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Exam I Review Material
Cell Biology
1.
Know the structure of the generalized cell
2.
Know the structure of the plasma membrane
a.
Phospholipid bilayer
3.
Be able to describe the basic function of cytoplasmic organelles
a.
Mitochondria
b.
Ribosomes
c.
Endoplasmic reticulum
d.
Golgi apparatus
e.
Lysosomes
4.
Know the structure and function of the nucleus
a.
Envelope
b.
Nucleoli
c.
Chromatin
Cell Life Cycle
The cell cycle includes all events from a cell’s formation until it divides.
The cell cycle includes two major periods:
1.
Interphase
2.
Cell division (mitosis)
A.
1.
2.
3.
4.
B.
1.
2.
3.
4.
Interphase: from cell formation until cell division
Metabolic or growth phase: all non-replication activities
Preparation for division
Subphases:
a.
G1: growth phase with little cell division related activites
b.
S: synthetic phase
c.
G2: brief period of growth
DNA replication
Cell Division
Mitosis and cytokinesis
Characteristics of mitosis
a.
Daughter cells (2) are identical to mother cell
b.
No gain or loss of genetic material
c.
Series of continuous events
d.
Lasts about two hours
Phases of mitosis
a.
Prophase
b.
Metaphase
c.
Anaphase
d.
Telophase
Cytokinesis
a.
Daughter cells separate
D.
1.
2.
3.
3.
Meiosis
Gamete production
a.
Two consecutive divisions produce four daughter cells each with half as many
chromosomes as mother cell
Nuclear divisions: Meiosis I and meiosis II
Meiosis I (preceded by interphase where DNA is replicated): Reduction Division
a.
Prophase I
i.
Synapsis: homologous chromosomes form tetrads; crossover points form
(chiasmata)
b.
Metaphase I
c.
Anaphase I
d.
Telophase I
Meiosis II (Like mitosis without DNA replication during interphase)
a.
Four daughter cells are produced each genetically unique from original mother cells
Endocrine System
I. Background:
A.
There are two types of glands:
1.
Endocrine
a.
Ductless
b.
Secrete hormones into surrounding tissue fluid
c.
Vascular or lymphatic drainage receive hormones
d.
Examples of endocrine glands:
i.
Pituitary
ii.
Thyroid
iii.
Parathyroid
iv.
Adrenal
v.
Pineal
vi.
Thymus
2.
Exocrine
a.
Have ducts
b.
Nonhormonal products are directed to membrane surfaces
II.
A.
1.
Hormones—chemical substances secreted by cells into extracellular fluids, that regulate
metabolic function of other cells in the body
Control of hormone release
Typically negative feedback
a.
Hormone secretion is triggered in response to a stimulus
b.
As hormone level increases, target organ is affected
c.
Further hormone release is inhibits
Major Endocrine Organs (Discuss only selected organs)
A.
Pituitary (hypophysis)
1.
General characteristics
a.
Connected to the superiorly lying hypothalamus
i.
Infundibulum—stalk-like connection
ii.
Hypothalamus is part of the brain
iia.
Connection between brain and endocrine system
b. Two major lobes
i.
Posterior
ii.
Anterior
c.
Posterior lobe + infundibulum = neurohypophysis
2.
3.
B.
1.
2.
3.
4.
5.
6.
C.
1.
d.
Anterior lobe (adenohyophysis) is comprised of glandular tissue
e.
Highly vascular
Connections between posterior pituitary and hypothalamus
a.
Posterior is an outgrowth of the brain and maintains its neural connections
b.
Neurons in the supraoptic and paraventricular nuclei of the hypothalamus give rise to
the hypothalamic-hypophyseal tract
i.
Hormones are synthesized in the secretory cells of the hypothalamus
ii.
Oxytocin and antidiuretic hormone
c.
When neurons fire, hormones are released into capillary bed in post. pituitary
Connections between anterior pituitary and hypothalamus
a.
Anterior lobe is derived from epithelial tissue
b.
No direct connection between post. pituitary or hypothalamus
c.
Vascular connection
i.
Hypophyseal portal veins
d.
Releasing and inhibiting hormones secreted by hypothalamus are carried by portal
system to anterior pituitary
i.
