S-B-8-1_Heredity PowerPoint

S-B-8-1_Heredity PowerPoint
Mendel’s Laws

Ask the students if they think the men in these portraits are related? What traits make you think that they are related? Students may say that they all have a long chin, face, or nose. These portraits belong to a few members of the royal family of Austria, Hungary and Spain: the Habsburgs Dynasty. They all have inherited the distinct trait, Mandibular prognathism, or more commonly known as the Habsburg Jaw or Habsburg Lip. Mandibular prognathism is a condition where the lower jaw outgrows the upper jaw. People always knew that traits were inherited. Ask students if they know a family where all the children look the same, there is no question that they are related? Do they know any brothers and sisters that don’t look alike, even though they have the same parents? Source:

How are traits inherited?
S-B-8-1_Heredity PowerPoint How are traits inherited? Selective Breeding Domestication of plants Higher yielding crops Mature faster, set fruit earlier Attractive fruit Domestication of animals Desired behaviors Desired qualities Gray Wolf For thousands of years farmers bred animals and crop plants for desired characteristics. Domestication is the result of choosing which seeds to plant and what animals to allow to mate. Farmers cultivated land with seeds from plants that matured faster and produced more fruit or grain. Calves from cows that produced more milk would be allowed to reproduce. Dogs were the first domesticated animals descending from Gray Wolves in East Asia. Today there are hundreds of recognized breeds of dogs, varying in size, shape, color and temperament. Dogs are bred for uniform characteristics, e.g. All German Shepherds have similar coloring, size and protective instincts. Since heredity was not really understood, breeding for desired characteristics could be “hit or miss.” Does anyone have a purebred dog or cat at home? Do they have characteristics typical to the breed? Answers will vary. If their dog/cat has an undesirable trait (e.g. crooked teethe, fearful), should they breed it? Answers will vary.

Gregor Mendel Born in 1822, Brno, Moravia (now the Czech Republic), the only son of a farming family Showed promise in school and entered the monastery to continue his education Went to the University of Vienna, studying physics and math Came back to the Abbey in Brno to teach and experiment in the garden Born Johann Mendel, July 20, 1822 in Brno, Moravia. His father farmed the land that had been in the family for over 130 years. Johann was expected to work on the farm as a child and take over as an adult. He gardened and became interested in bee keeping. He went to school and was very successful in his studies. He preferred the scholarly life to farming, attended Philosophical Institute in Olomouc. (Similar to a two year college) He entered the Augustinian Abbey of Saint Thomas in 1843 where he took the name Gregor. He was sent to the University of Vienna in 1851 to continue his studies. When he returned in 1853 he was expected to teach and perform his priestly duties at the local hospital. Mendel didn’t have the stomach for the hospital so he was given the task of cultivating the Abbey’s garden. Math has always been an integral part of physics, but Mendel was the first to use math in a biological context. What significance did this have for the science of biology? Answers will vary but try to lead the students into saying that biology became more “science-like” where biologists experiment and predict outcomes rather than just observe nature.

Mendel’s Experiment Mendel investigates inheritance in pea plants for eight years. He chose peas because: They are easy to cultivate. They reproduced sexually. They have easy to distinguish traits. Mendel wanted to know how traits were passed from one generation to the next. Both Darwin and Mendel investigated heredity using plants and although Darwin’s experiment yielded similar results to Mendel, Darwin, who had no background in math, did not see a pattern. At the time, most biologists assumed the idea of blending inheritance. Mendel was an experienced gardener. He also studied math and statistics at the university “preparing” his mind to analyze the data and see patterns in heredity. Why is “easy to grow” an important part of Mendel’s experimental design? If the plant was too delicate or required too much attention, he would be spending all his time on growing the plant. He probably would not have studied it for eight years.

