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Nucleic Acids

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Biology

Nucleic acids are the key macromolecules of life. They are polymers made of smaller monomers called nucleotides, which undergo condensation reactions. The two types of nucleic acids you'll learn about are deoxyribonucleic acid, or DNA, and ribonucleic acid, or RNA. Both DNA and RNA are essential in cellular processes and development. All living things - both eukaryotic and prokaryotic - contain nucleic acids, including animals, plants and bacteria. Even viruses, which are considered non-living entities, contain nucleic acids as you can see in the diagram below.

Nucleic acids, location of DNA, StudySmarterDNA is located in a eukaryotic cell (left) and a virus (right)

DNA and RNA are composed of three common components: a phosphate group, a pentose sugar and an organic nitrogenous base. The combination of these components, called the base sequence (shown below), holds all the genetic information needed for all life.

Nucleic acids, DNA base sequence, StudySmarterDNA base sequence

Why are nucleic acids important?

Nucleic acids are amazing molecules that contain the genetic instructions to make our cellular components. They are present in every cell (except mature erythrocytes) to direct the functioning of each cell and its functions.

DNA is a remarkable macromolecule found in both eukaryotic and prokaryotic cells that holds all the information needed to create proteins. The base sequence of DNA holds this code. This same DNA is passed down to offspring, so subsequent generations possess the ability to create these essential proteins. This means that DNA plays a major role in the continuity of life as it is the blueprint for organizational development.

Genetic information flows from DNA to RNA. RNA is involved in the transfer of the information stored in DNA and the 'reading' of the base sequence, both of which are processes in protein synthesis. This nucleic acid type is present in both transcription and translation, so it is needed in every step of protein synthesis.

This is highly important because, without RNA, proteins cannot be synthesized. There are different types of RNA that you will come across: messenger RNA (mRNA), transport RNA (tRNA) and ribosomal RNA (rRNA).

Nucleic Acids - Key takeaways

  • Nucleic acids are the essential macromolecules responsible for the storage and transfer of genetic material.
  • The two types of nucleic acids, DNA and RNA, share three common structural components: a phosphate group, a pentose sugar and a nitrogenous base.
  • DNA holds all the genetic information in the form of base sequences that code for proteins.
  • RNA facilitates the transcription and translation of the DNA base sequence in protein synthesis.
  • There are three different types of RNA, each with different functions: mRNA, tRNA and rRNA.

Nucleic Acids

Nucleic acids are macromolecules found in all living cells, like plants, and non-living entities, like viruses. DNA is the nucleic acid responsible for storing all the genetic information, while RNA facilitates the transfer of this genetic material to protein synthesis organelles.

There are two types of nucleic acids: deoxyribonucleic acid, DNA and ribonucleic acid, RNA. There are also different types of RNA: messenger, transport and ribosomal RNA.

Viruses contain nucleic acids, either DNA, RNA or even both. Even though viruses are not classified as 'living cells', they still require nucleic acids to store the code for their viral proteins.

Nucleic acids are organic molecules as they contain carbon, hydrogen and are found in living cells.

Nucleic acids are composed of monomeric units called nucleotides. In animals, these nucleotides are primarily made in the liver or obtained from our diet. In other organisms like plants and bacteria, metabolic pathways use available nutrients to synthesize nucleotides.

Final Nucleic Acids Quiz

Question

Both DNA and RNA are _____ acids.

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Answer

Nucleic.

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Question

Compare the functions of DNA and RNA.


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Answer

DNA stores genetic information while RNA transfers this genetic information for protein synthesis.

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Question

Where is DNA found in the cells of eukaryotes and prokaryotes?


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Answer

In eukaryotes, DNA is in the nucleus, mitochondria and chloroplast (in plants). 


In prokaryotes, DNA is in the nucleoid and plasmids.

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Question

Where is RNA found in the cells of eukaryotes and prokaryotes?


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Answer

In eukaryotes, RNA is in the nucleolus and ribosomes. 


In prokaryotes, RNA is in the nucleoid, plasmids and ribosomes.

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Question

Identify the three different types of RNA.


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Answer

Messenger RNA (mRNA), transfer RNA (tRNA) and ribosomes RNA (rRNA).

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Question

What nitrogenous bases can DNA nucleotides have?


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Answer

Adenine, thymine, cytosine or guanine.

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Question

What nitrogenous bases can RNA nucleotides have?


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Answer

Adenine, uracil, cytosine and guanine.

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Question

Identify the pyrimidine and purine bases. 


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Answer

The pyrimidine bases are cytosine, uracil and thymine. 


The purine bases are adenine and guanine.

