Sex-linked traits and reading a pedigree
Grade 9 Science Worksheet
Circle the best answer.
Bo fills an empty square for the X-linked eye color that Morgan studied in fruit flies, using model genotypes XWXw and XwY. Which list gives the eye colors?
- 2 red-eyed females : 2 white-eyed males
- 1 red-eyed female : 1 white-eyed female : 1 red-eyed male : 1 white-eyed male
- 3 red-eyed flies : 1 white-eyed fly
- 2 red-eyed females : 1 red-eyed male : 1 white-eyed male
Esme fills an empty square for model parents XBXB and XbY. Which statement is true?
- Half of the offspring have the trait and half are carriers
- The XY offspring have the trait, because the X comes from the XY parent
- The XX offspring have the trait, since the XY parent has it
- No offspring have the trait, but the XX offspring are carriers
Read this first
Use this
Model data: 200 offspring from a cross of model parents. Punnett square for color vision (model cross; XB is the typical color vision allele and is dominant to Xb, the red-green color vision difference allele; the Y has no copy of this gene).
Jun reads a square for 200 model offspring. About how many are expected to be XY individuals with the trait?
- 150 offspring
- 100 offspring
- 50 offspring
- 0 offspring
Two model groups, Northern European ancestry (model counts; rates from NIH MedlinePlus Genetics)
group number in model group rate with the red-green color vision difference XY individuals (men) 2,400 1 in 12 XX individuals (women) 2,400 1 in 200 Luz reads two model groups. About how many more XY than XX individuals are expected to have the trait?
- 0 more
- 212 more
- 188 more
- 2,388 more
Genotype card (model)
genotype chromosomes XBXB XX XBXb XX XbXb XX XbY XY. XB is dominant to Xb Milo sorts model genotypes. Which genotype is a carrier of the Xb allele?
- XbXb (an XX individual with two Xb alleles)
- XbY (an XY individual with one Xb allele)
- XBXb (an XX individual with one Xb allele)
- XBXB (an XX individual with no Xb allele)
Model offspring card (model)
item detail offspring XbY parent 1 an XX individual parent 2 an XY individual Noah reads a model offspring card. From which parent did the XbY offspring receive its Xb allele?
- From the XY parent, because an XY offspring takes its X from the XY parent
- From the XX parent, because the XY parent passes on a Y
- From either parent, because both parents pass on an X
- From both parents, because the trait needs two Xb alleles
Genotype list (model)
genotype chromosomes XBXB XX XBXb XX XbXb XX XBY XY XbY XY. XB is dominant to Xb Pia reads a genotype list. Which choice holds every genotype that shows the red-green color vision difference?
- XBXb, XbXb and XbY
- XbXb and XbY
- XbXb (the Y covers the Xb allele in XbY)
- XbY and XBY (both XY genotypes)
Use this
a circle with no dot is not marked either way.
Ren reads a made-up pedigree. II-2 is a filled square. From which parent did II-2 receive the Xb allele?
- From I-1 (an XY child takes its X from the XY parent)
- From both I-1 and I-2 (the trait needs two Xb alleles)
- From I-2 (an XY child takes its X from the XX parent)
- From neither, since neither parent has the trait
Tala reads the same pedigree. II-1 is a circle with no dot, so II-1 is not marked either way. What is the chance that II-1 carries Xb?
Use the picture in question 8.
- 1 in 4
- 1 in 2
- 1 in 1
- 0
Use this
Pedigree of a made-up family for the red-green color vision difference (squares are XY individuals, circles are XX individuals, a filled symbol has the trait, a circle with a dot is a marked carrier; a circle with no dot is not marked either way).
Zee reads a made-up pedigree. II-1 is a filled circle. Which statement fits the pedigree?
- II-1 has one Xb allele, and one is enough to show the trait
- II-1 has two Xb alleles: one from I-1 and one from I-2
- II-1 has two Xb alleles, and both came from I-2
- II-1 is a carrier, since a filled circle marks a carrier