9. (a) Explain the following terms used in genetics - Leaving Cert Agricultural Science - Question 9 - 2017
Question 9
9.
(a) Explain the following terms used in genetics.
(i) Haploid.
(ii) Homozygous.
(iii) Locus.
(b) The pure-breeding barley variety Alpha (AA) has a straw length... show full transcript
Worked Solution & Example Answer:9. (a) Explain the following terms used in genetics - Leaving Cert Agricultural Science - Question 9 - 2017
Step 1
Explain the following terms used in genetics.
(i) Haploid.
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Answer
Haploid refers to the condition of having half the diploid number of chromosomes, which means it contains one copy of each chromosome. In gametes (sperm and egg cells), the genetic material is halved to ensure that offspring inherit genetic information from both parents.
Step 2
(ii) Homozygous.
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Homozygous describes an organism's genetic status where both alleles for a specific gene are identical. For example, if a plant has two alleles for purple flower color, it can be considered homozygous for that trait.
Step 3
(iii) Locus.
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A locus is defined as the specific position or location of a gene on a chromosome. It serves as a reference point in genetics to identify the location of genes that control particular traits.
Step 4
What does this show about the genes that control straw length in this example?
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The observation that the hybrid has a straw length of 700 mm indicates that the genes controlling straw length exhibit incomplete dominance or co-dominance. This suggests that neither of the parental traits is completely dominant over the other, resulting in an intermediate phenotype in the offspring.
Step 5
(ii) Copy and complete the following in your answer book to show the cross between the Alpha and Beta varieties of barley.
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Parents:
Genotypes of parents: (AA) X (BB)
Gametes:
(A) X (B)
Genotype of offspring:
(AB)
Phenotype of hybrid offspring: 700 mm
Step 6
(iii) Copy and complete the following in your answer book, using the above hybrids as parents.
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Genotype of parents: (AB) X (AB)
Gametes: (A) (B) X (A) (B)
Genotypes of offspring: (AA), (AB), (AB), (BB)
Phenotypes of offspring: 800 mm, 700 mm, 600 mm
Step 7
State one advantage of using artificial insemination (AI) on a dairy farm.
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Answer
One advantage of using artificial insemination (AI) is that it allows farmers to select superior bulls based on genetic traits without the need to keep a bull. This can lead to improved offspring quality and breed performance.
Step 8
State one disadvantage of using AI on a dairy farm.
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One disadvantage of using AI is that it requires either a skilled technician to inseminate cows or more labor to monitor heat cycles and manage the timing of insemination, which can be time-consuming and labor-intensive.
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