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Pedigrees. These are diagrams that show the inheritance of characteristics within families They allow us to determine the pattern of inheritance and predict.

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Presentation on theme: "Pedigrees. These are diagrams that show the inheritance of characteristics within families They allow us to determine the pattern of inheritance and predict."— Presentation transcript:

1 Pedigrees

2 These are diagrams that show the inheritance of characteristics within families They allow us to determine the pattern of inheritance and predict characteristics of future offspring Conventions include

3 Autosomal dominant recessive crosses Pedigrees will show 2 phenotypes. Crossing a homozygous dominant with a homozygous recessive leads to heterozygous offspring with the dominant trait Crossing 2 heterozygous individuals leads to offspring which could show either trait B_ bb B_ Bb BB Bb bbB_

4 Autosomal co-dominant crosses Pedigrees will show 3 phenotypes. Crossing a homozygous dominant with a homozygous recessive leads to heterozygous offspring with the intermediate trait Crossing 2 heterozygous individuals leads to offspring which could show any of the three phenotypes SBSBSBSB SWSWSWSW SBSWSBSW SBSWSBSW SBSBSBSB SBSWSBSW SBSWSBSW SWSWSWSW

5 Determining patterns of inheritance 1 Autosomal recessive Heterozygotes don’t show trait so it may skip generations If both parents have it, all offspring will have it Parents don’t have to have it Autosomal dominant Heterozygotes do show trait so it can’t skip generations Even if both parents have it, offspring don’t have to show it At least one parent must have it Autosomal co-dominant 3 phenotypes are present

6 Sex linked inheritance Males and females have different chromosomes Males can only show 2 phenotypes (ie males can not be carriers) Females can show 3 phenotypes (if codominant) or 2 phenotypes (if dominant recessive, with a carrier) Males and females will show different patterns of inheritance

7 Determining patterns of inheritance 2 In sex-linkage mothers pass to sons, fathers pass to daughters Sex-linked recessive Mainly in males Females can only have it if father has it and mother is at least a carrier Affected females pass it to all their sons Sex-linked dominant Fathers pass to all daughters Mothers pass to half their sons Sex-linked co-dominant Only females can show intermediate trait

8 Reading pedigrees Autosomal recessive Autosomal dominant Sex linked recessive Autosomal recessive

9 Pedigree problem 1 a) How many males are there? b) How many females are there? c) How many males have long fur? d) How many females have short fur? e) What type of inheritance is this? f) Write the most likely genotype of each individual on the pedigree. g) Which individuals are definitely homozygous? h) Which individuals are definitely heterozygous? i) How could you confirm the genotypes of the short haired cats in the fourth generation? j) What offspring would you expect from a cross of III1 and II6?

10 Pedigree problem 1 a) How many males are there? 9 b) How many females are there? 9 c) How many males have long fur? 4 d) How many females have short fur? 3 e) What type of inheritance is this? Autosomal recessive f) Write the most likely genotype of each individual on the pedigree. g) Which individuals are definitely homozygous? Shaded ones h) Which individuals are definitely heterozygous? Unshaded ones with shaded children and/or a shaded parent i) How could you confirm the genotypes of the short haired cats in the fourth generation? Test cross (breed to long haired cat) j) What offspring would you expect from a cross of III1 and II6? Ll x ll = 50% Ll (short hair) 50% ll (long hair) L = short fur l = long fur LL Ll ll Ll Ll l l ll

11 Pedigree problem 2 a)Is this trait dominant or recessive? Give reasons to justify your answer. b)Is this trait autosomal or sex-linked? Give reasons to justify your answer. c)Which individuals are definitely homozygous? d)Which individuals are definitely heterozygous? e)What is the probability of individuals II2 and II8 having white coated offspring? Show all working.

12 Pedigree problem 2 a)Is this trait dominant or recessive? Give reasons to justify your answer. recessive b)Is this trait autosomal or sex-linked? Give reasons to justify your answer. autosomal c)Which individuals are definitely homozygous? Shaded ones d)Which individuals are definitely heterozygous? Unshaded ones with shaded children and/or a shaded parent e)What is the probability of individuals II2 and II8 having white coated offspring? Show all working. Bb x bb = ½ Bb black ½ bb white B = black b = white

13 Pedigree problem 3 a)Is this trait dominant or recessive? Give reasons to justify your answer. b)Is this trait autosomal or sex-linked? Give reasons to justify your answer. c)Which individuals are definitely heterozygous? d)What is the probability of individuals II1 and II7 have white coated offspring? Show all working.

