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Practical 1 Monohybrid cross. Learning objectives: By the end of the lesson you should be able to: Solve problems in relation to monohybrid crosses from.

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Presentation on theme: "Practical 1 Monohybrid cross. Learning objectives: By the end of the lesson you should be able to: Solve problems in relation to monohybrid crosses from."— Presentation transcript:

1 Practical 1 Monohybrid cross

2 Learning objectives: By the end of the lesson you should be able to: Solve problems in relation to monohybrid crosses from the P generation to the F2 generation using dominant and recessive alleles. To predict ratios of offspring genotype in monohybrid crosses. State the reasons for differences between observed and predicted figures in monohybrid crosses.

3 Introduction The shape of pea seeds can be either ______________ or _________________________ round wrinkled

4 Aim To carry out a simulation of a monohybrid cross

5 Method 1 The following cross is carried out: 2 collect a dish of seeds from the F1 generation 3 Count the numbers of round and wrinkled seeds and enter your results in the table P True Breeding Round seeds x True breeding Wrinkled seeds F1

6 Results Round seedsWrinkled seeds

7 Interpretation The results show that all of the F1 generation have __________________________ This shows that round is the _______________ This shows that wrinkled is the __________________________________ Round seeds Dominant allele Recessive allele

8 Symbols Round = dominant = R Wrinkled – recessive = r P phenotype Genotype F1 phenotype genotype Diagram of cross Round seed x wrinkled seed RR X rr All round Rr

9 4 Members of the F1 are crossed together to form the F2 generation Collect a dish of seeds from the F2 generation Count the numbers of each type of seed and enter them in the table

10 Results - group Round seedsWrinkled seeds Numbers Ratio

11 Results - class Group Round seedsWrinkled seeds Total Ratio 31

12 Interpretation When two of the F1 generation are crossed together some of the F2 are round and some are wrinkled. This can be explained by looking at the diagram of the cross F1 phenotyperound seedx round seed Genotype RrxRr F2 Male/Female R r R r Expected phenotype ratio 3 round:1 wrinkled RRRr rr

13 The class results Does this match more closely with the group or the class results? Why do the class results more closely match with the expected ratio? Evaluation Large numbers are used making the experiment more reliable

14 The Backcross

15 Round seeds from the F2 _______________________ To find out which a ______________ was carried out They were ____________________________ as the _____________________________________ The results of the cross will allow you to tell if the round seed was __________________________ This is known as a ____________ May have the genotype RR or Rr Further cross crossed with wrinkled seeds homozygous or heterozygous genotype of these is known backcross

16 7 Collect two dishes of seeds from cross A and cross B Collect the numbers of each type of seed from in each and enter your results in the table. CrossRound seedsWrinkled seeds A B

17 Interpretation What was the genotype of the cross A parent? Give a reason for your answer RR All of the offspring were round so all inherited the R allele from the round parent What was the genotype of the cross B parent? Rr Give a reason for your answer Some of the offspring were wrinkled so must have inherited the r allele from the round parent


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