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AP Biology Ch. 11 Inheritance
The document outlines the principles of genetics, primarily based on Gregor Mendel's experiments with pea plants, which established key concepts like dominance, segregation, and independent assortment. It covers various modes of inheritance including complete dominance, incomplete dominance, and codominance, as well as more complex patterns such as polygenic inheritance, epistasis, and X-linked traits. Additionally, the document explains how to utilize Punnett squares to predict the outcomes of genetic crosses and the implications of Mendel's work on understanding inheritance patterns in organisms.
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AP Biology Ch. 11 Inheritance
- 1. War m up Match the items on the left with one item on the right 1. HH A. heterozygous 2. Curly hair B. homozygous 3. Hh C. phenotype 4. Genotype D. tt
- 2. Hel pf ul CrashCourse Biology Hank Green Bozeman Biology Paul Anderson
- 3.
- 4. Main Topics GregorMendel’s work Mendel’s Laws Dominant/recessive Heterozygous/homozygous Alleles Codominance and incomplete dominance Epistasis, Pleiotropy, Multifactorial Inheritance, Polygenic Traits
- 5. The father ofgenetics Gregor Mendel is considered the Father of Genetics Born in 1822 Studied math & physics at an Austrian university He was the first person to study how traits are passed along from one generation to the next. He did his work with the pea plant Who’s your daddy?
- 6. Mendel’s Garden Analyzed observabletraits of peas growing in his monastery garden.
- 7. Mendel’s Garden Eightyears & 20 volumes of data and analysis on 7 distinctive traits Published in 1865
- 8. Why peas? Thegarden pea was a good choice for a variety of reasons. The garden pea: is easy to raise produces large numbers of offspring reproduces quickly has flowers which are self fertilizing but can be easily crossed to other varieties
- 9. Experimental Approach Can alsobe cross-fertilized by human manipulation
- 10. Mendel cross-fertilizedtrue-breeding garden pea plants having clearly contrasting traits
- 12. Allele for purpleflowers Homologous pair of chromosomes Allele for white flowers Locus for flower-color gene
- 13. Mendel's Theory of Segregation Diploid organisms inherit two genes per trait Each gene segregates from the other during meiosis so that each gamete will receive only one gene per trait
- 14. How can theChances of an Offspring’s Traits be Determined? The chance of an offspring showing a certain trait can be determined by using the Punnett square. The table contains spaces for the parent’s gametes and the possible offspring from that mating. The alleles are represented by their letters. Genes come in pairs and must be separated during gamete formation. These gametes (letter) of each pair are placed in each of the outside spaces. They are then combined to form the possible offspring.
- 15. Punnett Square: BbX Bb bbBbb BbBBB bBGametes
- 16. Monohybrid Crosses Mendel'sfirst experiments One trait Monohybrid crosses have two parents that are true-breeding for contrasting forms of a trait.
- 17. All theoffspring from the first cross showed only 1 form of the trait This trait seemed “stronger” so he called it DOMINANT When he crossed the offspring from the first cross, the other form of the trait reappeared, but only 1/4 of the time This trait seemed “weaker” so he called it recessive
- 18. Predicting the Outcome Whydoes one form of the trait disappear in the first generation (F1), only to show up in the second generation (F2)??
- 19. Artificial selection:populations could evolve (i.e. change) if members show variation in heritable traits Variations that improved survival chances in the wild would be more common in each generation This idea is known as natural selection Prevailing Theories
- 20. Mendel’s Experiments Naturalselection did not fit with prevailing view of inheritance-blending Blending would produce uniform populations; such populations could not evolve
- 21. Mendel’s Experiments Manyobservations did not fit blending A white horse and a black horse did not produce only gray horses
- 22. Test (Back) Crosses To support his concept of segregation, Mendel crossed F1 plants (Pp) BACK with homozygous recessives (pp) What ratio would Mendel have gotten? He didn’t know the letter combination of the F1 plants. The test (back) cross allowed him to figure it out
- 23. Dominant phenotype, unknown genotype: PPor Pp? If PP, then all offspring purple: p p P P Pp Pp Pp Pp If Pp, then 1 2 offspring purple and 1 2 offspring white: p p P P pp pp Pp Pp Recessive phenotype, known genotype: pp His back crossed supported his idea of 2 “factors” for each individual, and the idea that those “factors” are segregated
- 24.
- 25. Predicting the Outcome Whatis the predicted PHENOTYPIC ratio and the predicted GENOTYPIC ratio that Mendel saw?
- 26. Predicting the Outcome The F2 results showed 9/16 were tall and purple- flowered and 1/16 were dwarf and white- flowered-as were the original parents; however, there were 3/16 each of two new combinations: dwarf purple-flowered and tall white-flowered.
