Conventional Cytogenetics Analysis is an important tool in medical field. There are many applications of conventional cytogenetics analysis. It is good to know the strengths of this analysis technique so that we can know the most appropriate genetic assays to be used.

Generally, a clinician may ask for the conventional cytogenetics analysis even though it may not be appropriate for the information sought. Therefore, it is essential for the clinician to know the application of this analysis. On the other hand, the cytogeneticist may be consulted to use the best analysis for the patients.

Applications of Conventional Cytogenetics Analysis

1. Detect the Presence of Abnormal Cancer Cell

We can easily detect the abnormal clone by using karyotyping. It is helpful in differentiating between reactive conditions and malignancy if there is an abnormal clone present. For instance, detecting an abnormal clone is good when we are investigating a pleural effusion, anemia or lymphocytosis. Yet, there might more than one abnormality present in the same sample too. Sometimes, most of the analyzed cells are normal. But it does not mean that there is no abnormality. It might because of the abnormal cells were not grown well during the culture process.

2. Confirm the Diagnosis

The conventional cytogenetics analysis is useful to clarify the diagnosis. For instance, the clinician can only diagnose for the Down syndrome according to the physical appearance of the patient. We can use conventional cytogenetics analysis to help to confirm the diagnosis.

3. Indicate the Prognosis

Cytogenetics analysis is one of the most powerful prognostic indicators in hematologic malignancies. This effect persists despite advances in treatment. It is important for solid tumors prognosis too. Therefore, sometimes the cytogeneticists feel hesitate to report the karyotype as normal. The failure of finding a cancer clone implies only the normal cells were analyzed or the genetic abnormality was undetectable.

4. Help in Choosing the Best Treatment

The clinician will always take into account the cytogenetics analysis when choosing the treatment for the patients. For example, a bone marrow transplant will only be used when the risk of dying from the malignancy is relatively higher than the risk of doing the transplant according to the cytogenetics analysis. Besides, this analysis can assist the clinician to tailor the treatment according to the needs of the patient so that the risk of relapse against the risk of therapy-related death can be balanced.

5. Keep Tracking the Response of Treatment

Conventional cytogenetics analysis is good for monitoring the response of the treatment to the patient. For example, we can use this analysis to monitor the effectiveness of the bone marrow transplant to the patient.

6. Support Further Research

By using the result of conventional cytogenetics analysis, we can do the further research for particular abnormality. We can publish the usual findings as case reports to provide more information to the public. It will become useful when the same abnormality is discovered in other patients.

In conclusion, the cytogenetics study is still playing an important role for diagnostic investigations of patient who has hematologic malignancy or solid tumors. Yet, this can be assisted by other genetic assays too such as microarray. Personally, I really appreciate the applications of cytogenetics analysis. I will explore more about it so that I can really use it to help in increasing the accuracy of diagnosis and prognosis. Keep on reading more about cancer cytogenetics in Cytogenetics Cancer Research blog.

(Reference: Cancer Cytogenetics edited by John Swansbury)

6 Applications of Conventional Cytogenetics Analysis is a post from: Cytogenetics and Cancer Research

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After coming back from Singapore, I have been given a precious bone marrow sample to do the cytogenetic test from Prof. Hany to be tested. This was the first time for me to deal with the bone marrow sample. With excitement, I started off with the culturing process.

Obstacles of Cytogenetic Test

However, there were many obstacles for me to do the test. The materials and reagents that I need for doing this test are not available at that time, especially for the essential culture medium. Consequently, I need to think of the alternative. I tried to use the transfer medium provided by National University Hospital Singapore to do the culturing process with the hope to grow at least some leukemic cells from the sample.

Furthermore, I do not have the pre-made ethidium bromide solution yet. The ethidium bromide solution is important to elongate the chromosomes. So, I have to make it myself by using the powder-formed ethidium bromide.

Outcome of Cytogenetic Test

After culturing and harvesting the bone marrow cells, I used the cell suspension obtained to prepare the slide. Then, I viewed the slide under the microscope. There were just few metaphases and the chromosomes not spread well. I am going to stain the chromosome on the next day. I hope that I can still get some good metaphases to be analyzed via imaging system.

Troubleshooting the Problems

In my opinion, this is not a good result that I want to get from the cytogenetic test. Why?

1. There were a lot of dead cells when I viewed the slides under microscope. This might probably because of the cells not grow well during the culturing process.

