Inheritance of Sex-Linked Dominant Traits Quiz

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What is the term used to describe the disturbances of red and green color vision caused by abnormal visual dyes?

Daltonism

What is a Y-body?

A highly fluorescent body in the interphase cell nucleus

In North European populations, which type of color vision disturbance is 4-5 times more common than protanopia?

Deuteranomaly

How many Y bodies are typically found in male cells?

Equal to the number of Y chromosomes

What is the term for a person who can see correctly but carries the gene for a type of color vision anomaly?

Correctvision

What is the term for the genetic cross between a daughter with protanomaly and a son seeing correctly with deuteranomaly?

XP1Y

What is Lyonisation?

Inactivation process of one of the X chromosomes

How is lyonisation described?

Independent, random, indivertible

What are Ishihara pseudoisochromatic tables used to check?

Color vision ability

In the Ishihara full test, how many tables are there typically?

36

When does lyonisation occur in female embryonic cells?

Around 16 days of embryonic life

'Deuteranomaly' affects approximately what percentage of men in North European populations?

~4-5%

What is the purpose of lyonisation?

To balance the gene expression from X chromosomes in XX and XY individuals

Which cells exhibit Y-drummer's sticks?

Neutrophils

'Protanopia' affects approximately what percentage of women in North European populations?

~0.5%

What happens to genes located in the pseudoautosomal region during lyonisation?

They are not inactivated

What is the most common type of mutation detected in Haemophilia B?

Missense mutations

Which type of mutation accounts for 11% of all mutations detected in Haemophilia B?

Splicing mutations

What level of factor VIII or IX in plasma is associated with the mild form of haemophilia?

0.05-0.40 IU/ml (5-40% norm)

Which type of bleeding is characteristic of severe haemophilia?

Prolonged bleeding after minor injuries

What dominates over the deuteranomaly allele Xd1 in terms of colour vision?

X-norm allele

How are women affected when they possess an abnormal colour vision gene on each X chromosome?

They see correctly

In Haemophilia B, what percentage of all mutations are characterized as gene rearrangements?

<1%

Which clinical form of haemophilia exhibits severe bleeding as a result of injuries and micro-trauma?

Severe

What is the inheritance pattern when a female carrier and a healthy man have children?

50% of sons will be sick and 50% healthy; 50% of daughters will be carriers and 50% healthy

What happens when an ill man (hemizygous) has children?

He does not pass the disease to sons, but all daughters will be carriers

What is the phenotype of hemizygous men and heterozygous women with a mutated gene?

Both get ill

What is the likelihood that sick women (heterozygotes) pass the mutant gene to both daughters and sons?

50% probability to both daughters and son

What is the effect of the mutant dominant gene in men?

It is often lethal

What is the phenotype of XAXA genotype in women?

Ill, most common lethal genotype

In the inheritance of sex-linked dominant traits, what is the phenotype of XAY genotype in men?

Ill, often a lethal feature

What is the genotype and phenotype of XaXa individuals?

'Invisible' carrier

What is a useful feature of fruit flies in genetic studies?

The presence of polytene chromosomes in salivary gland cells

How is the human karyotype classified?

23 pairs of chromosomes, 22 autosomes, and 1 heterosome

According to the classical division, which group do chromosomes 1-3 belong to?

Group B - Large submetacentric

In human karyotyping, how are autosomes arranged following the rules?

By size, followed by sex chromosomes X and Y

Which feature of chromosomes is used for their classification into groups A to G?

Length and centromere position

What system describes the rules for recording cytogenetic test results?

ISCN (The International System for Human Cytogenetic Nomenclature)

How are chromosomes stained in human karyotyping using Giemsa reagent?

G-bands are used for staining

What is the term used to describe the giant chromosomes in fruit fly salivary gland cells?

Polytene chromosomes

What type of inheritance is described as the transmission of traits from father to son?

Holandric inheritance

In the inheritance of recessive sex-linked traits, what is the phenotype of individuals with the genotype XAXa?

Clinically healthy, carrier

In the case of female carriers (heterozygotes) of a mutated gene, what is the probability of transmitting the gene to daughters and sons?

50% to both daughters and sons

What term describes individuals who have only one X chromosome and one copy of each gene linked to the X chromosome?

Hemizygous

In the inheritance of sex-linked dominant traits, what is the phenotype of individuals with the genotype XAY?

Healthy

What is the genotype of Illman?

XAY XaXa

What is the term for individuals with only one copy of a particular gene on the sex chromosomes?

Hemizygous

What is the genotype of Healthywoman?

XAY XaXa

In the inheritance of sex-linked dominant traits, what is the expected phenotype of a female with the genotype XDXd1?

Expresses the trait

When an Illwoman and Healthyman have offspring, what percentage of sons will be ill?

0%

When a woman who is a carrier for a recessive sex-linked trait has a son, what is the probability that the son will inherit the mutated gene?

50%

What is the genotype of a female carrier of the mutated gene for hemophilia B?

XAXa

For individuals with hemophilia B, what type of mutation accounts for approximately 11% of all identified mutations?

Splicing mutations

When a hemizygous man with haemophilia A has children with an Illwoman, what percentage of daughters are expected to be healthy carriers?

~50%

If a woman carries an abnormal color vision gene on each of her X chromosomes, what is her visual perception like?

Normal color vision

What is the inheritance pattern when an ill man (hemizygous) has daughters?

They will be healthy carriers

In the inheritance of sex-linked recessive traits, what is the phenotype of XaXa genotype in women?

