Wondershare EdrawMind
MindMap Gallery chromosomal aberrations
- 62
chromosomal aberrations
This is a mind map about chromosomal aberrations. Chromosome aberration is abnormal changes in chromosomes in somatic cells or germ cells. It is a type of broad mutation.
Edited at 2023-11-23 10:55:19
- bacteria
This is a mind map about bacteria, and its main contents include: overview, morphology, types, structure, reproduction, distribution, application, and expansion. The summary is comprehensive and meticulous, suitable as review materials.
- Plant asexual reproduction
This is a mind map about plant asexual reproduction, and its main contents include: concept, spore reproduction, vegetative reproduction, tissue culture, and buds. The summary is comprehensive and meticulous, suitable as review materials.
- Reproductive development of animals
This is a mind map about the reproductive development of animals, and its main contents include: insects, frogs, birds, sexual reproduction, and asexual reproduction. The summary is comprehensive and meticulous, suitable as review materials.
chromosomal aberrations
- bacteria
This is a mind map about bacteria, and its main contents include: overview, morphology, types, structure, reproduction, distribution, application, and expansion. The summary is comprehensive and meticulous, suitable as review materials.
- Plant asexual reproduction
This is a mind map about plant asexual reproduction, and its main contents include: concept, spore reproduction, vegetative reproduction, tissue culture, and buds. The summary is comprehensive and meticulous, suitable as review materials.
- Reproductive development of animals
This is a mind map about the reproductive development of animals, and its main contents include: insects, frogs, birds, sexual reproduction, and asexual reproduction. The summary is comprehensive and meticulous, suitable as review materials.
- Recommended to you
- Outline
chromosomal aberrations
concept
Chromosome aberration is an abnormal change in chromosomes in somatic cells or germ cells, and is a type of broad mutation.
There are two major categories: numerical aberration and structural aberration.
Can be divided into euploidy changes and aneuploidy changes
Causes of chromosomal aberrations
Spontaneous aberration and induced aberration
chemical factors
drug
Anticancer drugs such as cyclophosphamide, nitrogen mustard, busulfan (Marylan), methotrexate, and cytarabine can cause chromosomal aberrations
The antispasmodic drug phenytoin can cause an increase in the number of polyploid cells in human lymphocytes
pesticide
Certain organophosphorus pesticides can increase the rate of chromosomal aberrations
industrial poisons
Such as benzene, toluene, aluminum, arsenic, carbon disulfide, chloroprene, vinyl chloride monomer, etc., can all cause chromosomal aberrations
food additives
Such as nitrofuranyl sugar amide AF-2, cyclohexyl saccharin, etc.
physical factors
The distortion rate increases with the increase of radiation dose
The most common types of aberrations: chromosome breaks, deletions, dicentric chromosomes, translocations, endoreduplication, nondisjunction, etc.
biological factors
Biotoxins produced by living organisms
Mycotoxins: stericillin, aflatoxin, patulin, etc.
Certain organisms such as viruses themselves can cause chromosomal aberrations
Rubella virus, hepatitis B virus, measles virus and cytomegalovirus
Mother's age
As the mother's age increases, the number of her children's somatic cells containing three chromosomes of a certain sequence number is more common than in the general population.
The older the mother (over 35 years), the higher the risk of having a child with Down syndrome
The longer the germ cells stay in the mother's body, the more opportunities they have to be affected by various factors
Chromosome number abnormalities and their mechanisms
All the chromosomes contained in normal human reproductive cells, sperm and eggs, are called a chromosome set
Sperm and eggs are haploid; fertilized eggs are diploid.
Taking the human diploid number as the standard, the increase or decrease in the number of chromosomes (whole set or whole piece) in somatic cells is called chromosome number aberration.
euploidy change
If the change in the number of chromosomes is an integral multiple of haploid (n), that is, with n as the base number, it increases or decreases exponentially, it is called a euploidy change.
On the basis of 2n, if one chromosome group (n) is added, the number of chromosomes is 3n, that is, triploid; if two n. are added on the basis of 2n, the number of chromosomes is 4n, that is, tetraploid.
Those above triploid are collectively called polyploid (polyploid)
If one chromosome group is reduced on the basis of 2n, it is called haploid
Only a very small number of triploid individuals survive to birth, and those who survive are mostly 2n/3n chimeras.
fertilization of two males
A normal egg fertilized by two normal sperm at the same time is called dispermy.
Double female fertilization
A diploid abnormal egg is fertilized by a normal sperm, resulting in a triploid zygote
Endoreduplication, also known as endomitosis
During a cell division, DNA is copied not once, but twice, while the cell divides only once.