2. The length of the chromosomes was short. This indicated that the elongation step was not performed well.

3. The mitotic index was low. This might because of the metaphase arrest step was not performed well. Yet, the mitotic index is closely related to the condition of the sample and the patients too.

4. The chromosomes not spread well. This might because of the slide preparation step was not performed well. This step closely related to the technique used by the technologist. I think I am not doing well when performing this step.

Solutions for the Problems

To solve those problems, there are many optimization steps that I need to carry out.

1. I have to use the appropriate culture medium in order to make sure the cells can grow well especially for the leukemic cells. I am ordering the Chang Medium for bone marrow culture from Irvine Company.

2. The home-made ethidium bromide solution seems like not work so well. Therefore, I decided to order the pre-made ethidium bromide solution too to make sure the chromosomes can be elongated.

3. The amount of the reagents used should be accurate.

4. I will try my best to improve my technique when performing the slide preparation step to make sure the chromosomes can spread well on the slide.

Summing up, after the first trial, there are still plenty of things for me to do and learn. Tomorrow I will continue with the staining step and start to analyze the metaphases. Stay tuned in Cytogenetics Cancer Research blog to see what I will get from this first trial.

First Trial of Cytogenetic Test on Bone Marrow Sample is a post from: Cytogenetics and Cancer Research

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After the second day of my training in National University Hospital (NUH) Singapore, I started to try to find the fastest ways to improve myself in cancer cytogenetics. As I mentioned in my previous post, I found that there are five deficiencies for me in doing leukemia cytogenetics. Therefore, I have to try my best to turn the things around.

Learning While Doing the Research

Yes, I have to admit that I do not have adequate knowledge about cancer cytogenetics. However, I can learn the knowledge while doing my leukemia cancer research. Thus, I planned to read through the reading materials about the leukemia first especially for the acute lymphoblastic leukemia (ALL). This will be the beginning step for me now.

Fully-utilized the Equipments

As it is almost impossible for me to get the new machines and equipments that are required for cancer cytogenetics, I will try my best to modify the protocols so that it may work well with the machine and equipments that we have currently. I will look through the whole University of Malaya Medical Centre (UMMC) to check the availability of the machines and equipments in other laboratories.

Analyzing Skill

In order to improve my analyzing skill, there are three ‘more’ that I have to achieve.

i. View More

I have to view more metaphases especially from the cancer patients so that I can familiar with the characteristics and morphologies of the abnormal cells.

ii. Try More

I have to try to karyotype and analyze more metaphases even though I might make a lot of mistakes. I will apply the try and errors method to make myself good in analyzing.

iii. Consult More

During the time I do my cancer cytogenetics research, I might need a lot of guidance from an experienced Cytogeneticist. So, I will consult more people by using internet discussion group, email and so on.

Accumulate my Experience

Although I need some times to accumulate my experience in cancer cytogenetics, I can consult the experienced staffs in my laboratory. I think they are willing to teach me as they are friendly, helpful and kind.

Spend my Time Wisely

Yes, another main problem for me is the time. I need to race with the time. Anyway, what I can do is just try my best and do the best. I have to more focus to cancer cytogenetics now. Then how about blogging? I might not update the blog as frequent as now start from today. I have to do so. I am so sorry about this. But I will not just dump this blog away. I love this blog very much. How about you? Haha…

Summing up, there are a lot of things that I need to do start from now so that I can catch up the pace for cancer cytogenetics. Before I end up this blog post, I would like to thank to all the members of NUH Cytogenetics Lab. They have taught me a lot of things. Thanks to Prof Hany too!

5 Ways to Improve Myself in Cancer Cytogenetics is a post from: Cytogenetics and Cancer Research

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After the first day of my training in National University Hospital (NUH) Singapore, I have found out that there are five of my deficiencies in doing leukemia cytogenetics.

1. Basic Knowledge

Firstly, I am lacking of basic knowledge about leukemia as well as cytogenetics. When listening to the explanation of one of the staffs in NUH, I found out that I cannot fully understand what she was talking about. There are a lot of things that I never heard before.

2. Analysis Skill

The second deficiency is I still do not have the ability to analyze the chromosome yet. As what you know, we have to analyze the result after we have done the cytogenetics test. However, I have not mastered the analyzing skill yet. Without the analyzing skill, I could not identify the chromosomal abnormality even though I manage to get a good result.

3. Equipments and Materials

Besides, not all the equipments and materials that are necessary for the bone marrow cytogenetics analysis are available in my laboratory in University of Malaya Medical Centre (UMMC). I have to spend a lot of money to buy the new equipments and materials for doing the leukemia cytogenetics. Most of these equipments and materials are very expensive.

