Science 9 Heredity: Inheritance and Variation Module 3 PDF

9 Science 9 Quarter 1 – Module 3: Heredity: Inheritance and Variation AIRs - LM LU_Q1_Science9_Module3 SCIENCE 9 Quarter 1 - Module 3: Heredity: Inheritance and Variation Second Edition, 2021 Copyright © 2021 La Union Schools...

9 Science 9 Quarter 1 – Module 3: Heredity: Inheritance and Variation AIRs - LM LU_Q1_Science9_Module3 SCIENCE 9 Quarter 1 - Module 3: Heredity: Inheritance and Variation Second Edition, 2021 Copyright © 2021 La Union Schools Division Region I All rights reserved. No part of this module may be reproduced in any form without written permission from the copyright owners. Development Team of the Module Author: Lorraine R. Lachica Editor: SDO La Union, Learning Resource Quality Assurance Team Content Reviewer: Lorena C. Delizo Language Reviewer: Ma. Cherry Barrairo Illustrator: Ernesto F. Ramos Jr. Design and Layout: Mariza R. Mapalo Management Team: Atty. Donato D. Balderas Jr. Schools Division Superintendent Vivian Luz S. Pagatpatan, Ph D Assistant Schools Division Superintendent German E. Flora, Ph D, CID Chief Virgilio C. Boado, Ph D, EPS in Charge of LRMS Rominel S. Sobremonte, Ed. D, EPS in Charge of Science Michael Jason D. Morales, PDO II Claire P. Toluyen, Librarian II Printed in the Philippines by: _________________________ Department of Education – SDO La Union Office Address: Flores St. Catbangen, San Fernando City, La Union Telefax: 072 – 205 – 0046 Email Address: [email protected] LU_Q1_Science9_Module3  9 Science Quarter 1 - Module 3: Heredity: Inheritance and Variation LU_Q1_Science9_Module3 Introductory Message This Self-Learning Module (SLM) is prepared so that you, our dear learners, can continue your studies and learn while at home. Activities, questions, directions, exercises, and discussions are carefully stated for you to understand each lesson. Each SLM is composed of different parts. Each part shall guide you step-by- step as you discover and understand the lesson prepared for you. Pre-tests are provided to measure your prior knowledge on lessons in each SLM. This will tell you if you need to proceed on completing this module or if you need to ask your facilitator or your teacher’s assistance for better understanding of the lesson. At the end of each module, you need to answer the post-test to self-check your learning. Answer keys are provided for each activity and test. We trust that you will be honest in using these. In addition to the material in the main text, Notes to the Teacher are also provided to our facilitators and parents for strategies and reminders on how they can best help you on your home-based learning. Please use this module with care. Do not put unnecessary marks on any part of this SLM. Use a separate sheet of paper in answering the exercises and tests. And read the instructions carefully before performing each task. If you have any questions in using this SLM or any difficulty in answering the tasks in this module, do not hesitate to consult your teacher or facilitator. Thank you. LU_Q1_Science9_Module3  Target This module focuses on how genetic information is organized on genes in chromosomes and the different patterns of inheritance. It also describes the location of genes in chromosomes, explain the different patterns of non- Mendelian inheritance and describe the molecular structure of the DNA. Gregor Mendel’s principles form the base for the understanding of heredity and variation. Although Mendel’s work failed to discuss thoroughly the ‘factors or genes he mentioned in his laws of inheritance, his findings prompted other scientists to probe further into the mystery of heredity. Furthermore, it helps and guides the learners to answer the many questions that puzzle them on how traits were being passed from parents to offspring, how unique an organism is and to clarify them about the role of DNA and chromosomes in coding the instructions for traits passed from parents to their offspring. Most Essential Learning competency: Explain the different patterns of non -Mendelian inheritance STL9-Id-29 The module is divided into 4 lessons, namely: ⚫ Lesson 1- Structure and components of DNA ⚫ Lesson 2- Incomplete Dominance ⚫ Lesson 3- Codominance ⚫ Lesson 4- Multiple Alleles ⚫ Lesson 5- Sex Chromosome and Sex Determination After going through this module, you are expected to attain the following objectives: 1. Describe the location of genes in chromosomes. a) Identify the component of DNA molecule b) Explain the chromosomal basis of inheritance 2. Explain the different patterns of non-Mendelian inheritance. 