1. To what extent can chromosomes exchange DNA during meiosis? 2. Is it possible for one cell to receive more chromosomes than the other? 3. Where are the checkpoints in meiosis?
In response to your first question, chromosomes can be crossed over any amount of times without limit. The process largely depends on how much is crossed over during the time that is provided to do so.
2) It is my understanding that this is exactly what occurs in chromosomal non-disjunction in meiosis. The mistakes in either Meiosis I or II result in gametes that vary in chromosomal count, either having extra or missing chromosomes in comparison to the others. This usually means that all cells from that point on will have that abnormality. However, there are cases, as in the case of Mosaic Down Syndrome, where not all of the cells are affected in such a way. This is because the mutation occurs in cell division after fertilization, as opposed to during meiosis prior to the creation of the gametes.
To answer your first question, the theory is that meiosis originated in the common ancestor of all eukaryotes as a way of removing damaged or incorrect DNA in order to protect the organism's offspring
To answer your 3rd question, there is a case in which crossing over does not occur. This is seen in the Drosophila melanogaster (a fruit fly) chromosome 4. Source: https://www.tandfonline.com/doi/full/10.1080/19336934.2017.1321181
1. What are the most common abnormalities/mutations that can happen during meiosis? 2. What is the synaptonemal complex? 3. What type of mutations can come from mistakes in crossing over of chromosomes?
To answer your first question, chromosomal non-disjunction is the most common error of meiosis, and the most common case of non-disjunction is down syndrome.
In response to your second question, the synaptonemal complex is defined as a "protein structure that forms between two homologous chromosomes during meiosis", and it typically is known to help with chromosome pairing, synapsis, and recombination. Below are a couple sources going into further detail about this complex, I hope this helps!
1. Is there a max amount of alleles that can be created when crossing over in meiosis? or is it simply infinite amount of options? 2. Other than Trisomy 21, what is most common? 3. Is it possible for an organism that has an uneven number of chromosomes to reproduce?
To answer your third question, yes, an organism with an odd number of chromosomes can reproduce. Not only are there organisms that have an odd number or chromosomes (I couldn't find names, only references to them), but female humans with down syndrome have been found to fertile, but men with down syndrome are always infertile. So yes, it is possible, but no, it is not common.
I believe since crossing over is generally completely random except for genetic linkage so there are infinite possibilities as to what combinations can be created from the parent. While it is not really infinite because there are only so many alleles, there are just many possibilities.
In response to your second question, there are many other common chromosomal abnormalities. An examples is Edward Syndrome which is due to a trisomy of chromosome 18 and results in a low birth weight and abnormally shaped head.
1. How many illnesses can be attributed to genetic mutations? 2. Is there any variation within the meiosis process depending on the species. 3. Are chiasmata anything else besides the points of crossing over?
In response to your first question, scientists have found over 4,000 illnesses and diseases that can be attributed to genetic mutations, although there is definitely a chance of there being more that are currently undiscovered. Below are a couple sources on genetic disorders, hope this helps!
To answer your first question, there are approximately 4,000 diseases that can be caused by genetic mutation, here is a link that should have more information. https://kidshealth.org/en/teens/genes-genetic-disorders.html
To answer your 3rd question, no, chiasmata are not anything else besides the points of crossing over. They are simply the point, sort of like labeling a part helps with a process. Source: https://www.topperlearning.com/answer/explain-the-difference-between-chiasmata-and-crossing-over/deme6moo
To help answer your 3rd question, here is a bioninja article about chiasmatas: https://ib.bioninja.com.au/higher-level/topic-10-genetics-and-evolu/101-meiosis/chiasmata.html
What are most common errors in the process of meiosis? In Down Syndrome, where the extra chromosomes originate from? What are common issues in the processes of crossing genes?
To answer your first question, the most common errors within meiosis is the misplacement of chromosomes, leading to gametes missing or with extra chromosomes, which also leads into your second question.