4. Experience

This is my major deficiency in doing leukemia cytogenetics. I am lacking of experience. For doing leukemia cytogenetics, experience is essential. Sometimes, it depends to our experience when analyzing the chromosomes. Without the experience, it is too difficult for me to do everything alone without any guidance.

5. Time

Last but not least, I am lacking of time now. I just have another 4 days time to learn everything in NUH. After that, I have to start the research on bone marrow cytogenetics analysis in UMMC. Is it an impossible task for me? I hope that I can go through it smoothly.

Thus, there are a lot of things that I need to do to improve myself. I have been given some reading materials about the hematology malignancy. I have to read through it as soon as possible. That’s all for today blog post. Thanks for visiting Cytogenetics Cancer Research blog!

5 of My Deficiencies in Doing Leukemia Cytogenetics is a post from: Cytogenetics and Cancer Research

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After taking about an hour flight, finally I am able to be in Singapore and waiting for the training in National University Hospital (NUH) Singapore. I think this will be an exciting and challenging journey for me. It is because I have to learn everything especially about the leukemia cytogenetics technique within one week time!

Get Ready for the Leukemia Cytogenetics Training

Since arriving Changi Airport, I have to adapt to this new environment so that I can feel comfortable to learn something here. After settling myself in a nearby hotel, I started to plan and think for my training. What am I going to learn for this training?

i. Objectives and Implications

First of all, I wish to find out the objectives and implications of doing the leukemia cytogenetics. As far as I know, the researcher used cytogenetics analysis to look for the chromosomal abnormalities that occurred for the leukemia patients. The study serves two objectives. The first one is to increase the accuracy of leukemia diagnosis as well as providing prognostic information and allowing the more rational selection of therapy for a particular patient. The second reason is to detect the sites of consistent rearrangements so that we can know the precise localization required for the isolation and cloning of DNA from these regions. This is important for the further investigation of leukemia disease. There will be more objectives and implications that I wish to know from this training.

ii. Materials and Methods

In my opinion, this is the main purpose for me to come for this training. I wish to learn the methods and the materials that required for leukemia cytogenetics. The chance will be given for me to see step by step how the scientists in NUH doing the cytogenetics analysis for leukemia patients. For your information, the scientists in NUH have done a great job in cytogenetics analysis for leukemia. Their skills are awesome! I am sure that I can learn a lot of applicable skills from them.

iii. Knowledge

Next, I wish to gain more knowledge about cytogenetics analysis and leukemia from this training. Before this, I can only read through the related books and learn some theories from it. Theories are not enough in cancer research. However, start from tomorrow, I can absorb more applicable knowledge by asking a lot of questions to the scientists here. Their experience and professional skills will be my precious treasure to be hunt during the time in Singapore.

iv. Troubleshooting

Besides, I hope that I can get the ideas on how to troubleshoot the problems that might occurred during the cytogenetics analysis. This is essential for me as I will do the whole process of cytogenetics analysis alone after this one week in Singapore. If I was unable to troubleshoot the problems, it is not possible for me to know how to modify or optimize my skills or techniques when I cannot get the result. As we all know, there are plenty of factors that might influence our experiment results. The condition and environment in NUH might not exactly the same with University of Malaya Medical Centre. Thus, I have to prepare myself for that.

v. Attitude

Another thing that I wish to highlight is the attitude. In my opinion, the attitude can make things different. We can copy the same methods, but without the right attitude, we might achieve nothing. For this reason, I will observe the professionalism and attitude of the scientists in NUH as example to follow.

Lastly, there are five days for me to learn everything from here. I hope that I can be humble and enthusiastic in the whole learning process. Thanks to Professor Hany Ariffin for arranging all of these for me! Thanks to UMCRI to support me for this training! I will grab this opportunity to improve myself.

5 Things I Wish to Learn in Singapore for Leukemia Cytogenetics is a post from: Cytogenetics and Cancer Research

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Leukemia research is an important and interesting effort that can help in designing more effective diagnosis approaches and treatment strategies. There are a lot of techniques or tools that used in leukemia research. Today, I’m going to introduce a little bit about those techniques and tools used in leukemia research so that we can understand more when we go further.

