Chapter Four: Sex Chromosomes Flashcards
Walter sutton studied meiosis in ___
grasshoppers
cells in the testes that will eventually go through meiosis to become sperm are maintained by ___
mitosis
two types of sperm formed after meiosis
half have X and have have Y
type of ehh formed after meiosis
all have X
does an XX chromosome always indicate a female for every animal
no
what did Sutton conclude about X and Y chromosomes
they are sex chromosomes that determine sex
children receive a ___ chromosome from their mother and a ___ chromosome from their father
X
X or Y
there is approximately a ___ ratio of females:males
1:1
the primary determinant of maleness is a single gene called ___
SRY (sex determining region of Y)
___ helped provide evidence implicating that the SRY gene determines male gender
sex reversal (XX males and XY females)
SRY is ___ in XX males
SRY is ___ in XY females
present
nonfunctional
human sex chromosomes also contain genes that are ___
unrelated to sex
the end regions of sex chromosomes that contain genes which enable sex chromosomes to pair during meiosis one
pseudoautosomal regions (PARs)
in Drosophila (flies), the ___ determines gender
ratio of X chromosomes to autosomes, number of sex chromosomes
in humans, the ___ determines gender
presence or absence of a Y chromosome
why can humans tolerate extra X chromosomes
extra X chromosomes become nonfunctional in an XX female anyway, so the extra X chromosomes also become nonfunctional; may cause some issues but the individual is still viable
what is the nonfunctional X chromosome called
Barr body
complete absence of an X chromosome is ___ for humans and flies
deadly
effect of additional Y chromosomes in humans or flies
has little effect
the Y chromosome in flies does not determine ___, but it is necessary for ___. an XO male is ___
maleness
male fertility
sterile
sex with two different kinds of gametes (XY)
heterogametic
sex with one type of gamete (XX)
homogametic
in some species (lizards and turtles), sex is determined by ___, specifically ___
environment
temperature
specialized diploid cells set aside during embryogenesis that will eventually form gametes
germ line
gamete formation
gametogenesis
in humans, oogenesis produces ___ from each ___
one ovum
primary oocyte
in humans, spermatogenesis produces ___ from each ___
four sperm
primary spermatocyte
diploid germ cells in ovaries of female embryos
oogonia
oogonia divide via ___ to become ___ and arrest in prophase one before entering meiosis one
mitosis
primary oocytes
after puberty, one primary oocyte per month resumes meiosis at ___
ovulation
completion of meiosis one in oogenesis produces ___ and ___
a large secondary oocyte
small first polar body
secondary oocyte arrests in ___
metaphase of meiosis two
at ___, meiosis two is completed to produce ___ and ___
fertilization
mature ovum
second polar body
polar bodies ___
disintegrate
long meiotic arrest may contribute to ___
chromosome segregation errors
there are about ___ eggs in females, and they release about ___ in their lifetime
300,000-400,000
300-400
diploid germ cells found only in testes
spermatogonia
spermatogonia divide via ___ to form ___
mitosis
primary spermatocytes
after puberty, ___ begins to form sperm
maturation
primary spermatocytes undergo meiosis one to produce ___
two haploid secondary spermatocytes
secondary spermatocytes undergo meiosis two to produce ___
two spermatids
spermatids mature into ___
sperm
___ of X and Y sperm are produced
equal numbers
spermatogenesis occurs throughout ___ of males
adult life
entire process of spermatogenesis takes about ___
48-60 days
___ of sperm produced over a male lifetime
billions
why is it not smart for males to reproduce later in life
the occurrence of chromosome anomalies increases with age
the wild type allele for flies is denoted with ___
superscript +
the recessive mutant allele for flies is denoted with ___
lowercase letter
gene symbol for white eye genes in flies is ___, for red eye gene is ___
w
w+
a dominant mutant allele for flies is denoted with ___
uppercase letter
gene symbol for normal eye in flies is ___, for abnormal eyes is ___
Bar+
Bar
the drosophila white eye gene is located on the ___
X chromosome
when daughters inherit the phenotype of their father and sons inherit the phenotype of their mother
crisscross inheritance
crisscross inheritance occurs with ___ traits
X linked recessive
because males only have one X chromosome, they have ___ as females with two X chromosomes
half the number of alleles
reduced allele number due to sex-linkage and possession of a single sex chromosome rather than heterozygosity of autosomal alleles
hemizygosity
a ___ mutation led to 1/2000 male progeny of flies of white females having red eyes
nondisjunction
successfully predicting the movement of chromosomes based on phenotypes in drosophila provided compelling evidence that ___
specific genes exist and are transmitted via specific chromosomes
chromosome theory explains that mutations can be heritable is they occur ___
in germ cell lines
red-green colorblindness is inherited as ___ trait
X linked recessive
x linked recessive traits never pass from ___
father to son
daughters of affected males of a x linked recessive trait are ___, ___ of those daughters son’s will inherit the trait
carriers
1/2
an x linked dominant trait is seen ___
in every generation
a male affected with an x linked dominant trait will produce ___ daughters and ___ sons
affected
unaffected
y linked traits show up in ___
only males
hemophilia is a ___ triat
x linked recessive
the first in a family tree to demonstrate a trait
proban
hypophosphatemia is a ___ trait
x linked dominant
in the early female embryo, each cell independently inactivates ___
one X chromosome (could be from mom or dad in each cell)
___ in females arises from this independent inactivation of an X chromosome
mosaicism
affect a structure or process found in only one sex
sex-limited traits
appear in both sexes but hormonal differences may cause difference between the sexes
sex-influenced traits
