Genes and Chromosome Alterations Flashcards
What is a telomere?
The tip of a linear chromosome
What are the 4 types of chromosomes?
Submetacentric(centromere slightly high), metacentric(centromere at center), telocentric(centromere at telomere), acrocentric(higher than submetacentric)
What is a karyotype, and how do you obtain one?
The complete set of all chromosomes, obtained by taking a cell that is actively dividing(bone marrow/stem cell) and treating them with colchicine. lined up in descending order of size, cells are arrested in metaphase. Can either be done through amniocentesis(amniotic fluid, 14-16 wk fetus, few weeks processing) or chorionic villius sampling(taking from villi of placenta, few hours processing, 8-10 wk fetus)
What is the difference between heterochromatin and euchromatin in a karyotype?
Heterochromatic regions(rich in adenine and thymine) stain darker in g-banding, and euchromatic regions(guanine and cytosine) stain lighter. Euchromatin is more transcriptionally active
What is array CGH?
Compares patient’s karyotype against a standard. Stained with fluorescence; red means deletion, green means duplication, yellow means it’s adequate.
What are the 4 types of chromosomal rearrangements?
Duplication, deletion, inversion, translocation
What is aneuploidy?
Possessing an abnormal number of chromosomes due to nondisjunction during meiosis
What is polyploidy?
When the complete set of chromosomes is multiplied by a factor(3n, 4n, 5n)
What is translocation?
The movement of a gene from one chromosome to another nonhomologous chromosome. This exchange can be reciprocal(more often) or nonreciprocal(less common)
What are the two sources of chromosomal rearrangements?
Double stranded DNA break, errors in crossing over
What is nullisomy?
Loss of a pair of homologous chromosomes
What is tetrasomy?
Gain of a pair of homologous chromosomes
What is autoploidy?
polyploidy caused by errors in mitosis/meiosis, artificially induced by chemicals such as colchicine that halt spindle formation
What is alloploidy?
Polyploidy caused by hybrid mating of different species with a different chromosome number
Why are cells with an odd number of chromosomes sterile?
In self-fertilization, the homologous chromosomes cannot pair during meiosis.