Regulate the activity of secretory cells in ant. pituitary
Anterior pituitary hormones
Anterior pituitary is referred to as the Master gland
6 hormones as well as a number of other active molecules
Tropic hormones (4/6)
a.
Regulate secretory activity of other endocrine glands
b.
TSH—thyroid-stimulating hormone
c.
ACTH—adrenocorticotropic hormone
d.
FSH—follicle-stimulating hormone
e.
LH—lutenizing hormone
Other hormones (2/6)
a.
Have neuroendocrine targets
b.
PRL—Prolactin
c.
GH—growth hormone
Gonadotropins: FSH and LH
a.
Regulate gonads
b.
FSH stimulates gamete production
c.
LH promotes production of gonadal hormones
d.
FSH and LH work in concert to cause follicle to mature
i.
LH causes egg to be extruded from follicle
e.
In males, LH stimulates interstitial cells of the testes to produce testosterone
f.
LH and FSH release is controlled by the hypothalamus
i.
GnRH—gonadotropin-releasing hormone
g.
Negative feedback inhibition regulates FSH and LH release
Prolaction
a.
Stimulates milk production
b.
PRH and PIH
i.
Serotonin and dopamine
c.
Levels parallel those of estrogen
Posterior pituitary hormones
Oxytocin
a.
Stimulates smooth muscle contraction
b.
Muscle response depends on number of oxytocin receptors
i.
Uterus and breast
ii.
iii.
2.
D.
1.
2.
3.
4.
Number of receptors increases during pregnancy
Afferent impulses as uterus stretches during pregnancy signals release of
oxytocin during late stages of pregnancy
c.
Hormonal trigger for milk ejection
d.
Positive feedback mechanism
ADH—antidiuretic hormone
a.
Inhibits or prevents urine production
Gonads
Same sex hormones as those produced by adrenal cortex
Ovaries produce estrogens and progesterone
a.
Sexual maturation and menstrual cycle
Testes produce testosterone
a.
Sexual maturation
b.
Sex drive
Release of gonadal hormones is regulated by gonadotropins
Background on Heredity
Individual genes (segments of DNA) contain the blueprints for proteins. These proteins dictate the
synthesis of virtually all the body’s molecules. Most genes do not act independently but instead require
the concerted and often sequential activation of many genes. Most human traits reflect the precisely
timed expression of 10’s if not 100’s of genes.
Terms:
1.
Autosomes—express non-sex-based traits
2.
Sex chromosomes—determine genetic sex
3.
Karyotype—diploid chromosomal compliment of all cells
4.
Genome—genetic (DNA) makeup of a cell
a.
Humans have a diploid genome
i.
One copy from egg (maternal copy)
ii.
One copy from sperm (paternal copy)
4.
Chromosome—structure carrying heredity factors
a.
Only visible during cell division
b.
Humans have 23 diploid chromosome (46 total)
i.
Homologous pairs
c.
Chromosomes include many genes
5.
Locus—location
6.
Allele—matched genes at the same locus on homologous chromosomes
a.
Alleles can code for same or alternate forms of a trait
7.
Homozygous—two genes controlling a single trait are alike
8.
Heterozygous—two genes controlling a single trait are dissimilar
9.
Dominant—one allele masks the expression of its partner
a.
Nomenclature—capital letter (J)
10.
Recessive—the masked allele
a.
Nomenclature—lower case letter (j)
11.
Genotype—an individual’s genetic makeup
a.
Reflects the allelic identity of that individual’s genes
12.
Phenotype—which genes are expressed
A.
1.
Sexual sources of genetic variation—why each one of us is unique
Three sources of variation
a.
b.
c.
B.
1.
3.
4.
5.
C.
1.
2.
3.
4.
Independent assortment of chromosomes
Crossover of homologues
Random fertilization of eggs by sperm
Segregation and independent assortment of chromosomes
Formation of tetrad during Prophase I of meiosis is random
a.
Maternal and paternal chromosomes are randomly distributed to daughter nuclei 2.
Allele pairs are segregated during meiosis
a.
Distributed to different gametes
Alleles on different pairs of homologous chromosomes are assorted independently of each
other
Net result:
a.
Each gamete has a single allele for each trait
b.
Allele represent only one of four possible parental alleles
Number of different gametes resulting from independent assortment
a.
