Topic 1 Flashcards
What does DNA do?
What is it’s structure?
What are it’s sub unit’s structure?
stores and transmits genetic information
it consists of 4 bases, ATGC
helical double-stranded molecule, held together by weak hydrogen bonds.
Nucleotide consists of Nitrogen base, Deoxyribose sugar and phosphate.
Compare Eukaryote DNA to Prokaryote DNA
DNA is unbound and circular in the cytosol of prokaryotes and in the mitochondria and chloroplasts of eukaryotes.
In eukaryotes, DNA is bound to proteins in linear chromosomes, which are found in the nucleus.
What is the purpose of replicating DNA?
How can DNA replicate?
Replication of DNA allows for genetic information to be inherited.
The structural properties of the DNA molecule, including nucleotide composition and pairing, and the weak bonds between strands of DNA, allow for replication.
• Describe and represent the process of semi-conservative replication of DNA.
Two original strands of DNA act as a template for two new complementary strands. the two new DNA strands have one new strand and one old strand.
What is a gene and what does it do?
A segment of DNA on a chromosome.
consists of a unique sequence of nucleotides.
codes for a functional protein or an RNA molecule.
Describe Exons and Introns:
Do prokaryotic cells have introns?
coding and non-coding segments of DNA found in genes.
Introns are spliced out
exons and introns are transcribed but only the information contained in exons is translated to form a polypeptide.
most prokaryotic cells do not have introns.
Describe protein synthesis
involves transcription of a gene into messenger RNA (mRNA), and translation of mRNA into an amino acid sequence at the ribosomes.
Describe protein structure:
Explain what determines this structure:
What can denature the structure?
Primary- the sequence of amino acids in the polypeptide chain. Determined by the sequence of bases on the mRNA which is determined by the sequence of bases on the DNA that is the gene
Secondary- Coiling or folding of localised sections of polypeptide chain, determined by the primary structure
Tertiary- 3D shape of polypeptide chain, determined by the primary & secondary structure. which is distorted through pH or Heat.
Quaternary- where it is made up of more than one polypeptide chain.
State functions of proteins:
Express why this 3D shape is important
Structural- hair nails ligaments Catalyse reactions- enzymes Contraction Transport Defence Coordination- hormones, receptors Storage
Specific shapes are required in proteins to be complementary to their substrate.
Describe the induced-fit model of enzyme–substrate binding.
Enzymes form a enzyme-substrate complex
enzymes put pressure(stress) on the bonds in the substrate
move after joining which is why it is called an induced fit
Lowering activation energy.
Factors affecting phenotypic expression of genes
how is cellular differentiation controlled?
depends on factors controlling transcription and translation.
Promoter: reigon on DNA. transcription factors can bind to assist in binding of DNA polymerase or decrease it. Activators and repressors
controlled by gene expression.
What is epigenetic change? Describe epigentic changes and what they can do?
It is a change in gene expression without altering the DNA sequence.
cytosine nucleotides in DNA can be methylated and this alters gene expression.
Epigenetic changes can cause human diseases.
describe mutations and their causes:
Will mutations transfer through generations?
Mutation is a random permanent change
errors in DNA replication or cell division, or from damage by physical or chemical factors in the environment.
it is not likely that it would transfer to kids because mutation is only in somatic cells, but if there is a mutation in the germ cells it is more likely.
Describe PCR, including roles of: – heating and cooling – primers – free nucleotides – heat-resistant enzymes.
DNA is heated to split the helix into two strands, primers are used to keep the DNA from rejoining when cooled, the single strands act as a template for DNA polymerase to replicate, the primer is included in a mixture of free nucleotides so that there is a higher chance that the primer will bond to the DNA strand upon cooling. This is done repeatedly until the primer or free nucleotides are exausted. Using heat resistant enzymes so they dont denature at the melting point of DNA.
Describe electrophoresis:
Different length DNA fragments are analysed, separated according to size, placed in the negative end of a gel block or amarose. A current is turned on and, cause DNA is negatively charged It will move towards the positive electrode, the smaller fragments moving faster than the larger fragments.
