Podcast
Questions and Answers
Which of the following accurately describes Down Syndrome in relation to chromosomal abnormalities?
What genetic condition is associated with the karyotype 47,XX,+21?
Which of the following statements about aneuploidies is correct?
Which statement accurately describes aneuploidy?
Signup and view all the answers
What is the primary difference between polyploidy and aneuploidy?
Signup and view all the answers
Which mechanism is primarily responsible for nondisjunction during meiosis?
Signup and view all the answers
What type of chromosomal abnormality is defined as having three copies of every chromosome, resulting in 69 chromosomes?
Signup and view all the answers
Which of the following best defines the process of polypoidy?
Signup and view all the answers
In what situation does nondisjunction occur in Meiosis I?
Signup and view all the answers
Which of the following terms describes a structural chromosomal abnormality without any gain or loss of genetic material?
Signup and view all the answers
Which karyotype represents a male with Turner syndrome?
Signup and view all the answers
Which structural abnormality involves a segment of a chromosome being reversed end to end?
Signup and view all the answers
What condition is characterized by a female having 46 chromosomes, with a structural translocation between chromosomes 1 and 6?
Signup and view all the answers
Which type of chromosomal abnormality is characterized by a change in the internal structure without altering the total number of chromosomes?
Signup and view all the answers
What is a common characteristic of unbalanced chromosome abnormalities?
Signup and view all the answers
Which of the following syndromes is most likely caused by a chromosomal deletion?
Signup and view all the answers
Which mechanism is primarily responsible for numerical abnormalities, such as Down Syndrome?
Signup and view all the answers
Polyploidy can result from which of the following processes?
Signup and view all the answers
Providing an example of a chromosomal rearrangement that may cause a phenotype change, which of the following is a correct pairing?
Signup and view all the answers
Which type of syndrome is often less severe due to the nature of genetic change?
Signup and view all the answers
Which statement about individuals with balanced rearrangements is true?
Signup and view all the answers
What is the primary cause of most structural chromosomal abnormalities?
Signup and view all the answers
What defines a karyotype?
Signup and view all the answers
Which of the following options describes unbalanced rearrangements?
Signup and view all the answers
Which chromosomes are known to be acrocentric and can participate in Robertsonian translocations?
Signup and view all the answers
What is the purpose of chromosomal band nomenclature?
Signup and view all the answers
What is the primary characteristic of balanced chromosomal abnormalities?
Signup and view all the answers
Which of the following is an example of an unbalanced chromosomal abnormality?
Signup and view all the answers
What is the expected phenotypic effect of individuals with balanced chromosomal rearrangements?
Signup and view all the answers
Why are deletion syndromes often more severe than duplication syndromes?
Signup and view all the answers
Which of the following statements accurately describes numerical abnormalities?
Signup and view all the answers
What type of chromosomal rearrangement could lead to conditions like Hemophilia A?
Signup and view all the answers
Which syndrome is likely caused by a chromosomal deletion?
Signup and view all the answers
What tends to be the result of many unbalanced chromosomal rearrangements?
Signup and view all the answers
What does the notation 'del(22)(q21)' in a karyotype signify?
Signup and view all the answers
What is the primary characteristic of a balanced rearrangement?
Signup and view all the answers
In the karyotype notation '46,XX,t(1;6)(p23;q21)', what does 't' indicate?
Signup and view all the answers
Which karyotype represents a structural abnormality involving an inversion?
Signup and view all the answers
What chromosomal feature is described by the term 'iso' in 'i(7)'?
Signup and view all the answers
What type of chromosomal abnormality does '47,XX,+21' represent?
Signup and view all the answers
What does a karyotype of '45,X/46,XX' indicate?
Signup and view all the answers
In which structural abnormality is there a segment of the chromosome reversed end to end?
Signup and view all the answers
Describe Non-Disjunction (Meiosis I)
Signup and view all the answers
If two chromosomes are not identical then non-disjunction occurred in.....?
Signup and view all the answers
If chromosomes are identical in the offspring then non-disjunction occurred in.....
Signup and view all the answers
Is it possible to determine where non disjunction occurred in monosomies or trisomies? (both examples of aneuploidy)
Signup and view all the answers
Non-disjunction in meiosis I leads to what chromosomal pattern in offspring?
Signup and view all the answers
Non-disjunction in Meiosis II leads to what chromosomal pattern in offspring?
Signup and view all the answers
Non-disjunction most often occurs in _____
Signup and view all the answers
polyploidy (such as triploidy and tetraploidy) is ........ compatible with life. (examples include 47 XXX, 47 XXY, 47 XYY)
Signup and view all the answers
What are balanced abnormalities in cytogenetics?
Signup and view all the answers
What are unbalanced abnormalities?
Signup and view all the answers
Syndromes caused by chromosomal deletions are __________ than those caused by duplications, suggesting that the loss of genetic material is more disruptive than a gain.
