jnjnuj Flashcards
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Role and structure of DNA
Substance that contains instructions that determine your characteristics
Deoxyribose nuclei acid, genetic material found in the nucleus in each one of your cells
Structure:
DNA -> nucleotide -> Base -> A, C, T, G
DNA is a polymer consisting of two long strands of small units that repeat throughout the structure, called nucleotides
A nucleotide is made up of a phosphate and a base attached to the sugar
Sugar and phosphates of nucleotides form the long strands
Attraction between opposite bases holds the two strands together
Place in size order:
Gene, chromosome, genome, DNA, nucleus, cell, nucleotide
Nucleotide (smallest)
Gene
DNA
Chromosome
Genome
Nucleus
Cell (largest)
Chromosome
Each long polymer of DNA
Nucleotides
The units that make up polymer of DNA
Each nucleotide is made up of…
1 phosphate
1 deoxyribose
1 organic base
O - ⭔ - ▭
Phosphate - Deoxyribose sugar - nitrogenous base
4 organic bases
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
What is a gene
Short section of DNA found upon a chromosome which codes for a specific protein
Protein that DNA coils around in the formation of a chromosome
Histone protein
Complementary base pairing
Adenine pairs with thymine
Cytosine pairs with guanine
Name of the structure formed by DNA, discovered by Watson and Crick in 1950s
Double helix
Who produced the first ever photograph of DNA, Photo 51, that lead to the discovery of DNA’s structure
Rosalind Franklin
Why double helix is described as being anti parallel
2 strands are parallel but run in opposite directions
Sugar phosphate backbone
The phosphate and deoxyribose molecules in a DNA polymer are joined
O - ⭔ - [C] ≡ [G] - ⭔ - O
/ \
O - ⭔ - [A] = [T] - ⭔ - O
Hydrogen bonds
Weak bonds formed between bases of opposing strands of DNA
O - ⭔ - [C] ≡ [G] - ⭔ - O
/ \
O - ⭔ - [A] = [T] - ⭔ - O
2 main sages of protein synthesis
Transcription
Translation
Where does protein synthesis take place
Transcription starts in nucleus and ends where mRNA strand leaves through nuclear pore towards the ribosomes
Translation happens in cytoplasm with assistance of ribosomes
Transcription
DNA unzips to allow mRNA to use it as template to make a copy of a section which codes for a specific protein
Once copied, mRNA detaches and leaves nucleus and DNA zips back up
Base T is replaced by U
Translation
mRNA is read by nucleus in groups of 3 codons to produce a protein
tRNA molecules are attracted to 3 complementary bases upon mRNA bringing specific amino acids with them
These join together into a chain to form a protein
Differences between DNA and RNA
DNA = Deoxynucleotides
Bases A T C G
Deoxyribose sugar
Double helix structure
Cannot leave nucleus
Long polynucleotide chain
DNA is completely protected by the body from degradation
Self replicating
RNA = Ribonucleotides
Bases A U C G - THYMINE REPLACED WITH URACIL
Ribose sugar
Single strand
Can move in and out of nucleus
Short polynucleotide chain - SHORTER THAN DNA
Strands are continually made, broken down and reused
Synthesised from DNA on an as-needed basis
Enzymes
Proteins
Biological catalysts - used to speed up reactions
Can’t be used up
What molecule do enzymes bind to
Substrate
Active site
Part of enzyme that binds to substrate
Has specific shape which is formed by way its amino acids are folded together within protein
Lock and key hypothesis
Only 1 substrate will fit into active site of 1 enzyme
They must be an exact fit
What is formed when a substrate binds to an enzyme
Enzyme-substrate complex
Factors affecting enzyme activity
Temperature
pH
Substrate availability / concentration
Enzyme concentration
Effect of temperature on enzyme activity
Rate of reaction increases due to increased kinetic energy, meaning increased number of successful collisions
Higher temperature = faster reaction
If temperature becomes too high, enzymes denature
Denatured
Structure of protein that forms enzyme has been altered due to high heat or a change in pH
Change of shape affects active site
Substrate can no longer bind to enzyme
If an enzyme is denatured, what happens to rate of reaction
Enzyme can no longer catalyse the reaction
Rate of reaction decreases
How substrate concentration affects enzyme controlled reactions
Higher the substrate availability, higher the rate of reaction,
until all the enzyme-substrate bases are used up
Genotype
All the genes you can have (blue/brown eyes)
All combinations of alleles present in an organism
Phenotype
Gene that is being expressed (brown eyes only)
Rate of reaction
Rate of reaction = Amount of product formed / Time
Rate of a reaction increases if:
Temperature is increased
Concentration of a dissolved reactant is increased
Pressure of a reacting gas is increased
Solid reactants are broken into smaller pieces
A catalyst is used
DNA database pros and cons
+
Check on heredity / establish family tree / find relatives
Look for genetic disorders / identify health risk factors
To choose correct medication / genomics
Confirm a person’s identity
-
Avoid being identified for a crime
Avoid high insurance costs
Remain unaware of family history / genetic disorders
Dislike of sharing personal details / privacy (reasons)
