Nucleic Acids: Structure & DNA Replication
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Questions and Answers

What is the primary function of DNA?

  • To act as a catalyst in biochemical reactions
  • To transfer genetic information
  • To produce proteins
  • To hold or store genetic information (correct)

RNA carries genetic information from the ribosomes back to the nucleus.

False (B)

What process occurs at the ribosomes to produce polypeptides?

Translation

Both DNA and RNA are essential for the proper functioning of cells because they are both involved in the production of _____ .

<p>proteins</p> Signup and view all the answers

Match the nucleic acids with their primary functions:

<p>DNA = Stores genetic information RNA = Transfers genetic code to ribosomes</p> Signup and view all the answers

Which term describes the directionality of the two DNA strands?

<p>Aniparallel (D)</p> Signup and view all the answers

Adenine pairs with guanine in DNA.

<p>False (B)</p> Signup and view all the answers

What is the shape of the DNA molecule?

<p>double helix</p> Signup and view all the answers

The nitrogenous base cytosine pairs with _____ in DNA.

<p>guanine</p> Signup and view all the answers

Match the nitrogenous bases with their corresponding pairs in DNA:

<p>Adenine = Thymine Guanine = Cytosine Thymine = Adenine Cytosine = Guanine</p> Signup and view all the answers

How many hydrogen bonds are formed between adenine and thymine?

<p>Two (B)</p> Signup and view all the answers

DNA consists of single-stranded polynucleotide strands.

<p>False (B)</p> Signup and view all the answers

What type of bonding holds the two DNA strands together?

<p>hydrogen bonds</p> Signup and view all the answers

Which of the following is true about RNA compared to DNA?

<p>RNA contains ribose sugar. (C)</p> Signup and view all the answers

RNA molecules are made up of two polynucleotide strands.

<p>False (B)</p> Signup and view all the answers

What type of bond forms the sugar-phosphate backbone of RNA?

<p>phosphodiester bond</p> Signup and view all the answers

An example of an RNA molecule is _____, which acts as a transcript copy of a gene.

<p>messenger RNA (mRNA)</p> Signup and view all the answers

Match the following RNA types with their functions:

<p>mRNA = Transcribes genetic information from DNA tRNA = Brings amino acids to ribosomes rRNA = Forms the core of ribosome structure snRNA = Involved in RNA splicing</p> Signup and view all the answers

Which of the following statements about RNA polynucleotide chains is accurate?

<p>They contain alternating ribose sugars and phosphate groups. (B)</p> Signup and view all the answers

All RNA molecules are longer than any DNA molecules.

<p>False (B)</p> Signup and view all the answers

What is the primary function of transfer RNA (tRNA)?

<p>To bring amino acids to ribosomes</p> Signup and view all the answers

What is the main function of ribosomes?

<p>Protein synthesis (C)</p> Signup and view all the answers

Ribosomes are surrounded by a membrane.

<p>False (B)</p> Signup and view all the answers

What type of RNA forms part of the structure of ribosomes?

<p>ribosomal RNA (rRNA)</p> Signup and view all the answers

Eukaryotic cells contain _____ ribosomes, which are larger than those found in prokaryotic cells.

<p>80S</p> Signup and view all the answers

Which type of ribosomes are found in prokaryotic cells?

<p>70S (D)</p> Signup and view all the answers

Match the ribosome type to its location:

<p>80S = Eukaryotic cells 70S = Mitochondria and chloroplasts of eukaryotic cells</p> Signup and view all the answers

The small subunit of a ribosome is the site of translation.

<p>False (B)</p> Signup and view all the answers

What is the primary role of rRNA during protein synthesis?

<p>Catalyse the formation of peptide bonds</p> Signup and view all the answers

Who was the first scientist to discover DNA?

<p>Friedrich Miescher (C)</p> Signup and view all the answers

The genetic information is primarily carried by proteins, not DNA.

<p>False (B)</p> Signup and view all the answers

What two components make up the building blocks of DNA?

<p>Nucleotides</p> Signup and view all the answers

In 1953, Watson and Crick confirmed the _____ structure of DNA.

<p>double-helix</p> Signup and view all the answers

Match the scientist to their contribution regarding DNA:

<p>Friedrich Miescher = First observed DNA Watson and Crick = Proposed double-helix model Rosalind Franklin = Provided X-ray data Hershey and Chase = Confirmed DNA as genetic material</p> Signup and view all the answers

What led scientists to initially doubt that DNA carried genetic information?

<p>The complexity of proteins (B)</p> Signup and view all the answers

What year did researchers begin to fully understand the role of DNA in genetic inheritance?

