Explain the following terms used in genetics:
(i) Heredity
(ii) Gene
(iii) Homozygous - Leaving Cert Biology - Question 11 - 2018
Question 11
Explain the following terms used in genetics:
(i) Heredity
(ii) Gene
(iii) Homozygous.
DNA has four bases: Adenine (A), Guanine (G), Cytosine (C), and Thymine (T).
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Worked Solution & Example Answer:Explain the following terms used in genetics:
(i) Heredity
(ii) Gene
(iii) Homozygous - Leaving Cert Biology - Question 11 - 2018
Step 1
Heredity
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Heredity refers to the passing on of characteristics from one generation to the next. It encompasses the transmission of traits through genetic information.
Step 2
Gene
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A gene is a segment of DNA that contains the instructions to make a specific protein, which ultimately influences a particular trait or function in an organism.
Step 3
Homozygous
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Homozygous describes an organism that has two identical alleles for a specific gene, meaning both alleles contribute the same genetic information for a trait.
Step 4
Which of the above four bases is represented by the letter X in the diagram?
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The letter X in the diagram represents Adenine (A).
Step 5
Which of the above four bases is represented by the letter Y in the diagram?
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The letter Y in the diagram represents Cytosine (C).
Step 6
Chromosomes are made of DNA and which other substance?
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Chromosomes are made of DNA and proteins.
Step 7
How many chromosomes are in a normal human cheek cell?
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A normal human cheek cell contains 46 chromosomes.
Step 8
Where are chromosomes located in the cell?
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Chromosomes are located in the nucleus of the cell.
Step 9
Another molecule in the cell also has four bases, one of which is uracil. Name this molecule.
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The molecule that also has four bases, including uracil, is RNA.
Step 10
In this molecule, uracil replaces one of the four DNA bases mentioned above. Which base does uracil replace?
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Uracil replaces Thymine (T) in RNA.
Step 11
DNA contains the code for making proteins. Where are proteins made in the cell?
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Proteins are made in the ribosomes of the cell.
Step 12
What molecule carries the DNA code to where proteins are made?
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The molecule that carries the DNA code to where proteins are made is messenger RNA (mRNA).
Step 13
Give the genotype for a heterozygous plant.
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The genotype for a heterozygous plant is Tt.
Step 14
Give the genotypes of the gametes of the plant mentioned in (i).
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The genotypes of the gametes are T and t.
Step 15
Give the genotype for a small plant.
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The genotype for a small plant is tt.
Step 16
Give the genotype of a male and the genotype of a female.
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The genotype of a male is XY, and the genotype of a female is XX.
Step 17
Explain fully why this is the case.
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Males determine the sex of the child because they can contribute either an X or a Y chromosome. Females only provide an X chromosome. If the male contributes an X chromosome, the child will be female (XX). If he contributes a Y chromosome, the child will be male (XY).
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