Healthy

What is the phenotype of hemizygous men and heterozygous women with a mutated gene?

Sick

When a sick woman (heterozygote) passes the mutant gene, what is the likelihood that her sons will inherit it?

50%

What happens to genes located in the pseudoautosomal region during lyonization in female embryonic cells?

They are silenced

In North European populations, which type of color vision disturbance is about 4-5 times more common than protanopia, protanomaly, and deuteranopia?

Deuteranomaly

Which term is used to describe the disturbances of red and green color vision caused by the abnormal amount of visual dyes?

Daltonism

What is the term for a person who can see correctly but carries the gene for a type of color vision anomaly?

Hemizygous

When a female carrier and a healthy man have children, what is the inheritance pattern observed for the mutated gene?

X-linked recessive

What is the term used to describe the genetic cross between a daughter with protanomaly and a son who sees correctly with deuteranomaly?

Protandutic cross

What is the term for individuals who possess only one copy of a recessive gene on the X chromosome?

Hemizygous individuals

In the inheritance of sex-linked recessive traits, what is the phenotype of females who are carriers of the mutated gene?

Normal phenotype

When a female carrier and a healthy man have children, what is the likelihood that their sons will inherit the mutated gene?

25%

What is the term used to describe individuals who carry a gene for a certain trait but do not express the trait themselves?

Silent carriers

In sex-linked dominant trait inheritance, how are females affected when they possess an abnormal gene on one X chromosome?

They exhibit the trait mildly

What is the term for the graphical set of chromosomes typical for a given individual or species?

Karyotype

In the inheritance of sex-linked recessive traits, what is the phenotype of individuals with the genotype X^AX^a?

Hemophilia

When an ill man (hemizygous) has children, what is the likelihood that his daughters will be carriers of the mutated gene?

50%

In the inheritance of sex-linked dominant traits, what is the phenotype of individuals with the genotype X^AY?

Hemophilia

For female carriers (heterozygotes) of a mutated gene, what is the probability of transmitting the gene to their sons?

~25%

What is the term for a person who carries the gene for a type of color vision anomaly but can see correctly?

'Carrier' individual

In the case of female carriers (heterozygotes) of a mutated gene, what is the probability of transmitting the gene to their daughters?

~50%

Which type of mutation accounts for 11% of all mutations detected in Haemophilia B?

Gene rearrangements

'Protanopia' generally affects what percentage of women in North European populations?

~0.5%

'Deuteranomaly' typically affects what percentage of men in North European populations?

~4-5%

Study Notes

Genetic Studies of Fruit Flies

  • Fruit flies are useful in genetic studies due to:
    • Presence of polytene (giant) chromosomes in salivary gland cells
    • High frequency of gene mutations affecting various morphological features

Human Karyotype

  • Human karyotype consists of 23 pairs of chromosomes: 22 pairs of autosomes and 1 pair of sex chromosomes (heterosomes)
  • X and Y chromosomes are classified as sex chromosomes
  • Sex chromosomes are arranged at the end of the karyotype, following the size and centromere position

Chromosome Classification

  • Chromosomes are classified into seven groups (A to G) based on:
    • Length
    • Centromere position
  • Table 1 shows the classical division of human chromosomes

Chromatin Y

  • Chromatin Y (Y-body) is a condensed, heterochromatic part of the long arms of Yq12
  • Visualized by the fluorescent method in the interphase cell nucleus
  • Number of Y bodies is equal to the number of Y chromosomes
  • Found in 30-50% of studied male cells, including sperm, lymphocytes, and oral epithelial cells

Lyonisation

  • Lyonisation is the process of inactivation of one X chromosome in female cells
  • Inactivation is:
    • Independent
    • Random
    • Irreversible
  • Compensatory mechanism to balance the level of gene expression on sex chromosomes

Inheritance of Sex-Linked Traits

  • Inheritance patterns of sex-linked traits:
    • Hemizygous men and heterozygous women both get ill
    • Heterozygous women with a mutated gene usually have a mild form of disease
    • Hemizygous men do not pass the disease to their sons, but all daughters will be carriers
    • Sick women (heterozygotes) pass the mutant gene to both daughters and sons with 50% probability

Haemophilia

  • Haemophilia A and B are recessive sex-linked diseases
  • Caused by mutations in the genes F8C and F9, respectively
  • Frequency of occurrence:
    • Haemophilia A: 1:10,000 to 1:20,000 births
    • Haemophilia B: 1:30,000 births
  • Clinically, Haemophilia A and B do not differ from each other, symptoms appear in early childhood

Colour Vision

  • Colour vision disturbances are caused by point mutations within the deutan gene
  • In North European populations, red and green colour vision disturbances affect:
    • About 8% of men
    • About 0.5% of women
  • Deuteranomaly is 4-5 times more common than protanopia, protanomaly, and deuteranopia

FISH Technique

  • FISH (Fluorescence In Situ Hybridization) is a cytogenetic technique to detect a specific DNA sequence in genetic material
  • Uses fluorescent DNA probes to identify specific DNA sequences
  • Applications:
    • Identification of additional genetic material (marker chromosomes)
    • Evaluation of structural aberrations
    • Detection of submicroscopic aberrations
    • Rapid detection of aneuploidy/polyploidy in pre- and postnatal diagnosis

Test your knowledge on the inheritance patterns of sex-linked dominant traits, including scenarios involving female carriers and ill men. Learn about the different outcomes for sons and daughters based on the genetic makeup of the parents.

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