2n, where n is the number of homologous pairs
i.
Human’s: 223 or 8.5 million possibilities
Crossover of homologues and gene recombination
Genes are arranged linearly along a chromosomes length
Genes on the same chromosomes are said to be linked
a.
These genes are transmitted as a single unit during mitosis
During meiosis, paternal chromosomes can precisely exchange gene segments with their
homologous maternal counterparts
a.
This process gives rise to recombinant chromosomes
This is referred to as a crossover or chiasma
D.
1.
Random fertilization
A single human egg will be fertilized by a single sperm
a.
Variation resulting from independent assortment and random fertilization: 8.5 million x
8.5 million or 72 trillion
E.
1.
Types of inheritance
Dominant-recessive inheritance—interaction of dominant and recessive alleles where dominant
trait masks recessive trait
a.
Dominant traits—always expressed
b.
Recessive traits—only expressed as homozygous recessive state
Incomplete dominance (intermediate inheritance)—heterozygote has a phenotype intermediate
between homozygous dominant and homozygous recessive individual
a.
Example: sickle cell amenia
i.
SS—normal RBC shape
ii.
ss—sickle shaped RBC due to substitution of one amino acid residue in ß chain
of hemoglobin
iii.
Ss—resistant to malaria; produces both normal and sickled RBC’s
Multiple allele inheritance
a.
Some genes have more than two forms
i.
We only inherit two alleles for each gene
b.
ABO blood types
Sex-linked inheritance—inherited genes on sex chromosomes
a.
X and Y are not homologous
b.
Y chromosomes contains genes that determine maleness
i.
Y (15 genes) is 1/3 the size of X (2500 genes)
2.
3.
4.
c.
d.
e.
5.
X codes for additional non-sexual characteristics
A gene found only on the X (and not Y) is said to be sex-linked
i.
Inheritance of sex-linked recessive genes cannot be masked by corresponding
gene on Y (i.e., there is no corresponding gene on the Y)
ii.
X-linked are never pasted from father to son (To be a son, must get Y from dad)
Characteristics present only on the Y are pasted onto male offspring and never to female
Polygenetic inheritance—different genes at different locations acting collectively
a.
Qualitative phenotypes varying between two extremes
b.
Skin color:
i.
Three separate genes
ii.
Two allelic forms per gene
iii.
A,a; B, b; C, c
iv.
A, B and C confer dark skin
v.
a, b and c confer pale skin
vi.
AABBCC genotype would be as dark-skinned as a human can be
vii.
aabbcc would be very fair
viii. Heterozygous condition at one or more alleles will result in a range of possible
pigmentations
Spermatogenesis
What is spermatogenesis?
Overview:
1.
Spermatogenesis is the process of producing sperm with half the number of chromosomes
(hapliod) as somatic cells.
a.
The germ cells progress first from the diploid to haploid state and then change shape to
become spermatozoa.
2.
The process of spermatogenesis then allows the recombination of male and female haploid
gametes at fertilization.
3.
This provides genetic contributions from both parents without increasing the number of
chromosomes each generation.
Where does spermatogenesis occur?
1.
Spermatogenesis occurs in medullary sex cords known as seminiferous tubules.
a.
Seminiferous tubules are part of the male gonad or testes.
Cells involved in spermatogenesis.
1.
Sertoli cells-"nurse cells"
a.
Nurse cells provide:
i.
Support for germ cells
ii.
Environment for germ cells to develop and mature
iii.
Substances initiating meiosis or the reduction from diploid to haploid cells
iv.
Hormonal signals effecting pituitary gland control of spermatogenesis
b.
Sertoli cells produce hormones
i.
Estrogen
ii.
Inhibin-suppresses pituitary FSH
2.
Leydig cells
a.
Produce testosterone
b.
Located adjacent to seminiferous tubules.
Spermatogenesis in the Sexually Mature Male
1.
Function of the testes is to produce the male gametes or spermatozoa
a.
This process is termed, spermatogenesis
b.
The site of spermatozoa production is the seminiferous tubules
2.
The spermatozoa originate from precursor cells that are called spermatogonia
a.
These cells line the basement membrane of the seminiferous tubule
3.
Spermatogenesis can be divided into three parts:
a.
