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Down Syndrome

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Dean Coelho

on 31 January 2014

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Transcript of Down Syndrome

DNA, Chromosomes, and the Cell Cycle
Down Syndrome In Depth
The Lives of Down Syndrome Carriers
Down Syndrome
What is Down Syndrome?
Errors In Cells
Also known as Trisomy 21
Dean Coelho
Down syndrome is a chromosomal disorder/abnormality caused by the presence of an extra copy of chromosome 21. It is also called Trisomy 21 because the word tri (three) in
Tri
somy means there is a third copy of chromosome 21. There is extra genetic material.
This disorder leads to impairments in cognitive ability and physical growth. Down syndrome carriers also have distinct physical features.
Down syndrome occurs at random and there is no purposeful reason as to why it occurs. We can only relate maternal age of women to this disorder.
Over
5.8
billion
people
across
the
world
have
D
O
N
W
R
SYNDROME
And it's completely random
Down syndrome all begins in the chromosomes, the essentials to create new cells. To have a solid understanding of why Trisomy 21 occurs, the basics have to be understood.
DNA (
d
eoxyribo
n
ucleic
a
cid) is a single molecule made of atoms and 4 chemical bases. It goes in the form of a spiraling ladder and is the blueprint to form organisms. DNA tells the amino acids how to form perfect proteins which are important in the cell cycle.
Chromosomes
Chromosomes are thread-like structures in the form of a coil. Their made of thousands of proteins called histoines and a single DNA molecule. The DNA molecule is so long that it has to be wrapped around the histoines several times.
The chromosomes ensures DNA is evenly distributed during cell division.
We inherit 46 chromsomes in each cell. 23 from our mother, and 23 from our father.
Cell Cycle
The cell cycle has 3 main stages, the Interphase, Mitosis, and Cytokinesis. If an error occurs, a chromosomal disorder is at risk. Chromosomes play a huge part in cell division and these disorders are totally random.
We can see DNA and chromosomes are strongly related. They both have an important part in cell division, in an organism's genes, and for both cells and organisms to function properly.
The Basics
But what happens if there's errors....?
The chromosomes located inside the nucleus of a cell hold the single gene molecule, DNA. These unique thread-like structures ensures DNA is properly and evenly distributed during cell division, aforesaid.
If a cell tried to reproduce with a wrong DNA code, it wouldn't be able to. DNA controls the cell cycle and if a change were to be made to the DNA, cells can go wrong. Cells could grow and divide out of control and ultimately result in disease. Cancer is an example of out of control cells.
What about errors in chromosomes?
Chromosomes are very important in cell division. They ensure DNA is accurately copied and distributed, They make sure nothing goes wrong with DNA.
The result is chromosomal abnormalities. An abnormality in the number of chromosomes in each cell results in several different kinds of "trisomies". The most common is Down syndrome or Trisomy 21.
Trisomies
Down syndrome
Trisomy 21
Edwards syndrome
Trisomy 18
Pateau syndrome
Trisomy 13
What Exactly is Down Syndrome?
Down syndrome is a chromosomal disorder caused by an extra 21st chromosome. Also known as Trisomy 21. Down syndrome carriers are affected physically and their cognitive and thinking skills are delayed. How much they are retarded can vary from different Down syndrome carriers and they have physical attributes on their face, hands, and feet. 95% of the cases of Down syndrome are not hereditary but unfortunately there is no cure, but treatments for it. Aforesaid.
Cause for Down syndrome?
Treatment?
Symptoms of Down syndrome?
Retardation?
Maternal Age?
How Does Down Syndrome Occur?
Screening and Diagnostics?
Down syndrome is caused because of an error in cell division. This error is called nondisjunction and it occurs during one of the 3 main stages of cell division, mitosis (also called meiosis 2).
The human body has diploid cells and haploid cells. We also inherit 46 chromosomes but Down syndrome carriers have 47 chromosomes, an extra 21st chromosome/genetic material.
What is Nondisjunction?
Haploid cells only have 23 chromosomes, they are reproductive cells. Almost all of our other cells are diploid cells, cells with 46 chromosomes.
Nondisjunction occurs much more frequently in egg cell formation rather than sperm cell formation.