Aneuploidy changes
The number of chromosomes in a somatic cell increases or decreases by one or several, which is called aneuploidy.
hypodiploidy
When the number of chromosomes in a somatic cell is one or several less, it is called hypodiploidy, which can be written as 2n-m (where m<n)
Common clinical haplotypes include haplotypes of chromosomes 21, 22 and X, with karyotypes of 45, XX (XY), -21; 45, XX (XY), -22 and 45,
If a pair of homologous chromosomes is missing at the same time in the patient's cells, that is, a pair of homologous chromosomes (2n-2) is reduced, which is called nullisomy.
hyperdiploidy
When the number of chromosomes in a somatic cell is one or more, it is called hyperdiploidy, which can be written as 2n m (where m<n)
If the number of chromosomes in a cell is 47, it constitutes a trisomy of the chromosome (2n 1)
Aneuploidies above trisomy are collectively called polysomy and are commonly found in sex chromosomes, such as sex chromosome tetratype (48, XXXX; 48, XXXY; 48, XXYY) and pentatype (49, XXXXX: 49, XXXYY)
An individual with two or more karyotypes of cell lines present at the same time is called a mosaic.
Sometimes the number of certain chromosomes in a cell is abnormal. Some of them increase and some decrease, and the number of increased and decreased chromosomes is equal, but it is not a normal diploid karyotype, which is called pseudodiploid.
Causes of aneuploidy
Chromosomes do not separate
Chromosome nondisjunction occurs during mitosis in the early stages of fertilized egg cleavage
If nondisjunction occurs at the first cleavage, a chimera with two cell lines is formed, one is a hyperdiploid cell line and the other is a hypodiploid cell line.
Nondisjunction occurs after the second cleavage, resulting in a chimera with three or more cell lines (46/47/45)
Chromosome nondisjunction occurs during meiosis
Chromosome nondisjunction occurs in the first meiosis, causing a pair of homologous chromosomes to not separate and enter a daughter cell at the same time. Half of the gametes formed will have 24 chromosomes (n 1), and the other half will have 22 Article(n-1)
Chromosome lose, also known as anaphase lag
During cell mitosis, a certain chromosome is not connected to the spindle and cannot move to the poles to participate in the formation of new cells. Or it moves slowly when moving to the poles and stays in the cytoplasm, causing the loss of the chromosome and forming hypodiploidy.
Molecular and Cell Biological Effects of Chromosomal Aberrations
Chromosomal aberrations (whether numerical or structural) will cause changes in genetic material, leading to changes in corresponding genes
Molecular and Cell Biological Effects of Chromosome Number Aberrations
Euploid
The entire set of chromosome number increases to form euploidy, such as triploidy (3n) and tetraploidy (4n)
tripolar spindle
Aneuploidy
Monosomy due to loss of one chromosome
Turner syndrome, karyotype 45, X (false dominant effect)
Trisomy is an extra chromosome
Down syndrome, trisomy 18 and trisomy 13
Molecular and Cell Biological Effects of Chromosome Structural Aberrations
Molecular and Cell Biological Effects of Missing (Human Chromosome Banding Technology)
Missing lethal effect
The deletion of large segments of chromosomes is fatal even in the heterozygous state, and only a part survives, such as 5p~ syndrome (cat-meowing syndrome)
missing false dominance
If the deleted segment contains a dominant gene, a recessive gene on the homologous chromosome corresponding to the deleted segment will be expressed. This phenomenon is called pseudodominance.
Repeated molecular and cell biology effects
Duplication will lead to unequal crossover of homologous chromosomes during meiosis, resulting in a chromosome with partial segment deletions and a chromosome with partial segment duplication.
Molecular and Cell Biological Effects of Inversion
segment length
When inverted chromosomes pair up with homologous chromosomes in meiosis, if the inverted segment is small, the segment may not pair, while the remaining segments pair normally.
If the inversion segment is very long, the inverted chromosome may invert and pair with the normal chromosome to form a loop, called an inversion loop.
In heterozygotes with intra-arm or inter-arm inversions, a single exchange of non-sister chromatids in the inversion ring occurs, and the products of the exchange all contain deletions or duplications, which cannot form functional gametes, or to a considerable extent Reduced recombination in heterozygotes, a phenomenon called crossover suppressor
Heterozygotes for interarm inversions
After an odd number of exchanges within the inversion ring, of the four chromosomes formed subsequently, one is a normal chromosome, one is an inversion chromosome, and the remaining two are partially duplicated and partially deleted chromosomes.
Heterozygotes for intrabrachial inversions
After an odd number of exchanges within the inversion ring, one of the four subsequently formed chromosomes is an exchange-type dicentric chromosome, which breaks to form a gamete with a deletion.
Molecular and cell biological effects of translocation (homozygotes for reciprocal translocation have no obvious cytological characteristics)
During the pachytene stage of meiosis, the translocated hybrid forms a characteristic tetramer due to the synaptic pairing of homologous parts.
