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Genetics and Genomics

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Dihybrid Crosses with Pig Color

GENES-XPYIAS

In domestic pigs, two of the main loci influencing coat color are the Extension (E) and the Belted (B) loci. Two alleles at the E locus determine black vs. red hair color, and two alleles at the B locus determine the presence or absence of a white belt.

Black, belted: By Amanda Slater from Coventry, England - August 27th "Porridge", CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=4672028; Red: By 4028mdk09 - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=15152773; Red,belted: By Photo made bei Axel Krampe, webmaster of http://www.husumer-landschweine.de/ with permission to use under GFDL. - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=575041; Black: By Amanda Slater from Coventry, England - Large Blacks, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=4672009. Created for Albert.io. Copyright 2016. All rights reserved.

It is possible to find true-breeding lines of pigs that are black, black-belted, red, and red-belted. However, when true-breeding black-belted lines are crossed with true-breeding red lines, the F1 animals are always black-belted.

Based on the available information, what proportions of these four color patterns (black-belted, black, red-belted, and red, in that respective order) should be observed among F2 pigs when the F1 animals described above are interbred?

A

1:1:1:1

B

3:1:3:1

C

1:2:2:1

D

9:3:3:1