1. Pedigrees

2. Pedigrees
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 bb BB Bb Bb Bb B_ B_ bb B_

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
SBSB
SWSW
SBSW
SBSW
SBSB
SBSW
SWSW
SBSW

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 L = short fur l = long fur ll ll LL LL ll ll ll ll
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 ll

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

12. Pedigree problem 2 B = black b = white
Is this trait dominant or recessive? Give reasons to justify your answer. recessive
Is this trait autosomal or sex-linked? Give reasons to justify your answer. autosomal
Which individuals are definitely homozygous? Shaded ones
Which individuals are definitely heterozygous? Unshaded ones with shaded children and/or a shaded parent
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

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

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

15. Pedigree problem 4
Is this trait dominant or recessive? Give reasons to justify your answer.
Is this trait autosomal or sex-linked? Give reasons to justify your answer.
Which individuals are definitely homozygous?
Which individuals are definitely heterozygous?
Individuals II8 and II9 are expecting another child. What is the probability it will be normal? Show all working.
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 XD Xd Xd XDXd XdXd Y XDY XdY
Is this trait dominant or recessive? Give reasons to justify your answer. Recessive : d = disease, D = normal
Is this trait autosomal or sex-linked? Give reasons to justify your answer. Sex linked
Which individuals are definitely homozygous? Shaded females
Which individuals are definitely heterozygous? Unshaded females with shaded children and/or a shaded parent
Individuals II8 and II9 are expecting another child. What is the probability it will be normal? Show all working. XDXd x XdY = 50% won’t have disease
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. XDY x XdXd = all XdXd or XdY = 0% with disease

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

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

20. Pedigree problem 6 l l L Ll Ll l ll ll
Is this trait dominant or recessive? Give reasons to justify your answer. Recessive: l = long hair, L = short hair
Is this trait autosomal or sex-linked? Give reasons to justify your answer. autosomal
Which individuals are definitely homozygous? Shaded ones
Which individuals are definitely heterozygous? Unshaded ones with shaded children and/or a shaded parent
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

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
CSCS = spotted
CDCD = dark
CDCS = sable
CSCS
CDCD CS CD
CDCS
CDCS
CDCS
CDCD CD
CDCD
CDCS
CDCS
CDCD
CDCSD
CDCD
CDCD CD
CDCS
CSCS
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 =
CDCS
CDCD
CSCS
CDCD
CDCS
CDCD
CDCS
CDCD
CSCS
CDCS