Question

part 3: dominant vs. recessive & homozygous vs. heterozygous
using the letter b for brown eyes (dominant) and b for blue eyes (recessive), determine the following:

1. what is the genotype of a homozygous dominant individual?
2. what is the genotype of a homozygous recessive individual?
3. what is the genotype of a heterozygous individual?
4. what is the phenotype of a bb individual?
5. what is the phenotype of a bb individual?

part 4: types of dominance
determine whether each scenario represents complete dominance, incomplete dominance, or codominance.

1. a red flower (rr) and a white flower (ww) produce a pink flower (rw).
2. a black chicken (bb) and a white chicken (ww) produce a black - and - white speckled chicken (bw).
3. a tall plant (tt) and a short plant (tt) produce a tall plant (tt).
4. a brown cow (bb) and a white cow (ww) produce a roan (brown and white mixed) cow (bw).
5. a straight - haired person (ss) and a curly - haired person (cc) have a wavy - haired child (sc).

bonus challenge:
explain, in your own words, why heterozygous individuals can sometimes show a blend of traits but other times show both traits fully expressed.

Explanation:

Part 3:

1. Homozygous dominant means two identical dominant alleles.
2. Homozygous recessive means two identical recessive alleles.
3. Heterozygous means one dominant and one recessive allele.
4. Dominant allele (B) masks recessive (b), so brown eyes show.
5. Recessive phenotype only shows with two recessive alleles.

Part 4:

1. Incomplete dominance creates a blended intermediate trait.
2. Codominance shows both parental traits fully expressed.
3. Complete dominance: dominant allele masks recessive trait.
4. Codominance shows both parental traits simultaneously.
5. Incomplete dominance creates a blended intermediate trait.

Bonus Challenge:

The difference depends on the type of dominance: In incomplete dominance, the dominant allele does not fully mask the recessive one, so the heterozygote has a blended, intermediate trait. In codominance, both alleles are fully expressed at the same time, so the heterozygote shows both distinct parental traits instead of a blend.

Answer:

Part 3:

1. BB
2. bb
3. Bb
4. Brown eyes
5. Blue eyes

Part 4:

1. Incomplete dominance
2. Codominance
3. Complete dominance
4. Codominance
5. Incomplete dominance

Bonus Challenge:

This depends on the type of genetic dominance. In incomplete dominance, the dominant allele does not fully suppress the recessive allele, so the heterozygote displays a blended, intermediate trait. In codominance, both alleles are fully and independently expressed, so the heterozygote shows both of the distinct parental traits at the same time rather than a blend.