3. Solve genetic problems related to incomplete dominance, codominance, multiple alleles and sex-linked traits. 1 LU_Q1_Science9_Module3  LESSON Structure and 1 Components of DNA Jumpstart Observing Yourself and Others I. Objective Observe some similarities and differences between you and your siblings II. Procedure Observe the differences in the physical traits of your siblings. Identify the features from the list below. TRAIT APPEARANCE Skin color Type of hair Hairline Dimples Nose Lips Earlobes Handedness V. Observation 1. Is there any similarity between you and your siblings? 2. What is the importance of assessing your trait? 2 LU_Q1_Science9_Module3  Discover The information in DNA is stored as a code made up of four chemical bases: the four nucleotide monomers are adenine (A), guanine (G), (Purines) cytosine (C), and thymine (T). (Pyrimidine). The sequence, of these bases determines the information needed for building and maintaining an organism, similar to the way in which letters of the alphabet appear in a certain order to form words and sentences. The four chemical bases form hydrogen bonds between the strands. Adenine complements with Thymine while Guanine compliments with Cytosine. DNA is organized structurally into chromosomes and then wound around nucleosomes as part of those chromosomes. Functionally, it's organized into genes, of which are pieces of DNA, which lead to observable traits. And those traits come not from the DNA itself, but actually from the RNA that is made from the DNA, or most commonly of proteins that are made from the RNA which is made from the DNA. So, the central dogma, so-called of molecular biology, is that genes, which are made of DNA, are made into messenger RNAs, which are then made into proteins. But for the most part, the observable traits of eye color or height or one thing or another of individuals come from individual proteins. Sometimes, we're learning in the last few years, actually, they come from RNAs themselves without being made into proteins- -things like micro RNAs. But those still are relatively the exception for accounting for traits. DNA stores the genetic information that instructs the cell on which proteins to make. So, DNA makes PROTEINS (both are biomolecules!) Responsible for determining all organism’s traits such as eye color, body structure, and enzyme production. https://images.app.goo.gl/Zk5jE6ebYMZ7Z8MYA The backbone of DNA molecule is composed of alternation sugar and phosphate groups. An important property of DNA is that it can replicate, or make copies of itself. Each strand of DNA in the double helix can serve as a pattern for duplicating the sequence of 6 bases. This is critical when cells divide because each new cell needs to have an exact copy of the DNA present in the old cell. DNA is made up of millions of building blocks called nucleotide, which contain 1 sugar (S) nitrogenous base either (cytosine, guanine, thymine or adenine (NB) 1 phosphate (P) 3 LU_Q1_Science9_Module3  https://images.app.goo.gl/gEV1W57yADzNDhfg7 Gene Structure and Chromosomes Gene Gene is the genetic carrier of traits that passed on from parents to offspring. Gene is also considered as basic unit of heredity and made up of DNA. And approximately there are 3000 genes that are organized into chromosomes. Some genes act as instruction to make molecules called proteins. However, many genes do not code for proteins https://images.app.goo.gl/YtZhS9RVv24wyxXH9 Gene Location In 1902 and 1903, Sutton and Boveri published independent papers proposing what we now call the chromosome theory of inheritance. This theory states that individual genes are found at specific locations on particular chromosomes, and that the behavior of chromosomes during meiosis can explain why genes are inherited according to Mendel’s laws. Chromosomes, like Mendel's genes, come in matched (homologous) pairs in an organism. For both genes and chromosomes, one member of the pair comes from the mother and one from the father. It is a thread-like structure found in the nuclei of both animal and plant cells. Chromosomes are carrier of hereditary traits located inside the nucleus of a cell. https://images.app.goo.gl/t31E27eewEdvgRX26 4 LU_Q1_Science9_Module3  Explore Activity 1.1 Objective: Make a DNA origami Materials: Blank DNA template Crayons Scissors Tape or glue Procedures 1. Write the letter of your DNA sequence (A, C, G, or T) in the top right corner and continue your sequence down the column on the right. 