Table of Contents Mendel’s Work Probability and Heredity The Cell and Inheritance The DNA Connection

Outlining - Mendel’s Work As you read, make an outline about Mendel’s work. Use the red headings for the main ideas and the blue headings for the supporting ideas. Mendel’s Experiments Crossing Pea Plants The F1 Offspring The F2 Offspring Experiments With Other Traits Dominant and Recessive Alleles Genes and Alleles Alleles in Mendel’s Crosses Symbols for Alleles Significance of Mendel’s Contribution

Mendel’s Work Introduction Pg. 218 Gregor Mendel experimented with hundreds of pea plants to understand the process of ______. heredity Heredity C- is the passing of traits from parents to offspring 3. Genetics A- is the scientific study of heredity. Traits B- are physical characteristics.

Crossing Pea Plants - Mendel’s Work Gregor Mendel crossed pea plants that had different traits. The illustrations show how he did this.

Mendel’s Experiments - Mendel’s Work In all of Mendel’s crosses, only one form of the trait appeared in the F1 generation. However, in the F2 generation, the “lost” form of the trait always reappeared in about one fourth of the plants.

Mendel’s Work Mendel’s Experiments Pg. 219-220 In a flower, the female sex cells, or eggs, are produced by the ____. Pollen, which contains the male sex cells, is produced by the _____. pistil stamens What are purebred organisms? They are the offspring of many generations that have the same trait.

Mendel’s Work Complete the flowchart: Purebred tall plants are crossed with purebred ____plants. short F1 offspring are all ____. tall F1 offspring are allowed to self pollinate. F2 offspring are ___and ____. tall and short Traits in garden peas that Mendel studied: pod, color, seed shape, and flower position.

Dominant and Recessive Alleles - Mendel’s Work Dominant and Recessive Alleles Mendel studied several traits in pea plants.

Mendel’s Work Two forms of the trait of seed shape in pea plants are ___ and ____. round and wrinkled Dominate and Recessive Alleles Pg. 221-223 Sentences that are true about alleles. Alleles are different forms of a gene. Dominant alleles always show up in the organism when the allele is present. 11. Only pea plants that have two recessive alleles for short stems will be short. True

Mendel’s Work Purebred short C- two alleles for short stems 13. Purebred tall A- two alleles for tall stems 14. Hybrid tall B- one allele for tall stems and one allele for short stems A dominant allele is represented by a(n) _____. capital letter

Mendel’s Work A recessive allele is represented by a(n) _____. lowercase letter 17. How would a geneticist write the alleles to show that a tall pea plant has one allele for tall stems and one allele for short stems? Tt Some scientists during Mendel’s time thought Mendel should be called the Father of Genetics. False

End of Section: Mendel’s Work

Building Vocabulary - Probability and Heredity After you read the section, reread the paragraphs that contain definitions of Key Terms. Use all the information you have learned to write a definition of each Key Term in your own words. Key Terms: Examples: homozygous heterozygous codominance Key Terms: Examples: probability An organisms that has two identical alleles for a trait is said to be homozygous. Probability is a number that describes how likely it is that an event will occur. Punnett square An organisms that has two different alleles for a trait is heterozygous for that trait. A Punnett square is a chart that shows all the possible combinations of alleles that can result from a genetic cross. In codominance, the alleles are neither dominant nor recessive. phenotype An organism’s phenotype is its physical appearance, or visible traits. genotype An organism’s genotype is its genetic makeup, or allele combinations.

Probability and Heredity Principles of Probability Pg. 226-227 A number that describes how likely it is that an event will occur is called _____. probability Circle the following that equals the probability that a tossed coin will land heads up. one in two ½ 50 Percent 3. When you toss a coin 20 times, you will always get 10 heads and 10 tails. False

Probability and Heredity If you toss a coin five times and it lands heads up each time, can you expect the coin to land heads up on the sixth toss? No, the results of the first five tosses do not affect the results of the sixth toss. Probability and Genetics Pg. 228-229 5. When Mendel crossed two hybrid plants for stem height (Tt), what results did he always get? He always found that about three fourths of the plants had tall stems and one fourth of the plants had short stems.

Probability and Heredity Mendel realized that the principles of probability could be used to _____ the results of genetic crosses. predict A chart that shows all the possible combinations of alleles that can result from a genetic cross is called a(n) _____. Punnett Square 8. Work on your own using a combination of alleles Tt and Tt.

