SL IB Biology - Protein Synthesis Quiz
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Questions and Answers

What enzyme is responsible for transcribing DNA into RNA?

RNA polymerase

Which base in DNA is replaced by uracil in RNA?

Thymine

What are the two strands of DNA involved in transcription called?

Coding strand and template strand

How does the mRNA's base sequence relate to the DNA template strand?

<p>It is complementary to the DNA template strand.</p> Signup and view all the answers

What type of bond forms between the bases of RNA and the DNA template strand?

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

What is the role of mRNA after its formation during transcription?

<p>It is translated into an amino acid chain.</p> Signup and view all the answers

In the transcription of the DNA sequence 'TAC GGA AGA CTT GGG', what will the corresponding RNA transcript be?

<p>AUG CCU UCU GAA CCC</p> Signup and view all the answers

What is the significance of having a 'coding strand' in DNA?

<p>It carries the genetic code that is transcribed into RNA.</p> Signup and view all the answers

What is the role of RNA polymerase in transcription?

<p>RNA polymerase is the enzyme that facilitates the bonding of RNA nucleotides to form the mRNA molecule during transcription.</p> Signup and view all the answers

Where does transcription occur in the cell?

<p>Transcription occurs in the nucleus of the cell.</p> Signup and view all the answers

How does mRNA differ from DNA?

<p>mRNA is single-stranded and contains uracil instead of thymine, while DNA is double-stranded and contains thymine.</p> Signup and view all the answers

What happens to the DNA molecule after transcription is complete?

<p>The hydrogen bonds between the mRNA and DNA strands break, allowing the double-stranded DNA molecule to re-form.</p> Signup and view all the answers

Why is mRNA referred to as 'messenger' RNA?

<p>mRNA is called 'messenger' RNA because it carries genetic information from the DNA in the nucleus to the cytoplasm for protein synthesis.</p> Signup and view all the answers

What triggers the process of transcription?

<p>The process of transcription is triggered when a segment of DNA unwinds, exposing a gene to be transcribed.</p> Signup and view all the answers

What ensures the complementary pairing of RNA nucleotides to DNA during transcription?

<p>The hydrogen bonds formed between the complementary bases of RNA nucleotides and DNA ensure the correct pairing during transcription.</p> Signup and view all the answers

What occurs to mRNA after it is synthesized?

<p>After synthesis, mRNA leaves the nucleus through a pore in the nuclear envelope to enter the cytoplasm.</p> Signup and view all the answers

What is a polypeptide and how is it formed during translation?

<p>A polypeptide is a sequence of amino acids covalently bonded together, formed during translation by synthesizing the amino acids based on the mRNA's genetic code.</p> Signup and view all the answers

What is the role of ribosomes in translation?

<p>Ribosomes serve as the site where mRNA binds and where amino acids brought by tRNA are linked together to form polypeptides.</p> Signup and view all the answers

How do mRNA and tRNA interact during translation?

<p>The anticodon on tRNA pairs with the complementary codon on mRNA, facilitating the correct amino acid addition.</p> Signup and view all the answers

What is the importance of the binding sites on ribosomes?

<p>The binding sites on ribosomes allow mRNA and two tRNA molecules to bind simultaneously, enabling efficient protein synthesis.</p> Signup and view all the answers

What are the components of a ribosome?

<p>A ribosome is composed of a large and small subunit, ribosomal RNA (rRNA), and proteins.</p> Signup and view all the answers

What initiates the process of translation?

<p>Translation is initiated when the mRNA molecule attaches to a ribosome after leaving the nucleus.</p> Signup and view all the answers

What is the function of tRNA in translation?

<p>tRNA brings specific amino acids to the ribosome, where they match their anticodons with the mRNA codons.</p> Signup and view all the answers

What is meant by complementary base pairing in the context of mRNA and tRNA?

<p>It refers to the specific pairing of nucleotides where Adenine pairs with Uracil and Cytosine pairs with Guanine.</p> Signup and view all the answers

How does transcription compare to translating between two languages?

<p>Transcription is like converting text from one language to another using the same characters, with minor adjustments.</p> Signup and view all the answers

Explain the analogy of translation with converting between languages that use different alphabets.

<p>Translation is akin to changing text from a language using a familiar alphabet to one using entirely different characters.</p> Signup and view all the answers

What would be the tRNA anticodon for an mRNA codon with the sequence CAG?

<p>The tRNA anticodon would be GUC.</p> Signup and view all the answers

In the analogy presented, what does the 'alphabet' of nucleic acids refer to?

<p>The 'alphabet' refers to the monomers, which are the nucleotides in DNA and RNA.</p> Signup and view all the answers

What are the main differences between DNA and RNA mentioned in the notes?

<p>The main differences are in the sugars they contain and the presence of Uracil in RNA instead of Thymine in DNA.</p> Signup and view all the answers

Why is understanding transcription and translation important in molecular biology?

<p>Understanding these processes is essential for grasping how genes are expressed and proteins are synthesized.</p> Signup and view all the answers

What role do codons play in the process of protein synthesis?

<p>Codons determine the specific sequence of amino acids in a protein by encoding genetic information.</p> Signup and view all the answers

What is a gene mutation, and what can it result in?

<p>A gene mutation is a change in the sequence of bases in a DNA molecule, which can result in a new allele.</p> Signup and view all the answers

Describe how point mutations can affect polypeptide structure.

