Practice set 8:
Covers lectures 14-19
Complete each set of questions as we advance through the course material.
Every question in this exam is connected!
PsbS gene is a gene in plants which codes for a protein called “pigment binding protein S” that is
essential for proper photosystem II functioning. When PsbS is mutated, plants have a much slower rate of
growth than is typical. They are “poor growing”.
PSBS denotes the normal allele for this gene. psbs denotes the mutated, recessive allele for this gene.
Pineapples have 25 chromosomes. PsbS is located on chromosome 22. Also on chromosome 22 and
located right next to PsbS, is the gene for spikes, where R represents the allele for sharp spikes and r
represents the allele for blunt spikes. Chromosome 21 contains the skin gene, where F represents the
allele for tough skin and f represents the allele for soft skin.
Questions 1-6 covers lectures 14-15
1. The wild ancestors of pineapples had two copies of each of their 25 chromosomes. Commercially
grown pineapples of present day have three copies of each of their 25 chromosomes. What is the
correct scientific notation for commercial pineapple chromosome number?
a) 25, 75
b) 75, 25
c) 25,3
d) 3,25
2. Kiara Jackson PhD is a plant geneticist working for a major university in southern California. She
has been tasked with assessing a local farmer’s pineapple crops to find out why 20% of them
displayed poor growth this season. Kiara takes samples of the well-growing pineapples and the
poor-growing pineapples. Kiara extracts an egg from one well-growing pineapple plant and
performs genetic analysis. The egg’s genotype is PSBS/R/f. How did the plant’s chromosomes
line up at the metaphase plate? (Assume the well-growing plant genotype is PSBSpsbs, Rr, Ff. In
other words, it is heterozygote for all genes.)
, 3. Which two alleles will most likely be inherited in a different combination than in their parent’s
chromosomes (recombination)?
a) PSBS/psbs and R/r
b) PSBS/psbs and F/f
4. Remember that the extracted egg’s genotype is PSBS/R/f. Kiara fertilizes this egg from a random
sampling of pollen (sperm) from a male pineapple plant with the genotype PSBS/psbs R/r f/f. In a
punnet square of this cross, how many gametic combination of the female’s must be represented?
How many gametic combinations of the male must be represented?
a) Female: 1. Male: 4
b) Female: 2. Male: 2
c) Female: 4. Male 4:
5. Kiara takes a sample from a different well-growing plant. It also has sharp spikes and tough skin.
She doesn’t know its genotype. She mates this plant with one that is poor-growing, has blunt
spikes and soft skin. Half of the resulting offspring are well-growing with sharp spikes and tough
skin. The other half is poor-growing with sharp spikes and tough skin. What is the genotype of
the unknown parent plant?
a) PSBSpsbs, RR, FF
b) PSBSpsbs, Rr, Ff
c) psbspsbs, RR, ff
6. Like humans, pineapple “males” contain X and Y chromosomes in their diploid cells while
“females” will contain two X chromosomes in their diploid cells. There is a gene located on the X
Covers lectures 14-19
Complete each set of questions as we advance through the course material.
Every question in this exam is connected!
PsbS gene is a gene in plants which codes for a protein called “pigment binding protein S” that is
essential for proper photosystem II functioning. When PsbS is mutated, plants have a much slower rate of
growth than is typical. They are “poor growing”.
PSBS denotes the normal allele for this gene. psbs denotes the mutated, recessive allele for this gene.
Pineapples have 25 chromosomes. PsbS is located on chromosome 22. Also on chromosome 22 and
located right next to PsbS, is the gene for spikes, where R represents the allele for sharp spikes and r
represents the allele for blunt spikes. Chromosome 21 contains the skin gene, where F represents the
allele for tough skin and f represents the allele for soft skin.
Questions 1-6 covers lectures 14-15
1. The wild ancestors of pineapples had two copies of each of their 25 chromosomes. Commercially
grown pineapples of present day have three copies of each of their 25 chromosomes. What is the
correct scientific notation for commercial pineapple chromosome number?
a) 25, 75
b) 75, 25
c) 25,3
d) 3,25
2. Kiara Jackson PhD is a plant geneticist working for a major university in southern California. She
has been tasked with assessing a local farmer’s pineapple crops to find out why 20% of them
displayed poor growth this season. Kiara takes samples of the well-growing pineapples and the
poor-growing pineapples. Kiara extracts an egg from one well-growing pineapple plant and
performs genetic analysis. The egg’s genotype is PSBS/R/f. How did the plant’s chromosomes
line up at the metaphase plate? (Assume the well-growing plant genotype is PSBSpsbs, Rr, Ff. In
other words, it is heterozygote for all genes.)
, 3. Which two alleles will most likely be inherited in a different combination than in their parent’s
chromosomes (recombination)?
a) PSBS/psbs and R/r
b) PSBS/psbs and F/f
4. Remember that the extracted egg’s genotype is PSBS/R/f. Kiara fertilizes this egg from a random
sampling of pollen (sperm) from a male pineapple plant with the genotype PSBS/psbs R/r f/f. In a
punnet square of this cross, how many gametic combination of the female’s must be represented?
How many gametic combinations of the male must be represented?
a) Female: 1. Male: 4
b) Female: 2. Male: 2
c) Female: 4. Male 4:
5. Kiara takes a sample from a different well-growing plant. It also has sharp spikes and tough skin.
She doesn’t know its genotype. She mates this plant with one that is poor-growing, has blunt
spikes and soft skin. Half of the resulting offspring are well-growing with sharp spikes and tough
skin. The other half is poor-growing with sharp spikes and tough skin. What is the genotype of
the unknown parent plant?
a) PSBSpsbs, RR, FF
b) PSBSpsbs, Rr, Ff
c) psbspsbs, RR, ff
6. Like humans, pineapple “males” contain X and Y chromosomes in their diploid cells while
“females” will contain two X chromosomes in their diploid cells. There is a gene located on the X