2. Write the corresponding complementary bases in boxes diagonally across from your sequence as shown 3. Fold in half lengthwise. Make all creases as firm as possible 4. Hold the Paper so that the thick lines are diagonal and thin lines are horizontal. Fold the top segment down and then unfold. 5. Start coloring the DNA sequence 6. Fold the top two segments down the next horizontal line. Unfold 7. Repeat for all segments 8. Turn the paper over 9. Fold along the first diagonal line. Unfold and fold along the second diagonal line. Repeat for all diagonal line. 10. Fold the white edge without letters up. 11. Fold the other edge away from you. Partly unfold both edges. 12. You can see how the model is starting to twist 13. Twist and turn the paper while pushing the ends towards each other. 14. Now let go! 15. Admire your completed DNA double helix! Guide Question: 1. Describe the shape of the DNA molecule. 2. What are the nitrogenous bases present in the DNA group of purines? 3. What are the nitrogenous bases present in the DNA group of pyrimidine? 4. What is the component that serves as the backbone or side of the ladder of the DNA? 5 LU_Q1_Science9_Module3 1. If we all have the same components of DNA, why do we look different from other people and from other organisms like plants and animals? Deepen Making DNA model using recycled materials Objective: Make a DNA model using recycled materials Materials: Recycled materials Procedure: Choose one of the sequences below. Sequence 1: T A C G T A T G A A A C -or Sequence 2: T G G T T T A G A A T T Gather your supplies. Guide questions: 1. What are the common parts of a nucleotide? 2. What is the one part of the nucleotide that differs among the other different nucleotides? 6 LU_Q1_Science9_Module3 3. What are the different kinds of nitrogen bases? 4. Are there always going to be an equal number of adenine and thymine nucleotides in molecule? Why? 5. Are there always going to be an equal number of guanine and cytosine nucleotides in a molecule? Why? 6-8. The sides of the ladder are made up of alternating _______and_________ molecules. The steps (or rungs) of the ladder are made up of _______ held together by hydrogen bonds. 9-10. What are the chemical base pair of the following? _____ =A, _____=C, _____ =T, _____=G Gauge Match and Pair Direction: Match Column A with those in Column B. Wherein Column A contains word related to genetics while Column B contains the definition. Write the letter of the correct answer on the blank before the number. n Column A Column B 1. Chromosome A. cell division 2. Cytogenetics B. new combinations of genes 3. Mitosis C. carries the hereditary materials 4. Genes D. pairs of genes 5. Recombinant E. segment of DNA 6. Alleles F. study of chromosomes and their role 7. Idiograms G. X and Y 8. Sex chromosomes H. molecular locations of gene on chromosome 9. Phosphate group I. A,T,C,G 10. DNA code J. Backbone or side of the ladder 11. Purine Group K. T,C 12. Pyrimidine Group L. The passing on of characteristics from one generation to the next 13. Heredity M. Chromosome that is made up of DNA tightly coiled proteins. 14. Inheritance N. A thing that is inherited 15. Histones O. A,G 7 LU_Q1_Science9_Module3  LESSON Incomplete Dominance 2 Jumpstart Incomplete dominance it is a form of intermediate inheritance in which one allele which expresses a specific trait is not completely dominant over the another allele which expresses a different trait. This type of interactions results in a third phenotype in which the phenotype of the trait expressed is a combination of the dominant and the recessive phenotypes. Observing Crossing Over of an Organism Objective : Observe the result of crossing between two organisms with different phonotype. Procedure : Describe the differences in the crossing between organisms with its physical traits PINK 1.What did you observe in the illustration? 2.Why does carnation pink is the result of cross-pollination between a red carnation? and a white carnation. 