In response to your second question, I could not find an exact answer, but I did find that because Chromosome 21 is one of the smallest chromosomes, it is more likely to have a mistake among it. Down Syndrome can also be caused as there is more genetic material from their chromosome 21. Hope this helped :)
3- A problem that occurs during the process of crossing genes is unequal crossing over. Unequal cross-over is caused by misaligned chromatids leading to distinct loci to go through homologous recombination. For more information this topic look here: https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/unequal-crossing-over
1- How does re combinase work along side the other enzymes in crossing over? 2- How fast does meiosis occur? 3- What is the most extreme genetic mutation that does not result in early death necessarily.
In response to your second question, in males the meiosis process takes about 74 hours and starts happening when they're around 12-13. In females, the process doesn't usually happen to the full extent as the products from meiosis are often re-absorbed into the body or leave the body all together before they are fully completed. I linked a good source below, i hope this helps!
In response to your third question, I am not exactly sure what you mean by "extreme" mutation, so I will list a few special mutations that I found. 1. A mutation on ACTN3 that makes muscles contract faster and improves atheletic ability. 2. KAT6A syndrome that impacts the body's ability to encode proteins and causes many problems. 3. Polymelia is a disorder that causes individuals to grow an extra limb that their species does not normally have.
In response to your 2nd question, here is an article that goes over the time and duration of meiosis: https://pubmed.ncbi.nlm.nih.gov/16285/#:~:text=However%2C%20even%20among%20species%20without,Homo%20sapiens%20and%20several%20Orthopterans.
1. What would the effect on the cell or organism be if crossing over didn't happen within meiosis? 2. What's the bare minimum amount of chromosomes a human needs to survive and could live with? 3. Is there any treatment or cure for some genetic disorders, and if so what stage of life would they need to be administered to be effective?
To answer your first question, if crossing over never occurred then the genetic information would be exactly the same as whichever parent the un-crossed over chromosomes come from. This is extremely rare and I can not find any records of this ever happening.
In response to your third question, treatments for genetic disorders are being created, such as the potential treatments for Sickle Cell Disease. These include adding proper DNA to cells or manually editing the DNA code to it's proper orientation. However, these treatments are experimental and will most likely take multiple years to be an absolute cure.
2- The minimum amount of chromosomes a human can have is 44 but this amount usually results in miscarriage or severe problems for the fetus in the future.
1. Are there other examples of genes jumping to a completely different chromosome (similar to how the SRY gene did in some species)? 2. Is it possible for more than 2 genes to be linked? 3. How do linked genes impact the inheritance of their phenotypes?
1- the idea of "gene jumping" happens frequently within eukaryotes and are known as transposable elements. There are different types of DNA transposons that can cause genetic mutations and increases the chance of disease development. The DNA transposons move DNA sequences to another location on the genome. For more detailed information look here: https://www.nature.com/scitable/topicpage/transposons-the-jumping-genes-518/
In response to your second question, I have been unable to find any proof that over 2 genes can be linked, so I would say that it is normally 2 linked genes. If you want more information on gene linkage, here is a good Khan Academy link: https://www.khanacademy.org/science/ap-biology/heredity/non-mendelian-genetics/a/linkage-mapping
1. I am having trouble grasping the idea of genetic linkage and the mechanics of it, could someone explain it further? 2.How many genetic variation combination are there? 3.What is the difference between random orientation and independent assortment?
To answer your 3rd question, the difference between random orientation and independent assortment is that random orientation is the random line up of chromosomes along the cell's equator while independent assortment is how the inheritance of one gene is not influenced by the inheritance of another gene. Source: https://www.differencebetween.com/difference-between-random-orientation-and-independent-assortment/#:~:text=What%20is%20the%20Difference%20Between,inheritance%20of%20any%20other%20gene.
In response to your first question, genetic linkage is when there are 2 genes very close together on a chromosome. The nearness of the two genes causes them to stick together when prophase I occurs. The 2 genes will not cross over and instead will stick with each other all the way to the daughter cells. In summary, the two genes like each other too much to leave each other during meiosis.
