Begin your pedigree with a woman and a man with the following genotypes for the color-blindness trait: Woman: XCXc Man: XCY
Begin your pedigree with a woman and a man with the following genotypes for the color-blindness trait: Woman: XCXc Man: XCY
2 With a lab partner, you will use coin-tossing to simulate the random nature of allele combinations in offspring, and “create” a family for which you will construct a pedigree. Review “Transmission of Sex-Linked Traits,” Table 4.3, and the key provided here for information and directions on the symbols to use. Although a Punnett square gives you all of the possible outcomes of various crosses and their probabilities of occurrence, this method will mimic the passing on of alleles for the particular outcome determined by your coin tosses.
Key: affected male affected female
mating
sibling
male female
Begin your pedigree with a woman and a man with the following genotypes for the color-blindness trait:
Woman: XCXc Man: XCY
a At the top of a blank piece of paper, draw the male and female pedigree symbols for this couple and draw a line between them to show that they are a mated pair. Record the genotypes for each next to the male and female symbols on your pedigree.
▪ Fill in the blanks for the woman and the man to show what alleles for color vision they will have in their gametes (Hint: See Fig. 4.17).
Woman: _________________________________ Man: _________________________________
b This couple has three children whose sex and color-vision acuity are determined by your coin tosses.
▪ The first coin toss will be to determine which chromosome (X or Y) the father contributes. Use heads for the X chromosome and tails for the Y chromosome.
▪ The second coin toss will be to determine which of the two alleles for color vision on the X chromosomes the offspring receives from the mother. Use heads for an X chromosome with a dominant allele and tails for an X chromosome with a recessive allele.
Offspring 1 Chromosome contributed by the father? _________________________________ (This will also determine sex of offspring. If he con- tributes an X, don’t forget to add the allele—C or c—for color vision.)
Chromosome contributed by the mother? _________________________________ (XC or Xc?)
Genotype of offspring? _________________________________
Offspring 2 Chromosome contributed by the father? _________________________________ (This will also determine sex of offspring. If he con- tributes an X, don’t forget to add the allele—C or c—for color vision.)
Chromosome contributed by the mother? _________________________________ (XC or Xc?)
Genotype of offspring? _________________________________
Offspring 3 Chromosome contributed by the father? ________________________ (This will also determine sex of offspring. If he contributes an X, don’t forget to add the allele—C or c—for color vision.)
Chromosome contributed by the mother? _________________________________ (XC or Xc?)
Genotype of offspring? _________________________________
c Draw these three offspring on your pedigree and write the genotypes next to the symbols for each. Throughout the pedigree, remember to darken the symbol if an individual is affected by color blindness.
d “Create” mates for each of these offspring—you will know the sex of the mate because it will be opposite from the offspring. Flip a coin to determine whether a male mate carries a C or a c on his X chromosomes, and to determine whether a female carries a C or a c on each of her X chromosomes. Draw these mates on your pedigree as well.
e Produce one offspring for each of these second-generation couples by coin-tossing for sex and to determine which alleles are passed on for the color-vision trait. Depending upon the parents’ genotypes, you may have to toss either more or fewer coins.
Record the genotypes for your third generation.
Offspring of Couple 1 Offspring of Couple 2 Offspring of Couple 3
____________________________ ____________________________ ____________________________
f Add them to your pedigree.
Pedigree for #3
Pedigree for #4
- Woman:
- Man:
- This will also determine sex of offspring If he con:
- tributes an X dont forget to add the alleleC or cfor color vision:
- Chromosome contributed by the mother:
- This will also determine sex of offspring If he con_2:
- tributes an X dont forget to add the alleleC or cfor color vision_2:
- Chromosome contributed by the mother_2:
- This will also determine sex of offspring If he contributes:
- an X dont forget to add the alleleC or cfor color vision:
- Chromosome contributed by the mother_3:
