Uniparental Disomy and Karotypes

Day 29: Uniparental Disomy

On our 29th day of MARCHING into TRISOMY AWARENESS we are going to share a little bit about UNIPARENTAL DISOMY. Uniparental disomy (UPD) occurs when a person receives two copies of a chromosome, or of part of a chromosome, from one parent and no copies from the other parent. UPD can be the result of heterodisomy, in which a pair of non-identical chromosomes are inherited from one parent or isodisomy, in which a single chromosome from one parent is duplicated. Because it may lead to the duplication of lethal recessive genes, isodisomy is potentially dangerous, while heterodisomy is essentially benign. This can also be the result of a TRISOMY CELL RESCUE (also known as trisomy rescue or trisomy zygote rescue) a genetic phenomenon in which a fertilized ovum containing three copies of a chromosome loses one of these chromosomes to form a normal, diploid chromosome complement. If both of the retained chromosomes came from the same parent, then uniparental disomy results. Share because you care...we did ♥

Day 30: Karotypes

On our 30th day of MARCHING into TRISOMY AWARENESS we are going to share a little bit about KAROTYPES A karyotype (Greek karyon = kernel, seed or nucleus) is the number and appearance of chromosomes in the nucleus of a eukaryotic cell. The term is also used for the complete set of chromosomes in a species, or an individual organism. Karyotypes describe the number of chromosomes, and what they look like under a light microscope. Attention is paid to their length, the position of the centromeres, banding pattern, any differences between the sex chromosomes, and any other physical characteristics.The preparation and study of karyotypes is part of cytogenetics. The study of whole sets of chromosomes is sometimes known as karyology. The chromosomes are depicted (by rearranging a microphotograph) in a standard format known as a karyogram or idiogram: in pairs, ordered by size and position of centromere for chromosomes of the same size.The study of karyotypes is important for cell biology and genetics, and the results may be used in evolutionary biology and medicine. Karyotypes can be used for many purposes; such as to study chromosomal aberrations, cellular function, taxonomic relationships, and to gather information about past evolutionary events. The normal human karyotypes contain 22 pairs of autosomal chromosomes and one pair of sex chromosomes. Normal karyotypes for females contain two X chromosomes and are denoted 46,XX; males have both an X and a Y chromosome denoted 46,XY. Any variation from the standard karyotype may lead to developmental abnormalities. Share because you care...WE DID ♥

Days 16, 17, 18, 19 and a Bonus for Trisomy 18

Day 16 - Ring Chromosomes

On our 16th day of MARCHING into TRISOMY AWARENESS MONTH, we are going to share about RING CHROMOSOMES. A ring chromosome is a chromosome in which both ends have been lost (deletion) and the two broken ends have reunited to form a ring-shaped figure. Ring chromosomes may form in cells following genetic damage by mutagens like radiation, but they may also arise spontaneously during development. The issue is that genetic information is often moved or deleted when a ring chromosome forms, and as a result, the genes on that chromosome may not express properly. This can lead to health problems which range from congenital conditions to cancer. Ring chromosomes are very rare, and they have been found in nearly all human chromosomes. Some people have ring chromosomes in their bodies and remain unaware of it, while in other cases, a suspected ring chromosome may be identified shortly after birth. The diversity of the spectrum from profound developmental delays to a blissfully unaware existence illustrates the diversity of human genetics. Share because you Care. ♥

Day 17 - Karotypes and Microarrays

On our 17th day of MARCHING into TRISOMY AWARENESS MONTH, we first want to wish our supporters a HAPPY ST. PATRICK'S DAY! Hope for Trisomy would love for you to share a photo of your blessing in GREEN! We are also going to share a genetic analogy. The process can be a little confusing, so we are hoping this analogy will help. Our chromosomes are like a set of 46 encyclopedia books. A chromosome analysis or karyotype is able to determine if there are any missing or extra books (chromosomes). Our genes are like the sentences on each page of the set of encyclopedia books (chromosomes), and each page of each book contains a unique set of sentences (genes). Each page contains the sentences for approximately 10 to 30 genes. A DNA microarray analysis is able to open up each of the 46 encyclopedia books to determine if there are any missing or extra pages. Our DNA are like the letters that make up each sentence (gene) on each page of the books (chromosomes). Each sentence is made up of a very specific sequence of letters (DNA). Genetic sequencing is able read a specific sentence to determine if there are any spelling mistakes (genetic mutations) in the sentence (gene). Share because you Care. ♥