Signup and view all the answers
Hemophilia A is an ______ that disrupts the ______ gene.
Signup and view all the answers
Female Duchenne Muscular Dystrophy is caused by a ______ mutation between the ______ and ______.
Signup and view all the answers
What happens when unequal crossing over occurs in chromosome bivalents?
Signup and view all the answers
What are acrocentric chromosomes in humans?
Signup and view all the answers
Describe Karyotype
Signup and view all the answers
What does colchicine and hypotonic saline do in karyotyping?
Signup and view all the answers
what does 47, XY, +18 mean?
Signup and view all the answers
what is q and p?
Signup and view all the answers
What is Robertsonian Translocation?
Signup and view all the answers
What are acrocentric chromosomes?
Signup and view all the answers
Describe a robertsonian translocation
Signup and view all the answers
what are ribosomal RNA genes?
Signup and view all the answers
Study Notes
Chromosome Abnormalities & Cytogenetics
-
Structural chromosome abnormalities change the structure of chromosomes, but not the total number.
-
Balanced abnormalities have no gain or loss of genetic material and typically have no phenotypic effect.
- Examples: inversions, translocations.
-
Unbalanced abnormalities result in a gain or loss of genetic material, almost always leading to phenotypic effects.
- Examples: deletions, duplications.
-
Balanced abnormalities have no gain or loss of genetic material and typically have no phenotypic effect.
Numerical Abnormalities
- Numerical abnormalities involve alterations in the normal number of chromosomes (46).
- Polyploidy is a change in the full set of chromosomes. For example, triploidy involves having three full copies, resulting in 69 chromosomes. Triploidy is incompatible with life.
- Aneuploidy is a change in the number of one or more chromosomes. Trisomy and monosomy, involving a single chromosome, are most common, but changes involving multiple chromosomes can also occur.
Causes of Aneuploidy
- Aneuploidy is caused by non-disjunction during parental meiosis.
- If in a trisomy, the two chromosomes from the same parent are identical, the non-disjunction occurred in Meiosis II.
- If they are different, the non-disjunction occurred in Meiosis I.
Structural Chromosome Abnormalities
- Unequal crossing over is the mechanism that causes most structural abnormalities. It involves misalignment of repeat sequences during a parental meiosis.
Nomenclature of Chromosome Bands
-
p
,q
,cen
,ter
describe chromosomal locations or features. -
del
,dup
,inv
,t
,/
,+
,-
describe structural abnormalities. -
ish
indicates in situ hybridization, a cytogenetic technique used to label specific genes or loci. -
i
signifies "iso" - two copies of the same chromosome arm attached to the centromere. - Normal karyotypes are represented as 46,XX or 46,XY.
Examples of Structural Abnormalities
-
46,XY,del(22)(q21)
: a male with 46 chromosomes and a deletion on chromosome 22 at band q21. -
46,XX,inv(7)(p11;q22)
: a female with 46 chromosomes and an inversion on chromosome 7 with breakpoints at bands p11 and q22. -
47,XX,+21
: a female with an extra copy of chromosome 21 (trisomy 21 or Down syndrome). -
46,XX,t(1;6)(p23;q21)
: a female with 46 chromosomes and a translocation between chromosomes 1 and 6 with breakpoints at band p23 on chromosome 1 and band q21 on chromosome 6. -
45,X/46,XX
: a mosaic female with some 45,X cells (Turner Syndrome) and some 46,XX cells.
Summary of Chromosome Abnormalities
- Numerical abnormalities involve alterations in the normal number of chromosomes.
- Structural abnormalities do not change the total number of chromosomes but alter their internal structure.
- Balanced rearrangements have no gain or loss of genetic material and usually have no phenotypic effect.
- Unbalanced rearrangements involve a gain or loss of genetic material and almost always have phenotypic effects.
A Karyotype
- A karyotype is an individual’s complement of chromosomes and a display of these chromosomes.
- Chromosomes 13, 14, 15, 21, and 22 are acrocentric and can take part in Robertsonian translocations.
- Chromosomal band nomenclature is a standard method used to describe chromosomal locations and can help identify locations of abnormalities.
- Karyotype nomenclature is a standard way to describe normal karyotypes and numerical and structural chromosome abnormalities.
Learning Objectives
- Contrast numerical and structural chromosomal abnormalities.
- Define polyploidy and aneuploidy and explain their effects on human viability.
- Determine the parental meiosis during which a non-disjunction causing a trisomy occurred.
- Describe the major types of structural chromosomal rearrangements.
- Determine if a chromosomal rearrangement is balanced or unbalanced and predict its phenotypic effect.
- Describe a karyotype and identify gross abnormalities on a karyotype display.
- Interpret chromosomal band nomenclature and karyotype nomenclature to recognize chromosomal abnormalities and use these to predict the resulting clinical condition.
