Development and Heredity :: these notes are a guide, refer to your text book for specifics.

I. Development :: Involves mitosis and Meiosis I, II in the process of gametogenesis, gamete formation.

1. Spermatogenesis

2. Oogenesis

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A. Gestation :: period of development, in humans lasting 280 days.

B. Period of the Egg --> Embryo ::

1. Fertilization :

occurs in the ampulla of the uterine tube and forms a zygote

2. Cleavage :: mitotic divisions of the zygote to create blastomeres (daughter cells)

a. when blastomere # = 16 --> MORULA

b. Blastocyst ==> will have a fluid filled hollow space called the Blastocele and the blastomeres will align into two regions :

1) Trophoblasts will form a single layer of cells that create the outer part of the sphere.

FXN: will provide food and eventually form the fetal portion of the placenta

2) Inner cell mass : cluster of cells that will form the embryo

3. Implantation ::

These cells are called syncytial trophoblasts.

A second group of trophoblasts called cellular trophoblasts will secrete

 HCG (Human Chorionic Gonadotropin Hormone) that will cause the corpus luteum to continue to produce progesterone, until the chorion of the embryo takes over.

              The inner cell mass will separate from the trophoblasts to create the amniotic cavity

4. Placentation :: formation of the placenta

Chorion formation from trophoblast will develop finger-like chorionic villi and be associated with the endometrium of the uterus to help form the placenta.

Fxn of placenta -> nutrition, respiration, excretion

      endocrine ( HCG, progesterone, estrogen, and relaxin)

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II. Embryonic Development ::

A. Embryonic Membranes

B. Germ Layers :: Primitive Tissues -->

Formation by GASTRULATION, into three tissues

C. Fetal Circulation ::

1. Umbilical Artery --> blood flow to the placenta return to the mother

2. Umbilical Vein --> blood return from the placenta from the mother to the fetus

3. Vascular Structures that create shunts ::

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III. Gestation :: prenatal development, divided into 3, 3 month sections each called a Trimester

Organogenesis :: organ formation -->

starts in the first trimester, continues development in the second trimester and systems become functional by the third trimester.

Maternal Changes with Pregnancy :

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IV. Labor Stages ::

a. dilation --> from labor onset to fully dilated cervix: 10cm

contractions start weakly, then incr. in force and frequency.

This is the longest of the labor stage

b. Expulsion --> childbirth

from fully dilated cervix to delivery of infant

crowning ... distention of the vulva by the infants head

c. Placental --> the placenta detaches from the uterine wall

due to contractions of the uterus and the change in

blood supply (constricted) to the placenta.

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HEREDITY ::

Genes --> DNA segments, the blueprints for protein synthesis and therefore enzymes

for chemical reactions

23 pairs of Homologous chromosomes :

Chromosomes are paired :: two genes, 1 from each parent

these genes are matched on the same locus on the homologous

chromosomes and are called ALLELES

Alleles are various forms of 1 gene that code for the same or alternate traits

     1. If two alleles controlling a trait are alike then called HOMOZYGOUS

     2. If two alleles controlling a trait are different, than called HETEROZYGOUS

     3. If an allele masks or suppresses the other allele, then it is DOMINANT, and represented by a capital letter

     4. The allele that is masked is RECESSIVE, &  is represented by a lower case letter

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Genotype :: genetic makeup

Phenotype :: the way the genotype is expressed, visible traits

Inheritance ::

1. Dominant-Recessive --> the interaction between dominant and recessive traits.

 Can be determined by a Punnett Square that is used to figure out the possible combinations of genes for a single trait,
and can also be used to predict the probability of that trait for the offspring.

Examples of dominant/recessive ...

See text or lab book for more traits

2. Incomplete Dominance --> the heterozygous genotype has a phenotype between homozygous dominant & homozygous recessive.

 Example :: sickle cell anemia

Ss has normal RBC and sickle RBC

3. Multiple Allele --> CoDominant, both alleles are expressed if present.  Example :: ABO blood group -->

Ia and Ib :: see lab book, or biology lab book

4. Sex-Linked --> inherent traits determined by genes on the sex chromosomes.

 Can be X-linked, or Y-linked

Examples :: hemophilia, colorblindness, baldness

5. Polygene --> phenotype depends on several genes

            Examples :: pigmentation of skin and iris

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Genetic Screening :: done on newborns to detect anatomical defects and PKU

Fetal Testing :: Routinely done on pregnant women over 35 yrs old and when suspecting a genetic  disorder

Cells are checked for chromosome abnormalities

Human Genome Project :

mapping of individual chromosomes---> banding patterns

Useful for detecting genetic disorders and cancers