6: Chromosomal Inheritance

Chromosome behavior in meiosis, sex-linkage, and the chromosomal basis of inheritance.

LibreTexts reference: Chromosomal Inheritance

Meiosis Prophase I Stages and Descriptions

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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
	Drop Your Choice Here	1. Early/Late Pachytene
	Drop Your Choice Here	2. Diplotene and/or Diakinesis
	Drop Your Choice Here	3. Zygotene
	Drop Your Choice Here	4. Leptotene

Drag one of the choices below:

• A. the swapping of genetic material occurs between homologous chromosomes
• B. the paired chromosomes being to separate
• C. the synapsis process forms numerous points of contact
• D. chromosomes first become visible in the form of thread-like structures

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Meiosis Terms and 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
	Drop Your Choice Here	1. sister chromatids
	Drop Your Choice Here	2. homologous chromosomes
	Drop Your Choice Here	3. synapsis
	Drop Your Choice Here	4. crossing over

Drag one of the choices below:

• A. two identical chromatids that are formed by replication of a chromosome
• B. the joining of the two homologous chromosomes
• C. a process by which parts of homologous chromosomes are interchanged
• D. two chromosomes containing identical genetic loci although possibly different allelic forms

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Sex Determination Systems and Descriptions

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Match each of the following sex determination systems with their corresponding descriptions.
Note: Each choice will be used exactly once.

	Your Choice	Prompt
	Drop Your Choice Here	1. X-Y system
	Drop Your Choice Here	2. X-O system
	Drop Your Choice Here	3. Haplo-Diploid system
	Drop Your Choice Here	4. Z-W system

Drag one of the choices below:

• A. sex of the offspring depends on whether or NOT a sex chromosome is present in the male ♂ sperm
• B. males ♂ are heterogametic and females ♀ are homogametic
• C. found in most birds, many reptiles, and some insects
• D. males ♂ develop from unfertilized eggs and thus have no fathers

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Meiosis Prophase I Stages

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Which one of the following stages of meiosis prophase I correspond to the partial description 'sister chromatids first become visible'.

• Diplotene and/or Diakinesis
• Early/Late Pachytene
• Leptotene
• Zygotene

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Meiosis Terms

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Which one of the following Meiosis terms correspond to the definition 'the matching-up of homologous pairs prior to their segregation'.

• chiasmata
• homologous
• homologous chromosomes
• synapsis

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Sex Determination Systems

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Which one of the following sex determination systems correspond to the description ' males ♂ have two different kinds of chromosomes'.

• Haplo-Diploid system
• X-O system
• X-Y system
• Z-W system

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True/False Statements About Mitosis and Meiosis

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Which one of the following statements is TRUE of mitosis and meiosis cell division?

• Meiosis is a special type of cell division that produces sex cells for reproduction
• In meiosis, the parent cell and the daughter cells are genetically identical
• Meiosis starts with two cells and mitosis starts with only one cell
• Each daughter cell formed by mitosis has the half the number of chromosomes as the parent cell
• During the process of mitosis several processes occurs that cause genetic variation among organisms

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Inheritance Patterns for X-Linked Recessive and Autosomal Dominant Disorders

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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 father (♂) 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?

• None, 0%
• 1/4, 25%
• 1/2, 50%
• 3/4, 75%
• All, 100%

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Inheritance Patterns from Pedigree Charts

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◻		◯		◻		⬤		◻		◯
◯	◻	◯		◼		⬤		◻	◻	◯
◼		⬤		◻		⬤		◯		◻
◻	⬤	⬤	⬤	◼	◯	⬤	◻	◯	◻	◻

 
Examine the pedigree above. Which one of the following patterns of inheritance is most likely demonstrated in the above pedigree inheritance?

• autosomal dominant
• autosomal recessive
• x-linked dominant
• x-linked recessive
• y-linked

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Inheritance Types from Pedigrees

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Match the following pedigrees to their most likely inheritance type.
Note: each inheritance type will only be used ONCE.

