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Incomplete Dominance & Co-Dominance

By William Thomas
Last updated almost 4 years ago
14 Questions

Incomplete Dominance & Co-Dominance

Watch the video, then complete the Incomplete Dominance & Co-Dominance examples below.

PART A - Incomplete Dominance

After mating a group of hybrid (GY) yellow green parakeets, a breeder noted the following average offspring numbers:

24 yellow , 26 green and 53 yellow green birds.

There are only two genes that control feather colour in birds – they are:
YY- Yellow
GG - Green
GY (or YG) - Yellow Green


EXAMPLE #1:

Work out a cross that would produce the following results:
50% of all offspring are light green

EXAMPLE #1:Fill out the Punnett square.

EXAMPLE #1: What are the parents' phenotypes - a)___________________ x b)___________________

EXAMPLE #1: What are the parents' genotypes - c)__________________ x d)_____________________

EXAMPLE #2:

Work out a cross that would produce the following results:
100% of all offspring are yellow green

EXAMPLE #2: Fill out the Punnett square.

EXAMPLE #2: What are the parents' phenotypes - a)___________________ x b)___________________

EXAMPLE #2: What are the parents' genotypes - c)__________________ x d)_____________________

EXAMPLE #3:

Work out a cross that would produce the following results:
50% of all offspring are yellow green.

EXAMPLE #3: Fill out the Punnett square.

EXAMPLE #3: What are the parents' phenotypes - a)___________________ x b)___________________

EXAMPLE #3: What are the parents' genotypes - c)__________________ x d)_____________________

PART B – Codominance

In the short-horn cattle breed coat colour is inherited and there are only two alleles
  • WW – White
  • RR – Red
Both are capital letters below both are dominant.

Roan cattle contain both red hair and white hair – giving their coat a mottled ‘roan’ appearance.
RW (or WR) - Roan

A roan cow, with both white and red shown without blending

1) Complete the following two crosses. EXAMPLE #1 is on the left; EXAMPLE #2 is on the right.

EXAMPLE #1: Fill out the Punnett square.

EXAMPLE #2: Fill out the Punnett square.

How many of the babies out of the total will be roan (part red & part white)?

Suggest how the farmer who owns these cattle could control the breeding so that the herd ultimately consisted of red cattle only