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| [Ultrasound] | the use of sound waves to obtain an image of body tissues and structures. prenatal ultrasound provides an image of the fetus in order to assess growth and development.
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| [Turner syndrome] | only one copy of the x chromosome, for a total of 45 chromosomes instead of the typical number, 46 chromosomes.
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| [Trophoblast cells] | after fertilization, the zygote begins to divide mitotically (each 2 daughter cells identical to the parent cell). the cells begin to differentiate into the inner cell mass (defined above) and trophoblast cells, creating a blastocyst. trophoblast cells are found all around the outside of the blastocyst, they are the cells that are responsible for implantation into the uterine wall and will eventually differentiate further into all the extra-embryonic tissues, such as placenta, amnion and chorion.
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| [Trisomy 21] | down syndrome£¬three copies of chromosome 21, for a total of 47 chromosomes instead of the typical number, 46 chromosomes.
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| [Trisomy 18] | edward syndrome£¬three copies of chromosome 18, for a total of 47 chromosomes instead of the typical number, 46 chromosomes.
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| [Trisomy 13] | patau syndrome£¬three copies of chromosome 13, for a total of 47 chromosomes instead of the typical number, 46 chromosomes.
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| [Trisomy] | three copies of a particular chromosome present in a cell, for a total of 47 chromosomes in the cell instead of the typical number, 46.
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| [Trisomic rescue] | if a fertilized egg initially contains 47 chromosomes, as a result of meiotic non-disjunction (instead of the normal 46), and loses the extra chromosome in subsequent cell divisions, this is known as trisomic rescue. the trisomic cell has been ¡°rescued¡± and is now a normal, disomic cell. |
| [Triploidy] | three copies of every chromosome in a cells, for a total of 69 chromosomes, instead of the typical number, 46 chromosomes.
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| [Translocation] | a chromosome rearrangement where a piece of one chromosome breaks off and joins to another chromosome. an individual with a balanced translocation has the normal amount of chromosomal material. a person with an unbalanced translocation will have a loss or gain of chromosomal material.
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