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Achieve formative test with answers
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FORMATIEVE TOETSEN ACHIEVEHoorcollege 1
1. Classify each example or definition as applying to either genotype or phenotype
• Genotype: an organism’s genetic makeup, a pair of alleles, Hh
• Phenotype: the way an organism looks or function as determined by its
genes, brown hair, sickle-cell anemia
2. At the end of your biology class, your professor asks you to develop a project to
determine the genotype of a plant with red flowers. Red petal Color (R) is
dominant to pink flower color (r). To accomplish this task, you cross the plant
with the unknown genotype with heterozygous red-flowered plants.
Which ratios are valid predictions of flower colors in the offspring? R R
All red flowers and 3 red : 1 pink flowers
?
3. Meiosis and mitosis are both forms of cell division. However, the
outcomes of these processes differ. Consider a diploid organism with ?
two sexes. Select the reasons why meiosis typically produces genetic
variation, whereas mitosis does not
• Independent assortment results in alleles for a gene being passed
separately to gametes during meiosis
• Sister chromatids are not genetically identical as a result of crossing
over during meiosis
• Meiosis produces four genetically different haploid cells
4. Suppose the tail length of two populations of lizards is controlled by one gene.
To determine the mode of inheritance, a homozygous short-tailed female is
crossed with a homozygous long-tailed male. Then, siblings from the F1 are
crossed and the number of short- and long-tailed animals are counted to
determine the phenotype ratio.
Mode of Autosomal Autosomal Sex-linked Sex-linked recessive
inheritance dominant recessive dominant
F1 phenotype All short- All long- All short- Long-tailed females,
tailed tailed tailed short-tailed males
Match each phenotypic ratio anticipated in the offspring from a cross of two
heterozygous individuals to the appropriate mode of inheritance for the short-
tailed allele.
• Autosomal dominant 1 long : 3 short
• Autosomal recessive 3 long : 1 short
• Sex-linked dominant males 1 long : 1 short, females all short
• Sex-linked recessive 1 long : 1 short
5. Huntington's disease, which causes degeneration of neurons, runs in Mark's
family. Huntington's is a heritable, autosomal dominant genetic disease. In an
autosomal dominant disease, only one abnormal allele is required to cause the
disease in offspring. However, it is possible that not all offspring will receive
the abnormal allele from an affected heterozygous parent. Family members that
have the disease include Mark's maternal grandfather and Mark's maternal
aunts. Mark's maternal grandmother does not have the disease. Because
symptoms of Huntington's disease do not appear until later in life, genetic
testing is necessary to determine whether a younger individual possesses the
allele for the disease. These tests determined that Mark's mother does not carry
the allele for Huntington's disease. Mark's paternal aunt suggested that Mark
, create a pedigree to track the disease in his family. Use the symbols provided to
complete the pedigree. Each symbol may be used more than once.
6. Suppose a novel disease has been studied in several families and is known to
be caused by a mutation in one gene. The given table shows families where the
disease is present. The four rightmost columns record the number of offspring
in each family. Family Father Mother Normal Normal Diseased Diseased
male female male female
1 Disease Normal 2 0 0 3
2 Disease Normal 0 0 0 2
3 Normal Disease 1 3 1 3
4 Disease Normal 3 0 0 2
5 Normal Disease 0 2 3 1
6 Normal Disease 1 2 0 2
• Select the most likely mode of inheritance of the disease.
Sex-linked dominant
• Select the description that best matches the female parent in family 3
Has one disease allele
• Select the description that best matches the male parent in family 6.
Has no disease alleles
7. Earwax type is a Mendelian human trait. Specifically, wet earwax (W) W W
is a dominant allele, and dry earwax (w) is a recessive allele. Given
parents with WW and Ww genotypes, what is the probability that their W WW WW
child will have a dry earwax phenotype? Enter your answer as a
w Ww Ww
percentage.
