Human Genome and Karyotype Flashcards
during which stage of mitosis do chromatin condense into chromosomes
prophase (after replication)
after DNA replication, forms pair of sister chromatids
what 2 principles increase genome complexity and size
- duplication
- incorporation (lateral transfer)
what type of mutation is this:
GCATT —> GTACT
inversion (of CAT)
genetic repeats can be substrates for abnormal recombination due to similar or identical nucleotide sequence. Which of these types is most likely to cause abnormal recombination?
a. long repeats (genes or blocks of genes)
b. short tandem repeats
c. transposons
long repeats more likely to cause abnormal recombination
recombination can cause inversions, duplications, or deletions
gene recombination can cause ____, _____, or _____
inversions, duplications, deletions
red-green color blindness is due to what kind of genetic mutation?
abnormal recombination of tandem repeat
long wavelength (red) and medium wavelength (green) photoreceptors are encoded by adjacent genes on X chromosome - they are tandem repeats
abnormal recombination during meiosis can delete one gene (green) from the X chromosome
DiGeorge (aka Velocardiofacial syndrome), Prader-Willi, and Angelman syndrome are all due to what kind of genetic mutation
recombination occurring between large repeats that results in deletion of a block of DNA containing multiple genes —> complex phenotypes
DiGeorge: failure of pharyngeal pouch to develop, also parathyroid, thymus, and cardiac defects (deletion in chromosome 22)
Prader Willi and Angelman syndrome - both due to deletion in chromosome 15 (affecting genes that are imprinted)
what does genetic anticipation refer to
short tandem repeat expansion occurring de novo in sperm/egg
results in heritable disease phenotype within single generation
more expansions = more severe disease
examples: Huntington’s, Kennedy’s, myotonic dystrophy, Fragile X
what enzyme is needed to generate a retrotransposon (type I transposon)
RETROtransposons need RT - creates ds cDNA from ssRNA
these can be caused by transposons: cystic fibrosis, hemophilia A, X-linked dystonia-parkinsonism
in what contexts should you consider a possible chromosome abnormality? (4)
- problems with physical or mental development of fetus or child
- infertility, spontaneous abortion, stillbirth
- pregnancy in women over 35
- cancer
do you need to know the location of a chromosomal abnormality to identify it with FISH?
YES: need to design a specific probe
FISH = fluorescent in situ hybridization
detects changes too small to see in G-banding
however, only detects presence/absence/ position of DNA to which probe binds (cannot rule out genetic defect elsewhere)
what can comparative genomic hybridization (CGH) detect?
deletions or duplications, even if location is unknown
when karyotyping with G-banding, chromosomes are incubated with _____, which arrests the cells in metaphase. They are then stained with ____ dye
colchicine - disrupts tubulin- dependent spindle function
Giemsa dye (heterochromatin are darker)
how do you identify chromosomes with G banding
size (1 largest, 22 smallest)
centromere position
banding pattern (of hetero/euchromatin)
what type of genetic material is contained in centromeres
satellite DNA (tandem repeats of non coding DNA)
can use centromere to identify chromosomes, esp when there are chromosomal abnormalities
