3. DNA Variation & Repair

Question 1

SRY Gene

Answer 1

codes for TDF (testis-determining factor) protein, called sex-determining region Y

Question 2

Testis-determining factor (TDF)

Answer 2

develops male traits, around 6th week of gestation

Question 3

Are X and Y chromosome homologous pairs?

Answer 3

Yes - even though Y is smaller and has less genes, Y still carries some of the same genes as X and there are sequences similarities throughout the Y, X and Y crossover

Question 4

Pseudoautosomal regions (PAR1)

Answer 4

regions on X and Y chromosome that can crossover, 5% of Y chromosome but holds about half of all genes

Question 5

Male-specific region (MSY)

Answer 5

everything on Y chromosome that i snot PAR1 and PAR2, repetitive/palindromic, 30-35% resembles X chromosome

Question 6

Colorblindness

Answer 6

X-linked recessive

Question 7

Hemophilia (factor IX disease)

Answer 7

X-linked recessive

Question 8

Incontinentia pigmenti

Answer 8

X-linked dominant

Question 9

Rett Syndrome

Answer 9

X-linked dominant, MECP2 gene, controls nerve cell development and expression of other genes

Question 10

Sex-limited traits

Answer 10

phenotype only expressed in one sex; ovarian vs prostate cancer, heavy vs thin beard, preeclampsia

Question 11

Sex-influenced traits

Answer 11

phenotype is expressed differently in both sexes; male pattern baldness

Question 12

X-inactivation

Answer 12

one X chromosome (75%) is inactivated in each cell, leads to mosaicism in females

Question 13

XIST gene

Answer 13

controls X-inactivation, completely random

Question 14

Polyploidy

Answer 14

each chromosome set is copied, extremely fatal

Question 15

Aneuploidy

Answer 15

wrong # of chromosomes, either more or less, could be deletion or addition of parts of a chromosome

Question 16

Nondisjunction

Answer 16

when chromosomes improperly align during meiosis at any stage and gametes end up with wrong number of chromosomes

Question 17

Nondisjunction in Meiosis 1 leads to…

Answer 17

all 4 gamete cells have aneuploidy, 2 with no chromosomes, 2 with extra chromosome
if fertilized, 2 are monosomic, 2 are trisomic

Question 18

Nondisjunction in Meiosis 2 leads to…

Answer 18

2 gametes have aneuploidy, 2 gametes are normal
if fertilized, 2 are normal (euploid), 1 is monosomic, 1 is trisomic

Question 19

Monosomic

Answer 19

only one pair of a chromosome, form of aneuploidy (-)

Question 20

Trisomic

Answer 20

extra copy of a chromosome, form of aneuploidy (+)

Question 21

Euploid

Answer 21

normal # of chromosomes

Question 22

Chromosome notation

Answer 22

[Total # of chromosomes],[Sex chromosomes],[abnormalities]

Question 23

Trisomy 21

Answer 23

Down syndrome, extra copy of 21st chromosome, least fatal
- intellectual disability, short neck, flat face

Question 24

Trisomy 18

Answer 24

Edwards syndrome, extra copy of 18th chromosome, very fatal
- low birth weight, microcephaly, micrognathia, scrunched fists, low-set ears

Question 25

Trisomy 13

Answer 25

Patau syndrome, extra copy of 13th chromosome, very fatal
- organs developing outside of body, cleft palates, small head

Question 26

Cri-du-chat syndrome

Answer 26

partial deletion of chromosome 5, mild-severe, mostly males
- cat-like cry, widely spaced eyes, small head, low birth weight

Question 27

Turner Syndrome (XO)

Answer 27

missing X chromosome (or partial missing X or mosaic) in females
- short, sexually underdeveloped, webbed necks, low set ears

Question 28

Klinefelter Syndrome (XXY)

Answer 28

affects males, extra X chromosome
- taller than family, low muscle mass, low testosterone, breast development, small genitalia, less facial and body hair

Question 29

Triple-X Syndrome (XXX)

Answer 29

females have extra X chromosome
- typically taller than average, X inactivation allows normal development

Question 30

XXYY Syndrome

Answer 30

like Klinefelter, affects males, intellectual/behavioral issues

Question 31

XYY Syndrome

Answer 31

affects males, taller than average, risk of learning disabilities, developmental delays, and behavioral issues