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7. (a) Explain each of the following terms: (i) F1 hybrids - Leaving Cert Agricultural Science - Question 7 - 2016
Question 7
7. (a) Explain each of the following terms: (i) F1 hybrids. (ii) Continuous variation. (iii) Back cross. (iv) Incomplete dominance. (b) In cattle, the allele for bl... show full transcript
Worked Solution & Example Answer:7. (a) Explain each of the following terms: (i) F1 hybrids - Leaving Cert Agricultural Science - Question 7 - 2016
Step 1
Step 2
Explain each of the following terms: (ii) Continuous variation.
Answer
Continuous variation refers to a characteristic that is controlled by multiple genes (polygenic inheritance). As a result, it produces a range of phenotypes rather than distinct categories, such as skin color or height.
Step 3
Step 4
Explain each of the following terms: (iv) Incomplete dominance.
Answer
Incomplete dominance occurs when neither allele is completely dominant over the other, resulting in a phenotype that is a blend of the two parental traits. For example, crossing red and white flowers may produce pink flowers.
Step 5
In cattle, the allele for black coat (B) is dominant to the allele for white coat (b), and the allele for the polled condition (P) is dominant to the allele for horned (p). A bull, heterozygous for both traits, is mated with a horned white cow. (i) Give the genotype of the bull used in this cross.
Answer
The genotype of the bull that is heterozygous for both traits would be BbPp.
Step 6
In cattle, the allele for black coat (B) is dominant to the allele for white coat (b), and the allele for the polled condition (P) is dominant to the allele for horned (p). A bull, heterozygous for both traits, is mated with a horned white cow. (ii) List the possible genotypes resulting from this cross.
Answer
The possible genotypes resulting from this cross are: BbPp, Bbpp, bbPp, and bbpp.
Step 7
In cattle, the allele for black coat (B) is dominant to the allele for white coat (b), and the allele for the polled condition (P) is dominant to the allele for horned (p). A bull, heterozygous for both traits, is mated with a horned white cow. (iii) What is the probability that a calf from this cross would be white and horned?
Answer
The probability that a calf would be white and horned (bbpp) is 25%. This is because there is a 50% chance for the calf to inherit the b allele from the bull and a 50% chance for the calf to inherit the p allele from the cow.
Step 8
In cattle, the allele for black coat (B) is dominant to the allele for white coat (b), and the allele for the polled condition (P) is dominant to the allele for horned (p). A bull, heterozygous for both traits, is mated with a horned white cow. (iv) Explain your answer.
Answer
The result is derived from the Punnett square analysis of the cross. Since the bull is BbPp and the cow is bbpp, generating a 1:2:1 ratio for the genotypes leads to the 25% probability of obtaining a calf that is both white (bb) and horned (pp).
Step 9
In cattle, the allele for black coat (B) is dominant to the allele for white coat (b), and the allele for the polled condition (P) is dominant to the allele for horned (p). A bull, heterozygous for both traits, is mated with a horned white cow. (v) State Mendel's Law of Segregation.
Answer
Mendel's Law of Segregation states that during the production of gametes, the two alleles for a trait segregate from each other, so that each gamete receives only one allele from each pair.
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Step 11
The Economic Breeding Index (EBI) is widely used in dairying to identify genetically superior animals to improve dairy production in Ireland. (ii) Outline the factors that determine each sub-index listed.
Answer
Factors determining the Fertility Index include:
- Calving interval
- Survival rates
Factors determining the Milk Production Index include:
- Milk yield
- Fat and protein content