If this didn't make sense or you want more information, here is a link to a Khan Academy lesson with linked genes:https://www.khanacademy.org/science/ap-biology/heredity/non-mendelian-genetics/a/linkage-mapping
1. Can mutations occur in DNA while undergoing meiosis, that is not part of crossing over? 2. How were scientists able to determine that crossing over occurs? 3. Can there be a mutation/mistake during meiosis that causes the sister chromatids not to divide evenly and one cell have 2 of a chromosome while another has none of a chromosome?
To answer your third question, yes! We talked about this briefly in class, and this is what's called non-disjunction. It causes the chromosomes to separate incorrectly during meiosis, which results in one extra or one missing chromosome in the gametes. These chromosomal errors will be in every cell of the body after developing as a zygote. Non-disjunction is what causes trisomy on chromosomes, such as that on chromosome 21 that causes Down Syndrome. I hope that this helps! Here is a link to BioNinja that describes and illustrates this concept: https://ib.bioninja.com.au/standard-level/topic-3-genetics/33-meiosis/non-disjunction.html
To answer your second question, I believe it was Gregor Mendel that originally observed the crossing over of traits and began to understand genetics using pea plants, here is a link that goes into more detail. https://www.khanacademy.org/science/high-school-biology/hs-classical-genetics/hs-introduction-to-heredity/a/mendel-and-his-peas
1) How come some aspects of meiosis are random, and some are very specific? 2) What makes Down syndrome as common as it is? Why? 3) What kind of mistakes form as a result of the "crossing over" process in Meiosis?
2) Down Syndrome is the most common chromosomal disorder. When researching your question, I came across some new information about Down Syndrome that I hadn't heard before. There are actually 3 types, not just the typical trisomy of chromosome 21 that we think of. There is also Mosaic Down Syndrome, where not all cells in the body are affected by the trisomy. This is caused by abnormalities in cell division after fertilization, rather than during meiosis. There is also Translocation Down Syndrome, where a part of trisomy 21 is translocated onto another chromosome. There aren't three copies of the chromosome, but rather some genetic material from chromosome 21 is located on another chromosome. These three possibilities of abnormality increase the chances of Down Syndrome during pregnancy. Other factors include age, as more errors in cell division and meiosis are likely to happen as the body gets older.
To answer your 3rd question, as a result of crossing over, genetic diseases could possibly form and be activated from now shared and mixed genetic material in the new gamete
1) I am having a hard time grasping what independent assortment is. Does anyone know how to explain it in simple terms? 2) How can crossing over affect the expression of dominant or recessive traits? 3) Due to random orientation, can the gamete receive more paternal chromosomes than maternal, or vice versa? I thought that we received one set of chromosomes from each parent, but it doesn't appear to be this way in some of the images.
1. How often does meiosis take place? 2. What is the most common recessive genetic mutation? 3. Do the chiasmata form in random places along the chromosomes or are there set locations
To answer your first question, meiosis occurs in males constantly, but in females it only occurs once every month before ovulation I believe. Here’s a link that goes into more detail. https://www.cliffsnotes.com/study-guides/biology/biology/meiosis-and-gamete-formation/meiosis-in-humans
1. To what extent can chromosomes exchange DNA during meiosis?
ReplyDelete2. Is it possible for one cell to receive more chromosomes than the other?
3. Where are the checkpoints in meiosis?
In response to your third question, Meiosis has the same checkpoints as Mitosis. It goes through both the G1 checkpoint and G2 checkpoint.
DeleteIn response to your first question, chromosomes can be crossed over any amount of times without limit. The process largely depends on how much is crossed over during the time that is provided to do so.
Delete2) It is my understanding that this is exactly what occurs in chromosomal non-disjunction in meiosis. The mistakes in either Meiosis I or II result in gametes that vary in chromosomal count, either having extra or missing chromosomes in comparison to the others. This usually means that all cells from that point on will have that abnormality. However, there are cases, as in the case of Mosaic Down Syndrome, where not all of the cells are affected in such a way. This is because the mutation occurs in cell division after fertilization, as opposed to during meiosis prior to the creation of the gametes.
DeleteTo answer your first question, They exchange at least once and can exchange multiple times at random points during prophase I.