8 LU_Q1_Science9_Module3  Discover Incomplete dominance is a form of intermediate inheritance in which one allele which expresses a specific trait is not completely dominant over the other allele which expresses a different trait. This type of interactions results in a third phenotype in which the phenotype of the trait expressed is a combination of the dominant and the recessive phenotypes. Example: A cross between a red-flowered (RR) and white-flowered (WW) four o’clock flowers (Marabilis jalapa). The resulting flowers have a pink color (RW) as shown in Figure 5. https://images.app.goo.gl/hZ7SQKtPVbHpSPdaA If you look at the Punnett square, you come up with the phenotypic and the genotypic ratio of the possible offspring. Phenotypic ratio: 100% pink Genotypic Ratio: 100% RW 9 LU_Q1_Science9_Module3  Explore Activity 1.1 Objective: Show a cross using a Punnett square. Determine the genotypic and phenotypic ratio of the offspring. Direction: Answer the following problem. R W R W What are the resulting offspring in the Punnett square? What would be the genotypic and phenotypic ratios of the offspring? 1. Show a cross between homozygous gumamela white (WW) x Homozygous gumamela red (RR) W W R R What are the resulting offspring in the Punnett square? What would be the genotypic and phenotypic ratios of the offspring? 10 LU_Q1_Science9_Module3 Activity 2: What’s My Phenotype and Genotype? Objective: Solve genetic problems related to incomplete dominance Procedure: 1. Refer to table below. Table1: Phenotype and genotype of Gumamela flower. Write the genotype and phenotype of the offspring when pink flower is crossed to a white flower. Phenotype Genotype RED RR WHITE WW PINK RW What are the resulting offspring in the Punnett square? What would be the genotypic and phenotypic ratios of the offspring Write the genotypic and the phenotypic ratio of the offspring. Ratio: Genotypic Ratio= Phenotypic Ratio= Deepen Objective: Describe incomplete dominance. Investigate incomplete dominance in your community. Give 7example of incomplete dominance that you observe in your community. Direction: Answer the following questions. 11 LU_Q1_Science9_Module3 Example: ❖ A child with wavy hair as a result of one parent's curly hair and the other's straight hair. Guide Question: What is incomplete dominance? What did you observe in your community? 3.What are the similarities of your given example? 4.Can you see species exhibiting this kind of inheritance in your backyard? 5.How do you recognize incomplete dominance? 6.Does incomplete dominance occur in humans? Gauge Objective: Determine the possible traits in each offspring. Show the phenotype and genotype of the offspring of a monohybrid cross Calculate the phenotypic and genotypic ratio of the offspring. Direction: Answer the following problem. A cross between a bird with blue feathers and a bird with white feathers produces offspring with silver feathers. The color of the birds is determined by only two alleles. 1. What are the genotypes of the parent birds? 2. What is the genotype of the bird with silver feathers? 3. Draw/solve through a punnet square 4. Can you figure out the phenotypic ratios of the offspring of two birds with silver feathers? 5. Can you figure out the genotypic ratio ratios of the offspring of two birds with silver feathers? 12 LU_Q1_Science9_Module3  LESSON Codominance 3 Jumpstart Another non-Mendelian pattern of inheritance is codominance neither of the alleles is recessive or dominant; neither of the gene expression is masked or expressed completely in the presence of the other gene. Instead, there is a blend of the two alleles which creates a new feature. In codominance both the alleles are expressed equally and their features are expressed in the phenotype. Codominance is different from incomplete dominance in a way that the former has both alleles manifesting the phenotypes whereas the latter produces an intermediate phenotype. https://images.app.goo.gl/TJxeiWMYfMCZbNQSA 1.Describe what will happen if black chicken crossed between white chicken? 2. Does the phenotype of a black and white chicken combine? What do you think is the reason? 13 LU_Q1_Science9_Module3  Discover In the codominance inheritance neither of the alleles is recessive or dominant; neither of the gene expression is masked or expressed completely in the presence of the other gene. Instead, there is a blend of the two alleles which creates a new feature. In codominance both the alleles are expressed equally and their features are expressed in the phenotype. Codominance is different from incomplete dominance in a way that the former has both alleles manifesting the phenotypes whereas the latter produces an intermediate phenotype. Below are examples of codominance. 