Cytogenetics – Powerful Tool in Leukemia Research

Conventional and molecular cytogenetics techniques are still the most important techniques for clinical diagnosis of specific subtypes of leukemia. These cytogenetics techniques are good in identifying novel genetic mutations. We can see the Fluorescence In Situ Hybridization (FISH) is one of the greatest tools for detection of chromosomal abnormalities. Molecular cytogenetics is also a powerful tool in identifying the cell lineage in which the leukemia specific chromosome rearrangement occurs with the combination of immunophenotyping technique. It has been used to detect putative preleukemic cells.

Polymerase Chain Reaction in Leukemia Research

Long Distance Inversed Polymerase Chain Reaction (LDI-PCR) and panhandle-PCR are very useful to identify the fusion transcripts rapidly in the case of chimeric fusions where only one of the partner genes is known. This is essential for risk-stratification (which I mentioned in “What is Acute Leukemia?”) for disease treatment and monitoring the minimal residual disease (MRD).

Array Technology in Leukemia Research

The progression of array technology and bioinformatics allow the researchers to get high-resolution global assessment of genetic changes in the leukemia cells. Array-based Comparative Genomic Hybridization (aCGH) is another tool used for analyzing the leukemia genome whereas the Single Nucleotide Polymorphisms (SNP) array is used for determining somatic changes in cancer. Both tools allow genome-wide detection of many kinds of submicroscopic somatic changes including loss, gain, and copy-neutral loss of heterozygosity (CN-LOH). Most of these submicroscopic somatic changes are oftenly cannot be detected by using cytogenetics and other conventional techniques.

Prenatal Backtracking for Leukemia Research

Yet, we should not forget the importance to identify the origin of the mutations as well as their functions in the leukemogenic processes. Luckily, prenatal backtracking is the best tool to trace back genetic events to early fetal origins using sensitive amplification methods. We can use it to identify the origin of the disease in pediatric leukemia effectively.

Summing up, these techniques effectively make the leukemia research much easier to be done. Maybe I will write the details about these techniques one by one in the future in Cytogenetics Cancer Research blog. I still need some times to explore more about these techniques. I hope that I can really manage to make full use of those techniques for my own research.

(Reference: Leukemia edited by Chi Wai Eric So)

Techniques Used in Leukemia Research is a post from: Cytogenetics and Cancer Research

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The Human Genome Project (HGP) was an international effort and collaborative research program to map and understand the entire human genome. This is a dream project for me to look through of it. I decide to write a review on it in Cytogenetics and Cancer Research blog so that more people can access to this tremendous project.
 

What is human genome?

Human genome is the complete set of DNA (deoxyribonucleic acid) in human body. The DNA contained within each of body cells. The DNA carries the signals to build and maintain the body cells to function so that the heart will keep pumping, brain will keep thinking and bones will keep growing.
 

Overview and History of Human Genome Project

The Human Genome Project was the natural culmination of the history of genetic research. Alfred Sturtevant, an undergraduate student in Thomas Hunt Morgan’s laboratory, found that he could map the locations of fruit fly (Drosophila melanogaster) genes whose mutations the Morgan laboratory was tracking over generations. This is the tremendous start of gene mapping and finally leads to the human genome sequencing project.
 
When the Human Genome Project started in 1990, the researchers had set a goal to complete the project within 15 years but completed it in 2003, with two years to spare. During that time, many volunteers gave blood to provide their DNA as a contribution for the HGP. However, the labels on the blood tubes were intentionally removed to protect the privacy of the donors. Therefore, the final human genome sequence which has been published in 2003 is a combination of many of the donors’ DNA. The researchers had found that 99.9% of everyone’s DNA sequence is exactly the same. However, there are still some tiny fractions of genome that varies among humans. These variations are very important and make all humans unique in physical appearance like colour of eyes and even influence the risk of disease and the response to drugs. Even so, the genome is just one part of the amazing puzzle of human. Lifestyle and environmental factors do influence humans’ health condition too.
 

Contributions of Human Genome Project

By knowing this, the successful of HGP to sequence human genome has made the job of finding genes that cause some genetic diseases easier. The researchers hope that they can find out the genetic basis of other diseases such as heart disease, diabetes and even mental illness so that the drugs and treatments that specifically target these diseases can be designed properly. For example, there are some genes that involved in cancer had already been identified and make the treatment designed much easier.

What have been done in Human Genome Project?

In Human Genome Project, the researchers have deciphered the human genome in three major ways:
 
i. The sequence of all DNA bases in human genome.
 
ii. Maps that show the locations of genes for major sections of human chromosomes.
 
iii. Linkage maps which inherited traits especially those for genetic disease can be tracked over generations.
 
