6: Chromosomal Inheritance
Students trace inheritance of X-linked genes through meiosis, predict progeny outcomes from sex-linked crosses, and explain the chromosomal basis of inheritance.
LibreTexts reference: Chapter 6: Chromosomal Inheritance 
Stages of Meiosis Prophase I Matching
Click to show Stages of Meiosis Prophase I Matching example problem
Match each of the following stages of meiosis prophase I with their corresponding partial descriptions.
Note: Each choice will be used exactly once.
| Your Choice | Prompt | |
|---|---|---|
| 1. Zygotene | ||
| 2. Leptotene | ||
| 3. Diplotene and/or Diakinesis | ||
| 4. Early/Late Pachytene |
Drag one of the choices below:
- A. chromosomes first become visible in the form of thread-like structures
- B. chromosomes continue to shorten and thicken
- C. stage where homologous chromosomes become paired
- D. both the nucleolus and nuclear envelope disappear while spindle fibers form
Meiosis Terms Matching
Click to show Meiosis Terms Matching example problem
Match each of the following Meiosis terms with their corresponding definitions.
Note: Each choice will be used exactly once.
| Your Choice | Prompt | |
|---|---|---|
| 1. homologous | ||
| 2. homologous chromosomes | ||
| 3. chiasmata | ||
| 4. sister chromatids |
Drag one of the choices below:
- A. specialized chromatin structures that link homologous chromosomes together
- B. corresponding or similar in position, value, structure, or function
- C. two identical copies of a chromosome joined together by a common centromere
- D. chromosomes which contain the same genes in the same order along their chromosomal arms
Match Sex Determination Systems
Click to show Match Sex Determination Systems example problem
Match each of the following sex determination systems with their corresponding descriptions.
Note: Each choice will be used exactly once.
| Your Choice | Prompt | |
|---|---|---|
| 1. Haplo-Diploid system | ||
| 2. X-O system | ||
| 3. Z-W system | ||
| 4. X-Y system |
Drag one of the choices below:
- A. this system is the reverse of the system found in humans
- B. unfertilized eggs develop into males ♂
- C. sex of an offspring depends on if the male ♂ sperm contains a sex chromosome or if it is missing
- D. males ♂ are heterogametic and females ♀ are homogametic
Stages of Meiosis Prophase I
Click to show Stages of Meiosis Prophase I example problem
Which one of the following stages of meiosis prophase I correspond to the partial description 'chromosomes start forming thin thread-like structures'.
Meiosis Terms Identification
Click to show Meiosis Terms Identification example problem
Which one of the following Meiosis terms correspond to the definition 'two chromosomes containing identical genetic loci although possibly different allelic forms'.
Sex Determination Systems
Click to show Sex Determination Systems example problem
Which one of the following sex determination systems correspond to the description ' males ♂ are homogametic and females ♀ are heterogametic'.
True/False Statements About Mitosis and Meiosis
Click to show True/False Statements About Mitosis and Meiosis example problem
Which one of the following statements is FALSE regarding mitosis and meiosis cell division?
Fraction of Daughters with Both AIS and HD
Click to show Fraction of Daughters with Both AIS and HD example problem
Deuteranomaly red-green color blindness is an X-linked recessive genetic disorder that is caused by mutations in the OPN1MW gene. This results in shift in the green retinal receptors toward red wavelength sensitivity. The disorder affects 1 in 20 males and 1 in 400 females of Northern European ancestry. Individuals affected with color blindness have decreased ability to see colors in which they are unable distinguish between shades of red and green. The defective gene for color blindness is located on the long arm of chromosome X at position 28.
Achondroplasia is an autosomal dominant genetic disorder that is caused by a mutation in the FGFR3 gene. This results in a mutated protein that interacts negatively with growth factors leading to complications with bone production. The disorder affects 1 in 27,500 people. Individuals affected with achondroplasia have dwarfism with short arms and legs, an enlarged head, and a prominent forehead. The defective gene for achondroplasia is located on the short arm of chromosome 4 at position 16.3.
A man (♂) with both color blindness and achondroplasia genetic disorders marries a wild-type phenotype woman (♀) with neither disorder. The father (♂) of the woman has the color blindness genetic disorder,but mother (♀) of the woman does not. The mother (♀) of the man is wild-type phenotype and does not have the achondroplasia genetic disorder.