<p>1940s</p> Signup and view all the answers

DNA is highly susceptible to hydrolysis compared to proteins.

<p>False (B)</p> Signup and view all the answers

What is the primary purpose of semi-conservative replication?

<p>To ensure daughter cells receive copies of parental DNA (A)</p> Signup and view all the answers

In semi-conservative replication, both strands of the new DNA molecule are originally from the parent DNA.

<p>False (B)</p> Signup and view all the answers

Why is it important that new cells inherit all their genes?

<p>To ensure they can perform the same functions as the old cells.</p> Signup and view all the answers

The process of copying DNA before cell division is known as __________ replication.

<p>semi-conservative</p> Signup and view all the answers

Match the terms with their correct definitions:

<p>Parent cell = The original cell that divides Daughter cells = The two new cells produced from the parent cell Genetic continuity = Inheritance of genes from parent to offspring Cell division = The process by which a parent cell splits into two cells</p> Signup and view all the answers

What does the term 'semi' in semi-conservative replication refer to?

<p>Half of the new DNA molecule being original (C)</p> Signup and view all the answers

New DNA strands created during semi-conservative replication are strictly identical to the parental original strands.

<p>False (B)</p> Signup and view all the answers

What role do 'parent cells' play in the process of DNA replication?

<p>They are the original cells that divide and replicate their DNA.</p> Signup and view all the answers

Flashcards

DNA function

Storing genetic information, containing instructions for growth and development

RNA function

Transfers genetic code from DNA to ribosomes for protein production

Nucleic Acids

Types of molecules that include DNA and RNA.

Ribosomes

Cellular structures where proteins are made using the RNA instructions.

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Different functions of DNA and RNA

DNA stores the genetic information, while RNA carries the information out of the nucleus and to the ribosomes where proteins are synthesized.

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Antiparallel DNA strands

DNA strands running in opposite directions (5' to 3' and 3' to 5').

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Hydrogen bonds in DNA

Bonds holding the two DNA strands together between nitrogenous bases.

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Complementary base pairing

Specific pairing of nitrogenous bases (A with T, G with C).

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DNA base pairs

Pairs of complementary nitrogenous bases (A-T and G-C).

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DNA double helix

Three-dimensional shape of DNA, formed by two antiparallel strands.

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Purines

Adenine (A) and Guanine (G) ; nitrogenous bases.

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Pyrimidines

Cytosine (C) and Thymine (T); nitrogenous bases.

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5' and 3' ends

Specific ends of DNA strands, defining directionality; Carbon numbers in the sugar backbone

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RNA Structure

RNA is a single-stranded polynucleotide made of ribose sugar, phosphate groups, and nitrogenous bases arranged in alternating order.

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RNA Nucleotide

The building block of RNA, consisting of a ribose sugar, a phosphate group, and a nitrogenous base.

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Phosphodiester Bond

A covalent bond that joins the 5' carbon of one nucleotide's sugar to the 3' carbon of the next nucleotide's sugar.

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Messenger RNA (mRNA)

A type of RNA that carries genetic information from DNA to the ribosomes to make proteins.

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Polynucleotide Strand

A long chain of nucleotides linked together by phosphodiester bonds.

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RNA vs. DNA (Strand Difference)

RNA is single-stranded, while DNA is double-stranded.

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RNA vs. DNA (Sugar Difference)

RNA uses ribose sugar, while DNA uses deoxyribose.

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RNA (Length)

RNA molecules are typically shorter than DNA.

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What are ribosomes?

Ribosomes are small organelles found in all cells, responsible for protein synthesis.

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Where are ribosomes located?

Ribosomes are either free in the cytoplasm (all cells) or attached to the rough endoplasmic reticulum (eukaryotic cells only).

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What do ribosomes make?

Ribosomes synthesize proteins by reading RNA and creating polypeptide chains.

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What are ribosomes made of?

Ribosomes are composed of ribosomal RNA (rRNA) and proteins.

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What is the role of rRNA?

Ribosomal RNA (rRNA) has enzymatic properties that catalyze the formation of peptide bonds between amino acids.

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How do eukaryotic and prokaryotic ribosomes differ?

Eukaryotic ribosomes (80S) are larger than prokaryotic ribosomes (70S).

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What is the function of the large subunit?

The large subunit of the ribosome holds tRNA molecules (with their amino acids) in place, enabling the formation of peptide bonds.

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How does mRNA interact with ribosomes?

mRNA sits between the ribosomal subunits, and the ribosome moves along it to translate the genetic code into a polypeptide chain.