Pisum sativum-The Pea Mendel chose seven traits to study for his experiments. Each trait had only two variations that were easy to distinguish, e.g. tall plants were over 6 feet tall while dwarf plants were under 2 feet. He planted and tested approximately 29,000 pea plants during his eight year study. Mendel was lucky. The traits that he chose were on different chromosomes. What is the difference between axial and terminal flower position? Terminal flowers bloom at the tip of the stem; axial flowers bloom in the middle of the stem.

Artificial Pollination
S-B-8-1_Heredity PowerPoint Artificial Pollination Explain that the flower is the sex organ of the plant. The pea plant self pollinates and each flower has both the male and female parts. The male part of the flower is the stamen. The male gametes are contained in the pollen released from the anther. The female part of the plant is the stigma which leads to the ovule. Demonstrate artificial pollination with available flowers such as lilies. Show students that the stamen is cut from the flower (emasculating the flower) while it is still immature or has unopened flowers. Flowers that are already opened are removed from the plant. Why do you think it is necessary to use only unopened flowers for artificial pollination? Opened flowers may have already been fertilized. The stigma is exposed by removing the petals. Pollen from another plant is applied to the stigma with a paint brush or feather. Plant is covered with a bag until fruit/seeds begins to mature. Plant stem is labeled. Why do you think the flower needs to be covered in a bag? To prevent flower from being pollinated naturally by the wind or a bee. Removing Stamen from flower Exposing Stigma and dusting with pollen Covering the flower with bag and labeling stem

Monohybrid Cross X Crossed Tall plants with Short plants, the parents or P Called the hybrid offspring, the First Filial, F1, generation What would you expect the F1 Generation to look like? P Mendel chose cultivars, plants that are true breeding, for the tall trait (over 6’ tall) and crossed them with the pea variety that was true breeding for dwarfism (2’ and under). Plants that are “true breeding” have been grown for multiple generations and produce offspring that possess traits found in the parent (i.e., Tall pea plants produce offspring that grow tall for over three generations). He uses artificial pollination to make the hybrid pea plants. Hybrids refer to offspring of cross bred parents (e.g., a liger is a hybrid of a lion and a tiger). Have students predict the phenotype of the F1 generation. Many will think that the traits will blend, producing 4’ plants. Explain that filial is Latin for son or daughter. If they are taking French, they may recognize it is the root for fils (son) and fille (daughter). F1 All offspring are tall.

Rule of Dominance DOMINANT traits The trait expressed in hybrid offspring, the F1 generation recessive traits The trait that is not expressed, or hidden, in the F1 generation Mendel thought that the dwarf trait was masked or hidden behind the tall trait. He called the tall trait dominant and the dwarf trait recessive (to move back or recede). Why is dominant a good name for the expressed trait? Because the trait overshadows or stands out over the completely unexpressed recessive trait What evidence does the F1 generation give to disprove the “blending” hypothesis? According to the blending hypothesis, their should be a blending of heights or all the offspring should be intermediate heights.

The F2 Generation Mendel allowed the F1 plants to self pollinate. What would you expect the offspring to look like? X P F1 Mendel allowed the F1 plants to self pollinate and produce seeds. He planted the F2 seeds and collected data What would you expect the offspring to look like? The F2 generation had a 3:1 ratio of dominant to recessive traits. Misconception Alert: Many students need to be reminded that these are probabilities. The F1 plant does not produce only four offspring, 3 having the dominant trait and one having the recessive trait. Mendel approximated or rounded his ratio to 3:1 787 tall plants and 277 dwarf plants F2

Rule of Unit Factors Mendel’s Explanation Individuals have two “heritable” factors for a trait . The two factors may or may not contain the same information: Homozygous individuals have identical factors . TT or tt Heterozygous individuals have 2 different factors. Tt F1 P F2 X TT tt Tt Mendel explained the results of the F2 cross with the “Rule of Unit Factors” He said that each individual had 2 factors for trait. One it received from its mother and the other came from its father. The factors may or may not contain the same information. Individuals that contain the same information for that factor are considered to be homozygous for that trait. Remind students that homo- means the same, -zygous means yolk (as in a fertilized egg) Heterozygous individuals have different factors for the trait. Hetero- means different. What trait do heterozygous individuals express? Heterozygous individuals express the dominant trait. TT Tt Tt tt

