Chapter 5 Heredity. Section 1: Objectives Explain the relationship between traits and heredity. Describe the experiments of Mendel. Explain the

Chapter 5Chapter 5

HeredityHeredity

Section 1: ObjectivesSection 1: Objectives

Explain the relationship between Explain the relationship between traits and heredity.traits and heredity.

Describe the experiments of Mendel.Describe the experiments of Mendel.

Explain the difference between Explain the difference between dominant and recessive traits.dominant and recessive traits.

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HeredityHeredity: passing of traits from : passing of traits from parent to offspringparent to offspring

Gregor Mendel was one of the first Gregor Mendel was one of the first scientists to study heredity.scientists to study heredity.

What are traits?What are traits?

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Gregor Mendel was born in 1822 in Gregor Mendel was born in 1822 in Austria.Austria.

He grew up on a farm where he He grew up on a farm where he learned about flowers and fruit trees.learned about flowers and fruit trees.

He entered a monestary when he He entered a monestary when he was 21 years old.was 21 years old.

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Here, he was taught science and Here, he was taught science and performed many scientific performed many scientific experiments.experiments.

He put most of his energy into He put most of his energy into research.research.

He discovered the principles of He discovered the principles of heredity.heredity.

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From working with plants, Mendel From working with plants, Mendel knew the patterns of inheritance knew the patterns of inheritance weren’t always clear.weren’t always clear.

For example, sometimes a trait may For example, sometimes a trait may be expressed in offspring that was be expressed in offspring that was not expressed in either parent.not expressed in either parent.

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Mendel wanted to learn more about Mendel wanted to learn more about what caused these patterns.what caused these patterns.

To keep it simple, he studied 1 type To keep it simple, he studied 1 type of organism: pea plants.of organism: pea plants.

Why would studying 1 organism at a Why would studying 1 organism at a time be helpful in studying patterns time be helpful in studying patterns of inheritence?of inheritence?

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Pea plants were a good choice for Pea plants were a good choice for several reasons:several reasons:– They grow quicklyThey grow quickly– There are many different kindsThere are many different kinds– They are self pollinatingThey are self pollinating

– A self pollinating plant has both male A self pollinating plant has both male and female structures.and female structures.

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Pollen from one plant can fertilize the Pollen from one plant can fertilize the ovule of the same plant.ovule of the same plant.

Mendel was able to grow true-Mendel was able to grow true-breeding plants.breeding plants.

In true-breeding plants, the offspring In true-breeding plants, the offspring have the same traits as the parent.have the same traits as the parent.

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Pea plants can also cross-pollinate.Pea plants can also cross-pollinate.

In cross-pollination, pollen from one In cross-pollination, pollen from one plant fertilizes another plant. plant fertilizes another plant.

Pollen can be carried by:Pollen can be carried by:– InsectsInsects– WindWind

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Mendel studied only 1 characteristic Mendel studied only 1 characteristic at a time.at a time.

A characteristic is a feature that has A characteristic is a feature that has different forms in a population.different forms in a population.

For example, hair color is a For example, hair color is a characteristic; different forms such characteristic; different forms such as red hair or brown hair is a trait.as red hair or brown hair is a trait.

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Mendel’s first experiments:Mendel’s first experiments: Mendel crossed pea plants to study 7 Mendel crossed pea plants to study 7

different characteristics.different characteristics.

The trait that appeared most of the The trait that appeared most of the time was called the time was called the dominant traitdominant trait..

The The recessive traitrecessive trait was the trait was the trait that appeared less. that appeared less.

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Mendel’s Second Experiments:Mendel’s Second Experiments: Mendel allowed the first generation Mendel allowed the first generation

plants to self-pollinate.plants to self-pollinate.

He completed the exact same He completed the exact same experiment for each of the 7 experiment for each of the 7 characteristics he was studying.characteristics he was studying.

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Mendel studied each of the following Mendel studied each of the following characteristics:characteristics:– Flower colorFlower color– Seed colorSeed color– Seed shapeSeed shape– Pod colorPod color– Pod shapePod shape– Flower positionFlower position– Plant heightPlant height

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A A ratio ratio is a relationship between 2 is a relationship between 2 different numbers.different numbers.

Mendel calculated the ratio for Mendel calculated the ratio for dominant to recessive traits.dominant to recessive traits.

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Ratio Example: Ratio Example:

Dominant = purple flowersDominant = purple flowers

Recessive = white flowersRecessive = white flowers

705 purple: 224 white705 purple: 224 white

Ratio = 3.15:1Ratio = 3.15:1

Calculate the Following RatiosCalculate the Following Ratios

A) 6,002 yellow: 2,001 greenA) 6,002 yellow: 2,001 green

B) 5,474 pink: 1,850 redB) 5,474 pink: 1,850 red

C) 428 green: 152 yellowC) 428 green: 152 yellow

D) 787 short: 277 tallD) 787 short: 277 tall

What do these ratios have in common?What do these ratios have in common?

