down syndrome results from a problem during what stage of cell cycle? course hero

How is Down syndrome generated in the cell cycle?

View Down Syndrome from NURS 5540 at Graceland University. Down Syndrome Down Syndrome is the result of abnormal splitting of the 21 st chromosome during meiosis. The abnormal splitting causes extra

What is the cause of Down syndrome?

Jul 25, 2021 · If dna replication does not occur , cell cycle will not proceed , cells will not divide and cell death occurs . Dna replication occurs during S stage or synthesis stage of cell cycle . DNA replication needs to occur because existing cells divide to produce new cells. So the DNA needs to be copied before cell division so that each new cell receives a full set of instructions

What chromosome is Down's syndrome on?

Mar 08, 2022 · Down syndrome is one of there. This disease is not due to a single abnormal gene, like Tay Sach's, but is due to a mistake during meiosis. Most likely it is a problem during Meiosis ll, where sister chromatids for chromosome 21 fail to separate. Thus, the resulting zygote would have 3 copies of chromosome 21, and the normal 2 copies of all the others.

Is Down syndrome caused by cell division errors?

7 During which stage of the cell cycle do chromosomes replicate A G1 B G2 C S D from BIOS 104 at University of Illinois, Chicago ... Who is most at risk for having a baby with Down Syndrome? A. ... Course Hero member to access this document. …

What stage of cell division does Down syndrome occur?

Down syndrome results when abnormal cell division involving chromosome 21 occurs. These cell division abnormalities result in an extra partial or full chromosome 21. This extra genetic material is responsible for the characteristic features and developmental problems of Down syndrome.Mar 8, 2018

Does Down syndrome occur in mitosis?

Down syndrome is caused by a random error in cell division that results in the presence of an extra copy of chromosome 21.Jan 31, 2017

What is the reason for Down syndrome and at what stage in meiosis can it occur?

In translocation, a piece of chromosome or a whole chromosome breaks off during meiosis and attaches itself to another chromosome. The presence of an extra part of the number 21 chromosome causes the features of Down syndrome.

What happens in stage S cell cycle?

In S phase, the cell synthesizes a complete copy of the DNA in its nucleus. It also duplicates a microtubule-organizing structure called the centrosome. The centrosomes help separate DNA during M phase.

When does Down syndrome occur?

It occurs when people have 47 chromosomes in each cell instead of 46. An error in cell division called nondisjunction causes trisomy 21. This error leaves a sperm or egg cell with an extra copy of chromosome 21 before or at conception. Mosaic Down syndrome: This type occurs in about 2% of people with Down syndrome.

What type of mutation results Down syndrome?

Trisomy 21: About 95% of people with Down syndrome have Trisomy 21. With this type of Down syndrome, each cell in the body has 3 separate copies of chromosome 21 instead of the usual 2 copies.Apr 6, 2021

During what phase does nondisjunction occur?

anaphaseNondisjunction can occur during anaphase of mitosis, meiosis I, or meiosis II. During anaphase, sister chromatids (or homologous chromosomes for meiosis I), will separate and move to opposite poles of the cell, pulled by microtubules.Aug 11, 2021

How could nondisjunction result in an individual with Down syndrome?

Trisomy 21 (Nondisjunction) Down syndrome is usually caused by an error in cell division called “nondisjunction.” Nondisjunction results in an embryo with three copies of chromosome 21 instead of the usual two. Prior to or at conception, a pair of 21st chromosomes in either the sperm or the egg fails to separate.

What happens in G1 G2 and S phase?

During the G1 phase, the cell shows first growth by copying organelles and making the molecular building blocks which are necessary for later steps; during the G2 phase, the cell shows second growth by making proteins and organelles and beginning to reorganize its contents in preparation for mitosis; during the S phase ...Nov 24, 2020

What happens during G1 phase?

G1 phase. G1 is an intermediate phase occupying the time between the end of cell division in mitosis and the beginning of DNA replication during S phase. During this time, the cell grows in preparation for DNA replication, and certain intracellular components, such as the centrosomes undergo replication.

What are the 4 stages of the cell cycle?