ReplyDelete1. What are theories to the origin of meiosis?
ReplyDelete2. What Promotes crossing over?
3. Are there life forms which do not cross over during meiosis?
To answer your first question, the theory is that meiosis originated in the common ancestor of all eukaryotes as a way of removing damaged or incorrect DNA in order to protect the organism's offspring
DeleteTo answer your 3rd question, there is a case in which crossing over does not occur. This is seen in the Drosophila melanogaster (a fruit fly) chromosome 4.
DeleteSource: https://www.tandfonline.com/doi/full/10.1080/19336934.2017.1321181
1. What are the most common abnormalities/mutations that can happen during meiosis?
ReplyDelete2. What is the synaptonemal complex?
3. What type of mutations can come from mistakes in crossing over of chromosomes?
To answer your first question, chromosomal non-disjunction is the most common error of meiosis, and the most common case of non-disjunction is down syndrome.
DeleteTo answer your third question, Deletion and Translocation. These happen often times due to crossing over.
DeleteIn response to your second question, the synaptonemal complex is defined as a "protein structure that forms between two homologous chromosomes during meiosis", and it typically is known to help with chromosome pairing, synapsis, and recombination. Below are a couple sources going into further detail about this complex, I hope this helps!
Deletehttps://www.rxlist.com/synaptonemal_complex/definition.htm
https://www.genetics.org/content/186/1/45
https://brainly.in/question/11874019
1. Is there a max amount of alleles that can be created when crossing over in meiosis? or is it simply infinite amount of options?
ReplyDelete2. Other than Trisomy 21, what is most common?
3. Is it possible for an organism that has an uneven number of chromosomes to reproduce?
To answer your third question, yes, an organism with an odd number of chromosomes can reproduce. Not only are there organisms that have an odd number or chromosomes (I couldn't find names, only references to them), but female humans with down syndrome have been found to fertile, but men with down syndrome are always infertile. So yes, it is possible, but no, it is not common.
DeleteTo answer your second question, it is trisomy 13.
DeleteI believe since crossing over is generally completely random except for genetic linkage so there are infinite possibilities as to what combinations can be created from the parent. While it is not really infinite because there are only so many alleles, there are just many possibilities.
DeleteIn response to your second question, there are many other common chromosomal abnormalities. An examples is Edward Syndrome which is due to a trisomy of chromosome 18 and results in a low birth weight and abnormally shaped head.
Delete1. How many illnesses can be attributed to genetic mutations?
ReplyDelete2. Is there any variation within the meiosis process depending on the species.
3. Are chiasmata anything else besides the points of crossing over?
In response to your first question, scientists have found over 4,000 illnesses and diseases that can be attributed to genetic mutations, although there is definitely a chance of there being more that are currently undiscovered. Below are a couple sources on genetic disorders, hope this helps!
Deletehttps://kidshealth.org/en/teens/genes-genetic-disorders.html
https://www.genome.gov/For-Patients-and-Families/Genetic-Disorders
To answer your first question, there are approximately 4,000 diseases that can be caused by genetic mutation, here is a link that should have more information. https://kidshealth.org/en/teens/genes-genetic-disorders.html
DeleteTo answer your 3rd question, no, chiasmata are not anything else besides the points of crossing over. They are simply the point, sort of like labeling a part helps with a process.
DeleteSource: https://www.topperlearning.com/answer/explain-the-difference-between-chiasmata-and-crossing-over/deme6moo
To help answer your 3rd question, here is a bioninja article about chiasmatas:
Deletehttps://ib.bioninja.com.au/higher-level/topic-10-genetics-and-evolu/101-meiosis/chiasmata.html
What are most common errors in the process of meiosis?
ReplyDeleteIn Down Syndrome, where the extra chromosomes originate from?
What are common issues in the processes of crossing genes?
To answer your first question, the most common errors within meiosis is the misplacement of chromosomes, leading to gametes missing or with extra chromosomes, which also leads into your second question.
