Sex-linked traits and reading a pedigree
Grade 9 Science Worksheet - Challenge Me
Circle the best answer.
Ari crosses model parents XBXb and XbY. What is the chance that one offspring is an XX individual with the trait?
- 1 in 4
- 0
- 3 in 4
- 1 in 2
Bo crosses model fruit flies XwXw and XWY. What is the chance that one offspring is a white-eyed XY fly?
- 1 in 4
- 3 in 4
- 0
- 1 in 2
Read this first
Use this
Pedigree of a made-up family for a made-up trait (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).
Jun reads a made-up pedigree. Neither parent has the trait, but daughter II-1 does. Which choice states what this rules out?
- Autosomal recessive: parents without the trait cannot carry it
- Both patterns: a parent without the trait has no allele
- Neither pattern: an XX parent can pass Xb to a daughter
- X-linked recessive: the XY parent would have the trait too
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).
Kira reads a made-up pedigree. Neither parent has the trait, but II-1 does. Which choice states what this rules out?
- An inherited trait of any kind, since both parents lack it
- An X-linked trait: II-1 would need its X from the XY parent
- A dominant trait: a parent with a dominant allele would show it
- A recessive trait: both parents would need to show it
Use this
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.
Luz reads a made-up pedigree. The trait appears in I-1 and III-1 but skips II-1. Which statement explains it?
- II-1 is a carrier of Xb from I-1
- III-1 got its Xb from II-2, the XY parent
- II-1 has the trait, but it is hidden
- I-1 passed Xb to II-1 on a Y chromosome
Notebook
Notes on a model cross (classmate's notebook), 4 lines. Columns: line, entry. Line 1: A model cross has parents XBXb and XBY. Line 2: XX offspring get one X from each parent. Line 3: XY offspring get their X from the XY parent. Line 4: So the XbY box is one of the four boxes.
Milo reads a classmate's notebook about a model XBXb × XBY cross. Which line has the mistake?
- Line 3: an XY offspring gets its X from the XX parent
- Line 2: XX offspring should get both X chromosomes from one parent
- Line 1: the XY parent should be written XbY
- Line 4: XbY should be a carrier, because the Y holds a second allele
Notebook
Notes on color vision data (classmate's notebook), 4 lines. Columns: line, entry. Line 1: Northern European ancestry: the red-green color vision difference occurs in men at 1 in 12 and in women at 1 in 200. Line 2: The genes are on the X chromosome. Line 3: So XX and XY individuals should have the trait about equally often. Line 4: An XY individual has one X, so one Xb allele shows.
Noah reads a classmate's notebook about color vision data. Which line has the mistake?
- Line 2: the genes should be on the Y chromosome
- Line 4: an XY individual needs two Xb alleles to show the trait
- Line 3: the trait should be more common in XY individuals
- Line 1: the rate for women should also be 1 in 12
Notebook
Notes on pedigree symbols (classmate's notebook), 4 lines. Columns: line, entry. Line 1: Squares are XY individuals and circles are XX individuals. Line 2: A filled symbol is an individual with the trait. Line 3: A circle with a dot is a carrier, and it does not show the trait. Line 4: An XY individual with one Xb allele is a carrier.
Pia reads a classmate's notebook about pedigree symbols. Which line has the mistake?
- Line 4: an XY individual with one Xb allele has the trait
- Line 1: squares should be XX individuals
- Line 2: a filled symbol should mean a carrier
- Line 3: a circle with a dot should show the trait
Model offspring card (model)
item detail offspring XbY parent 1 an XX individual with genotype XBXb parent 2 an XY individual with genotype XBY Ren claims that the XbY offspring must have received its Xb from the XY parent. Do you agree?
- No, because the Xb came from the Y of the XY parent
- Yes, because the XY parent passes an X to each child
- No, because the XY parent passes on a Y, so the Xb came from the XX parent
- Yes, because the XX parent has typical color vision and holds no Xb
Zee claims that II-2, a circle with no dot, cannot pass an Xb allele to a child. Do you agree?
- Yes, because a carrier would show the trait
- No, because II-2 got a Y chromosome that holds Xb
- Yes, because a symbol that is not filled holds no Xb allele
- No, because II-2 got an Xb from I-1 and can pass it on
