Term
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Definition
| a single individual is the sole parent and passs copies of all its genes to its offspring without the fusion of gametes |
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Term
| define sexual reproduction |
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Definition
| two parents give rise to offspring that have unique combinations of genes inherited from the two parents |
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Definition
| genetically identical to parent becase the offspring are derived by mitosis in the parent |
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Term
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Definition
| asexual reproduction in plants |
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Term
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Definition
| asexual reproduction in which an egg develops without being fertilized |
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Term
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Definition
| an individual who has both male and female reproductive systems |
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Term
| The cons of Sexual Reproduction |
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Definition
1. Asexual reproduction has a numerical advantage. Sexual
reproduction numerical disadvantage.
2. Sex is anatomically and physiologically complex- sexual species -
one genome - two anatomies which must match (bits have to fit
other bits) etc! - Co-evolution of both sexes.
3. Evolution of sexual behaviour: desire to have sex, how to have
sex, who or what to have sex with, how to convince them to have
sex with you, how to find them, when to have sex, who or what
NOT to have sex with.
4. Cellular complexity – Gametes, meiosis (special cell division);
fertilisation; sperm from one organism needs to find egg from
another etc. |
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Term
| Pros of Sexual Reproduction |
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Definition
1) More genetic variety, recombination of alleles, new combinations of genotype
2) More adaptation to environment hence species lives longer
3) |
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Term
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Definition
| A phylogenetic tree or evolutionary tree is a branching diagram or "tree" showing the inferred evolutionary relationships among various biological species or other entities based upon similarities and differences in their physical and/or genetic characteristics. The taxa joined together in the tree are implied to have descended from a common ancestor. |
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Term
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Definition
Panama disease is a plant disease that attacks the roots of banana plants. It is a type of Fusarium wilt, caused by the fungus Fusarium oxysporum.
In the 1950s, Panama disease wiped out the Gros Michel banana, the dominant cultivar of bananas |
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Term
| Why pathogens evolve so quickly than host? |
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Definition
1) Very simple genetic makeup
2) Short generation time
3) Ample opportunity for mutation |
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Term
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Definition
Gonorrhea : 1960's penicilin killed it off, now 1/4 are resistant to at least one antibiotic
Southeast Asia, 98% are resistant to penicilin |
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Term
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Definition
| evolutionary hypothesis which proposes that organisms must constantly adapt, evolve, and proliferate not merely to gain reproductive advantage, but also simply to survive while pitted against ever-evolving opposing organisms in an ever-changing environment. |
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Term
| 2 Examples of Environmental Sex Determination: |
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Definition
Blue head Wrasse:
sequential hermaphrodite, they live in groups with usually a male, When the male dies or is
removed, the largest female
in the group turns into a
male and produces sperm
within one week.
2) Temperature at nest site that depends upon their position on the beach, whether directly under the sun or partially can alter sex ratios of hatchlings
Lower temp = more females
higher temp = more males |
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Term
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Definition
Crickets : XX = female XO=male
Birds : Gametes from mother determine sex ZW= female and ZZ=male
bees : haploid = male and diploid = female |
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Term
| How was the SRY gene that controls sex determination identified? |
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Definition
The human SRY gene
was identified by searching for conserved sequences among
translocated Y chromosomal DNA from four XX male patients
(Sinclair et al., 1990). The presence of a similar gene, Sry, on the
mouse Y chromosome was consistent with this gene having a sexdetermining function (Gubbay et al., 1990). The role of Sry as the
switch gene for mammalian sex determination was confirmed in
experiments in which XX mice were converted to males by the
introduction of Sry (Koopman et al., 1991). |
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Term
| What does the SRY gene encode for and how does it work? |
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Definition
Logically, SRY activity must also directly or indirectly suppress the
female sex-determining pathway, which would otherwise continue
to be active, as it is in XX genital ridges. Differentiating Sertoli
cells then assemble into testis cords (tubular structures that contain
the germ cells; see Glossary, Box 1) (Fig. 2). The Sertoli cells then
stimulate the sex-specific development of germ cells, androgenproducing Leydig cells (see Glossary, Box 1), testis vascular cells
and other interstitial (i.e. non-cord) cell types. The formation of
testes is the hallmark of male sex determination.
In conclusion, SRY works by triggering a regulatory cascade – of other genes and their encoded proteins. |
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Term
| SRY encodes a class of proteins called the "Transcription Factor" |
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Definition
| This intronless gene encodes a transcription factor that is a member of the SOX (SRY-like box) gene family of DNA-binding proteins. This protein is the therian testis determining factor (TDF), referred to as the sex-determining region Y protein or SRY protein which initiates male sex determination. |
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Term
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Definition
| A gonad in an embryo that has not differentiated into a definitive testis or ovary. |
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Term
| Indifferent Gonad Components: |
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Definition
Mesonephros - embryonic
kidney – (distinct from adult
kidney).
Metanephric kidney –
persists as adult kidney.
