DankoMan
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#1
Report Thread starter 2 years ago
#1
Hi guys i've recieved this homework on genetics for A level biology and its really hard!!!

Labrador dogs vary in the colours of their coats. The most familiar colours are black or yellow (golden). Chocolate (brown) is slightly less common and the rarest of all combines different colours in patches and is called brindled.
Coat colour is controlled by alleles at two loci.
The colour locus alleles are B (black), br (brindled) and b (chocolate). The dominance hierarchy is B > br > b.
The second locus has two alleles. E allows expression of the colour locus so that dark hairs develop. Its recessive counterpart prevents the expression of dark hairs so the coat colour remains yellow.
A family tree of some Labradors is shown in Figure 1.

1) Identify the pattern of genetic inheritance shown by :
a) the coat colour locus
b) the action of locus E

Many thanks!
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DankoMan
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#2
Report Thread starter 2 years ago
#2
(Original post by DankoMan)
Hi guys i've recieved this homework on genetics for A level biology and its really hard!!!

Labrador dogs vary in the colours of their coats. The most familiar colours are black or yellow (golden). Chocolate (brown) is slightly less common and the rarest of all combines different colours in patches and is called brindled.
Coat colour is controlled by alleles at two loci.
The colour locus alleles are B (black), br (brindled) and b (chocolate). The dominance hierarchy is B > br > b.
The second locus has two alleles. E allows expression of the colour locus so that dark hairs develop. Its recessive counterpart prevents the expression of dark hairs so the coat colour remains yellow.
A family tree of some Labradors is shown in Figure 1.

1) Identify the pattern of genetic inheritance shown by :
a) the coat colour locus
b) the action of locus E

Many thanks!
Here is Figure 1
Name:  pedigree tree.jpg
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callyallen
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#3
Report 10 months ago
#3
i've just got this haha did u get the answers??
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liljoonie
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#4
Report 5 months ago
#4
I just got this and I have no idea how to answer. Do you have the answers???
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deskochan
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#5
Report 5 months ago
#5
I have tried this question: I get some ideas
Black: 17 E_B_
Chocolate: 3 E_bb
brindled: 7 E_brbr, E_brb
Yellow: 9 eeBB, eeBb, eebrbr, eebrb,eebb

It involves epistasis when a gene at one locus masks the expression of a gene at the second locus so its phenotype is not expressed. I do not have an answer and let me know if you get the answer.
2 genes: (E,e) & (B,br, b)
pigment (E) or no pgiment (e)
pigment concentration: Black (B) > brindled (br) > chocolate
Last edited by deskochan; 5 months ago
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