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Chapter Introduction
Lesson 1 How are traits inherited?
Lesson 2 Genetics After Mendel
Lesson 3 Adaptation and Evolution
Chapter Wrap-Up
What do you think?
Before you begin, decide if you agree or disagree with each of these statements. As you view this presentation, see if you change your mind about any of the statements.
1. Genes are on chromosomes.
2. Only dominant genes are passed on to offspring.
3. Modern-day genetics disprove Gregor Mendel’s ideas about inheritance.
4. Mutations can cause disease in an individual.
Do you agree or disagree?
5. A population that lacks variation among its individuals might not be able to adapt to a changing environment.
6. Extinction occurs when the last individual of a species dies.
Do you agree or disagree?
• How are traits inherited?
• Why do scientists study genetics?
• What did Gregor Mendel investigate and discover about heredity?
How are traits inherited?
• heredity
• genetics
• selective breeding
• dominant trait
• recessive trait
How are traits inherited?
• genotype
• phenotype
• heterozygous
• homozygous
• Heredity is the passing of traits from parent to offspring.
• Genetics is the study of how traits pass from parents to offspring.
• For most organisms, genes are sections of DNA that contain information about a specific trait of that organism.
From Parent to Offspring
From Parent to Offspring (cont.)
• A gene with different information for a trait is called an allele.
• Each chromosome pair has genes for the same traits.
• A gene’s alleles are in the same location on each chromosome of a pair.
• An organism passes its traits to its offspring in one of two ways—through asexual reproduction or through sexual reproduction.
• In asexual reproduction, one organism makes a copy of its genes and itself.
• In sexual reproduction, offspring receive half of their genes from an egg cell and the other half from a sperm cell.
How are traits inherited?
• Scientists began studying genetics to understand how traits are inherited.
• By studying genetics, scientists have learned that genes control how organisms develop.
• Studying genetics can help scientists determine how organisms are related.
Why do scientists study genetics?
Because the genes from these organisms are similar enough to produce normal eyes when exchanged, scientists suspect that these species share a common, ancient ancestor.
Heredity—the History and the Basics• Selective breeding is the selection and
breeding of organisms for desired traits.
• In the illustration below, a farmer would breed the rooster with the hen that produces the most eggs per year.
In 1856, Gregor Mendel began experimenting with pea plants to answer the question of how traits are inherited.
Heredity—the History and the Basics (cont.)
Pixtal/age Fotostock
Mendel chose plants that produced only green pods, called true-breeding, and crossed them with true-breeding plants that produced only yellow pods.
Heredity—the History and the Basics (cont.)
• All the offspring, called hybrids, produced only green pods.
• The yellow-pod trait seemed to disappear, not blend with the green-pod trait.
• Mendel proposed that some traits of organisms are dominant, while others are recessive.
Heredity—the History and the Basics (cont.)
• When Mendel crossed two hybrid plants with green pods, the cross resulted in offspring with green pods and offspring with yellow pods.
• These offspring were in a ratio of about 3:1, green to yellow.
Heredity—the History and the Basics (cont.)
• A dominant trait is a genetic factor that blocks another genetic factor.
• A recessive trait is a genetic factor that is blocked by the presence of a dominant factor.
• When an individual has one dominant allele and one recessive allele for a trait, the dominant trait is expressed.
Heredity—the History and the Basics (cont.)
• The alleles of all the genes on an organism’s chromosomes make up the organism’s genotype.
• How the traits appear, or are expressed, is the organism’s phenotype.
Heredity—the History and the Basics (cont.)
Heredity—the History and the Basics (cont.)
phenotype
from Greek phainein, means “to show”; and typos, means “type”
• When an organism’s genotype has two different alleles for a trait, it is called heterozygous.
• When an organism’s genotype has two identical alleles for a trait, it is called homozygous.
Heredity—the History and the Basics (cont.)
What did Mendel investigate and discover about heredity?
Heredity—the History and the Basics (cont.)
• Traits are passed from parent to offspring during asexual or sexual reproduction.
• Through selective breeding, Mendel showed that some traits are dominant and some traits are recessive.
• An organism’s genotype can be homozygous or heterozygous.
• Each gene has two types of alleles, dominant or recessive.
• A dominant allele is expressed over a recessive allele.
Which is a gene with different information for a trait?
A. allele
B. chromosome
C. genotype
D. offspring
A. dominant trait
B. genotype
C. phenotype
D. recessive trait
Which is a genetic factor that blocks another genetic factor?
A. asexual reproduction
B. genetics
C. selective breeding
D. sexual reproduction
Which is the process by which one organism makes a copy of its genes and itself?
1. Genes are on chromosomes.
2. Only dominant genes are passed on to offspring.
Do you agree or disagree?
