lecture 20

Question 1

what is it called when an individual differs from a normal individual by part of a chromosome set?

Answer 1

aneuploidy

Question 2

what is the chromosome number of a monosomic individual?

Answer 2

2n-1

Question 3

what is the chromosome number of a trisomic individual?

Answer 3

2n+1

Question 4

what is partial form aneuploidy?

Answer 4

all cells have the aneuploidy, but it is not the gain/loss of a whole chromosome. rather only part of a p or q arm of a chromosome is gained/lost

Question 5

what is mosaic form aneuploidy?

Answer 5

not all the cells have the aneuploidy

Question 6

what is disjunction?

Answer 6

the normal separation of homologous chromosomes during meiosis/mitosis

Question 7

what is the result of monosomic aneuploidy in autosomes(non-sex chromosomes)?

Answer 7

lethality

Question 8

what is the result of monosomic aneuploidy in allosomes(sex chromosomes)?

Answer 8

Turner’s Syndrome (XO)
- only affects women
- sterile, shorter, developmental/cognitive effects

Question 9

where can trisomic aneuploidy occur?

Answer 9

any chromosome (allosome or autosome)

Question 10

what is the most common instance of trisomy?

Answer 10

trisomy-16 resulting in miscarriage

Question 11

what forms of trisomy cause the most severe phenotypic effects?

Answer 11

trisomy-18(Edwards Syndrome) and trisomy-21(Downs Syndrome)

Question 12

what is Klinefelter’s Syndrome?

Answer 12

trisomy of the 23rd chromosome; XXY, relatively symptom-free, male, extra X chromosome interferes with male hormone production causing infertility

Question 13

what is Jacob’s Syndrome?

Answer 13

trisomy of the 23rd chromosome; XYY, taller, learning disabilities

Question 14

what is Triplo-X Syndrome?

Answer 14

trisomy of the 23rd chromosome; XXX, generally asymptomatic, X chromosome inactivation

Question 15

in euploidy, what happens to size, shape, and proportions?

Answer 15

size changes, but the shape and proportions generally stay the same

Question 16

in aneuploidy, what happens to size, shape, and proportions?

Answer 16

size may change, shape and proportions are altered in specific ways

Question 17

are aneuploids or euploids more common? why?

Answer 17

euploids are more common because they maintain the gene balance of the organism; additions/subtractions of single chromosomes to the karotype produces more of an effect on the phenotype than change the whole number of chromosome sets

Question 18

what causes euploidies?

Answer 18

defects in fertilization that result in whole set changesw

Question 19

what causes aneuploidies?

Answer 19

non-disjunction during mitosis/meiosis

Question 20

what causes chromosomal rearrangements?

Answer 20

double-stranded breaks in the chromosome or single-stranded breaks involving the telomeres as they are at the ends of the chromosomes

Question 21

what is non-homologous end joining(NHEJ)?

Answer 21

a repair mechanism that uses DNA ligase to use short segments of homologous sequences at the single-stranded ends of excised DNA and original DNA strand

Question 22

what is homologous recombination?

Answer 22

a repair mechanism that requires the presence of a nearly identical sequence to be used as a template(homologous chromosome)

Question 23

what complex is involved in homologous recombination?

Answer 23

rad-51 protein complex

Question 24

what are the causes of chromosomal breaks?

Answer 24

normal cellular processes(ex. DNA unwinding) and external forces(ex. radiation)

Question 25

what must be contained in a chromosomal rearrangement in order for it to be considered “recovered”?

Answer 25

ONLY one centromere and two telomeres