Karyotyping Flashcards
What is the karyotype?
The number and appearance of the chromosomes in an organism.
What can be deduced from a karyotype?
The gender of a person and the abnormalities that the person will have.
How can a karyotype test be performed before the birth of a baby?
By obtaining cells from the fetus via amniocentesis or chorionic villus sampling.
What is amniocentesis?
The sampling of amniotic fluid fromt eh amniotic sac around the fetus. A hypodermic needle is inserted through the mom’s skin and uterus to draw out the amniotic fluid (which contains cells from the fetus).
What is chorionic villus sampling?
Chorionic villus, the fetal tissues in the placenta, contains cells which can be removed via a hypodermic needle.
When are chromosomes most easily visable?
During metaphase.
What is the process of karyotyping after the cells have been obtained?
They are incubated with chemicals in order to divide, then other chemicals are used to stop mitosis during metaphase. Then a fluid is used to burst the cells and spread the chromosomes. Then these are photographed under a microscope, and they are then cut out and sorted by size and structure.
What is non-disjunction?
It is the non-seperation of chromosomes during the divisions of meiosis.
What happens when there is a non-disjunction?
The gametes produced either have one chromosome too many or one too few.
What happens when gametes have one chromosome too few?
They usually quickly die.
What happens when gametes have one chromosome too many?
They sometimes survive.
In anaphase one, what does non-disjunction look like?
Three chromosomes are taken to one side rather than equal numbers. (2 and 2 in this case)
In anapahse two, what does non-disjunction look like?
Rather than equal numbers of chromatids on each side, an extra chromatid goes to one pole.