HOMOLOGOUS CHROMOSOMES
S-B-8-1_Heredity PowerPoint Genetics Modern Genetics Individuals have two copies of a gene (one on each homologous chromosome). The various forms of a gene are called alleles: Dominant alleles are expressed when they are present. Recessive alleles are expressed only when the individual is homozygous for the gene form. Tall allele Genes at the same location Dwarf allele We now know Mendel’s unit factors are genes. The alternate forms of the genes are called alleles. Individuals receive one allele for a gene from the mother and the other allele from the father during fertilization. The alleles that are expressed when another form is present is the dominant allele. The alternate form of the gene that can be expressed only when identical form is on the homologous chromosome is the recessive allele. HOMOLOGOUS CHROMOSOMES

Phenotypes vs. Genotypes
S-B-8-1_Heredity PowerPoint Phenotypes vs. Genotypes Phenotypes refer to what is expressed or the organism’s outward appearance. TT and Tt pea plant will be over 6 feet tall. tt pea plant will be under 2 feet tall. Genotypes refers to the specific alleles that make up the organism. A TT pea plant is homozygous Tall while a tt pea plant is homozygous dwarf. A Tt pea plant is heterozygous Tall. Which phenotype is the same as the genotype? If the phenotype is recessive, then the genotype of the individual must be homozygous recessive.

THINK-PAIR-SHARE If the black rabbit and the white rabbit were bred and all the offspring were black, what conclusion can you make? If the hybrid offspring were allowed to mate, would you expect some of the litter to be white? Why? X Answer #1: It is likely that the black fur is dominant. (However you may need more tests to make that distinction since probabilities require more data than one litter.) Answer #2:Yes, if the hybrids are heterozygous, some of their litter should be homozygous for white. Have students check each other’s notes for content. If their partner has more information, give them a minute to copy their notes.

THINK-PAIR-SHARE Are the genotypes homozygous dominant, homozygous recessive, or heterozygous? DdFF RrYy LLww ggSs The letters used in genotypes usually represent the dominant trait, e.g., Y-yellow seed and y-green seed. Decide on traits to represent the genotypes above, and describe the phenotypes. Answer #1: DdFF-heterozygous for D and homozygous dominant for F RrYy-heterozygous for R and Y LLww-homozygous dominant for L and homozygous recessive for w ggSs-homozygous recessive for g and heterozygous for S Answer #2:Answers will vary, check for reasonableness i.e. do the letters represent a dominant trait? DdFF could have dimples and freckles Red flowers with yellow seeds Lacey wings with Brown eyes (white being dominant) Yellow leaves (green being dominant) with stripes

Law of Segregation Mendel’s Explanation Alleles separate when forming gametes. Parents pass only one allele for each trait. Modern Genetics What process ensures that alleles separate during gamete formation? What process ensures that alleles separate during gamete formation? Meiosis Point out that segregation occurs at the end of meiosis I and meiosis II.

Dihybrid Cross Mendel repeated his experiment with plants that are bred true for two traits. He again allowed the F1 generation to self pollinate. Phenotypic ratio: 9:3:3:1 X P F1 F2 315 108 101 32 How did Mendel know that the parent plants were purebred? They parent plants and offspring were identical for those traits. Can you determine the genotype of the F2 generation? 9 R?Y?:3yyR?:3Y?rr:1yyrr Even though the Dihybrid cross shows a phenotypic ratio 9:3:3:1 ratio, they still show a 3:1 phenotypic ratio independently. R-Round r-wrinkled Y-Yellow y-green

