ratios + genetic cross diagram

Question 1

define ratio

Answer 1

measure of the relative size of 2 classes that are expressed as a proportion

Question 2

why are results of genetic crosses never the same as predicted results

Answer 2

this is due to stastical error as each event is independent

chance determines what sperm fertilises what egg
each allele is inherited independently

(chance determines which alleles fuse together due to random fertilisation. Each allele is inherited indepedently)

Question 3

what do punnet squares show in terms of gametes

Answer 3

the chance of what gametes fuse with which

Question 4

why are having large sample sizes important when using genetic cross diagrams

Answer 4

results are more likely to come near to matching theoretical (predicted) ones

so large number of organisms in genetic crosses are important if representative results are to be obtained

Question 5

what is the classic Mendelian ratio

Answer 5

3 : 1

Question 6

explain the law of independent segregation (4 marks)

Answer 6

alleles are inherited in pairs: only one of each allele per gamete

alleles can be dominant or recessive and are inherited independently

so alleles have an equal chance of being passes from parent to offspring

offspring phenotypes can therefore be predicted

Question 7

explain why a large sample size is important when studying genetic crosses

Answer 7

with a large sample size results are more likely to match predicted ratios