Genes and Proteins
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Questions and Answers

The transcription initiation complex is formed by additional transcription factors binding to the DNA along with ______.

RNA polymerase II

As enzymes, proteins ______ reactions.

catalyse

Transport proteins such as haemoglobin carry ______.

oxygen

Antibodies defend against ______.

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

Structural proteins provide support to cells and ______.

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

The first person to suggest that genes dictate ______.

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

Alkaptonuria is a condition where urine turns black upon exposure to ______.

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

Sir Archibald Garrod suggested that genes make ______.

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

A prototroph can synthesise all its amino acids for ______.

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

The One Gene One ______ hypothesis was proposed by Beadle and Tatum.

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

Myoglobin is an example of a ______ protein.

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

The central dogma describes the flow of genetic information from ______ to RNA to protein.

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

Several transcription factors must bind to the DNA before ______ polymerase II can do so.

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

The synthesis of a ______ occurs during translation.

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

Aminoacyl-tRNA ______ attach amino acids to their corresponding tRNA molecules.

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

During translation, the ______ cycle involves the addition of amino acids to the growing polypeptide chain.

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

Proteins act as ______, catalyzing biochemical reactions within the body.

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

Proteins such as ______ proteins are essential for muscle contraction.

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

The genetic code was deciphered to understand how information is ______.

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

Not all ______ are enzymes, but they all play vital roles in biological processes.

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

Nirenberg and Matthaei conducted experiments in 1961 to decipher the ______ code.

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

The One Gene One Enzyme hypothesis was based on experiments with the bread mould ______ crassa.

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

The triplet code consists of 4 ______ which produce 64 possible combinations.

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

In eukaryotes, the transcription process begins at a specific site called the ______ box.

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

An auxotroph has lost the ability to synthesise certain substances required for its ______.

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

Haemoglobin is an example of a ______ protein as it consists of multiple polypeptide chains.

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

What is the primary role of the transcription initiation complex in gene expression?

<p>To initiate the transcription of DNA into RNA</p> Signup and view all the answers

Which of the following types of proteins is responsible for facilitating biochemical reactions?

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

What is the significance of aminoacyl-tRNA synthetase in protein synthesis?

<p>It attaches amino acids to the appropriate tRNA molecules</p> Signup and view all the answers

In which process do proteins perform a role as antibodies?

<p>Defense against pathogens and diseases</p> Signup and view all the answers

What is the role of the E site in a ribosome during translation?

<p>To release uncharged tRNA from the ribosome</p> Signup and view all the answers

Which statement best describes the prototroph?

<p>It can synthesize all its amino acids for growth.</p> Signup and view all the answers

What does the One Gene One Polypeptide hypothesis suggest?

<p>One gene corresponds to the synthesis of one polypeptide chain.</p> Signup and view all the answers

What is the main function of the TATA box in eukaryotic promoters?

<p>To initiate transcription by recruiting transcription factors.</p> Signup and view all the answers

What is a key feature of the genetic code?

<p>It consists of 64 possible combinations of three nucleotides each.</p> Signup and view all the answers

In relation to Alkaptonuria, what biochemical process is impaired?

<p>The breakdown of tyrosine and phenylalanine.</p> Signup and view all the answers

Which enzyme is responsible for synthesizing RNA during transcription in eukaryotes?

<p>RNA polymerase II.</p> Signup and view all the answers

What does the triplet code in genetics refer to?

<p>A sequence of three nucleotides that codes for a specific amino acid.</p> Signup and view all the answers

Which of the following is NOT a transcription factor's role during transcription initiation?

<p>Altering the genetic sequence of the DNA.</p> Signup and view all the answers

What is the main function of the transcription initiation complex in the process of gene expression?

<p>To facilitate the binding of RNA polymerase II to DNA</p> Signup and view all the answers

Which protein type is primarily involved in defending the body against pathogens?

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

What term describes the role of certain proteins in regulating metabolic processes by increasing reaction rates?

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

What occurs during the elongation cycle of translation?

<p>Addition of amino acids to the growing polypeptide chain</p> Signup and view all the answers

Which of the following best describes the role of aminoacyl-tRNA synthetase in protein synthesis?

<p>To attach amino acids to their corresponding tRNA molecules</p> Signup and view all the answers

What does the One Gene One Polypeptide hypothesis propose about gene function?

<p>Each gene encodes a unique polypeptide chain.</p> Signup and view all the answers

Which of the following best describes a prototroph?

<p>An organism capable of synthesizing all necessary compounds for growth.</p> Signup and view all the answers

What is the significance of the TATA box in eukaryotic gene transcription?

<p>It helps determine the start point for transcription.</p> Signup and view all the answers

In the context of genetic code, what does the triplet code refer to?

<p>Three nucleotides coding for a single amino acid.</p> Signup and view all the answers

Which statement correctly describes the role of transcription factors in eukaryotic transcription?

<p>They facilitate the binding of RNA polymerase to the promoter.</p> Signup and view all the answers

What experimental organism did Beadle and Tatum use to support the One Gene One Enzyme hypothesis?

<p>Neurospora crassa.</p> Signup and view all the answers

What is a primary function of myoglobin within muscle tissue?