There are about 20,500 human genes revealed in Human Genome Project. This finding appeared to be significantly fewer than previous estimates, which ranged from 50,000 genes to 140,000. This final human genome sequence has given the world a resource of detailed information about the structure, organization and function of the complete set of human genes. This can be considered as the basic set of inheritable information for the development and function of a human being.
 
According to Francis Collins, the director of National Human Genome Research Institute (NHGRI), the genome could be imagine as a book with multiple uses. He said: “It’s a history book – a narrative of the journey of our species through time. It’s a shop manual, with an incredibly detailed blueprint for building every human cell. And it’s a transformative textbook of medicine, with insights that will give health care providers immense new powers to treat, prevent and cure disease.”
 
The Human Genome Project had created many tools that can be used in characterize the genomes of other organisms used extensively in biological research. For examples, mice, fruit flies and flatworms are the model organism that can be used to identify the sequence or function of a homologous (similar) gene in human beings.
 
In conclusion, the Human Genome Project might appear as a perfect project at the first glance. Most probably is the genome was successfully sequenced and the involvement of the government in the project. Yet, the ultimate success of HGP still remains unclear.
 
Reference: National Human Genome Research Institute
 

Is Human Genome Project really beneficial to humans? Leave your precious opinion to start the discussion.

Human Genome Project – Find out Human Database is a post from: Cytogenetics and Cancer Research

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Angelman syndrome (AS) was first described by Dr. Harry Angelman, who is an English physician. He noticed that there are 3 children under his care with similar developmental problems. They looked very happy and tend to flap their hands when excited. Therefore, Dr. Harry Angelman described these children in his paper called “Puppet Children” as these children’s characteristics just like the puppet.
 
Angelman Syndrome is now a familiar genetic disorder to most clinical geneticists and child neurologists in Cytogenetics. It is a recognizable syndrome which related to mental retardation and infantile seizures. Unlike Prader-Willi syndrome that I described last week, individual with Angelman syndrome is because the loss of maternally inherited region 15q11 – q13 of chromosome 15. Simple to say, the AS individual does not inherit the region 15q11 – q13 of chromosome 15 from his/her mother but only from father.

 
The Angelman syndrome clinical diagnosis is heavily dependent on the combination of some common behaviour like excessive laughter, apparent happiness with tremulous movements and gait ataxia (lack of coordination of muscle movement). Usually, the normal prenatal and birth history do not provides any clues in diagnosis of AS in Cytogenetics. CT scans, laboratory tests of blood and urine are usually normal including metabolic screening. Consequently, it is difficult for the clinical experts to encounter the AS especially when the child is less than 12 months of age. It is because the tremulous movements, ataxia and severe lack of speech may not be apparent during that time.
 
There are many common features of Angelman syndrome.

i. Severe speech deficit (usually absent speech)
 
ii. Mental retardation
 
iii. Microcephaly (small head)
 
iv. Seizures (convulsions in which AS patient’s body shakes rapidly and uncontrollably)
 
v. Developmental delay
 
vi. Feeding problems
 
vii. Hypopigmentation (the loss of skin color)
 
viii. Frequently drooling
 
ix. Tend to put objects in mouth
 
The facial features general physical appearances are generally normal for the individual of Angelman syndrome. As the child with AS growing up, the correct diagnosis may become evident when speech is essentially absent and the attempts at walking are compromised because of sever ataxia. In addition, the seizures will occur more frequently after 1 year of age.
 
In conclusion, the individual of Angelman syndrome may be hyperexcitable with excessive laughing, grabbing and pulling to engage others. They are just like the ‘Angels’ who always bring happiness to people. Usually, the parents may be the first to suggest the possibility of Angelman syndrome. Thus, earlier detection of this genetic disorder may help the children to overcome the learning problem through the assessment from the clinical experts.
 

My ultimate hope is this Cytogenetics and Cancer Research blog can really help in increasing the awareness of people about the genetic disorders and cancer.

Angelman Syndrome – Angel-like Genetic Disorder is a post from: Cytogenetics and Cancer Research

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Prader-Willi syndrome or PWS syndrome is thought to be one of the most common genetic disorders. Prader-Willi syndrome and Angelman syndrome were the first examples in humans of genomic imprinting in Cytogenetics. Angelman syndrome has an entirely different clinical condition with PWS syndrome. I will explain about the Angelman syndrome in my future post.
 
