Lesson 11 - Embryonic Development and Heredity Flashcards
embryonic development: day 0 (2)
zygote
how is the zygote formed?
sperm and egg nuclei fusion
embryonic development: day 3
morula
embryonic development: days 4-6
blastocyst
the zygote divides without growth to form small cells called _____
blastomeres
morula
when zygotic division reaches 32 cells
blastocyst
hollowed out morula
the inner cell mass of a blastocyst forms the…
embryonic body
the outer layer of the blastocyst forms the _____ layer
trophoblast
the blastocyst also forms the _____ and part of the fetal _____
chorion, placenta
implantation
blastocyst attaches to uterine wall
embryonic development: day 7 (3)
- blastocyst implants
- trophoblast secretes enzyme to erode uterine mucosa to expose vascular network
- chorionic villi from trophoblast and uterine tissue will form placenta
as the implanted blastocyst grows, three embryonic layers form
- amnion
- yolk sac
- allantois
amnion
encases embryo in fluid-filled chamber
what is the function of the amnion?
protects against trauma, temp, and adhesion from rapid embryonic growth
yolk sac (2)
(1) forms the embryo’s first blood cells and (2) primordial germ cells here migrate to embryo body to form become germ cells in gonadal tissue
allantois
helps from umbilical cord
embryonic development: day 14
the uterine mucosa envelops the embryo
what stage is the embryo in at day 14?
gastrula
gastrula
three primary germ layers are present and begin to differentiate for the next 6 weeks
the uterine mucosa that envelops the embryo is called?
decidua capsularis
what is the uterine wall beneath the inner cell mass of the embryo called?
decidua basalis
three embryonic layers
- endoderm
- ectoderm
- mesoderm
the endoderm forms the… (2)
- mucosa of digestive system
- mucosa of respiratory system and their associated glands
the ectoderm forms the (2)
skin and nervous system
the mesoderm forms…(5)
- everything in between
- skeleton
- skeletal muscles
- walls of digestive organs
- urinary and circulatory system
when is the embryo referred to as a fetus?
week 9
what is the major focus of development at week 9?
fetal growth and tissue/organ specialization/growth
gene
unit/area on DNA that contains hereditary info
alleles
genetic info coding for the same traits found on each pair on homologous chromosomes
homozygous trait
both alleles express the same info
heterozygous trait
one allele is dominant, while the other allele is recessive
recessive
masked by the expression of the dominant allele
dominant gene
requires one copy of the gene for the expression
recessive gene
requires both alleles to contain the gene for expression
genotype
an individual’s genetic makeup
phenotype
the physical appearance of the genes
four main types of inheritance
- dominant/recessive inheritance
- incomplete dominance
- sexlinked inheritance
- codominance
dominant-recessive inheritance/mendelian genetics (3)
- dominant alleles are expressed
- recessive alleles are expressed only when they are homozygous
- genotype and phenotype determined using Punnett square
examples of dominant/recessive traits (3)
- D: regular skin/hair/eyes R: albinism
- D: dwarfism R: regular height
- D: heterochromia R: both eyes same color
dwarfism is technically called…
achondroplasia
incomplete dominance
heterozygous alleles yield phenotype different than from homozygous dominant phenotype
Many genetic medical disorders that appear to be dominant-recessive are actually better described as being having what kind of dominance?
incomplete dominance
explain the difference between having sickle cell anemia and the sickle cell trait
- sickle cell anemia: have two copies of the recessive allele and produce 100% irregular blood cells
- sickle cell trait: has one copy of the recessive allele and makes 50% normal and 50% irregular
sex-linked inheritance
inheritance of genes from the X (23rd) chromosome
the X chromosome contains genes that determine….(3)
- color vision
- blood clotting
- baldness
autosomes
all of the chromosomes except the sex chromosomes
why is the X chromosome unique?
it is the only chromosome of which you only require one copy
the Y chromosome has very few genes, including…(2)
- production of testosterone during fetal development
- adolescent maturity in males
-Y in an embryo results in…
failed pregnancy
Interestingly, having extra copies of X in females and extra Ys in males…
does not appear to cause nay physiological problems for people
X- results in…
Turners syndrome
XXY results in…
Klinefelters syndrome
XXX and XYY result in…
normal physiology
hemophilia
blood clotting disorder
hemophilia: Xh-Y results in…
a hemophiliac
hemophilia: Xh-X results in…
a carrier of hemophilia
hemophilia: Xh-Xh results in
a hemophiliac
co-dominance
all alleles are expressed in the phenotype
what is the best example of co-dominance?
A and B blood groups
what is the only thing that can be used reliably to assign parentage?
a genetic paternity test
_____ _____ occur all the time and can alter the expected genotype
random mutations
______ _____ can alter the appearance of the expected phenotype from a genotype
masking genes
Label A-C
A: zygote (fertilized egg)
B: 4-cell stage (day 2)
C: morula (a solid ball of blastomeres on day 3)
Label D and D1
D: early blastocyst
D1: implanting blastocyst
early blastocyst (4)
- morula hollows out
- fills with fluid
- hatches from the zona pellucida
- 4 days
implanting blastocyst (2)
- consists of a sphere of trophoblast cells and an eccentric cell cluster called the inner cell mass
- 7 days
Label E-G
E: ovary
F: ovulation
G: oocyte (egg)
Label H-J
H: fertilization
I: uterine tube
J: sperm
Label K-N
K: blastocyst cavity
L: inner cell mass
M: blastocyst cavity
N: trophoblast
Label O-Q
O: uterus
P: endometrium
Q: cavity of uterus
Label A-C
A: endometrium
B: amniotic cavity
C: endometrial epithelium
Label D-F
D: chorion being formed
E: chorionic villus
F: chorion
Label G-I
G: amnion
H: yolk sac
I: lumen of uterus
Label J-L
J: amniotic cavity
K: primary germ layers
L: ectoderm
Label M-O
M: mesoderm
N: endoderm
O: forming umbilical cord
Label P-R
P: allantois
Q: decidua basalis
R: maternal blood
Label S-U
S: chorionic villus
T: umbilical blood vessels in umbilical cord
U: amnion
Label V-X
V: yolk sac
W: chorion
X: decidua capsularis
Label A-C
A: placenta
B: decidua basalis
C: chorionic villi
Label D-F
D: yolk sac
E: amnion
F: amniotic cavity
Label G-I
G: umbilical cord
H: uterus
I: decidua capsularis
Label J-L
J: chorionic villus containing fetal capillaries
K: fetal arteriole
L: fetal venule
Label M-O
M: amnion
N: umbilical cord
O: myometrium
Label P-R
P: stratum basalis of endometrium
Q: maternal portion of placenta (decidua basalis)
R: fetal portion of placenta (chorion)
Label S and T
S: umbilical arteries
T: umbilical vein