In eukaryotes, the cell cycle consists of four discrete phases: G1, S, G2, and M. The S or synthesis phase is when DNA replication occurs, and the M or mitosis phase is when the cell actually divides. The other two phases — G1 and G2, the so-called gap phases — are less dramatic but equally important.

How many copies of chromosome 21 are there in Down syndrome?

So after the egg and sperm unite, the resulting cells will also have three copies of chromosome 21. The complete extra copy of chromosome 21 is in all of the person's cells—or a complete trisomy. Almost all Down syndrome cases result from complete trisomy 21. 1, 2, 3. Mosaic trisomy 21.

What is nondisjunction in Down syndrome?

In nondisjunction, something goes wrong and both chromosomes from one pair go into one cell and no chromosomes for that pair go into the other cell. Most of the time, the error occurs at random during the formation of an egg or sperm. To date, no behavioral activity of the parents or environmental factor is known to cause Down syndrome. 1, 2.

What type of chromosome changes only part of an extra copy of chromosome 21?

Translocation trisomy 21. In this type of chromosomal change, only part of an extra copy of chromosome 21 is in the cells. The extra part of the chromosome gets "stuck" to another chromosome and gets transmitted into other cells as the cells divide. This type of change causes a small number of Down syndrome cases.

Where does the extra chromosome 21 come from?

In the majority of cases, the extra copy of chromosome 21 comes from the mother in the egg. In a small percentage (less than 5%) of cases, the extra copy of chromosome 21 comes from the father through the sperm. In the remaining cases, the error occurs after fertilization, as the embryo grows.

Is every cell in the body the same?

Not every cell in the body is exactly the same. In a small percentage (less than 5%) of Down syndrome cases, most of the cells in the body have the extra chromosome, but some of them don't. This is called "mosaicism.". Mosaic trisomy 21 can occur when the error in cell division takes place early in development but after a normal egg and sperm unite.

Can a parent with Down syndrome have a translocation?

Sometimes, a parent who does not have Down syndrome may carry a translocation in chromosome 21 that can be passed on to children and cause Down syndrome. Studying the parents' chromosomes can reveal whether this is the cause of the syndrome.

What are the other causes of Down syndrome?

What are the other causes of Down's Syndrome? The remaining 5 percent of Down syndrome cases are due to conditions called mosaicism and Robertsonian translocation. Mosaicism in Down syndrome occurs during or after conception. When cell division in the body are normal, while others have trisomy 21.

When was Down syndrome first described?

In 1958, almost 100 years after the original description, Jerome Lejeune, a French geneticist, discovered that down syndrome responded to a chromosomal abnormality. Down syndrome - or trisomy of chromosome 21 - was then the first syndrome of chromosome origin described and is the most frequent cause of identifiable mental retardation ...

What is the name of the chromosome that breaks down during cell division?

When cell division in the body are normal, while others have trisomy 21. Another form is the Robertsonian Translocation that occurs when part of chromosome 21 breaks down during cell division and binds to another chromosome, usually chromosome 14. The presence of this extra part of chromosome 21 causes some features of Down syndrome.

Why do we have three chromosomes together instead of two?

That is, three chromosomes together instead of two, because they are normally grouped in pairs in the cell nucleus. This is called scientifically trisomy 21, which results in Down syndrome. This syndrome is characterized by the presence of a variable degree of learning ability and peculiar physical features that give it a recognizable appearance.

How many chromosomes does 21 have?

In the image you can see how the number 21 has three chromosomes, which results in Down syndrome, while the others have only two chromosomes. The word cell comes from Latin: Cellula , Which means small room. Cells make up life, because they are the structural basis of every living organ or tissue on planet earth.

Why are cells important to life?

Cells make up life, because they are the structural basis of every living organ or tissue on planet earth. Humans are multicellular because they possess several more complex cell types, also known as eukaryotic cells. In organisms such as bacteria, for example, they are unicellular because they have a single cell, and are known as Prokaryotic cells.

How many chromosomes are in a human cell?

Chromosomes in human eukaryotic cells are classified by sex. Usually, each cell contains 46 chromosomes; Are 23 of the father, called chromosomes X, And 23 inherited from the mother, called chromosome Y . The chromosomes are joined in 23 pairs. This means that each pair contains one X chromosome and one Y chromosome.