• How can you use models to predict genetic outcomes?
• What are the other patterns of inheritance?
• What role can mutations play in the inheritance of disease?
Genetics After Mendel
• monohybrid cross
• Punnett square
• incomplete dominance
• codominance
Genetics After Mendel• multiple alleles
• sex-linked trait
• polygenic inheritance
• pedigree
• mutation
• genetic engineering
• In 1900, scientists realized that genes were on chromosomes in the nucleus.
• They confirmed that genes were Mendel’s dominant and recessive factors.
Rediscovering Mendel’s Work
• If you flipped a coin ten times, you might predict a heads-to-tails ratio of 5:5.
• Probabilities are predictions; they do not guarantee outcomes. Your coin flips could result in ten heads in a row.
Predicting Genetic Outcomes
Brand X Pictures
• Mendel predicted the outcome of a monohybrid cross—a cross between two individuals that are hybrids for one trait.
• Mendel predicted a 3:1 ratio of the dominant phenotype to the recessive phenotype.
C Squared Studios/Getty Images
• A Punnett square shows the probability of all possible genotypes and phenotypes of offspring.
• This Punnett square predicts that 75 percent of the offspring will express the dominant phenotype of green pods.
Predicting Genetic Outcomes (cont.)
Predicting Genetic Outcomes (cont.)
How does a Punnett square help scientists predict genetic outcomes?
When an offspring’s phenotype is a combination of its parents’ phenotypes, it is called incomplete dominance.
Other Patterns of Inheritance
When both alleles can be independently observed in a phenotype, it is called codominance.
Other Patterns of Inheritance (cont.)
Nova Development
• Human blood type is an example of multiple alleles, or a gene that has more than two alleles.
• The IA and IB alleles are codominant to each other, but both are dominant to the i allele.
Other Patterns of Inheritance (cont.)
• When the allele for a trait is on an X or Y chromosome, it is called a sex-linked trait.
• In fruit flies, the allele for eye color is on only the X chromosome, not on the Y chromosome,
Other Patterns of Inheritance (cont.)
• Some traits, such as height, are controlled by many genes.
• Polygenic inheritance occurs when multiple genes determine the phenotype of a trait.
Other Patterns of Inheritance (cont.)
2007 Getty Images, Inc.
• A pedigree shows genetic traits that were inherited by members of a family.
• This illustration shows the pedigree for a family in which cancer was common in each generation.
Inheritance of Disease
• A mutation is any permanent change in the sequence of DNA in a gene or a chromosome of a cell.
• If mutations occur in reproductive cells, they can be passed from parent to offspring.
• Cancer, diabetes, and birth defects all result from mutations in genes.
Inheritance of Disease (cont.)
Inheritance of Disease (cont.)
mutation
from Latin mutare, means “to change”
Inheritance of Disease (cont.)
What role can mutations play in the inheritance of disease?
• Scientists today are using what they have learned about genetics to help people.
• In genetic engineering, the genetic material of an organism is modified by inserting DNA from another organism.
Inheritance of Disease (cont.)
Bacteria have been genetically engineered to produce human insulin.
• Scientists use Punnett squares and pedigrees to predict and analyze genetic outcomes.
• There are many patterns of inheritance, including incomplete dominance, codominance, and polygenic inheritance.
• Scientists use genetic engineering to help treat diseases and learn more about how organisms develop.
• Scientists use models like Punnett squares and pedigrees to predict and show patterns in inheritance that can be used to figure out why these diseases are passed on.
Which refers to an offspring’s phenotype which is a combination of its parents’ phenotypes?
A. codominance
B. complete dominance
C. incomplete dominance
D. mutation
A. incomplete dominance
B. multiple alleles
C. mutation
D. sex-linked trait
Which describes genes that have more than two forms?
A. pedigree
B. mutation
C. genetic engineering
D. codominance
What is any permanent change in the sequence of DNA in a gene or a chromosome of a cell?
3. Modern-day genetics disprove Gregor Mendel’s ideas about inheritance.
4. Mutations can cause disease in an individual.
Do you agree or disagree?
• How does natural selection occur?
• What is an adaptation?
• Why do traits change over time?
Adaptation and Evolution
• variation
• natural selection
• adaptation
• evolution
Adaptation and Evolution
• extinction
• conservation biology
Slight differences in inherited traits among individuals in a population are called variations.
Mutations, Variations, and Natural Selection
Creatas/PunchStock
The process by which individuals with variations that help them survive in their environment live longer, compete better, and reproduce more than those individuals without these variations is called natural selection.
Mutations, Variations, and Natural Selection (cont.)
Mutations, Variations, and Natural Selection (cont.)