1. Horse color The roan coat color of a horse is due to codominance. Roan is the result when a color appears in conjugation with white and red as shown in Figure 6. It is the graying out of a color, and in horses there are three types of roans: red, bay, and blue. All the colors follow similar co-dominance patterns. https://images.app.goo.gl/kc1ZtLxUKUadSZNr6 2. Flower colors If two plants were crossed to produce white and red flower, and if the alleles of the gene responsible for petal color were dominant in nature, the flower produced by the progeny plant would either be white with red spots or red with white spots https://images.app.goo.gl/Ztg5gfc9NrZgsHLv9 14 LU_Q1_Science9_Module3 3. AB Blood Type People with this blood type have A and B proteins at the same time. The ABO gene determines what blood type a person has, and everyone has two copies of this gene, one from each parent. There are several combinations of blood types that can result, but when a person has both an A and a B allele, it will lead to blood types visible in the blood, AB. Explore Objectives: 1. Describe the location of genes in chromosomes 2. Show the phenotype and genotype of the offspring of a monohybrid cross 3. Give the phenotypic ratios of the offspring Direction: Answer the following problems. Procedure: Read the given problem 1. In some chickens, the gene for feather color is controlled by codominance. The allele for black is B and the allele for white is W. The heterozygous phenotype is known as erminette. a. What is the genotype for black chickens? __________ b. What is the genotype for white chickens? __________ c. What is the genotype for erminette chickens?__________ 2. Show the possible outcome of the cross between two erminette chickens by using the Punnett square. Determine its genotypic and phenotypic ratio of the offspring. Genotypic ratio:_____________Phenotypic ratio:______________________ 15 LU_Q1_Science9_Module3  2. Using a Punnett square, show the offspring of a cross between a homozygous white fur cattle and one that is roan. Give the phenotypes and genotypes of the offspring. Cattle coat color key: CR = red CW= white CWCR or CRCW = roan (where both red and white are expressed) Genotypic ratio:_____ Phenotypic ratio:________________ Deepen Mystery Bull Objective: 1. Determine the possible traits in each offspring. 2. Show the phenotype and genotype of the offspring of a monohybrid cross 3. Investigate the possible offspring Direction: 1. Read the story and answer the following problems. Mang Peping owns purebred red cows. In his farm he noticed that after a typhoon several months ago, all of the fences that separate his cattle from his neighbor’s cattle were destroyed. During the time that the fences were down, three bulls, one from each neighbor, mingled with his cows. For a while, he thought that none of the bulls found his cows, but over the months, he noticed that all of his cows are pregnant. He suspected that one of the bulls is the father. Which bull is it? Help Mang Peping look for the father by solving the given problem. 2.Determine the possible traits of the calves if : a red (RR) bull is mated with a red (RR) cow 1 a red (RR) bull is mated with a white (WW) cow 2 a roan (RW) is mated with a red(RR)cow 3 16 LU_Q1_Science9_Module3  3. Illustrate your answers using a Punnett square. 4. Write your answers on the paper. 5. Will you be able to trace the father of the calves?______________ 6. What are the possible phenotypes of the calves for each cow?________________________________________________ 7. Do you think you will make Mang Peping happy about the result of your investigation? _________________________________ 8. How are you going to explain it to him? ________________________ 9. How would you apply what you have learned to improve the breeds of livestock in your area? _____________________________________________________________ 10. What possible suggestions can you give to animal breeders in your area? Gauge Objective: 1. Show the phenotype and genotype of the offspring of a monohybrid Cross 2. Calculate the genotypic and the phenotypic ratio of the offspring. Direction: 1. Solve genetic problems related to codominance Phenotype: Phenotype: Red Phenotype: Red Genotype: _____ Genotype: _____ Phenotype: Roan Phenotype: Roan Genotype: _____ Genotype: _____ Genotypic Ratio= Phenotypic Ratio= 2. What should be the genotypes and the phenotypes of the parent cattle if the breeder wants to only have white fur cattle. Show your cross on a Punnett square. 