What is a gene?
A gene is a sequence of nucleotides that forms part of a DNA molecule.
* Contains instructions for making one specific polypeptide (protein)
* A single DNA molecule contains many genes, each coding for a different protein.
Genes are fundamental units of heredity and play a crucial role in determining traits.
What are proteins made of?
- Amino acids joined together by peptide bonds
- Form polypeptide chains
- There are 20 different amino acids commonly used to build biological proteins.
The sequence and number of amino acids determine the protein’s structure and function.
What determines the shape and function of a protein?
The exact sequence of amino acids determines how the protein folds.
* This initial amino-acid sequence is called the primary structure.
* The primary structure determines the final 3D shape, which determines the protein’s function.
Protein folding is critical for its biological activity.
Why do genes control protein function?
Genes control protein function because they determine the sequence of nucleotide bases in DNA, which is transcribed into mRNA and read as codons. These codons specify the order of amino acids in a polypeptide, forming the protein’s primary structure. The primary structure determines how the protein folds into its three-dimensional shape, which ultimately determines the function of the protein.
What is meant by the triplet code?
The genetic code is read in groups of three nucleotide bases, called triplets.
* Each triplet codes for one specific amino acid.
The triplet code is fundamental to the process of translation in protein synthesis.
Why must the genetic code be read in triplets?
There are four DNA bases, but only four bases alone would not code for enough amino acids.
* Reading bases in groups of three allows 64 possible combinations, enough to code for all amino acids.
This coding system is essential for the diversity of proteins.
What is a codon?
A codon is a triplet of bases on mRNA.
* Each codon specifies one amino acid or a start/stop signal during protein synthesis.
Codons are crucial for the translation process in protein synthesis.
What is an anticodon?
An anticodon is a triplet of bases on a tRNA molecule.
* It is complementary to an mRNA codon and ensures the correct amino acid is delivered to the ribosome.
Anticodons play a vital role in matching tRNA to mRNA during translation.
What is the function of start codons?
Start codons signal the beginning of a gene/protein synthesis
* They ensure the ribosome starts reading the mRNA at the correct point.
* The start codon codes for methionine.
Start codons are essential for initiating protein synthesis.
What is the function of stop codons?
Stop codons signal the end of protein synthesis.
* They do not code for an amino acid but cause the polypeptide chain to be released.
Stop codons are crucial for terminating the translation process.
What does non-overlapping mean in the genetic code?
Non-overlapping means each base is read once only, as part of one codon.
* Each codon is read separately and does not share bases with neighbouring codons.
This feature ensures clarity in the genetic code.
Why is the genetic code degenerate?
Degeneracy exists because more than one codon can code for the same amino acid, this occurs because there are 64 codons but only 20 amino acids
* This reduces the impact of mutations, as a base change may still code for the same amino acid.
Understanding degeneracy is important for genetic stability.
How does degeneracy limit the effects of mutations?
Because multiple codons can code for the same amino acid so if there is a mutation the altered codon can still code for the same amino acid - this is called a silent mutation
What does it mean that the genetic code is universal?
Universal means that almost all organisms use the same codons for the same amino acids.
* There are only rare exceptions (e.g. mitochondria).
This universality is significant for genetic engineering and biotechnology.
Why is the universal genetic code important?
It means genes can be transferred between species and still be correctly translated.
* This is why genetic engineering is possible.
The universal nature of the genetic code facilitates advancements in genetic research.
What happens to mRNA after it is formed?
mRNA leaves the nucleus via nuclear pores in the nuclear envelope and binds with a ribosome which reads the mRNAs codons to build a specific protein with the help of tRNA brining the anticodons.
- It acts as a template for assembling amino acids into a polypeptide.
The transport of mRNA is a critical step in protein synthesis.
How do codons and anticodons ensure accuracy in protein synthesis?
Only tRNA molecules with complementary anticodons bind to each mRNA codon.
* This ensures the correct amino acid is added in the correct position.
This mechanism is vital for the fidelity of protein synthesis.
Why is accurate reading of the genetic code essential?
If codons are read incorrectly, the wrong amino acids are added. This changes the protein’s primary structure, altering its shape and function.
Errors in reading the genetic code can lead to dysfunctional or random proteins.
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2.1.2 - Fundementals Of Biological Molucles13
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2.1.2 - Molecular Building Blocks25
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2.1.2 - Properties Of Water24
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2.1.2 - Sugars And Carbohydrates18
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2.1.2 - Inorganic Componds12
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2.1.2 - Test For Biological Molecules15
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2.1.1 - Cell Biology40
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2.1.1 - Cell Structure36
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2.1.1 - Organelles And The Production Of Proteins11
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2.1.1 - The Cytoskeleton11
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2.1.3 - Nucleotides And Phosphodiester Bonds17
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2.1.5. - The Plasma Membrane39
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2.3.1 - Nucleic Acids15
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2.2 - The Cell Surface Membrane32
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The Cell Cycle18
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The Stages Of Mitosis11
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The Mammalian Gas Exchange System34
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DNA & RNA Structure - Nucleotides18
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Phosphodiester Bonds & Sugar Phosphate Backbone6
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The Genetic Code18
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DNA Replication13
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Transcription19
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Translation18
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Protein Structure36
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Specilised Cells35
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Gas Exchange In Animals30
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Gas Exchange In Insects And Fish25
