1. What is meant by the statement “DNA contains the instructions for the structu
ID: 205394 • Letter: 1
Question
1. What is meant by the statement “DNA contains the instructions for the structure and function of cells.”?
2. How do your cells know how to make a protein such as haemoglobin for your red blood cells to carry oxygen to all your body cells?
3. How do your cells know if a protein is needed?
4. Where do the amino acids that are added to proteins come from? Does our body make them? Do
we get them from our environment?
5. What might the effect of a small change in DNA be on the functioning of a protein in your body?
Would single DNA nucleotide change cause haemoglobin to stop functioning?
Explanation / Answer
1.DNA contains the instructions for the structure and function of cells - this means that it is the DNA that directs the synthesis of proteins via process of gene expression i.e transcription and translation.The proteins thus formed are required to maintain the structure as well as the functioning of the cell.Through codons, the DNA specify which aminoacids are required for whicb proteins to be formed in the cell.
2.The cells do not directly know how to make a protein such as haemoglobin for our red blood cells to carry oxygen to all your body cells,It is the DNA that tells the cells which protein is to be made indireclty via the process of transcription and translation.
3.The cells know that a protein is needed via the process of cell signalling.When there is a need of a specific protein in the cell,specific ligands bind to their specific receptors thereby activating a series of cascades that signal proteins known as the transcription factors in the nucleus to bind to specific DNA sequences or promoters of gene and activate it to carry out the process of gene expression.
4.The aminoacids come from both the cells in our body as well as from outside the body through our diet.Some aminoacids are made up in the cells of the human body and are added to proteins while some of them we have to get it through diet as our body cells cannot synthesize them and these are known as essential aminoacids.These include nine aminoacids i.e histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine.
5.The small change in DNA be have a great amount of effect on the functioning of a protein in our body.At times this can lead to non functioning of the protein as well or synthesis of a truncated protein that isleft with no function.The genetic code of DNA directs the synthesis of proteins through codons which are nothing but a triplet of three nucleotides that direct insertion of aminoacids into the proteins during translation process.Each codon specifies a specific aminoacid that is to be inserted into the protein.A gene that encodes a protein is a part of DNA consisting of a reading frame of codons.When a single base is changed in this codon due to mutation, that would result in insertion of a wrong aminoacid in the protein thereby making it non functional.If the DNA nucleotide change takes place in the gene for haemoglobin,then that would cause haemoglobin to stop functioning until and unless it is a silent mutation.
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