Download BEDE BUGS

BEDE BUGS
INTRODUCTION
This activity demonstrates the principles of “Independent assortment of
chromosomes” and shows how meiosis leads to tremendous genetic variation.
illustrates how independent assortment of chromosomes and random
fertilisation of haploid gametes produced by meiosis lead to genetic
variation
Bede Bugs are creatures that live in the College Social 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, Bede Bugs are excellent subjects for
genetic study, because they have some very distinctive features.
IMPORTANT INFORMATION!

Bede Bugs 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.

Bede Bugs have 2 copies (alleles) of each gene, carried on different pairs of
chromosomes.
E.G. A Bede Bug 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 Bede Bug. To check you
understand this table, fill in the phenotypes of the parent Bede Bugs in Table 1.
Table 1
Bede Bug Parents
Aa
Bb
Dd
Gg
Hh
Qq
Chromosome
Colour
Orange
Blue
Pink
Green
Yellow
Purple
XY
XX
White
White
Genotype
Phenotype
NOTE!
EVERYONE WILL BE
STARTING WITH
PARENTS OF EXACTLY
THE SAME GENOTYPE
– THE ONLY
DIFFERENCE BEING
THAT SOME OF YOU
WILL HAVE MALE
BEDE BUGS AND SOME
WILL HAVE FEMALES
Table 2
Your Baby Bede Bug
YOUR BABY BEDE BUG
Feature
Phenotype
(Appearance)
Antennae
Orange
Antennae
Blue Antennae
Number of
Three Eyes
Eyes
Two Eyes
One Eye
Colour of Legs
Pink legs
Purple legs
Colour of Body Green body
Yellow body
Colour of Tail
Golden Tail
Red Tail
Shape of Tail
Curly Tail
Straight Tail
Sex
Genotype
(Genetic
makeup)
AA or Aa
aa
BB
Bb
bb
DD or Dd
dd
GG or Gg
gg
HH or Hh
hh
QQ or Qq
qq
Male
(White Nose)
Female
(Pink Nose)
Chromosome
Colour
Genotype
Phenotype
Orange
Blue
Pink
Green
Yellow
Purple
XY
White
XX
White
Figure 1 Creating your Baby Bede Bug
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)
MEIOSIS SIMULATION
1. On your own, place your cards face down and shuffle them about.
These cards represent your parent Bede Bug’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 Bede Bug (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 Bede Bug 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 Bede Bug’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 Bede
Bug (use figure 1 to help you).
8. When you have finished, we will compare class results.
o Are any two Baby Bede Bugs 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 Baby Bede
Bug’s appearance have been different had you used these gametes
instead of the ones you chose first time round?
Dismantle your Bede Bugs & put your cards back into their original sets.
Thank you!