88% of the time, nondisjunction comes from the mother's egg cell
6% of the time, nondisjunction comes from the father's egg cell
The rest of the time, nondisjunction happens after fertilization, when the embryo grows and develops.
When a sperm cell fertilizes an egg cell (2 haploid cells), the zygote will have 46 chromosomes. This means both the egg cell and sperm cell have contributed their genetics equally.
Meiosis 2 or mitosis is the process of a reproductive cell's division where diploid cells divide to make haploid cells. 2 haploid cells merge at fertilization.
Diploid cells reproduce during mitosis to make 2 daughter cells that are exact replicas.
A chromosome is made of 2 chromatids and a centromere. During the anaphase, the centromere splits and the 2 chromatids seperate into 'daughter' chromosomes.
Nondisjunction occurs when the 2 sister chromatids fail to separate in the anaphase resulting in an uneven number chromosomes in the daughter cells.
Down syndrome is completely random because nondisjunction is completely random.
There is no known reason as to why nondisjunction occurs, but we can only relate maternal age to Down syndrome.
Maternal Age
What is Maternal Age?
Advanced maternal age is when a woman is at an older stage of reproduction. The advanced maternal age is 35 and women who have children beyond 35 have a much greater risk of having a child with down syndrome.
Women between the ages 18 and 25 have very low chance of having a Down syndrome baby - Approximately 1 in 2000
Women between the ages 25 and 35 have their chances increased of having a Down syndrome baby - Approximately 1 in 1200
Women at the age of 40 have their chances of having a Down syndrome baby increases dramatically - Approximately 1 in 100
Woman at the age of 50 and beyond have their chances on the verge of having a Down syndrome baby - Approximately 1 in 12
Why is is that Woman who are Older Have a Greater Risk of Having a Down Syndrome Baby?
Maternal age is relatable to Down syndrome, but why? In meiosis, when the chromosomes are lined up in the cell to separate, there is a protein complex which holds the chromosomes together while they are lined up.

Who is Affected by Down Syndrome?
Can Twins Be Born with Down Syndrome?
Symptoms of Down Syndrome
Down syndrome children have distinct physical attributes, mental differences, and health problems. Although different Down syndrome carriers may vary in the symptoms, they all have the basic ones most Down syndrome carriers have.
Physical Differences
eyes have upward slant
white spots on the iris
less muscle tone in several places
small/short neck
flat nasal bridge
upward tilt nose
a single deep crease along the palm of hand
a wide gap between first and second toe
small mouth
large tongue
thin upper lip
Health Issues
More prone to infections like lung, skin, and bladder infections
47% of Down syndrome carriers have heart problems - some can be very severe
Leukemia
Hearing and vision deteriorates
Most Down syndrome carriers only live till they're 55 or 60
Mental and Cognitive Issues
Most Down syndrome carriers are retarded - their mental retardness can vary
Learn and process information much more slowly
Intellectual impairments - can also vary
Delayed in cognitive and thinking skills
Individuals with Down syndrome are often retarded along with other problems. But why are Down syndrome carriers have a level of retardation to this extent?
Mental Retardation
Treatment for Down Syndrome
Unfortunately there is no cure for Down syndrome, but there are treatments and therapies to help Down syndrome carriers battle against the mental, physical, medical problems affiliated with this disability.
Screening & Diagnostics
Down syndrome can be diagnosed before or after birth. Pregnant others can find out if the fetus has a chance of or has Down syndrome.
Screening
Screening vs Diagnostic Tests
Screening:
screening tests are less invasive to a pregnant woman's body
screening tests only give an estimate if a fetus has Down syndrome
ultrasound procedures take a long time
results are received a lot later - By the time a pregnant mother would receive her results, she could be a long time into pregnancy. This forces he to think about possibly abortion which brings down a lot of stress, pressure, and depression
blood tests are easy and quick
much lower price
Diagnostic Tests:
screening tests cannot give a definite answer
diagnostics are 99% accurate
more invasive to a pregnant woman's body
a risk of harming the developing fetus
pregnant women won't know for sure if the developing baby has Down syndrome only till after it's born
risks of miscarriage, preterm labour, and fetal injury
Mosiacism & Translocation Down Syndrome
Mosaicism Down syndrome is when some cells are normal and healthy, while other cells are Down syndrome cells. This is also caused by an error in cell division
Translocation Down syndrome is when chromosome 21 breaks off and attaches itself to another chromsome.
Translocation Down Syndrome
Mosaicism Down Syndrome
Childhood
Adulthood
Jobs:
restaurant workers
office assistants
shipping data entry
shelters & workshops
photography & art
graphic design
Down syndrome was named after Dr. John Langdon Haydon Down. He was a British physician and he was the first person to observe Down syndrome as a mental disability. He noticed the symptoms and the outcomes of the disease.
Thank You
Any Questions?
problems in gross motor skills, learning, short term memory, speaking and communicating etc.
live happy and good lives - require support and care
impacted my therapies, support given, treatments, and how they are treated by the outside world
bullying and discouragement is another problem - they don't realize it but family members are socially affected by it
parents have to teach social skills at a young age
most live only till age 55 or 60
get discouraged by mental problems and by world around them'
lead good lives for themselves
years ago, people feared Down syndrome carriers would never lead a good life - today they are!
employment, own houses, relationships, and responsibilities
living independently (with support)
Full transcript