Law of Independent Assortment
S-B-8-1_Heredity PowerPoint Law of Independent Assortment Mendel’s Explanation Traits are inherited independently from one another. Modern Genetics What process ensures that genes are randomly assorted among the gametes? Remind students that Mendel did not have a microscope and did not witness mitosis or meiosis. His explanations were based solely on the rules of probability. e.g. He could predict the outcomes of his crosses based on the probabilities

Punnett Squares Punnett Square of Dihybrid Cross British biologist Reginald Punnett used a matrix to show the Laws of Segregation and Independent Assortment. The Punnett Square shows the probability of an offspring having a particular genotype. Parent Genotype RrYy Gametes’ Genotype In 1905, British biologist Reginald Punnett used the matrix to illustrate the Laws of Segregation and Independent Assortment in order to predict the genotype of the offspring from a particular cross.

Using Punnett Squares ♂Bb and ♀Bb
S-B-8-1_Heredity PowerPoint Using Punnett Squares Black colored fur (B) is dominant to tan colored fur (b) in dogs. Suppose you cross two hybrid dogs with black fur. What are the possible phenotypes and genotypes of the puppies? What are the expected ratios for each genotype and phenotype? Both parents are hybrids or heterozygous for black fur. ♂Bb and ♀Bb Step 1 Write the genotypes of the parents. These are sample problems to help students solve genetics problems. Click the mouse for the next step. Step 1: If the genotype of the parents are given, write it down.

Using Punnett Squares ♂ gametes ♀ gametes
S-B-8-1_Heredity PowerPoint Using Punnett Squares Black colored fur (B) is dominant to tan colored fur (b) in dogs. Suppose you cross two hybrid dogs with black fur. What are the possible phenotypes and genotypes of the puppies? What are the expected ratios for each genotype and phenotype? To find the number of different gametes is 2n, where n is the number of heterozygous gene pairs STEP 2 List the different gametes that each parent can make. Step 2: Remind students that 20=1, 21=2, 22=4, 23=8, In this case, there is one heterozygous gene pair then the number of different gametes is 21= 2 different gametes for both the male and female parent. ♂ gametes ♀ gametes B and b B and b

Using Punnett Squares Black colored fur (B) is dominant to tan colored fur (b) in dogs. Suppose you cross two hybrid dogs with black fur. What are the possible phenotypes and genotypes of the puppies? What are the expected ratios for each genotype and phenotype? Since the male and female can make 2 different gametes the grid will be 2 x 2. STEP 3 Make a grid of horizontal and vertical lines. Step 3: Explain that the size of the grid is determined by the number of different kinds of gametes that each parent can make. In this example, each parent can make 2 different gametes so there will be a grid that is 2 x 2.

Using Punnett Squares Black colored fur (B) is dominant to tan colored fur (b) in dogs. Suppose you cross two hybrid dogs with black fur. What are the possible phenotypes and genotypes of the puppies? What are the expected ratios for each genotype and phenotype? ♂ gametes STEP 4 Put the gametes from one parent on the top and the other parent’s gametes on the side. B b Step 4: Each different kind of gamete from the father becomes the head of a row or column. It doesn’t matter whether the father or mother’s gametes head the column or row, it only matters that one parent’s genetic contribution heads the columns and the other parent’s contribution heads the rows. ♀ gametes B b

Using Punnett Squares B b B b BB Bb Bb bb
S-B-8-1_Heredity PowerPoint Using Punnett Squares Black colored fur (B) is dominant to tan colored fur (b) in dogs. Suppose you cross two hybrid dogs with black fur. What are the possible phenotypes and genotypes of the puppies? What are the expected ratios for each genotype and phenotype? STEP 5 Fill in the boxes by copying the row and column headings. B b B b Step 5: Fill in the boxes with the alleles from the column head and with head of the row. Always arrange the alleles so the capital letter comes first in a heterozygous gene pair. Ask students what the last two gene pairs will be before you click. BB Bb Bb bb