DeleteIn response to your second question, I could not find an exact answer, but I did find that because Chromosome 21 is one of the smallest chromosomes, it is more likely to have a mistake among it. Down Syndrome can also be caused as there is more genetic material from their chromosome 21. Hope this helped :)
Delete3- A problem that occurs during the process of crossing genes is unequal crossing over. Unequal cross-over is caused by misaligned chromatids leading to distinct loci to go through homologous recombination. For more information this topic look here: https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/unequal-crossing-over
Delete1- How does re combinase work along side the other enzymes in crossing over?
ReplyDelete2- How fast does meiosis occur?
3- What is the most extreme genetic mutation that does not result in early death necessarily.
In response to your second question, in males the meiosis process takes about 74 hours and starts happening when they're around 12-13. In females, the process doesn't usually happen to the full extent as the products from meiosis are often re-absorbed into the body or leave the body all together before they are fully completed. I linked a good source below, i hope this helps!
Deletehttps://www2.palomar.edu/anthro/biobasis/bio_2.htm
In response to your third question, I am not exactly sure what you mean by "extreme" mutation, so I will list a few special mutations that I found.
Delete1. A mutation on ACTN3 that makes muscles contract faster and improves atheletic ability.
2. KAT6A syndrome that impacts the body's ability to encode proteins and causes many problems.
3. Polymelia is a disorder that causes individuals to grow an extra limb that their species does not normally have.
https://www.sciencealert.com/8-genetic-mutations-that-can-give-you-superpowers
https://rarediseases.org/rare-diseases/kat6a-syndrome/
https://www.indiatoday.in/education-today/gk-current-affairs/story/genetic-disorders-263627-2015-09-18
In response to your 2nd question, here is an article that goes over the time and duration of meiosis:
Deletehttps://pubmed.ncbi.nlm.nih.gov/16285/#:~:text=However%2C%20even%20among%20species%20without,Homo%20sapiens%20and%20several%20Orthopterans.
1. What would the effect on the cell or organism be if crossing over didn't happen within meiosis?
ReplyDelete2. What's the bare minimum amount of chromosomes a human needs to survive and could live with?
3. Is there any treatment or cure for some genetic disorders, and if so what stage of life would they need to be administered to be effective?
To answer your first question, if crossing over never occurred then the genetic information would be exactly the same as whichever parent the un-crossed over chromosomes come from. This is extremely rare and I can not find any records of this ever happening.
DeleteIn response to your third question, treatments for genetic disorders are being created, such as the potential treatments for Sickle Cell Disease. These include adding proper DNA to cells or manually editing the DNA code to it's proper orientation. However, these treatments are experimental and will most likely take multiple years to be an absolute cure.
Delete2- The minimum amount of chromosomes a human can have is 44 but this amount usually results in miscarriage or severe problems for the fetus in the future.
Deletehttps://genetics.thetech.org/original_news/news124
1. Are there other examples of genes jumping to a completely different chromosome (similar to how the SRY gene did in some species)?
ReplyDelete2. Is it possible for more than 2 genes to be linked?
3. How do linked genes impact the inheritance of their phenotypes?
1- the idea of "gene jumping" happens frequently within eukaryotes and are known as transposable elements. There are different types of DNA transposons that can cause genetic mutations and increases the chance of disease development. The DNA transposons move DNA sequences to another location on the genome. For more detailed information look here: https://www.nature.com/scitable/topicpage/transposons-the-jumping-genes-518/
DeleteIn response to your second question, I have been unable to find any proof that over 2 genes can be linked, so I would say that it is normally 2 linked genes. If you want more information on gene linkage, here is a good Khan Academy link: https://www.khanacademy.org/science/ap-biology/heredity/non-mendelian-genetics/a/linkage-mapping
Delete1. I am having trouble grasping the idea of genetic linkage and the mechanics of it, could someone explain it further?
ReplyDelete2.How many genetic variation combination are there?
3.What is the difference between random orientation and independent assortment?
To answer your 3rd question, the difference between random orientation and independent assortment is that random orientation is the random line up of chromosomes along the cell's equator while independent assortment is how the inheritance of one gene is not influenced by the inheritance of another gene.