Ureter – also in adult.
Mesonephros contributes
ducts to male and female
reproductive organs.
Gonads
Wolffian ducts
Műllerian ducts
Cloaca: a single posterior opening.
In mammals embryonic cloaca divides to create anus and different components of male and female urogenital systems. |
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Term
| How do Indifferent Gonads become different Sexes (SRY protein / sex hormones) |
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Definition
1. SRY – some somatic gonad cells differentiate into Sertoli cells.
2. Sertoli cells secrete Anti-Mullerian Hormone (AMH).
3. AMH promotes Leydig cell differentiation in gonad.
4. Leydig cells produce testosterone.
5. Testosterone promotes the male phenotype.
6. No SRY – default outcome is female.
7. Ovaries made and estradiol synthesised |
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Term
| The Key differences between Spermatogenesis and oogenesis |
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Definition
Step Wise:
1) Oogonium -- Spermatogonium
2) Meiosis I (Prophase)
3) Primary Oocyte -- Primary Spermatocyte
4) Meiosis I complete
5) Secondary Oocyte (1n) + polar body -- Secondary Spermatocyte (1n x2)
6) Meiosis II
7) Ovum + Entry of Sperm + polar body --- Spermatid (1n x 4)
8) Differentiation -> Spermatids into Sperm Cells (Spermatozoa ) under Sertoli Cells |
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Term
| Relate the detailed structure of the testis and ovaries to spermatogenesis and oogenesis |
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Definition
Spermatogenesis: Occurs in the Seminiferous tubule inside the testis with sertoli cells. Once mature they are released into the lumen into the epididymis.
Oogenesis occurs in the ovary, with a oocyte in a follicle then into a mature follicle, at ovulation the oocyte is release and the broken follice turns into a Corpus Luteum. Then degenerates.
page 1052 |
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Term
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Definition
(Acrosome which is an organelle that has hydrolytic enzymes, nucleus ) = head
neck , mitochondria = midpiece
tail (flagella funcion) |
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Term
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Definition
| Occurs in female tract as sperm swims to the oocyte out of the seminal fluid into the female tract secretions. There the acrosome membrane fuses with the sperm cell membrane ready to interact with the |
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Term
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Definition
| an egg that has been fertilized by two or more sperms |
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Term
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Definition
| 2-step recognition process. A) a molecule in Zona Pellucida (Jelly coat) binds to sperm receptor –acrosome reaction. B) sperm protein binds receptor in egg membrane. The cells then fuse and cortical granules fuse to plasma membrane. |
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Term
| How is Polyspermy avoided? |
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Definition
| The enzymes in the acrosome reaction react with the egg plasma membrane receptors induce the fusion of cortical granules with the plasma membrane. This toughens the vitelline layer into a fertilization envelope, not allowing other sperms to enter. |
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Term
| Placenta structure / functions |
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Definition
| disk shaped organ, containing both embryonic and maternal blood vessels. Fuction is to provide immune support, respiration, transport nutrients, and dispose of waste by the embryo/fetus. |
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Term
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Definition
1) Hypothalamus releases GnRH (gonadotropin-releasing hormone)
2) GnRH stimulates the Anterior Pituitary to secrete small amounts of FSH and LH
3) Follicle Stimulating Hormone (FSH)and LH stimulate Follicle growth in ovary
4) The Follicle starts to make Estradiol (Estrogen)
**All this called the Follicular Phase, when the Follicle keeps growing and the Oocyte matures with Estradiol slowly rising level ** Also, during Follicular Growth, the low levels Estradiol inhibits FSH and LH by the Pituitary
5) Estradiol secretion by Follicle rises to peak and FSH and LH levels increase again, this results in the Follicle to mature
6) The mature follicle ruptures near the surface of ovary releasing the Secondary Oocyte
7) Luteal Phase- LH stimulate the Follicle to turn into a Corpus Luteum, secreting estradiol and progesterone
8) Corpus Luteum degenerates and stay inside ovary if fertilization occurs |
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Term
| The Uterine (Menstrual) Cycle |
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Definition
1) During the Follicular phase of the ovarian cycle, the rise in estradiol causes the endometrium lining to thicken
2) After ovulation(egg leaves follicle), estradiol and progesterone by the Corpus Luteum stimulate the enlargement of the endometrium so it can sustain an embryo if fertilization occurs
3) Once Corpus Luteum Degenerates, the rapid drop in ovarian hormone levels cause the arteries in endometrium to constrict and desintegrate releasing blood that is shed with endometrial tissue
4) A new *Menstrual Flow Phase * begins with new follicle development |
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Term
| hormonal regulatory loop in males |
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Definition
Hypothalamus secretes GnRH --> Anterior Pituitary secretes FSH and LH
* FSH stimulates Sertoli Cells --> Spermatogenesis + Inhibin(communicates to Anterior Pituitary)
*LH stimulates Leydig Cells --> testosterone helps Spermatogenesis and also communicates with Anterior Pituitary |
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