2c - B/BC

epithelium function

covers the body surface and lines body cavities

mesoderm

middle germ layer; develops into muscles, and much of the circulatory, reproductive, and excretory systems and connective tissue

endoderm

the inner germ layer that develops into the lining of the digestive and respiratory systems and internal organs such as the stomach, colon, liver, pancreas, urinary bladder, epithelial parts of the trachea, the lungs, pharynx, thyroid, parathyroid, and intestines

p53

tumor suppressor gene halts the cell cycle and recruits enzymes to repair damaged DNA; if DNA cannot be repaired, p53 triggers apoptosis to prevent duplication.

embryonic development

zygote --> embryo --> morula (solid ball of cells) --> blastula (hollow ball) gastrulation: after implantation, forms the 3 germ layers (ectoderm, mesoderm, endoderm)

paracrine vs endocrine vs autocrine vs direct signaling

-Paracrine signals act on cells in the local area. -Endocrine signals involve secreted hormones that travel through the bloodstream to a distant target tissue. -Autocrine signals act on the same cell that secreted the signal in the first place. -Direct signaling can occur by transferring signaling molecules across gap junctions between neighboring cells. *The main difference between the different categories of signaling is the distance that the signal travels through the organism to reach the target cell.

stem cell

A stem cell is an unspecialized cell that can divide without limit as needed and can, under specific conditions, differentiate into specialized cells.

neural crest

The first sign of the nervous system is the appearance of a thin strip of cells called the neural plate. The inner portion of the neural plate gives rise to the central nervous system (CNS), while the outer part becomes the peripheral nervous system (PNS). As development proceeds, the future CNS appears as a cylindrical structure called the neural tube. In contrast, the future PNS appears as two strips of tissue called the neural crest, running lengthwise above the neural tube. The sequence of stages from neural plate to neural tube and neural crest is known as neurulation.

G1

The first stage of interphase is the G1 phase (first gap), the growing phase. All cells undergo G1. Here, the cell is quite active at the biochemical level. The cell grows and accumulates the building blocks of chromosomal DNA and the associated proteins as well as sufficient energy reserves to complete the task of replicating each chromosome in the nucleus. Cells increase in size and produce organelles.

pluripotency

The pluripotency of a stem cell is the ability of a stem cell to develop into more than one mature cell or tissue type, but it cannot form an organism.

sperm vs. ovum contribution to the next generation

Sperm only contributes to DNA (the egg actively destroys sperm mitochondria) while egg contributes to the production of DNA, mitochondria, organelles and epigenetic inheritance.

sperm vs. ovum formation

Spermatogonium renews its population by mitosis throughout life while oogonium stops renewing its population sometime before birth. During meiosis, the primary and secondary oocytes arrest in prophase I and metaphase II, respectively, while primary and secondary spermatocytes directly go through meiotic cell division to produce haploid cells. Between the secondary spermatocyte and the sperm, there's the spermatid. After secondary oocyte, ovum develops.

spindles

Spindles are microtubule fibers that arrange and move chromosomes. It is necessary to equally divide the chromosomes in a parental cell into two daughter cells during mitosis. Spindle fibers are also called the mitotic spindle.

epigenetics

Studies the same genotype that can be expressed in different ways. For instance, even if identical twins share the same genetic information, there remains an incredible number of variability in how gene expression can unfold throughout each twin's life

M checkpoint

The M checkpoint determines whether all the sister chromatids are attached to the spindle microtubules.

centromere

The centromere is a region of highly specialized chromatin. Without it, the cells cannot divide properly, and the overall process of mitosis fails. Its primary function is to provide the foundation for the assembly of the kinetochore, which is a patch of protein structure essential to proper chromosomal segregation. In addition to their kinetochore-related function, centromeres perform another essential role in mitosis by serving as the sites of sister chromatid attachment. For accurate mitoses, sister chromatids must remain connected until the spindle checkpoint permits.