14 Pedigree problem 3 a)Is this trait dominant or recessive? Give reasons to justify your answer. dominant b)Is this trait autosomal or sex-linked? Give reasons to justify your answer. autosomal c)Which individuals are definitely heterozygous? Shaded ones with unshaded children and/or an unshaded parent d)What is the probability of individuals II1 and II7 have white coated offspring? Show all working. rr x rr = all rr dark r = dark R = white

15 Pedigree problem 4 a)Is this trait dominant or recessive? Give reasons to justify your answer. b)Is this trait autosomal or sex-linked? Give reasons to justify your answer. c)Which individuals are definitely homozygous? d)Which individuals are definitely heterozygous? e)Individuals II8 and II9 are expecting another child. What is the probability it will be normal? Show all working. f)Individual II1 is marrying a woman from a family which is free of this disease. What is the probability of their children having this disease? Show all working.

16 Pedigree problem 4 a)Is this trait dominant or recessive? Give reasons to justify your answer. Recessive : d = disease, D = normal b)Is this trait autosomal or sex-linked? Give reasons to justify your answer. Sex linked c)Which individuals are definitely homozygous? Shaded females d)Which individuals are definitely heterozygous? Unshaded females with shaded children and/or a shaded parent e)Individuals II8 and II9 are expecting another child. What is the probability it will be normal? Show all working. X D X d x X d Y = 50% won’t have disease f)Individual II1 is marrying a woman from a family which is free of this disease. What is the probability of their children having this disease? Show all working. X D Y x X d X d = all X d X d or X d Y = 0% with disease XDXD XdXd XdXd XDXdXDXd XdXdXdXd YXDYXDYXdYXdY

17 Pedigree problem 5 a)Is this trait dominant or recessive? Give reasons to justify your answer. b)Is this trait autosomal or sex-linked? Give reasons to justify your answer. c)Which individuals are definitely homozygous? d)Which individuals are definitely heterozygous? e)Individuals II8 and II9 are expecting another child. What is the probability it will not have the disease? Show all working.

18 Pedigree problem 5 a)Is this trait dominant or recessive? Give reasons to justify your answer. Dominant : D = disease, d = normal b)Is this trait autosomal or sex-linked? Give reasons to justify your answer. Sex linked c)Which individuals are definitely homozygous? Unshaded females d)Which individuals are definitely heterozygous? Shaded females with unshaded children and/or an unshaded parent e)Individuals II8 and II9 are expecting another child. What is the probability it will not have the disease? Show all working. X D Y x X D X d = 25% chance of normal child XDXD XDXDXDXD XDXD XdXd XDXdXDXd YXDYXDYXdYXdY

19 Pedigree problem 6 a)Is this trait dominant or recessive? Give reasons to justify your answer. b)Is this trait autosomal or sex-linked? Give reasons to justify your answer. c)Which individuals are definitely homozygous? d)Which individuals are definitely heterozygous? e)What is the probability of III4 and III5 having long haired offspring? Show all working

20 Pedigree problem 6 a)Is this trait dominant or recessive? Give reasons to justify your answer. Recessive: l = long hair, L = short hair b)Is this trait autosomal or sex-linked? Give reasons to justify your answer. autosomal c)Which individuals are definitely homozygous? Shaded ones d)Which individuals are definitely heterozygous? Unshaded ones with shaded children and/or a shaded parent e)What is the probability of III4 and III5 having long haired offspring? Show all working: ll x Ll = 50% of offspring will be long haired l l LLl lll

21 Pedigree problem 7 a. What is the pattern of inheritance is this? b. Write the genotype for each individual. c. What offspring would you expect if you mated individual III 1 to: i) III 2? ii) III 3? iii) I 1?

22 Pedigree problem 7 a. What is the pattern of inheritance is this? codominance b. Write the genotype for each individual. c. What offspring would you expect if you mated individual III 1 to: i) III 2?x= ii) III 3?x= ½ : ½ iii) I 1?x= C S C S = spotted C D C D = dark C D C S = sable CSCSCSCS CSCSCSCS CDCSCDCS CDCSCDCS CDCSCDCS CDCSCDCS CDCSCDCS CDCDCDCD CDCDCDCD CDCDCDCD CDCDCDCD CDCDCDCD CDCSCDCS CDCD C D CS D CDCD CDCDCDCD CDCD CSCS CSCSCSCS CDCSCDCS CDCDCDCD CDCDCDCD CDCDCDCD CDCSCDCS CSCSCSCS CDCSCDCS CDCSCDCS CDCDCDCD


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