- 27. Out comes Monohybrid crosses Bothparents HETEROZYGOUS 3:1 phenotype Dihybrid crosses Both parents HETEROZYGOUS 9:3:3:1 phenotype
- 28. Theory of IndependentAssortment Each gene of a pair tends to assort into gametes independently of other gene pairs on non-homologous chromosomes
- 29. Theory in Modern Form Genes located on non- homologous chromosomes segregate independently of each other
- 30. Practice with yourneighbor For the following questions Work with your neighbor to answer the question. Answer the multiple choice question then, Use your notes to determine which one of Mendel’s principles it demonstrates
- 31. 1. A fathercarries 2 alleles for the gene for widow’s peak. He carries one dominant allele and one recessive allele. His gametes will a. All contain the dominant allele b. All contain the recessive allele c. ½ will get the dominant allele and ½ will get the recessive allele d. Each gamete will get both the dominant and the recessive allele
- 32. Which principle doesquestion number one best demonstrate? Principle of Segregation The dominant allele goes to one gamete and the recessive allele goes to another gamete
- 33. 2. A motherthat is homozygous dominant for bushy eyebrows (BB) and heterozygous for round ears (Rr). The gametes she can make will a. All have a B and a R in them b. ½ will have a B and ½ will have a R or a r in them c. ½ will have a B and a R and ½ will have b and r d. ½ will have B and R and ½ will have B and r
- 34. What principle doesnumber 2 demonstrate? The Principle of Independent Assortment All gametes will have a B, since mom only has B. The big B can be with the big R or the big B can be with the little r.
- 35. 3. In meiosis,a diploid cell divides twice to form 4 haploid gametes. Each gamete contains: a. A complete set of DNA identical to the parents b. A ½ set of DNA, with just one copy of each chromosome c. Homologous pairs of chromosomes d. Multiple copies of chromosomes, depending on which ones moved during meiosis
- 36. Which one ofMendel’s Principles does number 3 demonstrate? Principle of Segregation All the homologous pairs of chromosomes separate so that there is just one of each pair in each gamete.
- 37. 4. When Mendelcrossed a true breeding green pea plant (GG) with a true breeding yellow pea plant (gg), the offspring plants were a. All green b. All yellow c. ½ green and ½ yellow d. Green and yellow mixed
- 38. Which one ofMendel’s principles does number 4 demonstrate? Principle of Complete Dominance All offspring were Gg, and the dominant allele (G) masked the recessive allele (g)
- 39. 5. Mendel wantedto know if the color for pea seeds was linked to the shape of the pea seeds. He crossed a green, wrinkled seed plant (Ggrr) with a yellow, smooth seed (ggRr) plant. The offspring produced were: a. All green and wrinkled b. All yellow and wrinkled c. All green and smooth d. All yellow and smooth e. Some of each of the above
- 40. Which one ofMendel’s Principles does number 5 demonstrate? Principle of Independent Assortment The green trait can go with the smooth or the wrinkled trait The yellow trait can go with the smooth or the wrinkled trait
- 41. Mendel’s Work Thework that Mendel did helped explain patterns of inheritance in eukaryotes. But Mendel worked with traits that had a clear dominant/recessive pattern. Also, the traits he worked with were all controlled by a single gene.
- 42. Different Patterns ofInheritance As we now know, many traits do not follow Mendelian Inheritance patterns.
- 43. Degr ees ofDomi nance Complete Dominance - BB and Bb = same phenotype Incomplete Dominance - Bb has in- between phenotype Codominance - Bb has both B and b phenotype
- 44. Co-dominance When both allelesare expressed equally in the heterozygous individual. A and B blood type alleles are co-dominant, because a person with AB genotype will have both A and B blood proteins. Black and orange color in cats are co-dominant, because a heterozygous female will have both orange and black hair.
- 45. Incomplete Dominance Bothalleles are blended together in the heterozygous individual. Dominant allele cannot completely mask the expression of another
- 46. Multiple Alleles traitscontrolled by more that one gene (2 alleles) and so they have many different possible phenotypes. These alleles can show dominant/recessive patterns or codominant patterns.
- 47. Bl ood Types Genotypeof offspring Phenotype of offspring A i Ai B AB iA i A iA iA iB iB B iB i B ii o
- 48. Rh f actor Rh factor Possible genotypes Rh+ Rh- +/+ or +/- -/-
- 49. So farwe’ve only looked at how a single gene pair affects phenotype More often - multiple genes involved 2 primary cases: 1. 2 or more genes affect a single trait 2. 1 gene affects the phenotype of another gene
- 50. Epi st asis ( s t a nd i ng up o n) - 2 or mor e genes af f ect a si ngl e t r ai t Labs can be black, yellow, or chocolate
- 51. Black isdominant to chocolate BB and Bb = black bb = chocolate
- 52. AND -another gene P codes for whether or not any pigment is put into the hair PP and Pp = hair has pigment and dog will be black (BB or Bb) or brown (bb) pp = no hair pigment and dog will be yellow, regardless of the “b” alleles
- 53. So inthis case, the P gene “stands upon” the B gene P is epistatic to B We don’t get the classic 9:3:3:1 but some other version of it
- 55. Pl ei otropy A single gene can have multiple effects on phenotype e.g. pleiotropic alleles --> multiple symptoms of sickle cell anemia (pain, jaundice, infections, fatigue, etc)
- 56. Pol ygeni cInheri t ance 2 or more genes affect a single phenotypic trait Eye color, skin color, height
- 57. Skin coloris controlled by at least 3 separate gene pairs Genotype AABBCC would be very dark skin Genotype aabbcc would be very light skin Any other combination would be intermediate
- 58. And, ofcourse, skin color is also influenced by your environment - multifactorial inheritance
- 59. X-linked traits genesfound on the X chromosome. show different inheritance patterns in men than in women. X-linked traits may show dominant/recessive or codominant patterns.
- 60. X-linked traits Womenhave 2 X- chromosomes, men have an X and a Y. For women to express a recessive phenotype, they must inherit 2 X- chromosomes, both with the recessive allele. For men to express the recessive phenotype, they need only 1 recessive X
- 61. DNA in organelles DNA is also found in mitochondria and chloroplasts. Mitochondrial DNA is only passed from Mother to child.