4 interactive labs · AS & A Level Biology 9700
· Assemble nucleotides and ATP, join a strand by condensation, then pair an antiparallel partner strand base by base.
Assemble nucleotides and ATP, join a strand by condensation, then pair an antiparallel partner strand base by base.
You will be able to
Syllabus learning outcomes: 6.1.1, 6.1.2, 6.1.3, 6.1.5
· Step through replication at a fork: DNA polymerase, leading and lagging strands, DNA ligase, and the old and new strands in every daughter molecule.
Step through replication at a fork: DNA polymerase, leading and lagging strands, DNA ligase, and the old and new strands in every daughter molecule.
You will be able to
Syllabus learning outcomes: 6.1.4
· Follow a gene from the template strand to a primary transcript, spliced mRNA and a polypeptide built at a ribosome by tRNAs, and read the genetic code.
Follow a gene from the template strand to a primary transcript, spliced mRNA and a polypeptide built at a ribosome by tRNAs, and read the genetic code.
You will be able to
Syllabus learning outcomes: 6.2.1, 6.2.2, 6.2.3, 6.2.4, 6.2.5
· Substitute, insert or delete nucleotides in a gene, compare the altered codons and amino acids, and decide which mutations change the protein.
Substitute, insert or delete nucleotides in a gene, compare the altered codons and amino acids, and decide which mutations change the protein.
You will be able to
Syllabus learning outcomes: 6.2.6, 6.2.7
Each link is a piece of biology that carries an idea from one lab into another. Follow one to use what you found here in a new setting.
A single base substitution in the HBB gene changes one codon. Follow it through the protein and the phenotype to inheritance and a genetic test.
The codon GAG becomes GTG. What type of mutation is this, and what changes in the polypeptide?
A substitution, and a missense one: one amino acid (glutamic acid) is replaced by another (valine); the reading frame is not shifted.
Why can one amino acid change alter how haemoglobin behaves?
The new R group is non-polar, so it changes the interactions on the molecule's surface: at low oxygen the molecules stick together into fibres that distort the red blood cell.
Which phenotype does a person with two copies of the allele have?
Sickle cell anaemia: the HBB gene codes for β-globin, the altered β-globin gives abnormal haemoglobin and sickled cells.
Two parents each carry one copy (HbᴬHbˢ). What is the probability that a child is HbˢHbˢ?
0.25 for each child, independently: the Punnett square gives 1 HbᴬHbᴬ : 2 HbᴬHbˢ : 1 HbˢHbˢ as expected proportions, not a guaranteed family pattern.
A test amplifies the region by PCR and cuts it with a restriction enzyme whose site the mutation removes. How would the gel show the allele?
The normal allele is cut into two shorter fragments, which travel further towards the positive electrode; the sickle allele stays one longer fragment, so a carrier shows both patterns.