DeleteSource: https://www.differencebetween.com/difference-between-random-orientation-and-independent-assortment/#:~:text=What%20is%20the%20Difference%20Between,inheritance%20of%20any%20other%20gene.
In response to your first question, genetic linkage is when there are 2 genes very close together on a chromosome. The nearness of the two genes causes them to stick together when prophase I occurs. The 2 genes will not cross over and instead will stick with each other all the way to the daughter cells. In summary, the two genes like each other too much to leave each other during meiosis.
DeleteIf this didn't make sense or you want more information, here is a link to a Khan Academy lesson with linked genes:https://www.khanacademy.org/science/ap-biology/heredity/non-mendelian-genetics/a/linkage-mapping
Question 2- there are 8,324,608 combinations within the 23 chromosomes.
Delete1. Can mutations occur in DNA while undergoing meiosis, that is not part of crossing over?
ReplyDelete2. How were scientists able to determine that crossing over occurs?
3. Can there be a mutation/mistake during meiosis that causes the sister chromatids not to divide evenly and one cell have 2 of a chromosome while another has none of a chromosome?
To answer your third question, yes! We talked about this briefly in class, and this is what's called non-disjunction. It causes the chromosomes to separate incorrectly during meiosis, which results in one extra or one missing chromosome in the gametes. These chromosomal errors will be in every cell of the body after developing as a zygote. Non-disjunction is what causes trisomy on chromosomes, such as that on chromosome 21 that causes Down Syndrome. I hope that this helps! Here is a link to BioNinja that describes and illustrates this concept: https://ib.bioninja.com.au/standard-level/topic-3-genetics/33-meiosis/non-disjunction.html
DeleteTo answer your second question, I believe it was Gregor Mendel that originally observed the crossing over of traits and began to understand genetics using pea plants, here is a link that goes into more detail. https://www.khanacademy.org/science/high-school-biology/hs-classical-genetics/hs-introduction-to-heredity/a/mendel-and-his-peas
Delete1) How come some aspects of meiosis are random, and some are very specific?
ReplyDelete2) What makes Down syndrome as common as it is? Why?
3) What kind of mistakes form as a result of the "crossing over" process in Meiosis?
2) Down Syndrome is the most common chromosomal disorder. When researching your question, I came across some new information about Down Syndrome that I hadn't heard before. There are actually 3 types, not just the typical trisomy of chromosome 21 that we think of. There is also Mosaic Down Syndrome, where not all cells in the body are affected by the trisomy. This is caused by abnormalities in cell division after fertilization, rather than during meiosis. There is also Translocation Down Syndrome, where a part of trisomy 21 is translocated onto another chromosome. There aren't three copies of the chromosome, but rather some genetic material from chromosome 21 is located on another chromosome. These three possibilities of abnormality increase the chances of Down Syndrome during pregnancy. Other factors include age, as more errors in cell division and meiosis are likely to happen as the body gets older.
DeleteHere is my source! https://www.mayoclinic.org/diseases-conditions/down-syndrome/symptoms-causes/syc-20355977
DeleteTo answer your 3rd question, as a result of crossing over, genetic diseases could possibly form and be activated from now shared
Deleteand mixed genetic material in the new gamete
1) I am having a hard time grasping what independent assortment is. Does anyone know how to explain it in simple terms?
ReplyDelete2) How can crossing over affect the expression of dominant or recessive traits?
3) Due to random orientation, can the gamete receive more paternal chromosomes than maternal, or vice versa? I thought that we received one set of chromosomes from each parent, but it doesn't appear to be this way in some of the images.
1. How often does meiosis take place?
ReplyDelete2. What is the most common recessive genetic mutation?
3. Do the chiasmata form in random places along the chromosomes or are there set locations
To answer your first question, meiosis occurs in males constantly, but in females it only occurs once every month before ovulation I believe. Here’s a link that goes into more detail. https://www.cliffsnotes.com/study-guides/biology/biology/meiosis-and-gamete-formation/meiosis-in-humans
Delete