<p>Point mutations can alter a single base in the DNA sequence, potentially changing the amino acid sequence of the resulting polypeptide.</p> Signup and view all the answers

Explain why mutations in normal body cells are not inherited.

<p>Mutations in normal body cells are not inherited because these cells die and are eliminated, not passed on to offspring.</p> Signup and view all the answers

What is the consequence of a mutation leading to sickle cell disease?

<p>The mutation causes a single point mutation in the alpha-globin gene, leading to the replacement of glutamic acid with valine in haemoglobin.</p> Signup and view all the answers

How does the sickle cell mutation change the DNA triplet sequence?

<p>The sickle cell mutation alters the DNA triplet from GAG to GTG on the coding strand.</p> Signup and view all the answers

What is the role of mutations during DNA replication?

<p>Mutations occur during DNA replication as copying errors when the DNA is replicated in S phase.</p> Signup and view all the answers

List the two types of effects mutations can have on an organism.

<p>Mutations can be harmful, neutral, or beneficial.</p> Signup and view all the answers

What happens to a polypeptide when a point mutation changes an amino acid?

<p>The polypeptide may have altered structure and function due to the different properties of the new amino acid.</p> Signup and view all the answers

What is the primary result of a base substitution in the DNA molecule related to haemoglobin?

<p>It leads to a change in the amino acid at position 6 of the haemoglobin polypeptide.</p> Signup and view all the answers

How do sickle-shaped red blood cells impact oxygen delivery in the body?

<p>They have a limited oxygen-carrying capacity, which restricts oxygen supply to tissues.</p> Signup and view all the answers

What are the implications of sickle cell anaemia on blood flow?

<p>Sickle-shaped cells can block capillaries, limiting the flow of normal red blood cells.</p> Signup and view all the answers

Discuss the relationship between sickle cell disease and malaria.

<p>There is a correlation where increased malaria cases lead to a higher frequency of sickle cell alleles.</p> Signup and view all the answers

What causes the distortion in shape of red blood cells in sickle cell anaemia?

<p>The production of haemoglobin S instead of haemoglobin A causes the distortion.</p> Signup and view all the answers

What are some common symptoms experienced by individuals with sickle cell anaemia?

<p>Acute pain, fatigue, and anaemia are common symptoms.</p> Signup and view all the answers

Explain how sickle cell alleles provide a selective advantage in certain regions.

<p>They confer increased resistance to malaria, which is beneficial in malaria-endemic areas.</p> Signup and view all the answers

What structural change occurs in the polypeptide caused by a base substitution?

<p>The amino acid at position 6 changes, affecting haemoglobin's function.</p> Signup and view all the answers

Study Notes

SL IB Biology - Protein Synthesis

  • Protein synthesis is a two-stage process:
    • Transcription
    • Translation

Transcription in Protein Synthesis

  • Synthesis of RNA

    • DNA is transcribed to produce mRNA; mRNA carries the genetic code from the DNA to the cytoplasm
    • mRNA production requires RNA polymerase
    • Transcription occurs in the nucleus of the cell
    • A section of DNA unwinds (hydrogen bonds break)
    • Complementary RNA nucleotides bind to the exposed DNA strand
    • The enzyme RNA polymerase joins these RNA nucleotides to form the mRNA molecule
    • The mRNA molecule leaves the nucleus through nuclear pores
    • The original DNA strands reform hydrogen bonds
    • DNA polymerase is not involved in transcription; RNA polymerase is

  • The Process of Transcription

    • Part of a DNA molecule unwinds
    • The exposed gene is transcribed
    • Free RNA nucleotides pair up with the DNA template strand by hydrogen bonds
    • RNA polymerase joins the RNA nucleotides forming the mRNA molecule
    • The hydrogen bonds between DNA and mRNA break
    • The mRNA leaves the nucleus

  • Examiner Tip: Be careful, DNA polymerase is involved in DNA replication, not transcription. RNA polymerase is the enzyme involved in transcription.

The Genetic Code

  • The sequence of DNA bases is determined by a triplet code

  • Each triplet (three bases) codes for a specific amino acid

  • There are 20 different amino acids

  • Some triplets act as start and stop signals

  • Examples:

    • CAG codes for Valine
    • TTC codes for Lysine
    • GAC codes for Leucine
    • CCG codes for Glycine

  • Features of the Genetic Code

    • Non-overlapping; each base only read once in a codon
    • Degenerate; multiple codons may code for the same amino acids
    • Universal; almost all organisms use the same code

  • mRNA codons and amino acids: A table is used to deduce the amino acid coded by an mRNA sequence.

Protein Structure & Mutations

  • A gene mutation is a change in the DNA base sequence

  • Mutations occur randomly during DNA replication; some are harmful, others neutral and some beneficial

  • Mutations in genes for polypeptides can lead to changes in the amino acid sequence of the protein

  • Point mutations are changes in a single DNA base

    • Can lead to a change in the amino acid at that position

  • Example: Sickle cell anaemia

    • GAG (coding strand) mutation to GTG (coding strand)
    • This results in the amino acid Valine replacing Glutamic Acid.
    • This alteration causes a change in the structure of haemoglobin (a protein), and hence the shape and function of red blood cells, causing sickle-cell anemia symptoms.

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SL IB Biology Protein Synthesis PDF

Description

Test your knowledge on the process of protein synthesis, focusing on transcription. This quiz covers key concepts such as the roles of RNA polymerase and the steps involved in synthesizing mRNA from DNA. Challenge yourself with questions about the mechanisms and importance of this vital biological process.

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