Sex Chromosomes

Question 1

asexual

Answer 1

displaying no evidence of sexual reproduction

Question 2

Most diploid organisms use ___ for producing new members of the species.

Answer 2

Sexual Reproduction

Question 3

Sexual differentiation

Answer 3

Leads to gamete production

Question 4

More complex forms of life differentiation of sex is more evident due to

Answer 4

sexual dimorphism of males and femals

Question 5

What is the underlying basis of sex determination

Answer 5

genes on chromosomes, not the chromosomes themselves

Question 6

heteromorphic chromosomes

Answer 6

dissimilar chromosomes (XY) characterize one sex or the other in a wide range of species

Question 7

Are all genes on the xy chromosomes sex related?

Answer 7

no

Question 8

Are there any sex determining genes on autosomal chromosomes?

Answer 8

no

Question 9

X chromosome first identified during studies in

Answer 9

grasshoppers
- additional studies in butterflys

Question 10

heterogametic

Answer 10

XY

Question 11

homogametic

Answer 11

XX

Question 12

Klinefelter Syndrome

Answer 12

47 XXY
male genitalia and internal ducts
testes rudimentary and fail to produce sperm

Question 13

Turner Syndrome

Answer 13

46 X
female external genitalia and internal ducts, ovaries are rudimentary

Question 14

all human embryos are

Answer 14

hermaphroditic

Question 15

___ arise as gonadal ridges, can develop to form male or female gonads

Answer 15

gonadal primordia

Question 16

primordial germ cells

Answer 16

migrate to ridges and influence development of ovaries vs testes

Question 17

Primary sexual differentiation

Answer 17

only gonads- where gametes are produced

Question 18

secondary sexual differentiation

Answer 18

overall phenotype, external genitalia

Question 19

what part of the Y chromosome shares homology with the X chromosome

Answer 19

Psuedoautosomal regions (PARs)

Question 20

Male-specific region of the Y (MSY)

Answer 20

nonrecombining region of the Y, still some homology with X

Question 21

Sex-determining region of the Y (SRY)

Answer 21

critical gene controlling male development

Question 22

The SRY region of the Y includes the ___ transcription factor.

Answer 22

Testis determining factor (TDF)

Question 23

Euchromatic regions

Answer 23

regions containong functional genes

Question 24

Heterochromatic regions

Answer 24

regions lacking genes

Question 25

Paternal age effects (PAE)

Answer 25

paternal age associated with increased risk in offspring with genetic basis- schizophrenia, autism, cancers

Question 26

Y chromosome affects more or less than sex determiniation and male feritility

Answer 26

more

Question 27

Barr body

Answer 27

inactivated x chromosome- chromatin body, highly condensed structure that lies against the nuclear envelope

Question 28

Why does Turner's syndrome not develop the regular female phenotype

Answer 28

X inactivation is not immediate

Question 29

Lyon hypothesis

Answer 29

inactivation of x chromosome occurs randomly in somatic cells in embryonic development, likely during blastocyst stage. Once inactivation occurs, all descendednt cells have the same X chromosome inactivated.

Question 30

Example of Lyon hypothesis

Answer 30

Calico and tortiseshell cats

Question 31

Random inactivation leads to females being

Answer 31

mosaic for X-linked genes

Question 32

X-inactivation center (Xic)

Answer 32

major control region on X chromosome

Question 33

One part of xic is a long noncoding RNA

Answer 33

Xist

Question 34

Xist recruits a protien complex that ___ transcriptions at epigenetic level by spreading over and coating X chromosome to be inactivated

Answer 34

silences transcription

Question 35

Normal X chromosomes pair briefly, aligning at the Xic locus prior to random inactivation

Answer 35

random x chromosome inactivation

Question 36

Deletion of Tsix gene from xic region

Answer 36

blocks X-X pairing Chaotic X chromosome inactivation

Question 37

Addition of Xic transgenes (Tsix or Xite) blocks X-X chromosme pairing

Answer 37

no X chromosome inactivation

Question 38

C. Elegens

Answer 38

hermaphrodite- can self fertilize (XX) Male only have testes (X) No Y chromosome Ratio of X chromosome determines sex

Question 39

Sex determined by incubation temperature of eggs during embryonic development

Answer 39

Temperature-dependent sex detemination (TSD) Changes in steroids and their enzymatic synthesis based on temperature