How does natural selection occur?
• An adaptation is an inherited trait that increases an organism’s chance of surviving and reproducing in a particular environment.
• Structural adaptations involve physical characteristics, such as color or shape.
Adaptations
• Functional adaptations involve internal systems that affect an organism’s physiology or biochemistry.
• Behavioral adaptations, such as migration, involve the ways an organism behaves or acts.
Adaptations (cont.)
• Evolution is change in inherited characteristics over time.
• Evolution by natural selection is a way that populations change over time.
• As the environment changes, different inherited traits might enable survival, and the population can evolve again.
Evolution of Populations—Why Traits Change
Evolution of Populations—Why Traits Change (cont.)
Why do traits change over time?
When the last individual of a species dies, the species has undergone extinction.
Extinction and Conservation Biology
extinction
from Latin extinctus, means “wipe out”
• Organisms called invasive species may be introduced into a habitat, making it difficult for some native species to survive and reproduce.
• Conservation biology is a branch of biology that studies why many species are in trouble and what can be done to save them.
Extinction and Conservation Biology (cont.)
introduce
Science Use to bring a substance or organism into a habitat or a population
Common Use to make someone known to others
Extinction and Conservation Biology (cont.)
• Natural selection occurs when individuals with traits that better suit the environment survive longer and reproduce more successfully than individuals without the traits.
• An adaptation is an inherited trait that increases an organism’s chance of surviving and reproducing in an environment.
• Conservation biologists work to save species from extinction.
What has a species undergone when the last individual of that species dies?
A. adaptation
B. evolution
C. extinction
D. variation
A. behavioral
B. evolutionary
C. functional
D. structural
Migration is an example of which kind of adaptation?
A. adaptation
B. evolution
C. natural selection
D. variation
Which term refers to change over time?
5. A population that lacks variation among its individuals might not be able to adapt to a changing environment.
6. Extinction occurs when the last individual of a species dies.
Do you agree or disagree?
Key Concept Summary
Interactive Concept Map
Chapter Review
Standardized Test Practice
Mutations can change the traits in individuals that are passed from parents to offspring, producing variation in a population that can lead to greater success and survival in new environments.
• Traits are inherited as genes pass from parent to offspring.
• Scientists study genetics to learn more about the development of organisms as well as the development of disease. Scientists also can learn more about how organisms are related by studying genetics.
• Mendel studied how traits are passed from parents to offspring. He discovered that traits can be dominant or recessive and that the outcome of crosses between parents can be predicted.
Lesson 1: How are traits inherited?
Lesson 2: Genetics After Mendel
• Models, such as Punnett squares, can be used to predict the probability of certain allele combinations given the genotypes of the parents of a genetic cross.
• Traits can be inherited in ways other than dominant or recessive. Traits can be inherited as incomplete dominance, codominance, multiple alleles, and polygenic traits.
• Mutations are changes in genes and can cause disease. As genes are passed from parent to offspring, so is the disease.
• Natural selection is the process in which individuals with traits that better suit the environment are more likely to survive longer and reproduce successfully than those individuals without these traits.
• An adaptation is an inherited trait that increases an organism’s chance of surviving and reproducing in a particular environment.
• Traits change over time because individuals with adaptive traits tend to produce more offspring than individuals with traits that no longer give them an advantage in a particular environment.
Lesson 3: Adaptation and Evolution
Which is the selection and breeding of organisms for desired traits?
A. asexual reproduction
B. genetics
C. heredity
D. selective breeding
A. dominant trait
B. heredity
C. phenotype
D. recessive trait
Which is blocked by the presence of a dominant factor?
A. genetic engineering
B. incomplete dominance
C. mutation
D. polygenic inheritance
Which occurs when multiple genes determine the phenotype of a trait?
A. pedigree
B. mutation
C. genetic engineering
D. codominance
Which occurs when the DNA of an organism is modified by inserting DNA from another organism?
A. adaptation
B. evolution
C. natural selection
D. variation
Which is an inherited trait that increases an organism’s chance of surviving and reproducing?
A. phenotype
B. homozygous
C. heterozygous
D. genotype
Which describes an organism’s genotype when it has two identical alleles for a trait?
A. genetics
B. genotype
C. heredity
D. selective breeding
Which is the study of how traits pass from parents to offspring?
A. monohybrid cross
B. multiple alleles
C. pedigree
D. Punnett square
Which is used to model the possible genotypes and phenotypes of offspring?
A. monohybrid cross
B. mutation
C. pedigree
D. Punnett square
Which shows genetic traits that were inherited by members of a family?
A. behavioral
B. external
C. functional
D. structural
Which type of adaptation involves internal systems that affect an organism’s physiology or biochemistry?