Julif
suh
Extra Questions on Co-dominance and multiple alleles
Aim:
To become more confident in genetics work on multiple alleles.
Introduction
1. Human ABO blood types follow a co-dominant inheritance pattern with multiple alleles.
a. Describe what is meant by “multiple alleles.”
the aHernative
of the same
forms
gene p they influence
………………………………………………………………………………………….……………………………….………
the
same
traif
b. Complete the table of possible blood group genotypes below
IB
IA
i
alleles
IB
i
ii
I마 :
IA
IPi
오면습
I마
IB
IB
IAIB
IB I?
;
:
IB
,
c. Highlight the genotype and phenotype which is an example of codominance.
2. Complete this pedigree chart to show the inheritance of blood types in this family.
Ii
I'
IAi
-;
IBiTIpi
© David Faure, InThinking www.biology-inthinking.co.uk
1
Extra Questions on Co-dominance and multiple alleles
3. Sickle cell is another example of co-dominance. The allele for sickle cell disease is Hbs, the
allele for normal haemoglobin is HbA. In the heterozygous genotype the haemoglobin is said
to show ‘sickle trait’, both forms of haemoglobin are present.
a. State the phenotypes of these individuals.
HbAHbA
genotype
phenotype
HbAHbs
HbsHbs
normarrierckle
cell
b. Predict the phenotype ratios of offspring in the following crosses. Show all your working,
and set it out with the genetics headings . Take care with
upper and lower cases in the notation.
Genetics headings
i.
Carrier mother with affected father
noumal
.
Genotype of parents
carrier
이
ii.
Phenotype of parents
Affected father with unaffected mother.
normarsicklecerarrier
이
니
⑦
IIFn
매지 밥킴
'
Punnett Square
n
:
i
HbA
,
iii.
Carrier mother with carrier father.
novomanl carrier
.
1
=
그
si ( khe
'
cell
이
없시비잼,
II
c. Explain how the prevalence of sickle cell in regions of
Africa is an example of natural selection in action.
This
the
sickle
is because
…………………………………………………………………………
cell
해
allele
protects people fro
……………….……………………………;…….………
………….
HbS
.
Hbp
HbAHbz
Hbp
ub
☆
HbA
Mb ,
HbA HbAHbs
F1 genotypes ratio
F1 Phenotype ratio
malaria is
malavia
Because
……………………………………………………………………
common
in
Afvica in order to
…………….……………………………….……………………..
allele
sickle
the
cel
became
pVevey getting it
very
………………………………………………………………………………………….……………………………….………
,
common
in
Africar
………………………………………………………………………………………….……………………………….………
© David Faure, InThinking www.biology-inthinking.co.uk
2
Extra Questions on Co-dominance and multiple alleles
d. The pedigree chart below shows a family affected by sickle cell:
i.
A
B
C
D
E
HbaHbA
Deduce the genotype of each individual using the Key in the diagram.
F
Hbs
Hbs Hbs
ubs Hbs
HboHbn
Hb
□
Hbb
Hbs
G
H
$
#
Hbp HbA
Hbs Hbs
Hbs Hbs
Hbp HbA
© David Faure, InThinking www.biology-inthinking.co.uk
3