Reminder: color blindness is X-linked recessive and achondroplasia is autosomal dominant.
What fraction of their daughters (♀) will have both color blindness and achondroplasia genetic disorders?
X-linked Recessive Genetic Disorders
Click to show X-linked Recessive Genetic Disorders example problem
Deuteranomaly red-green color blindness is an X-linked recessive genetic disorder that is caused by mutations in the OPN1MW gene. This results in shift in the green retinal receptors toward red wavelength sensitivity. The disorder affects 1 in 20 males and 1 in 400 females of Northern European ancestry. Individuals affected with color blindness have decreased ability to see colors in which they are unable distinguish between shades of red and green. The defective gene for color blindness is located on the long arm of chromosome X at position 28.
Marfan syndrome (MFS) is an autosomal dominant genetic disorder that is caused by a mutation in FBN1 gene that makes fibrillin protein. This results in weaked connective tissue throughout the body. The disorder affects 1 in 10,000 people. Individuals affected with MFS have tall and thin features with serious complications involving the heart and aorta. The defective gene for MFS is located on the long arm of chromosome 15 at position 21.1.
A man (♂) and a woman (♀) are planning a family. The man (♂) has color blindness. The woman (♀) is a carrier for color blindness; her father has color blindness, but her mother does not. The man (♂) has MFS. The mother (♀) of the man (♂) does not have MFS. The woman (♀) does not have MFS.
Reminder: color blindness is X-linked recessive and MFS is autosomal dominant.
What fraction of their daughters (♀) will have both color blindness and MFS?
Pedigree Analysis
Click to show Pedigree Analysis example problem
| ◯ | ◼ | Â | ◯ | ◻ | Â | ◯ | ◻ | |||
| Â | Â | |||||||||
| ◯ | ◼ | ◼ | ◯ | Â | ◻ | ◯ | ◻ | ◯ | ||
| Â | Â | Â | Â | Â | ||||||
| ◻ | ◯ | Â | ◼ | ◯ | Â | ◻ | ◯ | |||
| ◻ | ◻ | ◯ | ◼ | ◼ | ◯ | ◼ | ◯ | ◯ | ◻ | ◻ |
Â
Examine the pedigree above. Which one of the following patterns of inheritance is most likely demonstrated in the above pedigree inheritance?
Match Pedigrees to Inheritance Types
Click to show Match Pedigrees to Inheritance Types example problem
Match the following pedigrees to their most likely inheritance type.
Note: each inheritance type will only be used ONCE.
| Your Choice | Prompt | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1.
 |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
2.
 |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
3.
 |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
4.
 |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
5.
 |
Drag one of the choices below:
- A. x-linked dominant
- B. autosomal dominant
- C. x-linked recessive
- D. y-linked
- E. autosomal recessive
X-linked Recessive Phenotype Cross
Click to show X-linked Recessive Phenotype Cross example problem
The white-eyed (mutant) phenotype is an X-linked recessive disorder in fruit flies. The red-eyed (wildtype) allele, +, is dominant to the white (mutant) allele, w. The offspring of size 200 from the mating of a single female (♀) and a single male (♂) are shown in the table below:
| phenotype | female (♀) | male (♂) |
|---|---|---|
| red-eyed (wildtype) | 93 | 107 |
| white-eyed (mutant) | 0 | 0 |
What are the genotypes of the parents in this cross?
Probability of Gender Distribution in Children
Click to show Probability of Gender Distribution in Children example problem
A woman has nine (9) children, what is the probability that she has exactly six (6) boys and three (3) girls?
X-linked Eye Color Inheritance
Click to show X-linked Eye Color Inheritance example problem
In fruit flies, eye color is X-linked with red eyes dominant to white eyes. A true-breeding white-eyed female is crossed with a true-breeding red-eyed male.
Which statement best describes the F1 offspring?
X-linked Coat Color Probability
Click to show X-linked Coat Color Probability example problem
In cats, coat color is X-linked. The orange (O) and black (B) alleles are codominant, so heterozygous females are tortoiseshell.
A orange female (♀) mates with a black male (♂).
What fraction of daughters (♀) are expected to be tortoiseshell?