Reproduction
The Cell Cycle and Mitosis
Meiosis
The reproductive system
The Cell Cycle
Control of the cell cycle
Mitosis
Meiosis I
Meiosis II
Male reproductive anatomy
Female reproductive anatomy
Sexual development
The menstrual cycle
D: a specific series of phases during which a cell grows synthesizes DNA and divides - dearrangement can lead to unchecked cell division and maybe responsible for formation of cancer.
Four stages: G1, S, G2, M
Interphase: the first 3 stages, spends the longest time here
When not dividing the cell spends time at G0 which is an offshoot of G1 - it is just living and serving its function
individual chromosomes are not visible under light microscopy - lless condensed form know as chromatin - the DNA has to be available for RNA polymerase so that genes can be transcribed
During mitosis -DNA are tightly coild to avoid losing of genetic material
G1 - Presynthetic gap
Create organelles for energy and protein production (mitochondria, ribosomes, endoplasmic reticulum)
Increase their size
Restriction point - governs passage to the next stage (S-synthesis)
Criteria 1: containing the proper complement of DNA
S - Synthesis of DNA
Cell replicates its genetic mtrl so that each daughter cell will have identical copies
After replication - chromosome consists of two identical chromatids, bound together in a specialized region known as centromere
Humans at this stage still have 46 chromosomes, eventhough 92 chromatids are present
Note: each chromatid is composed of a complete double stranded molecule of DNA - sister chromatids are identical copies of each other. Chromosome maybe used to refer to a single chromatid before S phase or the pair of chromatids attached at the centromere after S phase
G2 - Postsynthetic gap
The cell passes through another check
DNA has already been replicated
Cell checks to make sure there are enough organells and cytoplasm to divide between the two daughter cells
The cell checks that DNA replication proceeded correctly to avoid passing on an error to daughter cells
M- Mitosis
Mitosis and cytokinesis happen at the same time
Mitosis
prophase, metaphas, anaphase and telophase
Cytokinesis
splitting cytoplasm and organelles into two daugther cells
Note: autosomal cells are said to be diploid (2n) - means they contain two copies of each chromosome, haploids (n) only contain one copy of each chromosome
Note: autosomal cells - division results in two genetically identical daughter cells, in germ cells, the daughter cells are not equivalent
Check point 1
Check point 2
Cyclin- cyclin dependent kinases (CDK)
Cancer
Tumors
Metastasis
G1/S point where the goal is to make sure that the DNA is not damaged and is ready to be replicated - main protein in control of this is known as p53.
G2/M check point - make sure that the cell has acheived adequate size and the organelles to support the daughter cells - p53 does play a role in this again
CDK will be only activated when it is matched with the right cyclin - the pairing creates a CDK-cyclin complex which then phosphorylate transcription factors
Transcription factor - promote transcription of fenes required for the next stage of the cell cycle
When the cell cycle control becomes deranged, damaged cells go under mitosis and this may lead to cancer
Most common mutation - is mutation of a gene that produces p53. It is called TP53. This causes the cell production to not stop when the cell is damaged --
when the cell is being produced without a regard for damanged cell
when the cell produces factors such as proteases that can digest basement membrane or factors that encourage blood vessel formation the damanged cell travels to other parts of body -- this can lead to spread of cancer
Cancer causing genes
oncogenes - genes that when mutated, actively promote cell division
tumor suppressor genes - genes that when mutated, lose their ability to regulate or pause the cell cyle
Occurs in somatic cells - cells that are not active in sexual reproduction
Prophase
Metaphase
Anaphase
Telophase
Chromatin condenses into chromosomes
Centriole pairs separate and move toward opposite poles of the cell
They are located outside of the nucleus in a region known as centrosome
F: correct division of DNA
Once centriole pairs move towards the opposite sides of the cell they form spindle fibers (they are made of microtubules)
they are one of the two microtible organizing centers
other microtuble organizing center: basal body of flagellum or cilum
some microtubles form asters - that anchor the centrioles to the cell membrane
others extend toward the middle of the cell