17 LU_Q1_Science9_Module3  LESSON Multiple Alleles 4 Jumpstart Alleles are alternative form of a gene that controls a certain trait. Normally, a gene is controlled by only two alleles but there are genes that have two or more alleles. For example, in human, the ABO blood type. In this case three alleles are controlling the blood group, wherein blood type A is codominant with blood type B and blood type O is recessive. The four possible blood types are shown in Table 3 below. https://images.app.goo.gl/MPUEYv5o9nrmPqog9 I. Objective: Describe the given illustration by giving the correct word of the jumbled letter. NEOVIOTLU SEEDRB OMBCDENI IENCHNEARIT DBLOOD 18 LU_Q1_Science9_Module3 II: Guide Question: 1. What can you say to your answers in the jumbled letter? 2. Compare your answers in the jumbled word to the given illustrations 3. What is the main idea of the illustration? Discover Multiple alleles are defined as the type of non-Mendelian inheritance pattern that comprised of more than two alleles that code for a certain characteristic in a species. Multiple alleles mean there is more than two types of phenotypes present. It also depends on the dominant and recessive alleles that are present in the trait and the pattern of dominance the individual alleles follow when they are combined together. Multiple alleles examples: The ABO blood type in humans is a good example of multiple alleles. Red blood cells of humans are of type A (IA), type B (IB) or type O (i). These different alleles that code for blood groups can be combined in different ways by the Mendel's law of inheritance principle. The resulting genotypes are A, B, AB or type O blood group. The blood type A is a combination of two alleles (IA) or one A allele and one O allele (IA i). Similarly with the blood type B, it is coded by two B alleles (IBIB) or one B allele (IB) and one O allele (IBi). The blood type O can only be coded by two o alleles (ii), it is a recessive trait. https://images.app.goo.gl/9fhXN9DXhxPLvFnq8 19 LU_Q1_Science9_Module3  Explore What’s Your Blood Type? Objective: Infer the unknown phenotypes of individuals on the basis of the known phenotypes of their family members. Direction: Solve genetic problems related to multiple alleles. Procedure: 1. Given the blood types of the two family members, determine the possible blood type of the remaining member. Mother’s Blood Type Father’s Blood Type Child’s Blood Type A A B AB AB B O O 2. Determine child’s blood type if a mother has type A (AA) blood and the father has type B (BB) blood. Show your solution using a Punnett square. 3. Write the genotypic and phenotypic ratio of the offspring. Ratio: Genotypic Ratio= Phenotypic Ratio= Deepen Blood Matching Objective: Infer the unknown phenotypes of individuals on the basis of known phenotypes of their family members. Direction: Solve genetic problems related to multiple alleles. Procedure: Read the given problem. 1. Three children recently born in a hospital were accidentally mixed up. The blood types of the parents involved are given along with the blood types of the infants. Determine which baby belongs with which parents. Mother & Father 20 LU_Q1_Science9_Module3  Mother & Father Babie Parent 1 Type A & Type B Child X - Blood Type A Parent 2 Type O & Type AB Child Y - Blood Type O Parent 3 Type B & Type O Child Z - Blood Type AB 2. A man with blood type AB marries a woman with blood type O. Using the Punnett square below; show all possible genotypes of the offspring. Phenotypic Ratio: _______________ Genotypic Ratio: ________________ 3. Could a mother with type B blood and a father with type O blood produce an off spring with type AB? 4. In a paternity case, a woman with blood type O claims a man with blood type A to be the father of her child. Is there any possibility that the woman is correct? If so, show the genotypes of the people involved and likely cross to produce a child with blood type O. Gauge Possible offspring Objective: Show the possible outcome of the cross-blood types. 