Chromosome Abnormalities and Cytogenetics: An Overview
- Structural chromosome abnormalities alter the internal structure of chromosomes, without changing the total number.
- Balanced abnormalities involve rearrangements without loss or gain of genetic material. These are typically phenotypically normal, except when breakpoints occur within crucial genes. Examples include inversions and translocations.
- Unbalanced abnormalities involve changes in genetic material (gain or loss). These often result in phenotypic effects. Examples include deletions and duplications.
- Numerical abnormalities always involve an imbalance in chromosome number and are therefore unbalanced.
- Individuals with balanced rearrangements are usually phenotypically normal, however, exceptions exist. For example, Hemophilia A can be caused by an inversion disrupting the F8 gene, and female Duchenne Muscular Dystrophy can be caused by a translocation between the X chromosome and an autosome.
- Deletion Syndromes: Deletions are usually more severe than duplications, as losing genetic material can disrupt essential functions. Common examples include Williams Syndrome, DiGeorge Syndrome, Angelman Syndrome, and Prader-Willi Syndrome.
- Duplication Syndromes: These are less common than deletion syndromes. One example is the WBSCR syndrome.
Karyotype Nomenclature
- Descriptive terms: terms like "p" (short arm), "q" (long arm), "cen" (centromere), and "ter" (telomere) are used to describe chromosome locations and features.
- Structural abnormality notations: Symbols like "del" (deletion), "dup" (duplication), "inv" (inversion), "t" (translocation), "/", "+", and "-" indicate structural changes.
- In Situ Hybridization (ISH): This technique is used to label specific genes or loci on chromosomes.
- **"i" or "iso":**Indicates two copies of the same chromosome arm attached to the centromere.
- Normal karyotypes: 46,XX (female) or 46,XY (male).
Examples of Structural Abnormalities
- 46,XY,del(22)(q21): A male with 46 chromosomes and a deletion on chromosome 22 at band q21.
- 46,XX,inv(7)(p11;q22): A female with 46 chromosomes and an inversion on chromosome 7 with breakpoints at bands p11 and q22.
- 47,XX,+21: A female with an extra copy of chromosome 21, known as trisomy 21 or Down Syndrome.
- 46,XX,t(1;6)(p23;q21): A female with 46 chromosomes and a translocation between chromosomes 1 and 6, with breakpoints at band p23 on chromosome 1 and q21 on chromosome 6.
- 45,X/46,XX: A mosaic female with some 45,X cells (Turner Syndrome) and some 46,XX cells.
Summary of Chromosome Abnormalities
- Numerical abnormalities affect the total chromosome number (46).
- Polyploidy involves changes in complete sets of chromosomes, e.g., triploidy (three full copies, 69 chromosomes), which is incompatible with life.
- Aneuploidy involves unequal changes in the number of individual chromosomes. Trisomy (extra chromosome) and monosomy (missing chromosome) are the most common, but changes in multiple chromosomes can also occur.
- Aneuploidy is caused by non-disjunction events during parental meiosis.
- Trisomy: if the two identical chromosomes come from the same parent, the non-disjunction occurred during Meiosis II. If they are different, it occurred during Meiosis I.
- Structural abnormalities alter the internal structure of chromosomes without changing the overall number.
- Balanced rearrangements have no gain or loss of genetic material and are usually phenotypically normal, although exceptions can occur. Examples include inversions and translocations.
- Unbalanced rearrangements involve a gain or loss of genetic material and almost always result in phenotypic effects. Examples are deletions and duplications.
- Unequal crossing over during parental meiosis is the primary mechanism for most structural abnormalities. It involves misalignment of repetitive sequences.
Further Summary
- A karyotype displays an individual's chromosome complement.
- Chromosomes 13, 14, 15, 21, and 22 are acrocentric and can participate in Robertsonian translocations.
- Chromosomal band nomenclature describes specific chromosomal locations.
- Karyotype nomenclature describes normal karyotypes and numerical and structural chromosomal abnormalities.
Learning Objectives
- Differentiate between numerical and structural chromosomal abnormalities and explain the mutational mechanisms involved.
- Define polyploidy and aneuploidy, summarizing their effects on human viability.
- Determine the parental meiotic stage where non-disjunction occurred to cause trisomy.
- Describe the types of structural rearrangements.
- Identify if a rearrangement is balanced or unbalanced and predict its phenotypic effect.
- Interpret and identify gross abnormalities in karyotypes.
- Understand chromosomal band and karyotype nomenclature to recognize abnormalities and predict clinical outcomes.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
Test your knowledge on chromosome abnormalities, including both structural and numerical changes. This quiz covers concepts such as balanced and unbalanced abnormalities, polyploidy, and aneuploidy. Challenge yourself to understand the implications of these genetic variations.