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KEY | Biology: All Inheritance Patterns (Genetics Review WS) Directions: Answer the following questions and complete the Punnett Squares and Pedigree Charts. Autosomal Recessive Inheritance 1) Mendel noticed that when a tall (T) plant and a short (t) plant were crossed, all the offspring were tall in height. Cross a heterozygous tall plant with a short plant. Complete the Punnett square below to support your answer. T
t t T t t t
t T t
t t
a. What are the genotypes of each parent? T t, t t b. Which trait is dominant? Tall 2) What is the probability of getting a: c. Tall pea plant? 2/4 = 50% d. Hybrid pea plant? 2/4 = 50% Sex‐Linked Inheritance 6) The gene for normal blood clotting (Xh) is dominant to the gene for Hemophilia (XH), which is a sex‐linked recessive disorder found on the X‐chromosome of males and females. Marge is a healthy carrier of hemophilia and Homer is completely healthy. What would be Bart, Liza, and Maggie’s genotypes? Complete the Punnett square and pedigree chart for all mentioned in the story. Draw your Punnett Square below 3) Find the following ratios: a. Genotypic: 0 : 2 : 2 b. Phenotypic: 2 : 2 4) Phenylketonuria (PKU) is a recessive condition where sufferers lack an enzyme to break down tyrosine in their diet. This condition, if left untreated, causes brain damage and retardation. Both Rita and Dexter are carriers of this disorder and do not suffer from any symptoms. Their son, however, has PKU. Complete the Punnett square and pedigree chart for all mentioned in the story). H
h
H H H h Draw your pedigree chart below h
H h H h H h h h h h a. What are the phenotypes of each parent? Carriers of PKU 5) What is the probability of getting: b. Two healthy children? ¾ x ¾ = 9/16 = 56% c. A child who carries the disorder? 2/4 = 50% X X
X X X Xh Y
X Y Xh Y X Xh a. What is the genotype of Marge? X Xh Homer? X Y X X or X Xh X Y X Y or Xh Y X X or X Xh d. A child who has PKU? ¼ = 25% e. A Homozygous recessive child? ¼ = 25% f. If their child is a carrier of PKU, does this mean the child has the disorder? Explain: If a child is a carrier of PKU the child does not have the disorder, they just have the allele. In order to have a austosomal recessive trait you have to inherit TWO recessive alleles. b. Daughter with hemophilia? 0% c. A carrier? ¼ = 25% d. Son with hemophilia? ¼ = 25% e. Healthy child? ¾ = 75% 8) Can males be carriers of sex‐linked traits? Explain: Males cannot be carriers of sex‐linked traits because they only have one X and Y chromosome. The benefit to having two X chromosomes (like women) is that this allows for a second copy of a gene to hide it’s expression. 9) Duchene Muscular Dystrophy (DMD) is a sex‐linked recessive disorder found on the X chromosome. Sufferers with DMD (Xd) lack the protein called dystrophin. Because sufferers lack this protein, their muscle cells wear away sooner than those unaffected causing early death. Abby is homozygous recessive for DMD and Ray is healthy. They want to know, if they have a son, what his genotype will be? Create a Punnett square & pedigree chart for all mentioned in the story. Draw your Punnett Square below Draw your pedigree chart below d
d
d
d
d
d
a. What is the genotype of Abby? Xd Xd Ray? X Y 10) What is the probability of getting a: X
X Draw your pedigree chart below 7) What is the probability of getting a: H
e. Purebred plant? 2/4 = 50% Draw your Punnett Square below h
X X
X X X X Y
X Y X Y Xd Xd Xd Y b. A child with DMD? 2/4 = 50% c. Girl with DMD? 0% d. Homozygous child? 0% e. If this couple has a boy, what are the chances that the boy will have DMD? 100% X Y Autosomal Dominant Inheritance Codominant Inheritance 11) Huntington’s disease (abbrev. HD) is a dominant disorder where only 1 copy of a defected allele will cause the sufferer to lose brain function and eventually die. Russ and Leslie met at a HD support clinic and both contain the HD allele. However, they still want to plan a future together and what to know the chances of having a child without HD. Create a Punnett square and pedigree chart for all mentioned in the story (use “H” = HD and “h” = no HD). Draw your Punnett Square below Draw your pedigree chart below a. List the genotypes of each parent? H h, H h 12) What is the probability of getting a: b. A healthy child? ¼ = 25% c. A heterozygous child? 2/4 = 50% d. A homozygous dominant child? ¼ = 25% 17) Define codominance: When both alleles are dominant and equally and fully expressed. The colors do NOT H h H H H H h H h h
H h h h H H, H h, or hh H h blend together, but are equally seen. 18) There are 3 alleles for blood (A, B, O). A and B are both dominant, and only O is recessive. Keva has heterozygous type B blood and Kobe has type O blood. Complete the Punnett Square below. a. What is Keva’s genotype? B o Kobe’s? o o 19) What is the probability of getting: b. The same genotype as Keva? 2/4 = 50% c. The same phenotype as Kobe? 2/4 = 50% d. A child with codominant blood? 0% e. A child with homozygous B blood? 0% o
B o o o o
B o o o Additional Review Questions: 20) What is the point of a Punnett Square? Shows all the PROBABLE outcomes of crossing genotypes. 21) What is the Law of Segregation? The Law of Segregation states that organisms inherit two copies of each gene, one from each parent. Organisms donate only one copy of each gene in their gametes. 22) a. In terms of genetic material, what do you inherit from your mother? 22 autosomes and an X chromosome. Incomplete Dominance Inheritance b. Your father? 22 autosomes and either an X or Y chromosome. 13) Define incomplete dominance: 23) List and explain one example of how environment and genotype can interact. A heterozygous phenotype when neither allele is completely dominant nor completely recessive. 14) Circle the answer: Would you describe incomplete dominance or codominance as a blend of phenotypes? 15) Think about the flower color problems we previously did in class. How could one create all three colors at a time (red, pink, white)? Support your answer with a Punnett Square. a. What are the phenotypes of each parent? Pink, Pink 16) What is the probability of getting: b. White flowers? ¼ = 25% c. Homozygous flowers? 2/4 = 50% d. Heterozygous flowers? 2/4 = 50% R W R R R W R W o
B R W W W Phenotype is more than geneotype expression. Height is an example of how genotype and environment interact. If you live in an environment where there is not enough nutrition then it is possible that this interaction can negatively affect the expression of the genotype (meaning you could not reach your potential height). Other examples include hair color, skin color, sex of sea turtles. 24) What is a polygenic trait? List an example: A polygenic trait is a trait that is produced by two or more genes. Skin color is a result of 4 genes interacting with one another, eye color is a result of at least 3 genes interacting, and fur color in mammals is a result of at least 5 genes interacting to create one phenotype. 25) Describes what happens in epistasis. An epistatic gene can interfere with the expression of other genes. For example, albinism is a result of a single epistaic gene interfering with the expression of pigment in organisms.