Probability and Heredity Results of the cross Tt T t T t TT Tt tt

A Punnett Square - Probability and Heredity The diagrams show how to make a Punnett square. In this cross, both parents are heterozygous for the trait of seed shape. R represents the dominant round allele, and r represents the recessive wrinkled allele.

Probability and Genetics - Probability and Heredity Probability and Genetics In a genetic cross, the allele that each parent will pass on to its offspring is based on probability.

Phenotypes and Genotypes - Probability and Heredity Phenotypes and Genotypes An organism’s phenotype is its physical appearance, or visible traits, and an organism’s genotype is its genetic makeup, or allele combinations.

Probability and Heredity Phenotypes and Genotypes Pg. 230 Phenotype B- an organism’s physical appearance or visible traits 10. Genotype C- an organism’s genetic makeup or allele combinations 11. Homozygous A- describes an organism with two identical alleles for a trait

Probability and Heredity Heterozygous D- Describes an organism that has two different alleles for a trait 13. Mendel used the term ____ to describe heterozygous pea plants. hybrid Codominance Pg. 231 In codominance, the alleles are neither dominant nor recessive. True

Probability and Heredity In cattle, red hair and white hair are codominant. Cattle with both white hair and red hair are _____. heterozygous

Codominance - Probability and Heredity In codominance, the alleles are neither dominant nor recessive. As a result, both alleles are expressed in the offspring.

What Are the Genotypes? - Probability and Heredity Mendel allowed several F1 pea plants with yellow seeds to self-pollinate. The graph shows the approximate numbers of the F2 offspring with yellow seeds and with green seeds.

Percentages - Probability and Heredity Practice Problem Suppose 3 out of 12 coins landed with tails up. How can you express this as a percent? 25%

Percentages - Probability and Heredity One way you can express a probability is as a percentage. A percentage (%) is a number compared to 100. For example, 50% means 50 out of 100. Suppose that 3 out of 5 tossed coins landed with heads up. Here’s how you can calculate what percent of the coins landed with heads up. Write the comparison as a fraction. 3 out of 5 = 3/5 2. Multiply the fraction by 100% to express it as a percentage. 3/5 x 100%/1 = 60%

What Are the Genotypes? - Probability and Heredity Reading Graphs: How many F2 offspring had yellow seeds? How many had green seeds? Yellow–6,000; green–2,000

What Are the Genotypes? - Probability and Heredity Calculating: Use the information in the graph to calculate the total number of offspring that resulted from this cross. Then calculate the percentage of the offspring with yellow peas, and the percentage with green peas. 8,000; 75% have yellow peas and 25% have green peas.

What Are the Genotypes? - Probability and Heredity Inferring: Use the answers to Question 2 to infer the probable genotypes of the parent plants. (Hint: Construct Punnett squares with the possible genotypes of the parents.) Both parents probably had the genotype Bb.

End of Section: Probability and Heredity

Identifying Supporting Evidence - The Cell and Inheritance Identifying Supporting Evidence As you read, identify the evidence that supports the hypothesis that genes are found on chromosomes. Write the evidence in a graphic organizer. Grasshoppers: 24 chromosomes in body cells, 12 in sex cells. Chromosomes are important in inheritance. Fertilized egg has 24 chromosomes. Alleles exist in pairs in organisms.

The Cell and Inheritance Chromosomes and Inheritance Pg. 235 Sentences that are true about what Sutton observed about chromosome number. Grasshopper sex cells have half the number of chromosomes as body cells. When grasshopper sex cells join, the fertilized egg has the same number of chromosomes as the body cells of the parents. What is the chromosomes theory of inheritance? Genes are carried from parents to their offspring on chromosomes.

Meiosis - The Cell and Inheritance During meiosis, the chromosome pairs separate and are distributed to two different cells. The resulting sex cells have only half as many chromosomes as the other cells in the organism.

The Cell and Inheritance Meiosis Pg. 236-237 What is Meiosis? It is the process by which the number of chromosomes is reduced by half to form sex cells--sperm and eggs. 4. Complete the cycle diagram: Parent cell has four chromosomes arranged in ____ pairs. two Chromosome pairs ______and are distributed to sex cells, Each sex cell has ____ chromosomes. separate Four

The Cell and Inheritance The cycle continued: Sex cells combine to produce offspring. Each offspring has ____ chromosomes, one pair from each parent. two 5. A Punnett square is a shorthand way to show the events that occur during _____. meiosis 6. During meiosis, the two alleles for each gene stay together. False- separate

Punnett Square - The Cell and Inheritance A Punnett square is actually a way to show the events that occur at meiosis.

