SAC 1 REVISION Flashcards
Subunits of DNA
Nucleotides
Structure of DNA
Anti-Parallel Double Helix
Role of tRNA
Transfer RNA molecules supply specific amino acids to the growing polypeptide chain at the ribosome. Complementary base pairing between tRNA anticodons and mRNA codons ensure the synthesis of the correct primary structure
What is the primary structure of proteins
Sequence of amino acids in a polypeptide chain
Units of RNA
Phosphate group, Ribose sugar, Nitrogenous base
Explain RNA processing
Introns are spliced out and removed and the exons join back together. A methyl cap is added to the 5’ end and a poly(A) tail is added to the 3’ end
Describe translation
Translation involves the synthesis of a polypeptide chain at a ribosome as it reads a specific sequence of mRNA codons. At each codon, a tRNA molecule with a complementary anticodon enters the ribosome to add a specific amino acid to the growing polypeptide chain
What do the 3’ and 5’ ends represent
The 5’ and 3’ mean ‘five prime’ and ‘three prime’, which indicates the carbon numbers in the ribose component of each nucleotide. The 5’ carbon is attached to the phosphate group of the nucleotide and the 3’ carbon sits at the ‘sugar’ end of the nucleotide
Regulatory genes
A regulatory gene codes for a transcription factor that binds to a repressor protein, which changes its 3d conformation and detaches from the operator sequence of the gene
Types of secondary structure
Alpha Helices, Beta pleated sheets and Random coils
What is the tertiary structure
The tertiary structure refers to the way a polypeptide chain folds and coils to form a complex 3D functional conformation
What happens in prokaryotes in high Tryptophan levels
Tryptophan molecule binds to a repressor protein and changes its 3D conformation. Activated repressor protein binds to the operator region of gene preventing the RNA polymerase from binding to the promotor sequence, preventing transcription
Function of mRNA
Messenger RNA carries the genetic instructions of DNA (from a gene) to the ribosomes in order that the ribosomes synthesise the correct polypeptide chain
What happens in terms of Attenuation in high Tryptophan levels
The leader sequence is transcribed with high tryptophan levels. When ribosomes read the leader mRNA transcript, they do not pause at trp codons. A terminator hairpin loop forms on the mRNA and the ribosome detaches from the short mRNA transcript, which causes RNA polymerase to detach from the DNA, preventing transcription from being completed
Proteome
All the proteins that can be translated by an organism at a specific time
Function of RNA polymerase
RNA polymerase attaches to the promotor sequence and breaks hydrogen bonds to unwind DNA. It then re=ads the template strand in the 3’ to 5’ direction producing a copy of pre-mRNA
Name the molecule of inheritance
Deoxyribonucleic acid
DNA base sequences code for
Specific polypeptide chain
Nucleotides contain
Phosphate group, Pentose sugar, Nitrogenous base
Name the purines
Adenine and Guanine
Name the pyrimidines
Cytosine, thymine, uracil
Are purines single or double ringed
Double
DNA nucleotides contain
Phosphate group, Deoxyribose sugar, Nitrogenous base
RNA nucleotides contain
Phosphate group, Ribose sugar, Nitrogenous base
What DNA strand contains the genes
Template strand
Genotype
The allele combination of an individual
What are the temperatures and words used in steps of PCR?
94 (denature) , 55 (anneal) , 72 (extend)
Outline the 3 steps of PCR (polymerase chain reaction)
- DNA is heated to 94 degrees where the DNA is unzipped and DENATURED due to the broken hydrogen bonds.
- The 2 single stranded DNA strands are cooled to 55 degrees, where primers ANNEAL to the 3’ end of the DNA strands.
- It is reheated to 72 degrees, where Taq polymerase used the primers as a guide to where it should begin extending the singular DNA strands. It uses complementary base pairing to EXTEND the strands and synthesis 2 double strands.
This process is continued for as many times as needed.
Why do we use PCR?
PCR helps create millions of copies of DNA in a short amount of time. This is used mainly for Gel electrophoresis, since you need at least 20 pieces of evidence to convict someone of a crime.
What can CRISPR do to a gene?
Changed genome. It can add new nucleotides to change a gene, it can also remove nucleotides which can make it a non functioning gene. It can also edit nucleotides by replacing them to edit a faulty gene.
What is a name of a plasmid which is altered?
A transformed plasmid
Why do scientists add virus resistant genes into the plasmid?
It can see which bacteria has taken up the plasmid at the bacterias who are exposed and die haven’t taken up the plasmid whereas those resistant are bacteria which have taken up the transformed plasmid.
What is DNA ligases role in plasmid altering?
DNA ligase create phosphodiester bonds between the human gene and the original plasmid gene to make sure the human gene stays in the plasmid.
Why do scientists add a glow gene into transformed plasmids?
Scientist add a glow gene as it helps detect if the plasmid is present in the bacteria. Once the scientists put the bacteria in the petri dish, the bacteria will glow if the plasmid is present.
When does the polypeptide chain go through the rough ER and the Golgi?
It goes through them when the polypeptide chain will be transported out of the cell and into the body. When the cell needs the protein for itself, the cell will use free ribosomes to synthesis the protein and be kept in the cell.
What gives the rough Er its rough texture?
The ribosomes attached around the outside.
Why is it smaller fragments of DNA can travel through the gel quicker?
The smaller fragments can travel through the pores of the gel more easily, compared to the larger fragments which lag behind.
what is the role of Cas9 in gene editing?
It unwinds DNA and cuts at both strands at a specific target sequence
what is the role of sgRNA in gene editing?
It guides the cas9 to the target sequence on the DNA as it is complementary to the target sequence
What are the two ways CRISPR can edit genes?
- By gene knocking in (gene editing) where a new DNA sequence is inserted into the DNA. eg. replacing a faulty gene sequence with correct sequence to restore normal gene functioning
- By gene knocking out (gene silencing) where errors from the repair mechanisms used to mend broken DNA cause the insertion or deletion of bases. This changes how the sequence is read. eg. used to silence a faulty gene
what are the benefits of CRISPR?
it enables scientists to precisely and easily edit genes at a low cost. The process is also very quick in comparison to other gene editing tools.