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Semi-conservative replication

A process where a new DNA molecule is created using an existing DNA strand as a template, creating a new strand with half of the original DNA and half of a new strand.

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Parent cell

The original cell that divides to produce two new daughter cells.

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Daughter cell

The two new cells produced from the division of a parent cell.

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Importance of retaining one original DNA strand

Ensures genetic continuity between generations of cells, making sure new cells inherit the same genes from their parent cell.

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Why is DNA copied before cell division?

To ensure that each of the new daughter cells receives a full copy of the DNA, enabling them to function correctly

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Genetic Continuity

The inheritance of genetic information from one generation of cells to the next.

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Cell division for growth

DNA replication and cell division occur during growth, leading to an increase in the number of cells and the size of organisms.

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Cell division for replacement

Damaged or old cells in our bodies are replaced by new cells through division, maintaining tissue and organ function.

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Who discovered DNA?

Friedrich Miescher, a Swiss scientist, was the first to discover DNA in 1869. He originally called it 'nuclein'.

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Why did scientists doubt DNA's role in inheritance?

Scientists originally doubted DNA's role in inheritance because of its relatively simple chemical composition. They believed proteins, which have a more complex structure, were more likely to carry genetic information.

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What is the significance of the triplet code?

The triplet code allows for a vast amount of variation in the genetic information encoded by DNA, even though there are only four nucleotides. This is because three nucleotides code for a single amino acid.

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Why is DNA located in the nucleus?

DNA is safely stored in the nucleus to protect the genetic material from damage or degradation. The nucleus provides a controlled environment where the code is replicated and passed on.

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How is DNA easily copied?

DNA's structure allows for easy replication, ensuring accurate copying of the genetic code during cell division and inheritance.

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What year did Watson and Crick confirm DNA's structure?

In 1953, James Watson and Francis Crick confirmed the double-helix structure of DNA using X-ray data from Rosalind Franklin.

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When did research on DNA's function begin to gain traction?

It wasn't until the 1940s that the role of DNA in genetic inheritance started to be more extensively researched and understood, after earlier skepticism about its role.

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What is the key takeaway regarding DNA's initial reception?

The simplicity of DNA's structure initially led many scientists to doubt its ability to carry the genetic code, but its role was later confirmed through research.

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Study Notes

Nucleic Acids: Structure & DNA Replication

  • DNA and RNA are both types of nucleic acids found in all living cells. They are essential for proper cell functioning, involved in building proteins.
  • DNA holds or stores genetic information used for growth and development of organisms.
  • RNA transfers the genetic code from DNA out of the nucleus to carry it to ribosomes to make proteins (translation).
  • Nucleotides are the repeating units forming DNA and RNA polymers. Each nucleotide consists of a pentose sugar, a nitrogenous base, and a phosphate group.
  • DNA nucleotides use deoxyribose sugar and have four bases (adenine, cytosine, guanine, and thymine).
  • RNA nucleotides use ribose sugar and have four bases (adenine, cytosine, guanine, and uracil).
  • Phosphodiester bonds connect nucleotides in a chain, forming the sugar-phosphate backbone.
  • Purines (adenine and guanine) have a double ring structure.
  • Pyrimidines (cytosine, thymine, and uracil) have a single ring structure.
  • DNA exists as a double helix with antiparallel strands held together by hydrogen bonds between complementary base pairs.
  • Adenine pairs with Thymine (A-T), and Guanine pairs with Cytosine (C-G). Each pair has a specific number of hydrogen bonds.
  • RNA is single-stranded and shorter than DNA.
  • Ribosomes are organelles responsible for protein synthesis in all cells. Ribosomes are composed of ribosomal RNA (rRNA) and proteins, and can occur free in the cytoplasm or bound to the rough endoplasmic reticulum.
  • Semi-conservative replication is a process where each new DNA molecule contains one original strand and one newly synthesized strand.
  • The process of replication begins with Helicase unwinding the DNA double helix, then DNA polymerase creating new strands using free nucleotides.
  • DNA polymerase can only build new strands in the 5' to 3' direction.
  • One strand (leading strand) is synthesized continuously, while the other (lagging strand) is synthesized in short segments (Okazaki fragments) that are subsequently connected by the enzyme DNA ligase.
  • The process is vital for creating identical genetic copies for cell division and growth.

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AQA A Level Biology Nucleic Acids: Structure & DNA Replication PDF

Description

Explore the fascinating world of nucleic acids, focusing on the structure of DNA and RNA, and the process of DNA replication. This quiz covers key concepts including nucleotide components, the differences between DNA and RNA, and their essential roles in genetic information transfer and protein synthesis.

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