Day 18 - Trisomy 18

On our 18th day of MARCHING into TRISOMY AWARENESS MONTH, we are going to share about the 2nd most common Trisomy behind Trisomy 21 (Down syndrome). Trisomy 18 (also called Edwards syndrome) is a genetic disorder where there are 3 copies of the 18th chromosome instead of the normal 2, and because of the third copy...it affects the child both physically and mentally. Unfortunately, there is a high mortality rate amongst the babies born with this disorder because of how that extra copy affects the development of the body. However, each child is affected differently and there is a wide spectrum of severity amongst babies born with this disorder. Here is a link provided by the SOFT Organization about TRISOMY 18 FACTS. http://trisomy.org.s113588.gridserver.com/wp-content/uploads/2012/10/Trisomy-18-Facts-8-20-12.pdf Also, for the families caring for a child diagnosed with Trisomy 18, the SOFT Organization has a book provided at this link, http://trisomy.org/shop/care-of-the-infant-and-child-with-trisomy-18-or-trisomy-13/
and a guidebook provided at this link.http://trisomy.org/shop/trisomy-18-a-guidebook-for-families/ Share because you Care. ♥

Bonus T18 Share for the official Trisomy 18 Awareness Day!

One of the most notable things about trisomy 18 children are long and gorgeous eyelashes! Although eye problems are not one of the top concerns in a child with trisomy 18, we thought we'd share a photo example of their gorgeous eyes and share a list of some common Eye Features of Trisomy 18.

LONG EYELASHES - Although we can't find an actual publication that states this as a characteristic of trisomy 18, every T18 parent knows this! In fact, we like to joke that "the length of your eyelashes is directly proportional to the amount of 18th chromosomes you have." :-) That isn't really true, but there is definitely a correlation between long lashes and trisomy 18! All you have to do is look at just about any portrait of a T18 child.

WHORLED/ARCHED EYEBROWS - Commonly develop into a uni-brow too. http://www.ncbi.nlm.nih.gov/pubmed/22901740

COLOBOMA - A small keyhold in the iris or other area of the eye. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3520824/table/T2/

PHOTOPHOBIA - Extreme light sensitivity causing sneezing, closing of eyes, aversion to light, etc. http://www.ncbi.nlm.nih.gov/pubmed/23088440

Other eye anomalies can include blue sclerae, ptosis, microphthalmia, cataract, corneal opacities, strabismus.

If you look closely at this lovely T18 model's eyes, you can see somewhat tilted heart-shaped iris colobomas. ♥

Visit https://www.facebook.com/HopeForTrisomy13and18 for facts, fun, advocacy, hope, and more!

Please note - 
Unless your child has other health issues, developmental delays, and other symptoms of a genetic disorder, you should not have to worry if they have some of these eye conditions. All of these eye conditions can occur in genetically normal persons. However, the whorled eyebrows and long lashes are one common feature of trisomy 18 children that parents readily recognize. They do occur in some other genetic disorders as well. So we thought it would be interesting to point out some common eye features for those with trisomy 18 children that may not have realized are "normal" for trisomy 18.  So please do not worry if your child has long eyelashes and bushy eyebrows, it is most likely just hereditary! But for those already diagnosed with a genetic condition, it may simply be a "normal" trait of that condition.

Day 19 - Translocations

On our 19th day of MARCHING into TRISOMY AWARENESS MONTH, we are going to share a little more about TRANSLOCATION, which is a structural abnormality in reference to chromosomes. Translocation is used when the location of specific chromosome material changes. The two main types of translocations are reciprocal and Robertsonian. In a reciprocal translocation, two different chromosomes have exchanged segments with each other. In a Robertsonian translocation, an entire chromosome attaches to another at the centromere. Translocations can be balanced or unbalanced. The balanced translocation is a rearrangement of the genetic material without any gain or loss of DNA. An unbalanced translocation IS a gain or loss of DNA, so the cell has an abnormal amount of genetic material. Often times, unbalanced translocations result in a birth defect, stillbirth, or a spontaneous abortion. Share because you Care. ♥