Nuclear membrane dissolves during prophase -- allowing these spindle fibers to contact the chromosomes
Nucleoli become less distinct and may disappear completely
Kinetochores appear at the centromere
kintetochore are protein structures located on the centromere
F: attachement point for specific fibers of the spindle appratus (kinetochore fibers)
Align chromosomes at the metaphase plate (equatorial plate) - equidistant between the two poles of the cell
the kinetochore fibers interact with the fibers of the spindle appparatus to align the chromosomes
sister chromatids separate and each of them have its own centromere -
this happens by shortening o f the kinetochore fibers
Reverse of prophase
Spindle appratus disappears
Nuclear membrane reforms around each set of chromosomes
Nucleoli reapprear
Chromosomes uncoil, resuming the interphase form
Cytokinesis happens at the end of telophase
Cells go through 20-50 division before a programmed death
Meiosis occurs in gametocytes (germ cells)
results in upto four nonidentical sex cells (gametes)
Homologous chromosomes being separated - genetic haploid daughter cells - reductional division
Meiosis is involved in one round of replication and TWO rounds of division
separation of sister chromotids, equational divison
homologous pairs of chromosomes are separated from each other . Homologues are chromosomes that are given the same number, but are of opposite paternal origin
Prophase I - same as prophase of mitosis, except that homologues come together and intertwine in a process called synampsis
Tetrad - the four chromatids after there is synapsis
crossing over - when genetic material is exchanged from one chromatid with material from a chromatid in the homologous chromosome
Mendel's second law of independent assortment - inheritance of one allele has no effect on the likelihood of inheriting certain alleles for other genes
Metaphase I - homologous chromosomes line up on opposite side of the metaphase plate
Anaphase I - homologous chromosomes are segregated to opposite poles of the cell. This accounts for Mendel's first law of segregation
This is called disjunction - each chromosome of paternal origin disjoins from the homologue of maternal origin and either chromosome can end up in either daughter cell - thus the distribution of homologous chromosomes to the two intermediate daughter cells is random with respect to parental origin.
Telophase I - the chromosomes may or may not fully decondense, and the cell may enter interkinesis (rest period during which chromosomes partially uncoil) after cytokinesis
sister chromatids are separated in a process that is functionally the same as mitosis
sister chromatids - copies of same DNA held together at centromere
homologous choromosomes - related chromosomes of opposite parental origin (one parental chromosome, one maternal chromosome)
Teste
Seminiferous tubles
Interstitial cells (of Leydig)
F: Sperm is produced here and they are nourished by sertoli cells
F: secrete testostrone and other male sex hormones (androgens)
Located in the scrotum - the external pouch that hangs below the penis and maintains temp 2-4 degree lower than body
Sperm pathway
Produced in seminiferous tubles
passed to epididynis where their flagella gains motility
During ejaculation the sperm passes through vas deferens
and then to the ejaculatory ducts at the posterior edge of prostate gland
two ejaculatory ducts fuse to form the urethra
What mixes with sperm?
seminal fluid
produced by seminal vesicles, prostate gland and bulbourethral gland
Seminal vesicles contribute fructose to nourish sperm and give fluid slightly alkaline properties (helps with survival in acidic female body environmnet)
prostate gland - give fluid mildly alkaline properties as well
bulbourethral glands produce a clear viscous fluid that cleans out any remnants of urine and lubricates the urethra during sexual arousal
combination of sperm and seminal fluid >>> semen
Spermatagenesis
Formation of haploid sperm through meiosis - occurs in seminiferous tubules
Diploid stem cell - spermatogonia
After duplicating their genetic material (S stage) they develop into primary spermatocytes
Meiosis I >>> secondary spermatocytes
Meiosis II >>> spermatids
Spermatogenisis results in four functional sperm for each spermatogonium
Sperm
Head
Contains the genetic material
Midpieace
Filled with mitochondria and it generates the ATP from fructose so that it can swim through the female body
Flagellum
For motility
Sperm head is covered by acrosome - good for penetration of ovum
Derived from the Golgi apparatus