Ch. 5 Slides (Exam 2) - Sex Determination and Sex Chromosomes Flashcards
Successful fertilization depends on ____
____ in reproductive organisms.
Sexual differentiation
In complex life forms, differentiation of sexes is more evident as ____ ____ of males and females.
Phenotypic dimorphism
____ chromosomes (XY in mammals) characterize one sex or the other in a wide range of species:
– Labeled as ____ chromosomes.
– ____, not chromosomes, ultimately serve as basis for ____ ____.
Heteromorphic; Sex chromosomes; Genes; Sex determination
Nuclear structure in sperm of insect discovered in 1891—
labeled ____-____.
X-body
In butterfly (Protenor):
▪ Female somatic cells have ____ chromosomes, including ____ X chromosome(s).
▪ Male somatic cells have ____ chromosomes with ____ X chromosome(s).
14; 2; 13; 1
Protenor and Lygaeus insects:
- Males produce unlike gametes (____ sex).
Their gametes determine the sex of ____.
- Female produce like gametes (____ sex) -
uniform gametes.
Heterogametic; Progeny; Homogametic
In some organisms, females produce ____ gametes:
- Protenor ____/____or Lygaeus ____/____ mode of sex determination.
Unlike; XX/XO; XX/XY
____: Failure of sex chromosomes to segregate during meiosis.
Nondisjunction
Turner syndrome has karyotypes other than ____,____.
45, X
____: Somatic cells display two different genetic cell lines with different karyotypes.
Mosaics
Presence of additional Y chromosome is only deviation from ____.
Diploidy
Y chromosome houses ____ information for maleness—gene provides “____.”
Genetic; Signal
In humans: By 5th week, gonadal ridges form either ovaries or testes (____ ____).
Bipotential gonads
In early embryonic development human embryo ____—gonadal phenotype sexually
indifferent.
Hermaphroditic
If cell of ridge has XY constitution, ____
develops into testes.
Medulla
Absence of Y chromosome:
▪ ____ of ____ forms ovarian tissue.
▪ ____ ____ forms oviducts (Fallopian tubes),
uterus, cervix, and portions of vagina.
Cortex of ridge; Mullerian duct
____ regions (PARs):
– Present on both ends of ____ chromosome—share homology with regions on ____ chromosome.
– Synapse and recombine with ____ chromosome during meiosis.
Pseudoautosomal; Y; X; X
____ region critical for segregation of X and Y chromosomes during male gametogenesis.
Pairing
____: Male-specific region of Y:
– ____% of Y chromosome which does not recombine with X chromosome.
– Some portions share ____ with genes on X chromosome.
MSY; 95; Homology
____: Sex-determining region Y:
▪ Critical gene controlling sexual development.
▪ Gene becomes active in XY embryos at ____–____ weeks of development.
SRY; 6-8
SRY gene encodes protein ____:
Present in all ____- Causes undifferentiated gonadal tissue of embryo to form ____.
TDF; Mammals; Testes
Females with one X chromosome and one Y chromosome are missing ____ gene.
SRY
TDF believed to be ____ factor: Behaves as ____ switch controlling genes involved in sexual differentiation.
Transcription; Master switch
____ sex ratio: Reflects proportion of males to females conceived in population.
Primary