1: Construct the Punnett square and show the possible outcome of the cross. AB B O B A AB AB O A O 2. Interpret the result 3. Write the genotypic and phenotypic ratio of the offspring. 21 LU_Q1_Science9_Module3  LESSON Sex Chromosomes and Sex 5 Determination Jumpstart Humans have 46 chromosomes in each cell. According to study human body cells show 23 pairs of chromosomes for both males and females. Twenty-two pairs are somatic chromosomes. The 23rd pair consist of sex chromosomes. In human males and some other organism havr non-identical sex chromosome (XY). Females have identical (XX) sex chromosomes. Boy or Girl? Objective: Identify how sex in human is determined Procedure: 1. Draw a punnet square which shows the inheritance of the sex chromosomes. Represent the female sex chromosomes with XX and the male sex chromosome with XY. Guide Question: 1. What will be the sex of a child produced when an egg is fertilized by a sperm that has a Y chromosome? 2. What type of sperm must fertilize an egg to result in a female child? 3. Based on this punnett square, what percentage of children would you expect to be male and female? 22 LU_Q1_Science9_Module3  Discover Sex linked genes are genes that are in the sex chromosomes and that are therefore inherited differently between males and females. In mammals, were the female has two X chromosomes (XX) and the male has one X and one Y chromosome (XY), recessive genes on the X chromosome are more often expressed in males because their only X chromosome has this gene, while females may carry a defective recessive gene on one X chromosome that is compensated by a healthy dominant gene on the other X chromosome. Common examples of sex-linked genes are those that code for colorblindness or those that code for hemophilia (inability to make blood clots) in humans. EXAMPLE OF X-LINKED TRAIT 1. Colorblindness Colorblindness is a recessive gene that is only expressed on the X chromosome (let’s use X* for the X chromosome carrying the recessive colorblind gene). If a male receives the colorblind gene from the mother, this individual will be colorblind (X*Y). If, on the other hand, a female receives one colorblind gene (either from the mother or the father) and another healthy gene (not colorblind, either from the mother or the father), then this female organism (XX*) will not be colorblind because the healthy gene is dominant and the recessive colorblind gene will not be expressed. She will be however, a carrier, which implies that she can pass on the colorblind gene to her offspring. Finally, if a female receives a colorblind gene from the mother and another colorblind gene from the father, this female will be colorblind (X*X*). 2. HEMOPHILIA Hemophilia is a sex-linked disease. It is a recessive disorder and it impairs the ability to clot blood, this happens due to the missing blood clotting factor. The alleles of hemophilia are present on the X chromosome. Most of the males have this disorder, females also have this disease, but the cases are few. Example Of A Y-Linked Trait: *Y-linked traits never occur in females, and occur in all male descendants of an affected male. Hypertrichosis Pinnae Auris Hypertrichosis pinnae auris, a genetic disorder in humans that causes hairy ears. Since the trait is found in the Y chromosome, then the only males can have the trait. A father who has the condition will pass it on to all his sons, and they, in turn, will pass it. 23 LU_Q1_Science9_Module3 Sex-Limited Traits Sex-limited genes are autosomal genes (genes located on autosome chromosomes, i.e., not located on the sex chromosomes) that affect traits which appear only in one sex, but not in the other sex. Traits of this kind are called sex- limited traits e.g., milk production in dairy cattle, the formation of breast in human and the ability to produce eggs in chicken. The genes involved in these traits operate in females but not in males. Sex-Influenced Traits The expression of some gens may be sex influenced. The traits controlled by these autosomal genes appear in either sex, but either the frequency of occurrence in the two sexes are different or the relationship between genotype and phenotype is different. An example is pattern baldness in humans, though the condition is not restricted to males. This gene has two alleles, “bald’ and “non-bald.” The behaviors of the products of these genes are highly influenced by the hormones in the individual, particularly by the hormone testosterone. Explore Are You an XX or XY? Objective: In this activity you will learn how sex in human is determined. Procedure: Study the Punnett square and complete the statements below. X Y X X 1.The sex of the child produced is ______ if the egg is fertilized by an X bearing sperm. 