Exam 2

Question 1

What is a karyotype and what is an ideogram?

Answer 1

karyotype: number and appearance of chromosomes in a cell

ideogram is a graphic representation of the karyotype (?)

Question 2

How big do mutations have to be in order to be seen on a karyotype?

Answer 2

4mB or larger

Question 3

What are the parts of a chromosome?

Answer 3

short arm (p), long arm (q), centromere

Question 4

How may pairs of autosomes, and how many sex chromosomes do humans have?

Answer 4

22 pairs of autosomes, 2 sex chromosomes

Question 5

How does the medical and general usage of the word “gene” differ?

Answer 5

medical: gene is an area of the chromosome that codes for a protein
general: a functional unit of the chromosome

Question 6

What is a locus?

Answer 6

The exact physical location of a gene on a chromosome

Question 7

What are alleles?

Answer 7

2 or more variations of a gene

Question 8

What is the difference between genotype and phenotype?

Answer 8

genotype: combination of alleles
phenotype: the observable trait that is a result of genotype

Question 9

What is a SNP?

Answer 9

single nucleotide polymorphism- a genetic variation in a single nucleotide

Question 10

List the ways autosomal dominant and autosomal recessive modes of inheritance differ?

Answer 10

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

Question 11

Which parent do you inherit mitochondrial DNA from?

Answer 11

mother

Question 12

What are the genetic principles of pleiotropy, aneuploidy, and anticipation

Answer 12

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

Question 13

For X-linked recessive inheritance, who is affected and who is a carrier (i.e. male vs. female)?

Answer 13

males are affected, females are carriers

Question 14

Why are females more likely to get an X-linked dominant disease than males?

Answer 14

because females have two chances of getting the affected allele, whereas males have only one chance to be affected.

Question 15

What are the major features of Turner syndrome, and why is it called a mosaic disease

Answer 15

45X/46X/47XXX- short stature, ovarian dysgenesis. A mosaic disorder because some cells of the body have varying numbers of X chromosomes.

Question 16

Why should we consider many sex chromosome aneuploidies as traits, and not diseases as they have been classified in the past?

Answer 16

because there is no outward pathology. classifying sex chromosome aneuploidy as disease only leads to stigmatization/ostracism

Question 17

Why is fragile X syndrome called “fragile,” and what are some of its major features?

Answer 17

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…..

Question 18

What is the difference between imprinting of the X chromosome, and imprinting of the autosomes? (???)

Answer 18

imprinting is maintained in all somatic cells of the offspring

Question 19

Prader-Wili and Angelman syndrome are examples of this epigenetic disease process ______?

Answer 19

imprinting (PWS is paternal imprinting, AS is maternal imprinting of locus 15q)

Question 20

What are the 5 points of control for gene expression?

Answer 20

Chromatin stage, transcriptional stage, translational stage, post translational control in the cytoplasm, post translational modification

Question 21

Which stage of control for gene expression is most studied? (???)

Answer 21

chromatin stage?

Question 22

Why does DNA naturally wrap around histones and what epigenetic changes can occur to histone tails to encourage/discourage winding/unwinding?

Answer 22

DNA is negatively charges and the histones are positively charged. epigenetic modifications- methylation acetylation ubiquination…..

Question 23

What is a promoter region on a gene and why are promoter regions generally not methylated?

Answer 23

hypermethylation at CpG islands in promoter regions generally associated with gene inactivation

Question 24

What is a non-mutagen epigenetic carcinogen?

Answer 24

compounds that dont directly change the DNA but are known to cause tumors, likely due to epigenetic changes. Eg nickel compound, arsenite, hexachlorobenzez

Question 25

How do HAT-HDAC drugs work?

Answer 25

inhibit histon acetyltransferases and histoine deacetylases known to play a role in oral squamous cancer