5 interactive labs · AS & A Level Biology 9700
· Step a 2n = 4 cell through meiosis I and II, track alleles through crossing over and random orientation, then fertilise a gamete.
Step a 2n = 4 cell through meiosis I and II, track alleles through crossing over and random orientation, then fertilise a gamete.
You will be able to
Syllabus learning outcomes: 16.1.1, 16.1.2, 16.1.3, 16.1.4, 16.1.5, 16.1.6, 16.1.7
· Make gametes, fill Punnett squares for dominant, codominant, ABO, X-linked and dihybrid crosses, then breed seeded samples beside the expected numbers.
Make gametes, fill Punnett squares for dominant, codominant, ABO, X-linked and dihybrid crosses, then breed seeded samples beside the expected numbers.
You will be able to
Syllabus learning outcomes: 16.2.1, 16.2.2, 16.2.4
· Test-cross linked and unlinked genes, follow a two-step pigment pathway, then use the chi-squared test to judge observed against expected.
Test-cross linked and unlinked genes, follow a two-step pigment pathway, then use the chi-squared test to judge observed against expected.
You will be able to
Syllabus learning outcomes: 16.2.1, 16.2.3, 16.2.5
· Follow TYR, HBB, F8, HTT and the pea Le gene from allele to protein to phenotype, and see where the environment changes the outcome.
Follow TYR, HBB, F8, HTT and the pea Le gene from allele to protein to phenotype, and see where the environment changes the outcome.
You will be able to
Syllabus learning outcomes: 16.2.6, 16.2.7
· Add lactose to E. coli and watch the repressor leave the operator, test mutant strains, then switch genes on with gibberellin and DELLA proteins.
Add lactose to E. coli and watch the repressor leave the operator, test mutant strains, then switch genes on with gibberellin and DELLA proteins.
You will be able to
Syllabus learning outcomes: 16.3.1, 16.3.2, 16.3.3, 16.3.4
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.
