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 
Matching Meiosis Prophase I Stages to Descriptions
Click to show Matching Meiosis Prophase I Stages to Descriptions 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. Leptotene | ||
| 2. Pachytene, early or late | ||
| 3. Diplotene or Diakinesis, combined | ||
| 4. Zygotene |
Drag one of the choices below:
- A. exchange of segments between homologous chromosomes may occur
- B. thread-like chromomeres become visible along the chromosomes
- C. homologous chromosome pairs begin to separate and chiasmata become visible
- D. synapsis of homologous chromosomes occurs
Matching Meiosis Terms to Definitions
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Match each of the following Meiosis terms with their corresponding definitions.
Note: Each choice will be used exactly once.
| Your Choice | Prompt | |
|---|---|---|
| 1. chiasmata | ||
| 2. crossing over | ||
| 3. synapsis | ||
| 4. homologous chromosomes |
Drag one of the choices below:
- A. the exchange of genes between two homologous chromosomes, resulting in a mixture of parental characteristics
- B. homologous chromosomes pair with their counterparts and remain bound
- C. specialized chromatin structures that link homologous chromosomes together
- D. one chromosome from the mother and one chromosome from the father
Matching Sex Determination Systems to Descriptions
Click to show Matching Sex Determination Systems to Descriptions 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. Z-W system | ||
| 2. X-O system | ||
| 3. Haplo-Diploid system | ||
| 4. X-Y system |
Drag one of the choices below:
- A. sex of an offspring depends on which sex chromosome is contained with the female ♀ egg (ovum)
- B. males ♂ have two different kinds of sex chromosomes
- C. male ♂ sperm normally contain either one sex chromosome or no sex chromosomes at all
- D. only system where males ♂ have no fathers
True/False Statements About Mitosis and Meiosis
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Which one of the following statements is FALSE regarding mitosis and meiosis cell division?
Meiosis Prophase I Stages from Descriptions
Click to show Meiosis Prophase I Stages from Descriptions example problem
Which one of the following stages of meiosis prophase I correspond to the partial description 'thread-like chromomeres become visible along the chromosomes'.
Meiosis Terms from Definitions
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Which one of the following Meiosis terms correspond to the definition 'the exchange of genes between homologous chromosomes, resulting in a mixture of parental characteristics'.
Sex Determination Systems from Descriptions
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Which one of the following sex determination systems correspond to the description 'found in insects, such as ants and bees'.
Fraction of Daughters with Both AIS and HD
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Hemophilia A (HemA) is an X-linked recessive genetic disorder that is caused by a mutation in the HEMA gene. This results in blood cannot clot properly due to a deficiency of a clotting factor. The disorder affects 1 in 1,000 American males. Individuals affected with HemA have prolonged bleeding from common injuries. The defective gene for HemA is located on the long arm of chromosome X at position 28.
Huntington's disease (HD) is an autosomal dominant genetic disorder that is caused by an increase in trinucleotide repeats in the HTT gene. This results in a mutated Huntington protein that is toxic to certain cell types, particularly brain cells. The disorder affects 1 in 10,000 adults of European descent. Individuals affected with HD have physical abilities that gradually worsen and mental abilities that decline into dementia. The defective gene for HD is located on the short arm of chromosome 4 at position 16.3.
A man (♂) with both HemA and HD genetic disorders marries a wild-type phenotype woman (♀) with neither disorder. The father (♂) of the woman has the HemA genetic disorder,but mother (♀) of the woman does not. The mother (♀) of the man is wild-type phenotype and does not have the HD genetic disorder.
Reminder: HemA is X-linked recessive and HD is autosomal dominant.
What fraction of their daughters (♀) will have both HemA and HD genetic disorders?
Combined Dominant and X-Linked Recessive Inheritance Variations
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Hemophilia A (HemA) is an X-linked recessive genetic disorder that is caused by a mutation in the HEMA gene. This results in blood cannot clot properly due to a deficiency of a clotting factor. The disorder affects 1 in 1,000 American males. Individuals affected with HemA have prolonged bleeding from common injuries. The defective gene for HemA 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 (♂) does not have HemA. Genetic testing shows the woman (♀) is not a carrier for HemA. The man (♂) does not have MFS. The woman (♀) does not have MFS.
Reminder: HemA is X-linked recessive and MFS is autosomal dominant.
What fraction of their daughters (♀) will have MFS but not HemA?
Parent Genotypes in X-Linked Recessive Crosses
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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 | 0 |
| white-eyed (mutant) | 0 | 107 |
What are the genotypes of the parents in this cross?
X-linked Eye Color Inheritance
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In fruit flies, eye color is X-linked with red eyes dominant to white eyes. A true-breeding red-eyed female is crossed with a white-eyed male.
Which statement best describes the F1 offspring?
X-linked Coat Color Probability
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In cats, coat color is X-linked. The orange (O) and black (B) alleles are codominant, so heterozygous females are tortoiseshell.
A black female (♀) mates with a orange male (♂).
What fraction of all kittens are expected to be tortoiseshell?