Exam 2 Flashcards
What is a karyotype and what is an ideogram?
karyotype: number and appearance of chromosomes in a cell
ideogram is a graphic representation of the karyotype (?)
How big do mutations have to be in order to be seen on a karyotype?
4mB or larger
What are the parts of a chromosome?
short arm (p), long arm (q), centromere
How may pairs of autosomes, and how many sex chromosomes do humans have?
22 pairs of autosomes, 2 sex chromosomes
How does the medical and general usage of the word “gene” differ?
medical: gene is an area of the chromosome that codes for a protein
general: a functional unit of the chromosome
What is a locus?
The exact physical location of a gene on a chromosome
What are alleles?
2 or more variations of a gene
What is the difference between genotype and phenotype?
genotype: combination of alleles
phenotype: the observable trait that is a result of genotype
What is a SNP?
single nucleotide polymorphism- a genetic variation in a single nucleotide
List the ways autosomal dominant and autosomal recessive modes of inheritance differ?
in AD, only one allele is required for the trait to be expressed. in AR both alleles are required for the trait to be expressed
Which parent do you inherit mitochondrial DNA from?
mother
What are the genetic principles of pleiotropy, aneuploidy, and anticipation
pleiotropy: a single mutation causes disease in multiple organs (eg marfan syndrome)
aneuploidy: deviation from the normal amount of chromosomes (eg. trisomy)
anticipation: more recent generations with a mutation develop symptoms earlier/with more severity. (eg. huntingtons) likely due to expanding polymorphisms
For X-linked recessive inheritance, who is affected and who is a carrier (i.e. male vs. female)?
males are affected, females are carriers
Why are females more likely to get an X-linked dominant disease than males?
because females have two chances of getting the affected allele, whereas males have only one chance to be affected.
What are the major features of Turner syndrome, and why is it called a mosaic disease
45X/46X/47XXX- short stature, ovarian dysgenesis. A mosaic disorder because some cells of the body have varying numbers of X chromosomes.
Why should we consider many sex chromosome aneuploidies as traits, and not diseases as they have been classified in the past?
because there is no outward pathology. classifying sex chromosome aneuploidy as disease only leads to stigmatization/ostracism
Why is fragile X syndrome called “fragile,” and what are some of its major features?
unstable CGG repeat at Xq27, leading the bottom of the X chromosome to look as if it’s hanging by a thread “fragile”. causes mental retardation in males, hypotonia, elongated forehead, crossed eyes…..
What is the difference between imprinting of the X chromosome, and imprinting of the autosomes? (???)
imprinting is maintained in all somatic cells of the offspring
Prader-Wili and Angelman syndrome are examples of this epigenetic disease process ______?
imprinting (PWS is paternal imprinting, AS is maternal imprinting of locus 15q)
What are the 5 points of control for gene expression?
Chromatin stage, transcriptional stage, translational stage, post translational control in the cytoplasm, post translational modification
Which stage of control for gene expression is most studied? (???)
chromatin stage?
Why does DNA naturally wrap around histones and what epigenetic changes can occur to histone tails to encourage/discourage winding/unwinding?
DNA is negatively charges and the histones are positively charged. epigenetic modifications- methylation acetylation ubiquination…..
What is a promoter region on a gene and why are promoter regions generally not methylated?
hypermethylation at CpG islands in promoter regions generally associated with gene inactivation
What is a non-mutagen epigenetic carcinogen?
compounds that dont directly change the DNA but are known to cause tumors, likely due to epigenetic changes. Eg nickel compound, arsenite, hexachlorobenzez
