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Chapter 8 Part Two

Chapter 8 Part Two. By: Brianna Shields. Punnett Squares. 1. Diagram that predicts the outcome of a genetic cross by considering all possible combinations of gametes in the cross. Mendel’s Study of Traits. Punnett Squares. 2. 4 boxes in a large square

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Chapter 8 Part Two

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  1. Chapter 8 Part Two By: Brianna Shields

  2. Punnett Squares 1. Diagram that predicts the outcome of a genetic cross by considering all possible combinations of gametes in the cross Mendel’s Study of Traits

  3. Punnett Squares 2. 4 boxes in a large square 3. One parent’s gametes written across top, other down left side 4. Fill boxes by combining alleles from top and left sides (creates possible genotypes) Mendel’s Study of Traits

  4. Punnett Squares 5. Steps: A. Set up boxes B. Create dominant and recessive key C. Write parental gametes across top and down left side D. Perform monohybrid cross E. Record genotype percentages F. Record phenotype percentages Mendel’s Study of Traits

  5. Punnett Example: TT x Tt T T Genotypes: 50% TT Homozygous Dominant 50% Tt Heterozygous TT TT T Tt Tt t Phenotypes 100% Tall T= Tall t=Short

  6. Complete the Cross • Brown eyes is dominant. Blue eyes is recessive. Cross a homozygous dominant and a homozygous recessive. • What percentages of blue-eyed and brown eyed offspring will you get?

  7. Punnett Example: BB x bb B B Genotypes: 100 % Heterozygous Bb Bb b Bb Bb b Phenotypes 100% Brown Eyed B= Brown b=Blue

  8. Perform the cross • A couple is hoping their child will have the tongue rolling ability when it is born. • Tongue rolling is a dominant trait. Non tongue rolling is recessive. • If the mother is heterozygous and the father is heterozygous- what are their chances of having a child with the tongue rolling ability?

  9. Punnett Example: Rr x Rr R r Genotypes: 25% Homozygous Dominant 50% Heterozygous 25% Homozygous Recessive RR Rr R Rr rr r Phenotypes 75% Tongue Rolling 25% Non-tongue Rolling R= Tongue Rolling r= Non-tongue Rolling

  10. Punnett Squares 6. Used by horticulturists and animal breeders to predict the crosses that will most likely produce offspring with desirable phenotypes Mendel’s Study of Traits

  11. Determining homo and heterozygosity Test Cross- individual with dominant phenotype but unknown genotype is crossed with a homozygous individual Ex: Yellow seeded (Y?) crossed with green seeded (yy) If all offspring yellow, their genotype must by Yy and unknown parent must be YY If half are yellow, half are green, unknown parent must’ve been Yy Mendel’s Study of Traits

  12. Probability Likelihood that a specific event will occur (used to predict genetic crosses) Number of one kind of possible outcome divided by total number of all possible outcomes Mendel’s Study of Traits

  13. Probability Ex: Probability of flipping a coin and getting heads is 1/2 Ex: Probability of a eertain seed color when there are 2 possible alleles for seed color is 1/2 Mendel’s Study of Traits

  14. Probability Probability of the outcome of a cross (getting an allele from one parent is separate from getting an allele from the other) 1/2 x 1/2 equals 1/4 (2 independent events occurring should be multiplied) Mendel’s Study of Traits

  15. Pedigree Family history that shows how a trait is inherited over generations Useful in tracking genetic disorders to see if an individual is a carrier or may pass it the disorder to their offspring Click here to watch a tutorial about pedigrees Mendel’s Study of Traits

  16. Carrier Heterozygous for an inherited disorder but does not show symptoms of the disorder Mendel’s Study of Traits

  17. Autosomal Traits Occur on chromosomes not related to gender Appear in both sexes equally Mendel’s Study of Traits

  18. Sex-linked Traits Trait whose allele is located on x chromosome Most are recessive Males mainly affected because they only have one x chromosome Females usually just carriers (presence of dominant trait to mask recessive one) Females would have to be homozygous recessive to show trait (less likely to inherit) Mendel’s Study of Traits