The Cell and Inheritance If the male parent cell is heterozygous for a trait, Tt, what alleles could the sperm cells possible have? Half the sperm cells will have the T allele and the other half will have the t allele. A Lineup of Genes Pg. 238 How many pairs of chromosomes do human body cells contain? 23 pairs of chromosomes 9. How are the genes lined up in a pair of chromosomes? Genes are lined up in the same order on both chromosomes.

A Lineup of Genes - The Cell and Inheritance Chromosomes are made up of many genes joined together like beads on a string. The chromosomes in a pair may have different alleles for some genes and the same allele for others.

End of Section: The Cell and Inheritance

Sequencing - The DNA Connection Sequence is the order in which the steps in a process occur. As you read, make a flowchart that shows protein synthesis. Put each step in the flowchart in the order in which it occurs. Protein Synthesis DNA provides code to form messenger RNA. Messenger RNA attaches to ribosome. Transfer RNA “reads” the messenger RNA. Amino acids are added to the growing protein.

The DNA Connection The Genetic Code Pg. 240 Sentences that are true about genes, chromosomes, and proteins. Genes control the production of proteins in an organism’s cells. Proteins help determine the size, shape, and other traits of an organism. A DNA molecule is made up of four nitrogen bases: a. Adenine (A) Thymine (T) Guanine (G) Cytosine (C)

The DNA Connection What is the genetic code? The genetic code is the order of nitrogen bases along a gene that specifies what type of protein will be produced. One group of three nitrogen codes for one _____. amino acid

The DNA Code - The DNA Connection Chromosomes are made of DNA. Each chromosome contains thousands of genes. The sequence of bases in a gene forms a code that tells the cell what protein to produce.

How Cells Make Proteins - The DNA Connection How Cells Make Proteins During protein synthesis, the cell uses information from a gene on a chromosome to produce a specific protein.

The DNA Connection How cells Make Protein Pg. 241-243 During protein synthesis, the cell uses information from a ____ on a chromosome to produce a specific _____. gene protein Proteins are made on _____ in the cytoplasm of the cell. ribosomes

The DNA Connection Complete the Venn Diagram: In DNA: Thymine stays inside the nucleus. In RNA: Uracil goes out into the cytoplasm. In both DNA and RNA: Cytosine, adenine, and guanine. 8. List two kinds of RNA and tell their jobs. a. Messenger RNA copies the coded message from the DNA in the nucleus and carries the message to the ribosomes in the cytoplasm.

The DNA Connection b. Transfer RNA carries amino acids to the ribosome and adds them to the growing protein. Circle the letter of the first step in the protein synthesis. DNA “unzips” to direct the production of a strand of messenger RNA. 10. Circle the letter of the last step in protein synthesis. The protein chain grows longer as each transfer RNA molecule adds an amino acid.

The DNA Connection 11. What is a mutation? Mutations Pg. 244-245 11. What is a mutation? A mutation is any change in a gene or chromosome. 12. How can mutations affect protein synthesis in cells? Mutations can cause a cell to produce an incorrect protein during protein synthesis. 13. Sentences that are true about mutations. Some mutations occur when one nitrogen base is substituted for another. Some mutations occur when chromosomes don’t separate correctly during meiosis.

The DNA Connection 14. Mutations can be a source of genetic _____. variety All mutations are harmful. False Mutation that are ____ improve an organism’s chances for survival and reproduction. helpful 17. Whether a mutation is harmful or helpful depends partly on an organism’s _____. environment

Mutations - The DNA Connection Mutations can cause a cell to produce an incorrect protein during protein synthesis. As a result, the organism’s trait, or phenotype, may be different from what it normally would have been.

The DNA Connection Key Terms Meiosis Punnett Square Phenotype Messenger RNA Heterozygous Probability Dominant Allele Trait Gene Genetics Purebred

End of Section: The DNA Connection

Graphic Organizer RNA Messenger RNA Transfer RNA includes functions to Copy the coded message from the DNA Carry the message to the ribosome in the cytoplasm Add amino acids to the growing protein Carry amino acids

End of Section: Graphic Organizer