<p>Storing oxygen for muscle contraction.</p> Signup and view all the answers

Which of the following represents a true statement regarding RNA viruses?

<p>They use reverse transcriptase to produce DNA from RNA.</p> Signup and view all the answers

What role do transcription factors play in the formation of the transcription initiation complex?

<p>They bind to DNA and assist in recruiting RNA polymerase II.</p> Signup and view all the answers

Which statement best describes the function of aminoacyl-tRNA synthetase in protein synthesis?

<p>It attaches the correct amino acid to its corresponding tRNA molecule.</p> Signup and view all the answers

What is one primary biological function of proteins?

<p>They catalyze metabolic reactions.</p> Signup and view all the answers

Which type of protein is primarily responsible for carrying oxygen in the blood?

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

What is the main idea behind the One Gene One Enzyme hypothesis?

<p>Each gene encodes a specific enzyme.</p> Signup and view all the answers

What is a feature of a prototroph?

<p>It can synthesize all required substances for growth.</p> Signup and view all the answers

Which statement accurately describes the role of the TATA box in eukaryotic transcription?

<p>It is the region where RNA polymerase binds to initiate transcription.</p> Signup and view all the answers

What distinguishes an auxotroph from a prototroph?

<p>An auxotroph cannot grow without external supplements.</p> Signup and view all the answers

What is the primary function of reverse transcriptase in RNA viruses?

<p>To convert RNA back to DNA.</p> Signup and view all the answers

How many nucleotides are required to form a single codon in the genetic code?

<p>3 nucleotides</p> Signup and view all the answers

What characteristic distinguishes myoglobin from haemoglobin?

<p>Myoglobin consists of a single polypeptide chain, while haemoglobin has multiple chains.</p> Signup and view all the answers

What is the significance of the triplet code in genetics?

<p>It consists of three nucleotides that code for specific amino acids.</p> Signup and view all the answers

What is the purpose of the 5' cap and 3' poly(A) tail added to pre-mRNA during processing?

<p>They help in mRNA stability and translation.</p> Signup and view all the answers

What role do transcription factors play in eukaryotic transcription initiation?

<p>They form the transcription initiation complex.</p> Signup and view all the answers

What is the role of the ribosome during the elongation cycle of translation?

<p>It joins amino acids into a polypeptide chain.</p> Signup and view all the answers

What does the term 'wobble pairing' refer to in the context of tRNA?

<p>It permits tRNA to recognize multiple codons for the same amino acid.</p> Signup and view all the answers

What initiates the termination of translation?

<p>The recognition of a stop codon by a release factor.</p> Signup and view all the answers

What is the role of the 5' cap added to pre-mRNA during RNA processing?

<p>It protects the mRNA from degradation.</p> Signup and view all the answers

Which process allows tRNA to recognize multiple codons for a single amino acid?

<p>Base pairing wobble.</p> Signup and view all the answers

What happens during the termination phase of translation?

<p>A release factor binds to the ribosome A-site.</p> Signup and view all the answers

Which statement best illustrates the function of ribosomes during translation?

<p>They decode mRNA sequences to form polypeptides.</p> Signup and view all the answers

What is the significance of the poly(A) tail that is added to mRNA?

<p>It stabilizes the mRNA and prevents degradation.</p> Signup and view all the answers

What is the role of RNA polymerase during transcription?

<p>To bind to the promoter and synthesize RNA.</p> Signup and view all the answers

Which of the following correctly describes the addition of the 5' cap and 3' poly(A) tail during RNA processing?

<p>They enhance the stability and translation efficiency of mRNA.</p> Signup and view all the answers

What is the purpose of wobble pairing in translation?

<p>To allow tRNA to recognize multiple codons for the same amino acid.</p> Signup and view all the answers

What triggers the termination of translation?

<p>The recognition of a stop codon by the ribosome.</p> Signup and view all the answers

Where does the assembly of the transcription initiation complex primarily occur in eukaryotes?

<p>At the promoter region of the DNA.</p> Signup and view all the answers

RNA polymerase binds to the ______ to initiate transcription.

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

During RNA splicing, ______ are removed to convert pre-mRNA to mature mRNA.

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

The ______ is responsible for carrying amino acids to the ribosome during translation.

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

When a stop codon is reached, translation ends, and a ______ binds at the ribosome A-site.

<p>release factor</p> Signup and view all the answers

The addition of a 5' cap and a 3' ______ tail is part of mRNA processing.

<p>poly(A)</p> Signup and view all the answers

During transcription, RNA polymerase binds to the ______.

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

In eukaryotes, pre-mRNA is processed to mature ______.

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

The ribosome recognizes the codon during the ______ cycle of translation.

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

The ______ factor binds at the ribosome A-site to terminate translation.

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

Wobble pairing allows a single tRNA to recognize multiple ______ for the same amino acid.

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

During the process of transcription, RNA polymerase binds to the ______.

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

The addition of a 5' cap and a 3' poly(A) tail occurs during ______ processing.

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

Transfer RNA (tRNA) has an ______ that matches a codon on mRNA.