} Using Punnett Squares B b BB Bb B b Bb bb
S-B-8-1_Heredity PowerPoint Using Punnett Squares Black colored fur (B) is dominant to tan colored fur (b) in dogs. Suppose you cross two hybrid dogs with black fur. What are the possible phenotypes and genotypes of the puppies? What are the expected ratios for each genotype and phenotype? STEP 6 Determine the phenotypes of the possible offspring. B b B b BB Bb Bb bb Step 6: Count the different genotypes and list the ratios. Remember these are ratios, not number of offspring. It should be read, “There is a probability that 1 of 4 out of 4 puppies will have the genotype BB. There is a 2 out of 4 (or 1 of 2) chance that the puppies genotype will be Bb and a 1 in 4 possibility that a puppy will have the bb genotype.” After the genotypes are counted, determine the phenotypes. Which allele will be expressed with the Bb genotype? Only the dominant allele, black color, will be expressed. Therefore, there is a 3 of 4 probability that the puppies will be black or 1 in 4 chance that a puppy will be tan. 1-BB 2-Bb 1-bb 3-Black colored fur 1-Tan colored fur }

THINK-PAIR-SHARE What would a Punnett square look like for a monohybrid cross of a purple flowered pea plant allowed to self pollinate? What are the genotypic ratios of the monohybrid cross? Answer #1: See illustration Answer #2 1BB: 2Bb:1bb Have students check each other’s notes for content. If their partner has more information, give them a minute to copy their notes. Hand out “Genetics Problems-One Trait” and have students work the practice problems in class or as homework.

Problems with Two Traits
S-B-8-1_Heredity PowerPoint Problems with Two Traits Black colored fur (B) is dominant to tan colored fur (b) in dogs while smooth hair (h) is recessive to wire hair texture (H). Suppose you cross two hybrid dogs with black wiry coats. What are the possible phenotypes and genotypes of the puppies? What are the expected ratios for each genotype and phenotype? Both parents are hybrids or heterozygous for black and wiry coats. Step 1 Write the genotypes of the parents. Explain that solving genetics problems with two traits is like solving problems with one traits. The steps are the same but there are more possible gametes. Before you click on the slide ask the students, “what’s the 1st step in solving a genetics problem is?” ♂BbHh and ♀BbHh

S-B-8-1_Heredity PowerPoint Problems with Two Traits Step 1 Write the genotypes of the parents. ♂BbHh and ♀BbHh BH, Bh, bH, bh ♂ gametes ♀ gametes STEP 2 List the different gametes that each parent can make. BH, Bh bH bh ♂ gametes What is the second step? List the different gametes that each parent can make. How do you know how many different kinds of gametes a parent can make? The number of different gametes is 2n, where n is the number of heterozygous gene pairs How many heterozygous gene pairs are present in each parent? 2 How many different gametes can an individual that is a hybrid for 2 traits (Dihybrid) make? 22=4 Explain that determining the genotype of the gametes is similar to the “distributive property” in algebra. Show students. Which one of Mendel’s Laws does this represent? Law of Segregation and Law of Independent Assortment

S-B-8-1_Heredity PowerPoint Problems with Two Traits STEP 3 Make a grid of horizontal and vertical lines. ♂ gametes BH Bh bH bh STEP 4 Put the gametes from one parent on the top and the other parent’s gametes on the side. What is the next step in solving genetics problems? Make the grid. Remember that the number of gametes determine the number of horizontal and vertical lines. Since each parent can contribute 4 different gametes, How big does the grid need to be? 4 x 4 What is step 4 process? Putting the female gametes at the head of the column and the male gametes at the head of the rows. ♀ gametes

