Chromosomal Aberrations Overview

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Questions and Answers

Which condition is most likely to result from X chromosome monosomy?

Down syndrome

Turner syndrome (correct)

Fragile X syndrome

Klinefelter syndrome

What is the karyotype for a male with Down syndrome?

46, XY, +21

47, XX, +21

46, XY, +18

47, XY, +21 (correct)

Which best describes mixoploidy?

Presence of genetically different cell lineages within one individual (correct)

Presence of extra chromosomes in diploid cells

The presence of a Y chromosome in a female

Absence of a single homologous chromosome

How does mosaic Down syndrome occur?

By the failure of chromosome 21 chromatids to separate during mitosis (B) Signup and view all the answers

Which type of structural aberration occurs when a segment of one chromosome is inserted into another chromosome?

Insertion (B) Signup and view all the answers

What condition can result from the fusion of two different zygotes from double fertilization?

Dispermic chimeras (C) Signup and view all the answers

What characterizes balanced rearrangements in structural aberrations?

They are generally harmless to the carrier. (A) Signup and view all the answers

Which feature is NOT typically associated with Turner syndrome?

Increased intelligence (C) Signup and view all the answers

What characterizes the karyotype of an individual with Klinefelter syndrome?

47, XXY (D) Signup and view all the answers

What is the primary outcome of a deletion that involves loss of more than 2% of the total haploid genome?

Lethal outcome. (A) Signup and view all the answers

Which statement correctly defines monosomy?

Absence of a single chromosome (B) Signup and view all the answers

What occurs during a reciprocal translocation?

Genetic material is exchanged between two chromosomes. (A) Signup and view all the answers

In which situation would a karyotyping method most likely be used?

Identifying chromosomal abnormalities (D) Signup and view all the answers

Which structural aberration is likely to produce serious clinical effects due to an incorrect amount of chromosome material?

Unbalanced rearrangement (D) Signup and view all the answers

Which condition is typically associated with a karyotype of 47, XX, +21?

Down syndrome (C) Signup and view all the answers

Which of the following describes a condition where there is an entire extra set of chromosomes?

Polyploidy (C) Signup and view all the answers

Which scenario is most likely to result in triploidy?

Dispermy of an ovum by two sperm (A) Signup and view all the answers

Which of the following is true about aneuploidy concerning sex chromosomes compared to autosomes?

Aneuploidy involving sex chromosomes typically has milder phenotypes. (A) Signup and view all the answers

What is a known cause of aneuploidy linked to maternal age?

Non-disjunction (B) Signup and view all the answers

Which karyotype would represent a typical condition of tetraploidy?

92 chromosomes grouped as four sets per chromosome (D) Signup and view all the answers

Which of the following abnormalities is most likely associated with loss of a single chromosome?

Monosomy (A) Signup and view all the answers

What is the primary consequence of anaphase lag during cell division?

Failure of one chromosome or chromatid to be included in daughter nuclei (C) Signup and view all the answers

In which condition do the resulting cells have an abnormal chromosome number due to the addition of an extra chromosome?

Aneuploidy (D) Signup and view all the answers

What commonly leads to a triploid condition in a zygote?

Fertilization by the fusion of two sperm with an egg (D) Signup and view all the answers

What is the characteristic feature of balanced karyotypes?

Normal chromosome number with all segments present (C) Signup and view all the answers

What is the primary purpose of staining chromosomes during karyotyping?

To enhance visibility of chromosomes under a light microscope (A) Signup and view all the answers

Which statement accurately describes the karyotype formula for a normal male?

46,XY (B) Signup and view all the answers

In G-banding, which regions of DNA appear more darkly stained?

AT-rich heterochromatic regions (D) Signup and view all the answers

What would be the karyotype formula representation of a trisomy involving chromosome 8 in a female?

47,XX,+8 (A) Signup and view all the answers

What type of specimen is commonly used for karyotyping in cancer diagnoses?

Tumor biopsies (A) Signup and view all the answers

Which technique is NOT typically used for banding during karyotyping?

FISH analysis (A) Signup and view all the answers

What is indicated by a karyotype formula that includes a ‘-’ sign?

Loss of a chromosome (B) Signup and view all the answers

Which chromosome banding technique is particularly useful for analyzing chromosomes under a light microscope?

G-banding (B) Signup and view all the answers

Which of the following statements is true regarding X-linked dominant inheritance?

An affected female has a 50% chance of transmitting the trait to any offspring regardless of sex. (C) Signup and view all the answers

In X-linked hypophosphatemia, which characteristic differentiates males from females?

Males have a higher severity of skeletal changes than females. (D) Signup and view all the answers

Which of the following accurately describes Y-linked inheritance?

A affected male transmits Y-linked traits only to his sons. (C) Signup and view all the answers

What is a common result of deletions in Y chromosome genes?

Infertility due to azoospermia. (C) Signup and view all the answers

Which statement about karyotyping is correct?

Karyotyping can determine an individual's entire chromosome complement. (C) Signup and view all the answers

Why do females often exhibit less severe symptoms in X-linked dominant disorders?

They carry two X chromosomes, which offer a protective effect. (A) Signup and view all the answers

Which of the following conditions does NOT exemplify Y-linked inheritance?

Color blindness in males. (A) Signup and view all the answers

What distinguishes an X-linked dominant disorder from an X-linked recessive disorder?

Both males and females are affected in X-linked dominant, with female manifestations being more severe. (C) Signup and view all the answers

In families with X-linked dominant disorders, which outcome is typical?

There is a higher prevalence of affected females compared to males. (C) Signup and view all the answers

How does X chromosome inactivation impact the expression of X-linked traits in females?

It completely silences one X chromosome, leading to reduced expression of X-linked traits. (B) Signup and view all the answers

What is the expected chromosomal composition in a triploid individual?