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

When a stop codon is reached, translation ends and a release ______ binds at the ribosome.

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

Many ______ can translate the same mRNA at the same time, allowing for efficient protein production.

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

Study Notes

Genes and Proteins

  • Genes contain instructions for making proteins.
  • Proteins can act alone or in complexes to perform many cellular functions.
  • The genome is comprised of chromosomes, which contain genes.
  • DNA is the molecule that carries the genetic information.

Learning Objectives

  • Appreciate how the genetic code was deciphered.
  • Develop a basic molecular understanding of how genetic information is transcribed and translated.

Inborn Errors of Metabolism

  • Genes dictate the phenotype.
  • Alkaptonuria is an example, where urine turns black on exposure to air; tyrosine and phenylalanine are not broken down.
  • In 1909, Archibald Garrod suggested genes make enzymes.

Prototroph and Auxotroph

  • Prototroph: can synthesize all amino acids for growth.
  • Auxotroph: lost the ability to synthesize some substances required for growth.
  • Minimal medium: agar, inorganic salts, glucose, biotin
  • Complete medium: minimal supplemented with amino acids

One Gene-One Enzyme Hypothesis (Beadle and Tatum)

  • Genes are responsible for making specific proteins (enzymes) which function in different ways.
  • Mutation of a gene leads to the dysfunction of the specific enzyme.
  • Beadle and Tatum proposed that each gene in an organism is responsible for making a different protein, most of which function as enzymes.

One Gene-One Polypeptide Hypothesis

  • Not all proteins are enzymes.
  • Not all proteins are monomeric.
  • Myoglobin: monomeric
  • Haemoglobin: tetrameric

Central Dogma

  • DNA leads to RNA, which leads to protein.
  • RNA viruses (in exception): RNA → DNA (using the enzyme reverse transcriptase).

Flow of Genetic Information in Cells

  • Prokaryotic cells: transcription and translation occur in the cytoplasm.
  • Eukaryotic cells: transcription occurs in the nucleus, and translation occurs in the cytoplasm.

The Triplet Code

  • 20 amino acids found in cellular proteins.
  • 4 nucleotides give 64 possible 3-letter "words".
  • mRNA codons specify amino acids (e.g. UUU = Phe).

The Genetic Code

  • A table showing the correspondence between codons and amino acids.
  • Methionine (AUG): start codon initiating translation, and encodes the amino acid methionine.
  • UAA, UAG, and UGA are the three stop codons, terminating translation.

Nirenberg and Matthaei Experiment (1961)

  • Determined the genetic code.
  • Triplets are the codons, which specify amino acids.
  • Examples: UUU = Phenylalanine, AAA = Lysine; CCC = Proline

Eukaryotes Gene Structure

  • Gene structure: Promoter, 5' untranslated region (UTR), exons and introns, 3' UTR, start codon, stop codon.

Stages of Transcription

  • RNA polymerase binds to the promoter.
  • DNA unwinds locally.
  • RNA nucleotides bind.
  • RNA polymerase moves along DNA.
  • DNA rewinds.
  • RNA polymerase terminates transcription.
  • NTPs (nucleotide triphosphates) are used to form RNA.

Transcription Initiation in Eukaryotes

  • Transcription factors bind to DNA before RNA polymerase.
  • Additional transcription factors bind to form the transcription initiation complex.

RNA Processing and Splicing

  • Pre-mRNA is processed to mature mRNA.
  • Addition of 5' cap and 3' poly(A) tail.
  • Introns are removed using RNA splicing.

The Synthesis of Proteins (Translation)

  • mRNA carries the code from DNA to the ribosomes.
  • Ribosomes decode the mRNA sequence to produce a polypeptide chain.
  • tRNA carries amino acids.

Structure of Transfer RNA (tRNA)

  • tRNA has an anticodon that matches a codon on mRNA.
  • Amino acids are attached to the 3' end of tRNA

Aminoacyl-tRNA Synthetase

  • Attaches amino acids to tRNA molecules.
  • AMP (a type of nucleotide) is involved in the process.
  • Pyrophosphate is released.

Base Pairing Wobble

  • Wobble pairing: allows for multiple codons to specify the same amino acid.
  • Atypical base pairing: tRNA can recognize multiple codons for a single amino acid.

Synthesis of a Polypeptide

  • Eukaryotic translation initiation (initiator tRNA binds to the start codon and the 5' cap).

The Elongation Cycle of Translation

  • Ribosome recognizes the codon.
  • Amino acids are joined together.
  • Ribosome moves along the mRNA.

The Termination of Translation

  • When a stop codon is reached, translation ends, and a release factor binds at the ribosome A-site, causing the ribosome to release.
  • mRNA, tRNA and polypeptide are released from the ribosome.

Polyribosomes

  • Many ribosomes can translate the same mRNA at the same time.
  • Multiple ribosomes translate the mRNA.
  • Many proteins can be produced at the same time.

Proteins

  • Proteins perform many functions (enzymes, carrier proteins, antibodies, structural proteins, hormones, and transport proteins such as haemoglobin).

General

  • DNA transcribed into RNA which translated into protein, is a fundamental process known as the central dogma.

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