	Your Choice	Prompt
	Drop Your Choice Here	1. ◼ ◯   ◻ ◯   ◻ ⬤     ◯ ◻ ◼ ◯   ◯ ◼ ⬤ ◻           ⬤ ◼   ◻ ◯   ⬤ ◻ ◻ ⬤ ◼ ⬤ ◻ ◯ ◻ ◻ ◯ ◼ ◻
	Drop Your Choice Here	2. ◻ ⬤   ◻ ◯   ◻ ◯     ◯ ◻ ◯ ◻   ◯ ◼ ◻ ◯           ◯ ◻   ◯ ◻   ◯ ◻ ◻ ◻ ◯ ⬤ ◻ ◯ ◼ ◻ ◯ ◻ ◻
	Drop Your Choice Here	3. ◯ ◻   ⬤ ◻   ◯ ◻     ◯ ◻ ◻ ⬤   ◼ ◯ ◻ ◯           ◻ ◯   ⬤ ◻   ⬤ ◼ ◻ ◻ ◯ ◻ ⬤ ◯ ◼ ⬤ ⬤ ⬤ ◻
	Drop Your Choice Here	4. ◼ ◯   ◻ ◯   ◻ ⬤     ◯ ◻ ◯ ◻   ◯ ◼ ◼ ◯           ◻ ◯   ◼ ◯   ◯ ◻ ◻ ◻ ◯ ◯ ◼ ⬤ ◼ ◻ ◯ ◼ ◻
	Drop Your Choice Here	5. ◻ ◯   ◯ ◼   ◻ ◯     ◯ ◻ ◯ ◼   ◯ ◻ ◯ ◯           ◯ ◼   ◼ ◯   ◻ ◯ ◯ ◼ ◯ ◼ ◼ ◯ ◼ ◯ ◻ ◯ ◻

Drag one of the choices below:

• A. x-linked dominant
• B. autosomal dominant
• C. y-linked
• D. autosomal recessive
• E. x-linked recessive

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X-Linked Inheritance Patterns in Fruit Flies

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The white-eyed phenotype is an X-linked recessive disorder in fruit flies. The red allele, +, is dominant to the white allele, w. The offspring of size 600 from the mating of a single female and a single male are shown in the table below:

phenotype	female ♀	male ♂
red-eyed (wildtype)	310	148
white-eyed (mutant)	0	142

What are the genotypes of the parents in this cross?

• homozygous mutant female (ww) and mutant male (w–)
• heterozygous female (+w) and wildtype male (+–)
• homozygous wildtype female (++) and male of unknown genotype
• heterozygous female (+w) and mutant male (w–)
• homozygous mutant female (ww) and wildtype male (+–)

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Probability of Specific Gender Distributions in Offspring

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A woman has nine (9) children, what is the probability that she has exactly three (3) boys and six (6) girls?

• ( 6 ) 3

  (½)3⋅(½)6

  =

  6!   (6–3)! ⋅ 3!

  (½)6

  =

  6⋅5⋅4   3⋅2

  ×

  1   26

  =

  20   512

  =

  0.0391

  =

  3.9%

• ( 9 ) 3

  (¾)3⋅(¼)6

  =

  9!   (9–3)! ⋅ 3!

  (¾)3⋅(¼)6

  =

  9⋅8⋅7⋅6⋅5⋅4   3⋅2

  ×

  33   4346

  =

  84×27   262144

  =

  0.0087

  =

  0.9%

• ( 6 ) 6

  (½)6⋅(½)3

  =

  6!   (6–6)! ⋅ 6!

  (½)6

  =

  1   1

  ×

  1   26

  =

  1   512

  =

  0.0020

  =

  0.2%

• ( 9 ) 3

  (¼)3⋅(¾)6

  =

  9!   (9–3)! ⋅ 3!

  (¼)3⋅(¾)6

  =

  9⋅8⋅7⋅6⋅5⋅4   3⋅2

  ×

  36   4346

  =

  84×729   262144

  =

  0.2336

  =

  23.4%

• ( 9 ) 3

  (½)3⋅(½)6

  =

  9!   (9–3)! ⋅ 3!

  (½)9

  =

  9⋅8⋅7⋅6⋅5⋅4   3⋅2

  ×

  1   29

  =

  84   512

  =

  0.1641

  =

  16.4%

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