2. The sex of the child produced is ______ if the egg is fertilized by a Y bearing sperm. 3. The ____ sex chromosome is present in both male and female. 4. There is _____ % chance of having male child. 5. The ____ sex chromosome determines the person’s sex. 24 LU_Q1_Science9_Module3  Good job scientist! Now that you are familiar with the sex chromosomes, always remember that they also carry genes, which are factors of heredity. Deepen My X and Ys Objective: Solve problems related to sex-linked traits Direction: Answer the given genetic problem. Procedure: For each of the following crosses remember that hemophilia and color blindness are recessive sex-linked traits in humans. In sex linked traits men will always express the trait if they carry it on the X chromosome. Women can express the trait only if it is found on both X chromosomes. Women have two normal phenotypes: homozygous normal and carrier. Men have only one normal phenotype because they have only one X chromosome. Hemophilia for example: Normal Male: XH Y Hemophiliac Male: XhY Normal Female: XHXH&XHXh (carrier) Hemophiliac Female: XhXh *Draw a punnett square to solve the problem. 1. A woman that is a carrier of hemophilia marries a hemophiliac man. What is the probability that their children will be a hemophiliac? 2. A hemophiliac woman has a mother who is phenotypically normal. What are the genotypes of her mother and her father? 3. What is the probability that a normal vision woman who marries a man who is color blind will have a daughter who is color blind. 25 LU_Q1_Science9_Module3  Gauge Objective: 1. Give the genotypic and phenotypic ratios in the offspring if the mother is bald and the father is not bald. Direction: Solve the given problem If you look at the heterozygous gene pair of baldness (Bb), males’ express baldness, while females do not. Baldness may be expressed in females but it occurs more frequently in males. Such trait is sex-influenced because of a substance that is not produced equally in males and females. Procedure: Perform a cross using a Punnett square. Male Genotypes Male Phenotypes XYBB Male bald XYBb Male bald XYbb Male nonbald Female Genotypes Female Phenotypes XXBB Female bald XXBb Female nonbald XXbb Female nonbald 1. Interpret the result 2.Write the phenotypic and genotypic ratio 26 LU_Q1_Science9_Module3 Answer Key 27 LU_Q1_Science9_Module3 28 LU_Q1_Science9_Module3 References Alvarez, L., Angeles, D., Apurada, H., Carmona, M., Lahorra, O., Marcaida, J., Olarte, M., Osorio, E., Paningbatan, D., Rosales, M. and Delos Santos, M., 2014. Science-Grade 9 Learner's Module. 1st ed. Pasig City: Department of Education, pp.28-47. Aquino, M., Madriaga, E., Valdoz, M. and Biong, J., 2017. Science Links 9. Revised ed. Sampaloc,Manila: Rex Book Store,Inc, pp.44-55. Angeles, Delfin, Lieza Crisostomo, Darwin Quinsaat, and Salina Toledo. 2013. Science Vistas 9. Makati City: Salesiana Books by Don Bosco Press. Bergmann, D. C. (2011). The chromosomal theory of heredity. In Genetics lecture notes. Biosci41, Stanford University, 21 Dominance (genetics). (2015, November 3). Retrieved November 21, 2015 from Wikipedia: https://en.wikipedia.org/wiki/Dominance_%28genetics%29. Genome News Network. (2004). Theodor Boveri (1862-1915) and Walter Sutton (1877-1916) propose that chromosomes bear hereditary factors in accordance with Mendelian laws. In Genetics and genomics timeline. Retrieved from http://www.genomenewsnetwork.org/resources/timeline/1902_Boveri_Sutton.php https://www.slideshare.net/MMASSY/gene-action-and-modification-of-mendelian http://mail.nlesd.ca/~patrickwells/biology/genetics/sexlinked.html http://mail.nlesd.ca/~patrickwells/biology/genetics/incomplete.html 29 LU_Q1_Science9_Module3  For inquiries or feedback, please write or call: Department of Education – SDO La Union Curriculum Implementation Division Learning Resource Management Section Flores St. Catbangen, San Fernando City La Union 2500 Telephone: (072) 607 - 8127 Telefax: (072) 205 - 0046 Email Address: [email protected] [email protected] 30 LU_Q1_Science9_Module3