  19. Autosomal Dominant Condition Every individual with trait has a parent with the trait Mendel’s Study of Traits

  20. Autosomal Recessive Condition Individual can have one, two or no parents with the condition because trait is recessive Mendel’s Study of Traits

  21. Diagram: Who are the carriers? Who is infected?

  22. Assessment Three • Predict the expected phenotypic and genotypic ratios among the offspring of two individuals who are heterozygous for freckles (Ff) by using a punnett square • Summarize how a test cross can reveal the genotype of a pea plant with round seeds • Calculate the probability that an individual heterozygous for a cleft chin (Cc) and an individual homozygous for a cleft chin (cc) will produce offspring that are homozygous for a cleft chin • When analyzing a pedigree, how can you determine if an individual is a carrier (heterozygous) for a trait being studied?

  23. Polygenic Trait When several genes influence a trait (all on one chromosome or on different) Ex: Eye color, height, weight, hair and skin color Have degrees of intermediate conditions between extremes Can be complex due to independent assortment and crossing over during meiosis Complex Patterns of Heredity

  24. Intermediate Traits Incomplete dominance- an individual displays a trait that is intermediate between the two parents Ex: white snapdragon x red snapdragon equals pink snapdragon Ex: curly hair x straight hair (both homoz dom) equals wavy hair Complex Patterns of Heredity

  25. Multiple Alleles Genes with three or more alleles EX: ABO blood groups A and B refer to carbohydrates on surface of red blood cells, O has none A and B dominant over O, but not over each other (codominant) Can only have 2 of the possibilities for the gene Complex Patterns of Heredity

  26. Possible Blood Type Possibilities

  27. Possible Blood Type Possibilities

  28. Codominance 2 dominant alleles are expressed at the same time and both forms of the trait are displayed Ex: AB blood group (has both A and B carbohydrates on the surface of red blood cells) Complex Patterns of Heredity

  29. Traits influenced by environment EXAMPLE 1: Hydrangea flowers Blue (acidic soil) to pink (neutral to basic soil) Complex Patterns of Heredity

  30. Traits influenced by environment EXAMPLE 2: Arctic Fox During summer, fox produces enzymes that make red brown pigments In cold, pigment producing genes don’t function and coat remains white Fox blends in with snowy white background Complex Patterns of Heredity

  31. Traits influenced by environment EXAMPLE 3: Siamese Cats Genotype results in darker fur color in cooler areas of the body (ears, nose, paws, tail darker than rest of body) Complex Patterns of Heredity

  32. Traits influenced by environment EXAMPLE 4: Human Height Nutrition and internal environmental conditions Complex Patterns of Heredity

  33. Traits influenced by environment EXAMPLE 5: Human Skin Color Exposure to sun Complex Patterns of Heredity

  34. Traits influenced by environment EXAMPLE 6: Human Personality Aggression influenced by environment and genes Complex Patterns of Heredity

  35. Traits influenced by environment Twins used to study environmental influences because their genes are identical, any differences between them are due to the environment Complex Patterns of Heredity

  36. Genetic Disorders Harmful effects produced by inherited mutations Damaged or incorrectly copied genes can result in the production of faulty proteins Mutations are rare, due to efficient correction systems in cells Often carried by recessive alleles in heterozygous individuals Genetic Disorders

  37. Genetic Disorders

  38. Sickle Cell Anemia Caused by mutated allele that produces defective form of protein hemoglobin In rbc’s, Hb binds to and transports oxygen Causes sickle shaped red blood cells that rupture easily, clog blood vessels and can’t transport oxygen well Carriers exposed to malaria can prevent infection when they have sickle cell. It kills malaria protozoans and healthy rbc’s can still transport enough oxygen Genetic Disorders

  39. Cystic Fibrosis Fatal, recessive trait Most common inherited disorder in Caucasians 1/25 babies are carriers 1/2500 babies have disease No known cure Have defective copy of gene needed to pump Cl in and out of cell Lung airways clog with mucus, liver and pancreas ducts get blocked Genetic Disorders

  40. Hemophelia Sex linked trait Impairs blood’s ability to clot Mutation on one of a dozen blood clotting genes on x chromosome is hemophelia A If male receives defect on x chromosome from mother, y chromosome can’t compensate - develops disease Genetic Disorders

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