Using Meiosis to make a Mini-Manc

Transcription

1 Using Meiosis to make a Mini-Manc INTRODUCTION This activity demonstrates the principles of Independent assortment of chromosomes and shows how meiosis leads to tremendous genetic variation. Mini-Manc s are creatures that live in the YOUR SCHOOL AREA, feeding on the dead skin of students. They are shy creatures, they only come out at night so you re very lucky to see one. But most importantly, Mini-Manc s are excellent subjects for genetic study, because they have some very distinctive features. IMPORTANT INFORMATION! Mini-Manc s have 7 pairs of homologous chromosomes these are represented by 7 pairs of different coloured card. The sex chromosomes X and Y are represented by white card. We are going to follow the inheritance of 7 different features (phenotypes), carried on 7 different pairs of chromosomes. Mini-Manc s have 2 copies (alleles) of each gene, carried on different pairs of chromosomes. E.G. A Mini-Manc of genotype Aa carries allele A on one (orange) chromosome and allele a on its homologous chromosome (orange) See Table 2 for possible phenotypes & genotypes of a Mini-Manc. To check you understand this table, fill in the phenotypes of the parent Mini-Manc in Table 1.

2 Table 1 Aa Bb Dd Gg Hh Qq XY XX Mini-Manc s Parents Chromosome Colour Blue Pink Green Yellow Purple NOTE! EVERYONE WILL BE STARTING WITH PARENTS OF EXACTLY THE SAME GENOTYPE THE ONLY DIFFERENCE BEING THAT SOME OF YOU WILL HAVE MALE MINI MANC S AND SOME WILL HAVE FEMALES Table 2 Feature Antennae Number of Eyes Your Baby Mini Manc (Appearance) Antennae Blue Antennae Three Eyes Two Eyes One Eye (Genetic makeup) AA or Aa aa BB Bb bb Chromosome Colour Blue Colour of Legs Pink legs DD or Dd Pink Purple legs dd Colour of Body Green body GG or Gg Green Yellow body gg Colour of Tail Golden Tail HH or Hh Yellow Red Tail hh Shape of Tail Curly Tail QQ or Qq Purple Straight Tail qq YOUR MINI MANC Sex Male ( Nose) Female (Pink Nose) XY XX

3 Figure 1 Creating your Mini Manc Antenna (small bent pipe cleaner: orange or blue) Eyes (drawing pins: 1,2 or 3) Tail large pipe cleaner: gold or red; straight or curly) Nose (marsh mallow on cocktail stick: pink or white) Legs (cotton buds: pink or purple) Body (pan scourer: yellow or green)

4 MIXED UP MEIOSIS 1. On your own, place your cards face down and shuffle them about. These cards represent your parent Mini Manc s chromosomes (diploid number). 2. Leave the cards face down and put them into homologous (coloured) pairs. Chromosomes actually do pair up like this during Prophase I of meiosis. 3. Pick one card any card- from each pair This simulates independent assortment of the chromosomes during Metaphase II, where the arrangement of the chromosomes above and below the spindle fibre equator occurs at random. 4. You should now have 7 cards, one of each colour. This set of cards represents your gamete (egg or sperm), which has half the number of chromosomes of your parent Mini Manc (haploid number). 5. Now mate with your partner! Combine your 7 cards with your partner s. This simulates random fertilisation. Remember you could have mated with any other Mini Manc in the class! 6. Congratulations! You are pregnant! Bet you can t wait to see what your baby is going to look like! It s time to record your Baby Mini Manc s genotype (genetic makeup) in Table 2 and work out its phenotype (appearance). 7. TIME TO GIVE BIRTH! Use your data in Table 2 to create your Baby Mini Manc (use figure 1 to help you). 8. When you have finished, we will compare class results. o Are any two Baby Mini Manc s from our class the same? o If not, why not? o What other event during meiosis can create even more genetic variation? 9. If you have time, take the sets of cards (gametes) that you and your partner did not use during fertilization. How would your Mini Manc s appearance have been different had you used these gametes instead of the ones you chose first time round?

5 TEACHERS NOTES Equipment Required (per pair of students) 3 drawing pins 2 small pipe cleaners (one orange one blue) 2 large pipe cleaners (one red one gold) 2 small marshmallows (one pink one white) 8 cotton buds (four pink four purple) 2 pan scourers (one green one yellow) 2 x card with A printed on. 2 x card with a printed on. 2 x Blue card with B printed on. 2 x Blue card with b printed on. 2 x Pink card with D printed on. 2 x Pink card with d printed on. 2 x Blue card with B printed on. 2 x Green card with G printed on. 2 x Green card with g printed on. 2 x Yellow card with H printed on. 2 x Yellow card with h printed on. 2 x Purple card with Q printed on. 2 x Purple card with q printed on. 1 x card with Y printed on. 3 x card with X printed on. Relevance to GCSE syllabus AQA: B2.7.1 Cell division Edexcel: Unit B2: The components of life Topic 1: The building blocks of cells