genetics Flashcards
what is robersornian translocation
a translocation of two acrocentric chromosomes with a loss of satelite material from their short arms
what is the genetic mechanism behind imprinting
imprinting is when a gene can have different levels of expression depending on the parent of origin
what is independent assortment and when does it occur
different genes independedntly separate from one another when reproductive cells develop. This occurs in meiosis
what sort of disorder is haemophila A
x-linked recessive where clotting factor VIII is affected. Due to an inversion in the X chromosome, where the chromosome breaks in two places and segemnts become inverted.
define homozygous
the presence of two identical alleles ona pair of homologous chromosomes
define heterozygous
different alleles on homologous chromosomes
what type of genetic defect occurs in Prader-Willi syndrome
a deletion in the long arm of chroosome 15, almost always on the fathers chromsome.
what is the phenotype of Prader-Willi syndrome
Results in mental retardation, obesity in later lafe (after feeding problems in infancy)
What is the genetic defect which occurs in Angelman syndrome
deletion on the maternal chromosome 15. Small heads, developmental disability, speech and balance problems, seizures, sleep problems.
what is anticipation
when a gene repeats and the effects are amplified from generation to generation.
what is de novo mutation
a new mutation that is nont inherited
what is genomic imprinting
the differing expression of genetic material dependent on the sex of the transmitting parent
what is germline mosaicism
the presence of the gonadal (or germline) tissue of two populations of cells that differ genetically
what is variable expression
when there is a variation in the expression of the severity of a phenotyic features seen in people with autosomal dominant disorders
in familial hypercholesterolaemia, the apoB/E receptor extracts what type of cholesterol
this is an autosomal dominant disease
what are proto-oncogenes
genes which stimulate the cell to grow and divide
what do ongogenes do, what happens if they at amplified or deleted
a mutated proto-oncogene which keep division turned on. Create a gain of function, are domninant in their actions, cause excessive cells to be produced.
what do tumour suppressor genes do, what happens if they are amplified or deleted
work to slow or stop cell growth, when they fail growth goes on unchecked, meaning mutation is a loss of function.
what is an example of a tumor suppressor gene
RB - retinoblastoma. TP53 - on chromo 17, codes for p53, which regulates cell apoptosis.
what is fragike X syndrome
an X linked recessive disorder of mental retardation. Females carry, men affected. Often shows anticipation. Men have prominent ears, long faces, large jaws with learning difficulties.
what is Soto’s syndrome
a genetic mutation which results in children with overgrowth (tall), learning disabilities, large heads, long narrow faces, high foreheads, flushed cheeks, small pointed chin, downward pointing eyes
what is the karyotype and phenotype of Turner’s syndrome
45 X. Female disorder where one X chromosome is absent. Phenotype - webbed neck, low set ears, low hairline, short stature, swollen hands and feet at birth. Puberty and reproductive failure.
what is the karyotype 47 XXY
Klinefelter’s syndrome - males with and extra X resulting in sterility, small testes, delayed or absent puberty, gynecomastia, reduced facial hair.
what is the karyotype XYY
XYY syndrome, males with an extra Y chromosome. May be taller than average, often no other abnormalitites. Can have haight risk of intelectual disabilities or developmental delay.