Complete the Following CrossComplete the Following Cross

In daisies, yellow flower color is dominant In daisies, yellow flower color is dominant over white. Cross a homozygous yellow over white. Cross a homozygous yellow flowered plant with a homozygous white flowered plant with a homozygous white flowered plant. flowered plant.

1) Offspring Genotype (include 1) Offspring Genotype (include percentages):percentages):

2) Offspring Phenotype (include 2) Offspring Phenotype (include percentages):percentages):

3) Ratio of dominant to recessive traits:3) Ratio of dominant to recessive traits:


Pick any 2 offspring from the last slide and Pick any 2 offspring from the last slide and complete a cross. Dominant and recessive complete a cross. Dominant and recessive traits remain the same.traits remain the same.


2) Offspring Phenotype (include 2) Offspring Phenotype (include percentages): percentages):



In crimson clover, red flowers are In crimson clover, red flowers are dominant over pink. Cross a heterozygous dominant over pink. Cross a heterozygous red crimson clover plant with a red crimson clover plant with a homozygous pink crimson clover plant. homozygous pink crimson clover plant.










In grapes, purple color is dominant over In grapes, purple color is dominant over green. Cross a heterozygous purple green. Cross a heterozygous purple colored grape plant with a homozygous colored grape plant with a homozygous green colored grape plant. green colored grape plant.

1) Offspring Genotype (include 1) Offspring Genotype (include percentages)percentages)

2) Offspring Phenotype (include 2) Offspring Phenotype (include percentages)percentages)







Chapter 5 Notebook QuizChapter 5 Notebook Quiz

1) __________ was one of the first scientists 1) __________ was one of the first scientists to study heredity.to study heredity.

2) What is the difference between self-2) What is the difference between self-pollination and cross pollination?pollination and cross pollination?

3) What type of plants did Mendel study?3) What type of plants did Mendel study? 4) What is a characteristic?4) What is a characteristic? 5) What is a ratio?5) What is a ratio? 6) How many characteristics did Mendel 6) How many characteristics did Mendel

study?study?


Explain how genes and alleles are Explain how genes and alleles are related to genotype and phenotype.related to genotype and phenotype.

Use the information in a Punnett Use the information in a Punnett square.square.

Explain how the probability can be Explain how the probability can be used to predict possible genotypes in used to predict possible genotypes in offspring.offspring.

Describe 3 exceptions to Mendel’s Describe 3 exceptions to Mendel’s observations.observations.

Phenotype vs. GenotypePhenotype vs. Genotype

The first generation carries the The first generation carries the instructions for both dominant and instructions for both dominant and recessive traits.recessive traits.

Scientists now call these instructions Scientists now call these instructions genesgenes, one set of instructions for an , one set of instructions for an inherited trait.inherited trait.

The different forms of a gene are The different forms of a gene are allelesalleles..


Genes affect the traits of offspring.Genes affect the traits of offspring.

An organism’s appearance is known An organism’s appearance is known

as as phenotypephenotype..

Examples: Red flower color, white Examples: Red flower color, white flower color, yellow flower colorflower color, yellow flower color

Phenotype vs.GenotypePhenotype vs.Genotype

Both inherited alleles together form Both inherited alleles together form an organism’s genotype.an organism’s genotype.

HeterozygousHeterozygous: one dominant and : one dominant and one recessive traitone recessive trait

HomozygousHomozygous: 2 dominant or 2 : 2 dominant or 2 recessive traits recessive traits


Probability: “The mathematical Probability: “The mathematical chance that something will happen”chance that something will happen”

In a coin toss, you have a 50% In a coin toss, you have a 50% chance of getting heads or tails.chance of getting heads or tails.

This is the case with inherited traits This is the case with inherited traits as well.as well.


Probability is written as a fraction or Probability is written as a fraction or percentage.percentage.

If you toss a coin, the probability of If you toss a coin, the probability of tossing tails is 50%. (You will get tails tossing tails is 50%. (You will get tails half the time.)half the time.)

Probability ExampleProbability Example

If you roll a pair of dice, what is the If you roll a pair of dice, what is the probability you will roll 2 three probability you will roll 2 three separate times?separate times?– Count the number of faces on the dice. Count the number of faces on the dice.

Put this number in the denominator. (6)Put this number in the denominator. (6)– Count the number of ways you can roll 3 Count the number of ways you can roll 3

with one dice. Put this number in the with one dice. Put this number in the numerator. (1)numerator. (1)

Probability ExampleProbability Example

– To find the probability that you will To find the probability that you will throw 2 threes, multiply the probability throw 2 threes, multiply the probability of throwing the first 3 by the probability of throwing the first 3 by the probability of throwing the second 3: 1/6 X 1/6 = of throwing the second 3: 1/6 X 1/6 = 1/36.1/36.