0%
8. John and Sue are expecting a child, but are concerned about a rare autosomal
recessive disease that is present in both of their families. In the pedigree, John
is represented as individual III-11 and Sue is represented as individual III-12;
both are unaffected. John's sister, III-10, and Sue's brother, III-13, both do not
show evidence of the disease, but John's paternal grandmother and Sue's
maternal grandfather both had the disease. Assign the appropriate symbol to
each individual in the pedigree.
What is the probability that John is a carrier?
66.6%
What is the probability that neither John nor
Sue is a carrier?
16.6%
, 9. Determine all the possible modes of inheritance for the pedigrees.
10. Cystic fibrosis is an autosomal recessive disorder
that runs in Ann's family. Consider the figure of a
pedigree of the known occurrences of cystic
fibrosis in her family. Filled (red) circles
represent affected females. Filled (red) squares
represent affected males. Unfilled (tan) circles,
such as Ann's circle, represent symptomless
females. Unfilled (tan) squares represent
symptomless males.
Which individuals are symptomless carriers?
Ann, Ann’s grandfather, Ann’s female cousin
11. X-linked, recessive diseases, such as hemophilia, are extremely rare in the
population. However, many women are carriers and show no sign of the disease.
The pedigree illustrates the inheritance of an X-linked, recessive disease.
Determine whether the unknown individuals are affected by the disease,
unaffected by the disease, or carriers of the X-linked recessive allele. Unaffected
individuals are not carriers of the X-linked recessive allele.
12. Suppose Louise wants to breed guinea pigs that are black with short fur.
However, when she bred several guinea pigs that were black with short fur, she
found that there were four different offspring phenotypes. Based on the
offspring data provided, determine the number of genes and alleles that control
these phenotypes. Phenotype Number
Number of genes and alleles:
Short black fur 18
2 genes; 2 alleles each
Which phenotypes are coded for by the same gene? Different Long black fur 6
genes are separated by semicolons. Short brown fur 6
Black and brown; short fur and long Long brown fur 2
13. Suppose Jonathan breeds flowers and wants to optimize
production of offspring with both short stems and white flowers, which are
, coded for by two genes with the recessive alleles t and p, respectively. In
flowers, T codes for tall stems and P codes for purple flowers. Jonathan crosses
two heterozygotes that produce 544 offspring.
How many of these 544 offspring are predicted to have both short stems and
white flowers?
Number of offsprings: 34
14. In a hypothetical mouse species, brown fur (B) is completely dominant to white
fur (b), and long fur (L) is completely dominant to short fur (l).
If two mice heterozygous for both traits mate and produce a litter of pups, what
is the probability that an individual pup will have white, short fur?
1/16
15. In fruit flies, long wings (W) are dominant over short wings (w), and
brown pigments (N) are dominant over yellow pigments (n). Each individual
possesses two alleles for each trait.
If a fly that is homozygous dominant for both traits is crossed with a fly that is
homozygous recessive for both traits, what is the predicted genotype of
the offspring?
WwNn
16. Mendel formulated the law of independent assortment to explain the basic
rules of inheritance based on his experiments with pea plants.
With the modern understanding of chromosomes, alleles, and the process of
gamete formation, what is the physical basis for the law of
independent assortment?
Alleles on nonhomologous chromosomes separate randomly into
gametes during meiosis.
17. In the fruit fly, Drosophila, eye color is a sex-linked recessive trait located on
the X chromosome. Red eyes are dominant over white eyes. If a heterozygous
female breeds with a white-eyed male, what percentage of the offspring are
expected to have white eyes?
Red eyes: 50%
18. In the pedigree is a family with a rare genetic disorder.
Use the pedigree to determine the mode of
inheritance of the disorder.
Autosomal recessive
19. A man with a specific unusual genetic trait marries an unaffected woman. For
each type of inheritance, place the pedigree that would result from the cross.
Assume the trait is fully penetrant and rare.
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