Most organisms contain both nucleic acids, RNA and DNA. (i) Name the biologically active entities, each of which contains only one type of nucleic acid. (ii) Name two locations in eukaryotic cells where RNA but no DNA is found. Gregor Mendel studied the inheritance of various traits in pea plants. The results of some of his investigations are presented in the table. Parental Cross F1 Phenotype Round x Wrinkled Seeds All Round Yellow x Green Seeds All Yellow Purple x White Flowers All Purple Tall x Dwarf Plants All Tall (i) As a result of his work, he put forward two laws, the Law of Segregation and the Law of Independent Assortment. State each of these laws. (ii) A dwarf pea plant with green seeds was crossed with a plant heterozygous for both height and seed colour. Indicate by means of a genetic cross, the possible genotypes and phenotypes of the progeny of this cross, if there is no linkage of genes. (iii) Explain how the results of the cross in (ii) above would differ if the genes for height and seed colour were linked. (c) (i) What is meant by the term evolution? (ii) Outline the theory of evolution by natural selection. (iii) Describe evidence in support of evolution from any one named source.

Leaving Cert Biology Genetics, DNA & Evolution: Most organisms contain both nucl

Most organisms contain both nucleic acids, RNA and DNA - Leaving Cert Biology - Question 13 - 2018

Question 13

Most organisms contain both nucleic acids, RNA and DNA. (i) Name the biologically active entities, each of which contains only one type of nucleic acid. (ii) Name ... show full transcript

Worked Solution & Example Answer:Most organisms contain both nucleic acids, RNA and DNA - Leaving Cert Biology - Question 13 - 2018

Step 1

Name the biologically active entities, each of which contains only one type of nucleic acid.

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Answer

The biologically active entities that contain only one type of nucleic acid are:

Viruses: These are infectious agents that can carry either RNA or DNA, but not both.

Step 2

Name two locations in eukaryotic cells where RNA but no DNA is found.

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Answer

In eukaryotic cells, RNA can be found in the following locations where DNA is not present:

Cytoplasm: This is where mRNA exists as it is translated into proteins.
Ribosomes: These structures are essential for protein synthesis and contain rRNA.

Step 3

Law of Segregation

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Answer

The Law of Segregation states that:

Traits (or characteristics) are controlled by pairs of factors (or genes) that separate during the formation of gametes.

Step 4

Law of Independent Assortment

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Answer

The Law of Independent Assortment states that:

Members of a pair of factors (genes or alleles) separate independently of members of another pair during gamete formation.

Step 5

A dwarf pea plant with green seeds crossed with a plant heterozygous for both height and seed colour.

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Answer

The genetic cross for these two plants is as follows:

Parents: ttYy (dwarf, green) x TtYy (tall, yellow)
Gametes: tY, ty x TY, Ty, tY, ty
F1 Genotype: 50% TtYy (Tall, Yellow), 25% Ttyy (Tall, Green), 25% ttyy (Dwarf, Yellow), 25% ttyy (Dwarf, Green).

Step 6

Explain how the results of the cross in (ii) would differ if the genes for height and seed colour were linked.

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Answer

If the genes for height and seed colour were linked, the offspring would display fewer combinations of phenotypes.

Specifically, we would expect mostly parental phenotypes (tall green and dwarf yellow) and less variation in the offspring's appearance.

Step 7

What is meant by the term evolution?

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Answer

Evolution refers to the:

Inheritable (or genetic) change within a population or species in response to changes in the environment or over time.

Step 8

Outline the theory of evolution by natural selection.

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The theory of evolution by natural selection involves:

Variation among individuals within a population.
Competition for limited resources leading to survival of the fittest.
Better adapted organisms have greater reproductive success, passing advantageous traits to the next generation.

Step 9

Describe evidence in support of evolution from any one named source.

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Answer

Evidence for evolution can be derived from:

Fossils: Fossils show changes in species over time and provide a record of the organisms that lived in the past.

Most organisms contain both nucleic acids, RNA and DNA - Leaving Cert Biology - Question 13 - 2018

Worked Solution & Example Answer:Most organisms contain both nucleic acids, RNA and DNA - Leaving Cert Biology - Question 13 - 2018

Name the biologically active entities, each of which contains only one type of nucleic acid.

Name two locations in eukaryotic cells where RNA but no DNA is found.

Law of Segregation

Law of Independent Assortment

A dwarf pea plant with green seeds crossed with a plant heterozygous for both height and seed colour.

Explain how the results of the cross in (ii) would differ if the genes for height and seed colour were linked.

What is meant by the term evolution?

Outline the theory of evolution by natural selection.

Describe evidence in support of evolution from any one named source.

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