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Pedigrees
PedigreesThese are diagrams that show the inheritance of characteristics
within familiesThey allow us to determine the pattern of inheritance and predict
characteristics of future offspring Conventions include
Autosomal dominant recessive crossesPedigrees will show 2 phenotypes.Crossing a homozygous dominant with a homozygous recessive leads to
heterozygous offspring with the dominant traitCrossing 2 heterozygous individuals leads to offspring which could show
either trait
B_
bb
B_
Bb
BB
Bb Bb
bbB_
Autosomal co-dominant crossesPedigrees will show 3 phenotypes.Crossing a homozygous dominant with a homozygous recessive
leads to heterozygous offspring with the intermediate traitCrossing 2 heterozygous individuals leads to offspring which could
show any of the three phenotypes
SBSB SWSW
SBSWSBSW
SBSBSBSWSBSW
SWSW
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
Sex linked inheritance
Males and females have different chromosomesMales 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
Determining patterns of inheritance 2In 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
Reading pedigrees
Autosomal recessive
Autosomal dominant
Sex linked recessive
Autosomal recessive
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?
Pedigree problem 1
a) How many males are there? 9b) How many females are there? 9c) How many males have long fur? 4d) How many females have short fur? 3e) What type of inheritance is this? Autosomal recessivef) Write the most likely genotype of each individual on the pedigree.g) Which individuals are definitely homozygous? Shaded onesh) Which individuals are definitely heterozygous? Unshaded ones with
shaded children and/or a shaded parenti) 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 furl = long fur
LL LL
LL LL LL LL
Ll Ll LlLl
LlLl
ll ll
ll ll ll ll
ll
L l
llLll
l Ll ll
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.
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 onesd) Which individuals are definitely heterozygous? Unshaded ones with
shaded children and/or a shaded parente) 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 = blackb = white
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.
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 = darkR = white
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.
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 femalesd) Which individuals are definitely heterozygous? Unshaded females with
shaded children and/or a shaded parente) 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 diseasef) 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
XD Xd
Xd XDXd XdXd
Y XDY XdY
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.
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 femalesd) Which individuals are definitely heterozygous? Shaded females with
unshaded children and/or an unshaded parente) 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
XD
XDXDXD
Xd
XDXd
Y XDY XdY
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
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 onesd) Which individuals are definitely heterozygous? Unshaded ones with
shaded children and/or a shaded parente) 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
L Ll Ll
l ll ll
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?
Pedigree problem 7
a. What is the pattern of inheritance is this? codominanceb. 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 =
CSCS = spottedCDCD = darkCDCS = sable
CSCS
CSCS
CDCSCDCS CDCS
CDCS
CDCS
CDCD
CDCD
CDCD
CDCD
CDCD CDCS
CDCDCSD
CD
CDCD
CD CS
CSCS
CDCS
CDCD
CDCD
CDCD
CDCS
CSCS CDCS
CDCSCDCD