4.6.1.5 DNA structure Flashcards
Describe DNA.
- A polymer made from four different nucleotides
What does each nucleotide consist of?
- Each nucleotide consists of a common sugar and phosphate group with one of four different bases attached to the sugar
What four bases does DNA contain?
- DNA contains 4 bases:
- thymine, T
- adenine, A
- guanine, G
- cytosine, C
What is a sequence of three bases?
- A sequence of three bases is the code for a particular amino acid
What does the order of bases control?
- The order of bases controls the order in which amino acids are assembled to produce a particular protein
What do the long strands of DNA consist of?
- The long strands of DNA consist of alternating sugar and phosphate sections
What is attached to each sugar?
- One of four bases
What the DNA polymer made up of?
- The DNA polymer is made up of repeating nucleotide units
Recall a simple description of protein synthesis.
- The process of making proteins
- Transcription (taking a single gene of DNA and copping it into a structure called mRNA)
- Translation (taking the mRNA strand and turning it into protein)
Explain simply how the structure of DNA affects a protein made.
- DNA structure determines the protein synthesised. If this changes a different protein will be made.
- A copy of the DNA is made, but is now mRNA.
- The copy moves to the ribosome into to the cytoplasm. Amino acids are connected together in a specific order at the ribosome
to create a specific protein molecule.
Describe how genetic a variants may influence phenotype.
- in coding DNA by altering the activity of a protein and in non-coding DNA by altering how genes are expressed
- The structure of DNA is important in synthesising specific proteins needed in biological processes.
- Not all parts of the DNA code for proteins, there is a coding and non-coding part of DNA, which can switch genes on and off, so variations in these areas may affect gene expression, and if the correct protein is synthesised or not.
In complementary strands what happens?
- In a complementary strands a C and a G on the opposite strand and a T to an A
Explain how a change in DNA structure may result in a change in the protein synthesise by a gene.
- A mutation changes the sequence of bases in DNA and hence the triplet code.
- It therefore changes the sequence of amino acids in the protein’s primary structure.
- This changes the side groups that are available to form covalent or ionic bonds to form the proteins specific tertiary structure.
Where are proteins synthesised?
- Proteins are synthesised on ribosomes, according to a template
What do carrier molecules bring?
- Carrier molecules bring specific amino acids to add to the growing protein chain in the correct order
What happens when the protein chain is complete?
- When the protein chain is complete it folds up to form a unique shape
What does the unique shape enable?
- The unique shape enables the proteins to do their job as enzymes, hormones, or forming structures in the body such as a collagen
When do mutations occur?
- Mutations occur continuously
Why do mutations not alter the protein?
- Most do not alter the protein or only alter it slightly so that its appearance or function is not changed
What do a few mutations code for?
- A few mutations code for an altered protein with a different shape
Why can’t an enzyme no longer fit the substrate?
- An enzyme may no longer fit the substrate binding site or a structural protein may lose its strength
Not all parts of DNA code for protein.
- what do non-coding parts of DNA do?
- Non coding parts of DNA can switch genes on and off, so variations in these areas of DNA may affect how genes are expressed