Probability Example # 2Probability Example # 2

What is the probability that you will What is the probability that you will roll an even number with one dice?roll an even number with one dice?– Count the number of faces on the dice Count the number of faces on the dice

(denominator)(denominator)– Count the number of ways you can roll Count the number of ways you can roll

an even number. (numerator) an even number. (numerator)


Incomplete dominance: Incomplete dominance: Sometimes, one trait is not completely Sometimes, one trait is not completely

dominant over another. dominant over another.

It is possible to have 2 dominant traits (co-It is possible to have 2 dominant traits (co-dominance).dominance).

SometimesSometimes genes can affect more than genes can affect more than one trait.one trait.


Genes aren’t the only influence on traits.Genes aren’t the only influence on traits.

In some ways, the environment affects In some ways, the environment affects how you grow and develop.how you grow and develop.

Example: Your genes make it possible for Example: Your genes make it possible for you to grow tall, but you need a healthy you to grow tall, but you need a healthy diet to reach your full potential.diet to reach your full potential.

Incomplete Dominance ExampleIncomplete Dominance Example

In a rare breed of roses, white and In a rare breed of roses, white and red flower colors are dominant. What red flower colors are dominant. What would happen if a red rose was would happen if a red rose was crossed with a white rose?crossed with a white rose?– Genotype:Genotype:– Phenotype:Phenotype:– Ratio:Ratio:

Chapter 5 Pop QuizChapter 5 Pop Quiz

1) What is the probability of rolling 1) What is the probability of rolling an odd number with one dice?an odd number with one dice?

2) In a rare breed of sunflowers, 2) In a rare breed of sunflowers, yellow and orange are both dominant yellow and orange are both dominant flower colors. What would happen if a flower colors. What would happen if a yellow flower was crossed with an yellow flower was crossed with an orange flower? Write all genotypes, orange flower? Write all genotypes, phenotypes, and ratios. phenotypes, and ratios.


Explain the difference between Explain the difference between mitosis and meiosis.mitosis and meiosis.

Describe how chromosomes Describe how chromosomes determine sex.determine sex.

Explain why sex-linked disorders Explain why sex-linked disorders occur in 1 sex more often than in the occur in 1 sex more often than in the other.other.

Interpret a pedigree.Interpret a pedigree.

MeiosisMeiosis

Chromosomes that carry the same Chromosomes that carry the same sets of genes are called sets of genes are called homologous chromosomeshomologous chromosomes..

These are like a “pair of shoes” These are like a “pair of shoes” because there are 2.because there are 2.

Sex cells are different because they Sex cells are different because they have 1 chromosome.have 1 chromosome.

MeiosisMeiosis

Sex cells are made during meiosis.Sex cells are made during meiosis.

MeiosisMeiosis is a copying process that is a copying process that produces cells with half the usual produces cells with half the usual number of chromosomes.number of chromosomes.

MeiosisMeiosis

What does meiosis have to do with What does meiosis have to do with chromosomes?chromosomes?

Genes are located on chromosomes.Genes are located on chromosomes.

Understanding meiosis was critical to Understanding meiosis was critical to finding the location of genes.finding the location of genes.

MeiosisMeiosis

During mitosis, chromosomes are During mitosis, chromosomes are copied once.copied once.

During meiosis, the nucleus divides During meiosis, the nucleus divides twice. twice.

The result is sex cells, with half the The result is sex cells, with half the number of chromosomes as a normal number of chromosomes as a normal body cell.body cell.

MeiosisMeiosis

Info. contained on chromosomes Info. contained on chromosomes determine many of our traits.determine many of our traits.

Sex cellsSex cells carry genes that carry genes that determine sex of an individual.determine sex of an individual.

Females: XXFemales: XX Males: XYMales: XY

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A A pedigreepedigree is a diagram that shows is a diagram that shows the occurrence of a genetic trait in the occurrence of a genetic trait in several generations of a familyseveral generations of a family

Pedigrees are helpful in Pedigrees are helpful in tracing/predicting diseases and traits tracing/predicting diseases and traits from one generation to the next. from one generation to the next.

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Useful in predicting if a person is a Useful in predicting if a person is a carrier for a certain trait/disease.carrier for a certain trait/disease.

Carriers do not always show signs of Carriers do not always show signs of the trait/disease.the trait/disease.

MeiosisMeiosis

Cystic fibrosis causes serious lung Cystic fibrosis causes serious lung problems.problems.

People with cystic fibrosis disease People with cystic fibrosis disease have 2 inherited recessive alleles.have 2 inherited recessive alleles.

Both parents must be carriers of the Both parents must be carriers of the trait for it to show up in their trait for it to show up in their children.children.

Documents

Chapter 5 Heredity. Section 1: Objectives Explain the relationship between traits and heredity. Describe the experiments of Mendel. Explain the