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Question

DNA contains the _____ pentose sugar while RNA contains the _____ pentose sugar. 


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Answer

Deoxyribose. 

Ribose.

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Question

________ reactions form polynucleotides while _____ reactions break polynucleotides. 

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Answer

Condensation. 

Hydrolysis.

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Question

What are phosphodiester bonds and how are they formed?


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Answer

Phosphodiester bonds link nucleotides together. They are formed between the phosphate group of one nucleotide and the hydroxyl group at the 3 'pentose sugar of another nucleotide.

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Question

Compare the structure of a DNA and RNA molecule. 


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Answer

DNA is an anti-parallel double helix made of 2 polynucleotide strands while RNA is a single-stranded molecule made of 1 polynucleotide strand.

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Question

What is complementary base pairing? 


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Answer

Complementary base pairing is the joining of a pyrimidine base to a purine base via hydrogen bonds.

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Question

In complementary base pairing, how many hydrogen bonds are formed between the base pairs?


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Answer

Adenine forms 2 hydrogen bonds with thymine in DNA, or uracil in RNA. 


Cytosine forms three hydrogen bonds with guanine.

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Question

DNA and RNA are polynucleotides. The monomers that make up these polynucleotides are called _____.

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Answer

Nucleotides.

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Question

When does DNA replication happen?


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Answer

During the S phase of the cell cycle, before cell division. 


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Question

Where does DNA replication occur in a cell?


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Answer

In the nucleus, in eukaryotic cells.

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Question

After one round of DNA replication, what does the semiconservative model state?


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Answer

The new DNA molecule contains one original strand of DNA and one new strand of DNA.

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Question

Why is DNA replication important?


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Answer

DNA replication ensures that the daughter cells contain the correct amount of DNA. It is also required for cell division.

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Question

What is the function of DNA helicase?

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Answer

DNA helicase breaks the hydrogen bonds between complementary base pairs. This unzips the DNA double helix to expose the DNA bases.

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Question

What is the function of DNA polymerase?


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Answer

DNA polymerase catalyses the formation of phosphodiester bonds between adjacent nucleotides.

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What is the function of DNA ligase?


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Answer

DNA ligase catalyses the formation of phosphodiester bonds between Okazaki fragments in discontinuous replication.

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Question

In what direction does the new DNA strand extend?


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Answer

The 5 'to 3' direction.

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Question

The _____ strand undergoes continuous replication as it is being continuously synthesized by DNA polymerase.


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Answer

Leading.

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Question

The lagging strand undergoes _______ replication as Okazaki fragments are made. 


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Answer

Discontinuous.

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Question

The enzyme ___ _______ joins together Okazaki fragments by catalysing the formation of what bond?


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Answer

DNA ligase. 


Phosphodiester bonds.

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Question

What model did Meselson and Stahl prove correct in the 1950s?


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Answer

The semiconservative model of DNA replication.

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Question

Describe the replication fork.


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Answer

The replication fork is a Y-shaped structure that forms due to the unzipping action of DNA helicase. Each branch of the fork is an exposed strand of DNA.

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Question

Which end of the original DNA molecule does DNA polymerase initially bind to?


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Answer

The 3 'end.

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Question

Both ___ _______ and ___ _______ are enzymes involved in DNA replication that form phosphodiester bonds. 


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Answer

DNA polymerase. 


DNA ligase.

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Question

What kind of macromolecules are nucleic acids?

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Answer

Polymers made of monomers called nucleotides.

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Question

What are the two types of nucleic acids?

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Answer

DNA and RNA.

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Question

What are the components of both nucleic acid types?


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Answer

A phosphate group, a pentose sugar and a nitrogenous base.

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Question

What reaction is needed to synthesize nucleic acid?


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Answer

Condensation reactions between nucleotides.

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Question

What kind of cells contain nucleic acids?


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Answer

 Eukaryotic and prokaryotic cells, such as animals, plants and bacteria. Also, non-living entities such as viruses.

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Question

What is the base sequence in DNA?


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Answer

The combination of DNA nucleotides that encode proteins.

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Question

What process requires RNA?

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Answer

Protein synthesis (transcription and translation).

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Question

What are the different types of RNA?


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Answer

Messenger RNA (mRNA), transport RNA (tRNA) and ribosomal RNA (rRNA).

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Question

What cells do not contain nucleic acids?


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Answer

Mature erythrocytes.

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Question

DNA is the abbreviation for ___________ ______.


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Answer

Deoxyribonucleic acid.

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Question

RNA is the abbreviation for ________ _____.


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Answer

Ribonucleic acid.

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