69 chromosomes with three copies of each chromosome (D) Signup and view all the answers

Which of the following best characterizes aneuploidy?

An abnormal number of chromosomes due to the loss or gain of individual chromosomes (B) Signup and view all the answers

What is a common outcome associated with tetraploidy?

Early developmental failures leading to miscarriage (B) Signup and view all the answers

Which statement regarding non-disjunction and its outcomes is accurate?

It can result from errors during meiosis I or meiosis II. (D) Signup and view all the answers

How is triploidy most commonly caused?

Resulting from fertilization by an egg with two sperm (A) Signup and view all the answers

What is a characteristic feature of X-linked recessive inheritance?

Males cannot transmit X-linked traits to their daughters. (A) Signup and view all the answers

In a family where the father is affected by an X-linked recessive disorder, what is the probability that his daughter will be a carrier?

50% chance of being a carrier. (D) Signup and view all the answers

What is the recurrence risk for sons of a carrier female for an X-linked recessive disorder?

50% chance of being affected. (C) Signup and view all the answers

Which of the following statements is true regarding X-linked disorders like Duchenne muscular dystrophy?

Affected males often die before reaching reproductive age. (C) Signup and view all the answers

How do affected males typically contribute to the transmission of X-linked recessive disorders?

They contribute through their healthy female carriers. (B) Signup and view all the answers

What is a characteristic of autosomal dominant (AD) inheritance concerning affected individuals?

Each affected person has an affected parent. (A) Signup and view all the answers

Which of the following is true regarding the transmission of autosomal dominant traits?

Vertical transmission is commonly observed. (D) Signup and view all the answers

What role does a pedigree serve in genetic studies?

It traces the inheritance pattern of traits within a family. (B) Signup and view all the answers

How are autosomal dominant traits typically manifested in individuals?

In the heterozygous state, often showing a milder phenotype. (D) Signup and view all the answers

What is a common characteristic of traits that follow non-Mendelian inheritance patterns?

They can be influenced by multiple genes or environmental factors. (A) Signup and view all the answers

What is the primary difference between mosaic Down syndrome and standard Down syndrome?

Mosaic Down syndrome contains cells with varying chromosome counts, while standard has uniform counts. (B) Signup and view all the answers

Which of the following best describes how chimeric embryos are formed?

Through the fusion of two zygotes from different fertilizations. (C) Signup and view all the answers

What does the karyotype (45, X) indicate about an individual?

The individual is likely female and has Turner syndrome. (B) Signup and view all the answers

Which scenario describes mixoploidy involving mosaicism?

A zygote develops with cells having different chromosome configurations due to disjunction failure. (C) Signup and view all the answers

What is a common characteristic of individuals with Turner syndrome?

They display normal intelligence but may experience learning disabilities. (C) Signup and view all the answers

Study Notes

Chromosomal Aberrations (Numerical & Structural)

Interpreting chromosomal abnormalities is a key skill.
Aneuploidy vs. polyploidy differentiation is important. Aneuploidy involves an abnormal number of chromosomes (not a multiple of the haploid number), while polyploidy involves a multiple of the haploid number.
Balanced vs. unbalanced karyotypes are distinguished by the presence or absence of genetic material.
Phenotypic outcomes relate to the type of chromosomal aberration.

Numerical Aberrations

Euploidy refers to the normal chromosome number for a species. In humans, this is 46 (2n) in somatic cells and 23 (n) in gametes.
Polyploidy is a condition where the chromosome number is a multiple of the haploid set.
- Triploidy (3n): A cell has three copies of each chromosome, often resulting from fertilization by two sperm or failure of reduction division in meiosis. Typically results in miscarriage.
- Tetraploidy (4n): A cell has four copies of each chromosome, usually due to a failure of the first zygotic cell division. Typically results in miscarriage.

Aneuploidy

Aneuploidy is an abnormal chromosome number due to an extra or missing chromosome, not a multiple of the haploid number. This is more severe when affecting autosomes than sex chromosomes.
- Trisomy: The presence of three copies of an autosome or sex chromosome (2n+1). Examples include Down syndrome (trisomy 21).
- Monosomy: The absence of a single chromosome (2n-1). Commonly incompatible with survival. Example: Turner syndrome (45,X).

Mixoploidy

Mixoploidy involves two or more genetically different cell lineages within an individual. This can result from mosaicism or chimerism.

Structural Aberrations

Structural aberrations involve chromosome breakage and subsequent reunion, resulting in a variety of changes in chromosome structure. These changes can be balanced or unbalanced.
- Deletions (del): Loss of part of a chromosome.
- Inversions (inv): A segment of a chromosome is reversed in orientation (balanced).
- Insertions (ins): Insertion of a segment from one chromosome into another (balanced or unbalanced).
- Duplications (dup): Repetition of a chromosomal segment.
- Translocations: Transfer of genetic material from one chromosome to another.
  - Reciprocal translocations: Exchange of segments between non-homologous chromosomes.
  - Robertsonian translocations: Fusion of the long arms of two acrocentric chromosomes.
- Ring chromosomes: A chromosome forms a ring due to breaks and rejoining.

Karyotyping

Karyotyping is a technique used to visualize and analyze chromosomes. Chromosomal abnormalities can be identified by looking at chromosome number and structure.
Karyotype formulae provide an exact description of chromosomal abnormalities, using a standardized nomenclature. For example, 46,XX (normal female) or 47,XX,+21 (Down syndrome).

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Description

Explore the fascinating world of chromosomal aberrations in this quiz. Test your knowledge on numerical and structural abnormalities, including aneuploidy and polyploidy. Understand the phenotypic outcomes and the distinction between balanced and unbalanced karyotypes.