Spermatocytogenesis-proliferative phase
b.
Meiosis-production of the haploid gamete
c.
Spermiogenesis
i.
Spermatids mature into spermatozoa (sperm)
4.
The adult male mammal that is a continuous breeder.
a.
Males continue to produce spermatozoa throughout life.
Spermatocytogenesis and Meiosis
1.
Spermatogonia divide
a.
Located near outer surface of seminiferous tubule
b.
Originate at puberty
c.
One or two divisions of spermatogonia occur to maintain their population in a stem cell
pool (type A spermatogonia)
d.
These divisions are mitotic
e.
Spermatogonia proliferate several times and undergo 1 to 5 stages of division and
differentiation
f.
After the last division, the resulting cells are termed primary spermatocytes
2.
The primary spermatocytes then undergo the first of the two divisions that constitute meiosis
a.
The first meiotic division produces two secondary spermatocytes
b.
Division of the secondary spermatocytes completes meiosis and produces the
spermatids
Spermiogenesis: morphological conversion of round spermatid into spermatozoa without a division
1.
This part of spermatogenesis is defined as the nuclear and cytoplasmic changes in the spermatid
that results in the spermatozoa
2.
Events associated with spermiogenesis:
a.
Condensation of nuclear material
b.
Removal of extraneous cytoplasm
c.
Formation of the acrosome
d.
Formation of tail structures
3.
Spermiogenesis ends in the testis with release of the spermatozoa from the Sertoli cell
a.
Throughout spermiogenesis, spermatozoa are embedded Sertoli cells
b.
The process by which spermatozoa are shed into the lumen of the seminiferous tubule
for transport out of the testis is spermiation
What is the overall result of spermatogenesis?
1.
The overall result of spermatogenesis:
a.
Cell proliferation
i.
More cells are produced than originally present
ii.
Each spermatogonia may produce up to 256 spermatozoa per cycle (25 x 4)
b.
Maintenance of a reserve germ cell population
i.
Production of new spermatogonia is faster than maturation of spermatozoa
c.
Haploid gametes are produced
d.
Genetic variability is introduced
i.
Independent assortment during meiosis
e.
ii.
Crossing-over during Prophase I of meiosis
Spermatids mature into spermatozoa
Hormonal Control of Spermatogenesis
1.
Hormones that affect spermatogenesis
a.
Testosterone
i.
Produced by Leydig cells
ii.
Androgen
iii.
Promotes Sertoli cell function
b.
FSH-follicle stimulating hormone
i.
Produced by anterior pituitary
ii.
FSH regulates the mitotic divisions and efficiency of type A spermatogonia
development
iii.
FSH controls entry of stem cell type A spermatogonia into proliferating pool
iv.
The yield of spermatozoa is increased by FSH by preventing the degeneration of
differentiating A type spermatogonia
v.
FSH is necessary during development: required to establish Sertoli cell function
c.
LH-lutenizing hormone
i.
Produced by anterior pituitary
ii.
Increases testesterone production by Leydig cells
d.
GnRH-gonadotropic releasing hormone
i.
Hypothalamic hormone that controls release of anterior pituitary hormones (LH
and FSH)
2.
Once the Sertoli function is developed, testosterone alone will maintain spermatogenesis
a.
The yield of spermatozoa is increased if FSH is present
Gametogenesis: Oogenesis
1.
Know the general processes involved in oogenesis and the cells produced by each process
a.
Proliferation
b.
Differentiation
c.
Growth
d.
Meiosis
2.
Know the general characteristics and genetic makeup of each cell type involved in oogenesis
a.
Oogonia
b.
Primary oocytes
c.
Secondary oocytes
d.
Oocytes
3.
Know where oogenesis occurs and the general characteristics and function of the cells involved
a.
Ovary
b.
Follicles
c.
Corpus luteum
4.
Know how oogenesis is controlled
a.
Neuroendocrine system
i.
GnRH
ii.
FSH
iii.
LH
b.
Ovary
i.
Estrogen
c.
d.
5.
ii.
Progesterone
Uterus
Fertilized egg
i.
hCG
Know the basic anatomy of the female reproductive structures involved in oogenesis
a.
Neuroendocrine system
b.
Ovary
c.
Uterus