Alternate segregation is also called parasegregation
One is a normal gamete and the other is a translocated gamete, with neither duplication nor deletion.
adjacent segregation-1
The two adjacent chromosomes with A and B and A and D go to the same pole, and the other two adjacent chromosomes go to the other pole.
adjacent segregation-2
The chromosomes with A and B go to the same pole as the two adjacent chromosomes with C and B, and the rest go to the other pole.
3:1 separation
One of the chromosomes goes to one pole alone, and the other three chromosomes go to the other pole.
Chromosome structural aberrations and their mechanisms
First, the chromosome breaks (breakage), and then the broken fragments rejoin (rejoin). If the broken segments are rejoined in their original positions, it is called healing or reunion.
If a chromosome fails to rejoin in situ after being broken, that is, the broken fragment moves to connect with other fragments or is lost, it can cause chromosome structural aberrations, also known as chromosomal rearrangement.
Methods of describing chromosomal structural aberrations
The International System of Human Cytogenetic Nomenclature (ISCN) has developed naming methods for human chromosomes and chromosomal aberrations (see Chapter 8 for details)
In the simplified form, changes to the chromosome structure are represented only by its breakpoints. According to international nomenclature regulations, the total number of chromosomes, the composition of sex chromosomes should be stated in order, and then the type of rearranged chromosome should be written with a letter (such as t) or a triplet symbol (such as del), followed by the first bracket. The sequence number of the aberrant chromosome, the second bracket indicates the area code where the breakpoint is located, and the band number indicates the breakpoint.
In the detailed form, in addition to the content that should be stated in the short form, the last bracket does not only describe the break point, but describes the composition of the rearranged chromosome band.
Chromosome breakage and rejoining of broken fragments are the basic mechanisms that produce various chromosome structural aberrations.
Missing
Deletion is the loss of a chromosomal segment. The deletion causes the gene located in this segment to be lost as well.
Terminal deletion: After the chromosome arm is broken, rejoining does not occur, and the non-centromere fragment cannot be connected to the spindle fiber, and fails to move to the poles in the later stages of cell division and is lost. As shown in Figure 9-3A, band 2 and band 1 of the long arm of chromosome 1 are broken, and its distal segment (q21→qter) is lost. This chromosome is composed of the end of the short arm to zone 2 and 1 of the long arm.
Interstitial deletion refers to two breaks on the same arm of a chromosome. The acentric fragment between the two breakpoints is lost and the remaining two fragments are rejoined.
repeat
Duplication is a phenomenon in which more than one copy of a certain segment of a chromosome is added, resulting in one or more copies of the genes of these segments.
The reasons are unequal exchange between homologous chromosomes or unequal exchange between sister chromatids and insertion of chromosome fragments, etc.
inversion
Inversion is when a chromosome breaks twice, and the segment between the two breakpoints is rotated 180° and then rejoined, resulting in a rearrangement of the gene sequence on the chromosome.
Paracentric inversion: Two breaks occur simultaneously on a certain arm of a chromosome, and the segment between the two breakpoints is rotated 180° and then rejoined.
Pericentric inversion: The long and short arms of a chromosome are broken once each, and the middle fragments are inverted and then rejoined, forming a pericentric inversion chromosome.
Translocation
A segment of one chromosome is transferred to the arm of another non-homologous chromosome. This structural aberration is called translocation.
Reciprocal translocation is when two chromosomes break at the same time, and the fragments exchange positions and then rejoin. Form two derivative chromosomes
When a reciprocal translocation only involves a change in position and does not result in an increase or decrease in chromosome segments, it is called a balanced translocation.
Robertsonian translocation, also known as centric fusion, occurs when two acrocentric chromosomes break at or near the centromere. join together to form a derivative chromosome composed of the long arms of the two chromosomes; the two short arms form a small chromosome. The small chromosome is often lost during the second division, which may be due to its lack of centromere or is due to the fact that it is composed entirely of heterochromatin
Because the lost small chromosome is almost entirely heterochromatin, the chromosome composed of two long arms contains almost all the genes of the two chromosomes.
Insertional translocation, two non-homologous chromosomes break at the same time, but only a fragment of one chromosome is inserted into the non-terminal part of the other chromosome
Insertional translocation is only possible when three breaks occur
ring chromosome
The long and short arms of a chromosome are broken at the same time, and the two broken ends of the segment containing the centromere are rejoined, forming a circular chromosome.
dicentric chromosomes
After two chromosomes break simultaneously, the broken ends of the two centromeric fragments are connected to form a dicentric chromosome.
isochromosomes
The two arms of a chromosome are identical in morphology and genetic structure and are called isochromosomes.
insert
Insertion is the insertion of a segment of one chromosome into another chromosome. It is actually also a translocation. "Insertion" is only possible if a total of three breaks have occurred.