a parent will contribute during fertilization, the F.O.I.L contribute during fertilization, the F.O.I.L Method is used.Method is used.

FirstFirst

OutsideOutside

InsideInside

LastLast

Dihybrid crossDihybrid cross - - Cross between two pairs of Cross between two pairs of contrasting traits. Ex. Cross a pea plant with contrasting traits. Ex. Cross a pea plant with heterozygous round and heterozygous yellow pea heterozygous round and heterozygous yellow pea plant with a pea plant that has the same genotype. plant with a pea plant that has the same genotype. (Round is dominant over wrinkled; and Yellow is (Round is dominant over wrinkled; and Yellow is dominant over green)dominant over green)

First,First, identify the correct genotype for each parent.identify the correct genotype for each parent. (RrYy x RrYy).(RrYy x RrYy). Next,Next, identify all the possible types of gametes each identify all the possible types of gametes each

parent can produce. (use the F.O.I.L. Method)parent can produce. (use the F.O.I.L. Method) RY Ry rY ry RY Ry rY ry (see blackboard)(see blackboard)

Using a punnett squareUsing a punnett square show the possible offspring show the possible offspring that may be produced from these parents.that may be produced from these parents.

Dihybrid Example Dihybrid Example #1#1

Each parent produces4 possible gametes

RY,rY,Ry,ry

RY

rY

Ry

ry

RY rY Ry ry

RRYY

rryy

RrYY RRYy RrYy

RrYY

RRYy

RrYy

RrYy

RrYy

rrYY

rrYy

rrYy

Rryy

RRyy Rryy

Phenotypic Ratio = 9:3:3:1 (Round and Yellow, Round and Green, Wrinkled and yellow, Wrinkled and Green)

Dihybrid Example #2Dihybrid Example #2

What are the genotype and What are the genotype and phenotype ratios in the offspring phenotype ratios in the offspring resulting from a cross between resulting from a cross between two pea plants; a heterozygous two pea plants; a heterozygous Green, constricted plant with a Green, constricted plant with a yellow , heterozygous Smooth yellow , heterozygous Smooth

plant.plant.Note: G = green g = yellow and Note: G = green g = yellow and

N = Smooth n = constrictedN = Smooth n = constricted

Dihybrid Example #2Dihybrid Example #2

•Step 1 (Parents Genotype?)

•Ggnn x ggNn

•Step 2 (F.O.I.L for each parents gametes)

•Gn Gn gn gn

•gN gn gN gn

•Step 3 (Fill in the Punnett Squares)

•Step 4 (Calculate Phenotype Ratio (what are the physical traits)

Gn Gn gn gn

gN

gn

gN

gn

GgNn

GgNn

GgNn

GgNn

Ggnn

Ggnn

Ggnn

Ggnn

ggnn

ggNn

ggnn

ggNn

ggnn

ggNn

ggnn

ggNn

Multiple ChoiceMultiple Choice

1. What is a procedure in which an 1. What is a procedure in which an individual of unknown genotype is individual of unknown genotype is crossed with a homozygous recessive crossed with a homozygous recessive individual to determine the genotype of individual to determine the genotype of the unknown individual called?the unknown individual called?A. a monohybrid crossA. a monohybrid crossB. a dihybrid crossB. a dihybrid crossC. a hybrid crossC. a hybrid crossD. a testcrossD. a testcross

Standardized Test PrepChapter 9

Multiple Choice, Multiple Choice, continuedcontinued

1. What is a procedure in which an 1. What is a procedure in which an individual of unknown genotype is individual of unknown genotype is crossed with a homozygous recessive crossed with a homozygous recessive individual to determine the genotype of individual to determine the genotype of the unknown individual called?the unknown individual called?A. a monohybrid crossA. a monohybrid crossB. a dihybrid crossB. a dihybrid crossC. a hybrid crossC. a hybrid crossD. a testcrossD. a testcross



2. In a monohybrid cross of two 2. In a monohybrid cross of two heterozygous parents (Pp), what heterozygous parents (Pp), what would the expected genotypes of would the expected genotypes of the offspring be?the offspring be?F. 1 PP : 2 Pp : 1 ppF. 1 PP : 2 Pp : 1 ppG. 1 pp : 3 PPG. 1 pp : 3 PPH. 3 Pp : 1 ppH. 3 Pp : 1 ppJ. all PpJ. all Pp



3. Which of the following is an 3. Which of the following is an example of a genotype of a example of a genotype of a heterozygous individual?heterozygous individual?

A. pA. p

B. YYB. YY

C. ZzC. Zz

D. rrD. rr


chapter 9 fundamentalsofgenetics revised by: r. leblanc biology 1/12

Documents

n offspring

n heredity

objectives n

n white

n example

slide slide

mendels experiment n

conclusions n recessive