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Human Develop. Ch 21

Human Development and Genetics

Gestation the period from fertilization of the egg (zygote) until birth
when one of the millions of sperm joins the egg to combine DNA and form a zygote fertilization
occurs in the fallopian tube fertilization
a change or maturation of the sperm that takes place as it is swimming through the uterus and fallopian tubes Capacitation
becomes more fragile acrosome
acrosome the tip of the head of a sperm cell
allows acrosome to burst and digest the egg membrane
once a sperm enters the egg the membrane changes to block another ___________ from entering sperm
Nuclei fuse restoring the diploid number
22 pairs of autosomes
23 from mom
23 from dad
#23 is called the sex chromesomes
xx females
males xy
cleavage mitotic dividing of the zygote
consist of 16 cells morula
the point when the mass becomes hollow blastocyst
blastocoele hollow space filled with fluid
trophoblast outer cell mass layer of cells
what is the inner cell mass of the blastocyst inner cell mass
implantation bonding of zygote to the uterine wall 5-8 days after fertilization
this has four stages implantation
endometrium produces carbohydrates
surface proteins on the blastocyst combine with the carbohydrates
trophoblast secretes enzymes
trophoblast secretes enzymes that digest the surface of the endometrium
blastocyst sinks into the crater (placenta)
chorion embryonic membrane that forms the fetal portion of the placenta
chorion originates as the trophoblast
inner mass embryonic stem cells
all DNA can or cannot be expressed can
200 kinds of cells at birth
embryo developing human from implantation to 8th week
plate of cells within the blastocyst embryonic disc
germ layers ectoderm, mesoderm, and endoderm
outer germ layer is ectoderm
ectoderm consist of epidermis and its derivatives, nervous system, lens, cornea, internal ear
middle germ layer is mesoderm
mesoderm consist of dermis, bone, cartilage, muscle, kidneys, and blood
inner germ layer is endoderm
endoderm consist of GI mucosa, respiratory mucosa, liver, thyroid and pancreas
distinguished from the embryo at 20 days embryonic membranes
gives rise to the first blood cells and sex stem cells yolk sac
yolk sac becomes part of the umbilical cord
thin membrane that surrounds the embryo (amniotic sac) amnion
amnion contains amniotic fluid
amniotic fluid contains urine, sloughed off cells
sampling of amniotic fluid amniocentesis
what the trophoblast is called as it develops chorion
chorionic villi projections from the chorion into the endometrium that become the fetal part of the placenta
embryo takes form with head and limbs and beating heart 4-5 weeks
8 week organ system established
this happens 9th until 40th week fetal growth
maternal (endometrium) and fetal (chorion) tissue structure that separates fetal and maternal blood placenta
placenta is formed by the 12th week
placenta is a 7 inch diameter flat disc
produces hormones to maintain pregnancy placenta
hCG human chorionic gonadotropin
hCG is produced by chorion of embryo
hCG stimulates corpus luteum to secrete estrogen and progesterone
corpus luteum to secrete estrogen and progesterone to prevent uterine contractions
produced by uterus within a few weeks progesterone and estrogen
progesterone and estrogen prepare mammary glands
inhibits FSH and LH and further ovarian follicle development estrogen and progesterone
inhibits uterine contractions relaxin
permits stretching of pubic symphysis and ligaments
chorionic villi project into maternal blood sinuses
placenta birthed after the fetus after birth
connects fetus to placenta umbilical cord
umbilical cord transfers blood back and forth
2 arteries away from fetus
1 vein towards fetus
labor sequence of events that occur during birth
there are three stages of labor
dilation and effacement of the cervix
usually 8-12 hours, mucus plug released, amniotic sac breaks, dilation and effacement of the cervix first stage
caesarion section surgical removal of fetus
head up breech
oxytocin from posterior pituitary increases uterine contractions
delivery of the infant second stage
third stage delivery of the placenta
as soon as birth occurs the fetus is called an infant
chemo receptors stimulates medulla which starts respiration
breathing promotes pulmonary circulation which closes the foramen ovale
may occur as liver immaturity does not excrete bilirubin well jaundice
study of inheritance genetics
hereditary material DNA
double helix double strand of nucleotides twisted together
A, T, G, C double helix
sequence of A, T, G, C determines the genetic code
genome the entire code
gene the genetic code for one protein
each amino acid comes from a triplet of 3 bases called a codon
protein synthesis occurs in the ribosome
messenger RNA (mRNA) a mirror image of DNA made in nucleus
genetics chromosomes and genes
mRNA leaves the nucleus and attaches to a ribosome
mRNA-> protein (via tRNA) translation
anticodon transfer RNA (tRNA) attaches to the mRNA at a site called
anticodon complimentary to the codon
tRNA picks up the correspomding______ and forms peptide bonds to make a protien amino acids
DNA-> mRNA-> tRNA-> protein
if a gene's information is used for something such as making a protein it is said to be expressed
genotype the actual physical genetic makeup
the sequence of bases on the DNA
phenotype the appearance of how the alleles are expressed
the genotype determines the phenotype
alleles the 2 or more possibilities for the expression of a pair of genes
both alleles are the same homozygous
heterozygous the 2 alleles are different
dominant vs. recessive genes only matter in heterozygous alleles
the gene that is expressed of the 2 dominant
recessive the gene that is not expressed
must be homozygous recessive to be expressed
a diagram to illustrate how genes are expressed Punnett square
Punnett square dominant gene is capitalized
simplified eye color, sickle cell anemia dominant recessive
multiple alleles more than 2 alleles possible
mom type O, dad type AB 50% chance of A or B 0% chance of O
4 types O=OO AB=AB A=AA or AO B=BB or BO
sex linked traits X linked
recessive, but always expressed in ______ because there is no dominant gene to suppress its _________ males, expression
only expressed in females if homozygous recessive
heterozygous female carrier
most traits are not this simple as they are results of multiple genes
environmental factors are also important in determining phenotype
human genome project every gene has been mapped
diseases that are a result of malfunctioning DNA genetic disease
Created by: tiffanyheffernon



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