S-B-8-1_Heredity PowerPoint Problems with Two Traits STEP 5 Fill in the boxes by copying the row and column headings. BH Bh bH bh ♂ gametes BH Bh bH bh ♀ gametes BbHh BBHH BBHh BbHH BBHh BBhh BbHh Bbhh What is the next step in solving this genetics problems? Fill in the boxes. Make sure that you keep the same letters together, capital letter first and in alphabetical order. Have students determine the genotypes of the possible offspring before you click the mouse. Which of Mendel’s Laws does this represent? Law of Independent Assortment bbHH bbHh BbHH BbHh BbHh Bbhh bbHh bbhh

S-B-8-1_Heredity PowerPoint Problems with Two Traits STEP 6 Determine the phenotypes of the possible offspring. There is a 9 out of 16 chance that the offspring will have a black wiry coat. BBHH BBHh BBHh BbHH BbHH BbHh BbHh BbHh BbHh There is a 3 out of 16 chance that the offspring will have a black smooth coat. Bbhh Bbhh BBhh Finally, what is the last step in solving genetics problems? Counting and sorting the genotypes and phenotypes There is a 3 out of 16 chance that the offspring will have a wiry tan coat. bbHh bbHh bbHH There is a 1 out of 16 chance that the offspring will have a smooth tan coat bbhh

THINK-PAIR-SHARE In guinea pigs, short hair (H) is dominant to long hair (h) and a short tail (T) is dominant to long tails (t). If a hybrid short hair and tail guinea pig is crossed with a long hair and tail guinea pig, what are the expected genotypic and phenotypic ratios?

Hybrid parent Purebred Parent
S-B-8-1_Heredity PowerPoint Hybrid parent Purebred Parent HhTt hhtt Step 1: Hybrid gametes Purebred gametes HT, Ht, hT, ht ht Step 2: Step 3: HT Ht hT ht Step 4: ht HhTt Hhtt hhTt hhtt Step 5: There is a 1 in 4 chance that the offspring will have short hair and tail Step 6: HhTt There is a 1 in 4 chance that the offspring will have short hair and a long tail Hhtt After reviewing the Think-Pair-Share, hand out, “Genetics Problems 2” from the resource folder. hhTt There is a 1 in 4 chance that the offspring will have long hair and a short tail hhtt There is a 1 in 4 chance that the offspring will have long hair and tail

In pea plants Tall (T) is dominant to Short (t) and Purple flowers (P) are dominant to white (p). Cross two individuals who are heterozygous for both traits. What is the genotype ratio? Phenotype ratio? S-B-8-1_Heredity PowerPoint

Complete Dominance Every example so far has been complete dominance, when one allele completely masks another. Sometimes it’s more complicated than that. S-B-8-1_Heredity PowerPoint

Codominance Codominance is when two alleles are expressed simultaneously. They are dominant together. Ex. People with AB blood type, Roan Horses S-B-8-1_Heredity PowerPoint

Incomplete Dominance Similar to codominance but neither allele is completely expressed. Example: a red flower and a white flower give rise to a pink flower. (red and white are being expressed incompletely. S-B-8-1_Heredity PowerPoint

Sex Linked Traits Genes located on the X or Y chromosome (usually X) Males are more susceptible than Females. Why? S-B-8-1_Heredity PowerPoint

Example: In guinea pigs Black hair (B) is dominant to white (b) and Short hair (H) is dominant to long hair (h). Cross a male that is homozygous recessive for fur color and heterozygous for hair length with a female that is heterozygous for both color and length. List the genotype and phenotype ratios. S-B-8-1_Heredity PowerPoint

In human blood typing, A and B are both dominant and O is recessive. If blood typing displays codominance, what would result from a cross between a male with AB and a female with AO. S-B-8-1_Heredity PowerPoint

Hemophilia is a sex-linked genetic disorder on the X chromosome. If a normal male was crossed with a carrier female, what are the possible genotypes of the offspring? S-B-8-1_Heredity PowerPoint

X Y X Xh S-B-8-1_Heredity PowerPoint

Which sex is most likely to have hemophilia?
XX XY XXh XhY S-B-8-1_Heredity PowerPoint

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