What is genomic imprinting? Imprinting is a type of marking process that has a memory. Genomic imprinting is where a segment of DNA is marked or imprinted during gametogenesis. This mark will be retained and recognized throughout the life of the individual. Maternal and paternal inherited alleles will be marked differently and are expressed differently in the offsprings. Therefore, the offspring with the same genetic material will have different appearances. The individual with Prader-Willi syndrome is because the loss of paternally inherited region 15q11 – q13 of chromosome 15. Simple to say, the PWS individual does not inherit the region 15q11 – q13 of chromosome 15 from his/her father but only from mother.

Prader-Willi syndrome is the most common genetic cause of marked obesity in humans according to Cytogenetics. It is a complex disorder with cardinal features of
 
i)    Infantile hypotonia (low muscle tone)
 
ii)   Mild growth retardation
 
iii)  Frequent occurrence of breech presentation (baby enters the birth canal with the buttocks or feet first)
 
iv)  Small hands and feet with gracile and tapering fingers
 
v)   Microcephaly (smaller head)
 
vi)  Almond-shaped eyes
 
vii) Mental deficiency (average IQ of 65)
 
viii) Short stature and so on.
 
From the age of about one and half years onward, hyperphagia becomes a serious problem, leading to gross obesity. Due to hyperphagia and gross obesity, diabetes often sets in during adolescence or later. Epilepsy is found in a minority of cases. Mental development is characterised by moderate to severe retardation with tendency to behaviour disorders, especially reactive to food deprivation. Patients with this syndrome may need specialists for assessment and treatment of their behavioural and learning problems, at the beginning of childhood. Prader-Willi syndrome is present in all races and ethnic groups and most cases are sporadic.
 
In conclusion, Prader-willi syndrome is a genetic disorder that needs treatment and assessment to overcome the learning problem and obesity problem of the patients. I will write a series of Prader-Willi syndrome in this Cytogenetics and Cancer Research blog in order to give people a clear mind about this syndrome. Stay tuned!

Prader-Willi Syndrome – Genetic Disorder That Cause Obesity is a post from: Cytogenetics and Cancer Research

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Cytogenetic abnormalities are what I have learnt during my internship in Hospital Kuala Lumpur. Today, I’m going to introduce Autosomal Aneuploidy in this Cytogenetics and Cancer Research blog.
 
In Cytogenetics, the term aneuploidy refers to cytogenetic abnormalities in which all or part of one or more chromosomes is added or deleted. Autosomal aneuploidy is the abnormality that does not involve the sex chromosomes. Sometimes, the abnormalities can be either numerical or structural. Normally we only have pair of chromosomes which are structurally similar. Other than that, it can be recognized as abnormal. Those cytogenetic abnormalities can be present only in some cells which we called mosaicism or in all cells.

Meiotic Nondisjunction Causes Autosomal Aneuploidy

The origin of autosomal aneuploidy is because of meiotic nondisjunction. The meiotic nondisjunction is random for all autosomes except for chromosome 21. Chromosome 21 has shown the highest frequency of autosomal aneuploidy.
 
According to cytogenetic studies, the incidence of autosomal aneuploidy in spontaneous abortuses (die before birth) is much higher than incidences in newborns. So, what is the case for aneuploidy actually observed in spontaneous abortuses or liveborns? All trisomies for all autosomes have been reported in spontaneous abortuses. The fetal only can survive if and only if the trisomies are in mosaic form. However, there are still many exceptions for the trisomies 13, 18 and 21. Some of the foetus still can survive even though the trisomies 13, 18 or 21 are in nonmosaic form.
 
Why the frequencies of trisomy for each chromosome might be similar at the time of conception but differ greatly among abortuses and liveborns especially for trisomy 21? It can be explained by the devastating effect of chromosomal imbalance. Most of the autosomal aneuploidies are very deleterious and lethal in the pre-embryonic stage. As a result, those abnormalities are unrecognized and, therefore, unstudied spontaneous abortions.
 
Furthermore, the lethality of a particular autosomal aneuploidy is related to the gene content of the particular chromosome. Aneuploidies for the gene rich chromosomes are less likely to survive. However, the less gene rich chromosomes like chromosome 13, 18 and 21 are more likely to survive to term.
 
Anyway, we will just focus on those observed in liveborns for the autosomal aneuploidy in Cytogenetics. I will talk more details about the monosomies and trisomies in my future post. Stay tuned!

Autosomal Aneuploidy – Cytogenetic Abnormalities is a post from: Cytogenetics and Cancer Research

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