anaphase

Cohesin proteins that bind the sister chromatids break down Chromosomes pull toward opposite poles The non-kinetochore spindle fibers from one pole also push on the other pole, which causes elongation

Mechanisms of chromosome movement

Changes in microtubule length provide the mechanism for chromosome movement: In the first part of anaphase, the kinetochore microtubules shorten and draw the chromosomes toward the spindle poles. In the second part, the astral microtubules, which anchor to the cell membrane, pull the poles further apart.

telophase

Chromosomes arrive at opposite poles and begin to condense Nuclear envelope material surrounds each set of chromosomes Mitotic spindle breaks down

prophase

Chromosomes condense into chromatids Centromere connects each chromatid to its copy Nuclear envelope begins to disintegrate Mitotic spindles begin to assemble Centriole pairs move toward opposite poles

oogenesis

As with sperm production, oogenesis starts with a germ cell, called an oogonium -The cell starting meiosis is called a primary oocyte This cell will begin the first meiotic division, but be arrested in its progress in the prophase I stage. -At adolescence, anterior pituitary hormones cause the development of several follicles in an ovary. This results in the primary oocyte finishing the first meiotic division. *The cell divides unequally, with most of the cellular material and organelles going to one cell, called a secondary oocyte, and only one set of chromosomes and a small amount of cytoplasm going to the other cell. This second cell is called a polar body and usually dies. A secondary meiotic arrest occurs, this time at the metaphase II stage. At ovulation, this secondary oocyte will be released and travel toward the uterus through the oviduct. Summary: oogonium --> primary oocyte --(meiosis I)--> secondary oocyte + first polar body --(meiosis II)--> ootid + second polar body

asters

Asters are star-shaped radial arrays that form around each pair of centrioles. Aster guides the chromosome to ensure that each daughter cell has the right complement chromosome. It helps to organize and position spindle apparatus during mitosis and also determines the site of cleavage furrow that splits the dividing cell in half during cytokinesis.

When does the cell decide if it wants to grow?

Between G1 and S phase, the cell decides if it wants to grow. Some cells that do not divide include bone cells and blood cells (they do not undergo mitosis). These cells do not go through S or G2. They stop at G1 or G0.

G0

Cells in the G0 phase are not actively preparing to divide. The cell is in a quiescent (inactive) stage that occurs when cells exit the cell cycle. Some cells enter G0 temporarily until an external signal triggers the onset of G1. No more DNA replication or cell division happens at this phase. The cells that never or rarely divide include mature cardiac muscle and nerve cells, and they remain in G0 permanently.

centrioles

Centrioles are the main centers that help in the formation of microtubule fiber, which makes up the spindles. Without centrioles, there are no spindles that assist the movement of the chromosome.

Rb

Dephosphorylated Rb binds to E2F, which halts the cell cycle; when the cell grows, Rb is phosphorylated and releases E2F, which advances the cell cycle.

kinetochore

During anaphase, several microtubules appear to insert into the kinetochore which situates on the side of the chromosome facing the spindle pole to which the chromosome attaches. The purpose of the kinetochore is to pull the chromatids apart. Kinetochore microtubules: connect centromere to centrosomes/centrioles. Kinetochores also help during cell division by making sure that each new cell has one chromatid from each pair. Their shortening pulls sister chromatids apart

Neurulation

Following gastrulation, the neurulation process develops the neural tube in the ectoderm, above the notochord of the mesoderm. The ectoderm gives rise to the nervous system by folding into a neural tube.

G1 Checkpoint

G1 --> S checks for cell size, nutrients, growth factors and DNA damage

G2 checkpoint

G2 --> M The cell checks to make sure the DNA is copied correctly

G2

In the G2 phase, the cell replenishes its energy stores and synthesizes proteins necessary for chromosome manipulation. Here, the cell has double the DNA and again increases in size. Some cell organelles are duplicated, and the cytoskeleton is dismantled to provide resources for the mitotic phase. There may be additional cell growth during G2.

What are some reasons a cell could enter G0?

M phase due to mutation/damage Contact inhibition (crowding) Lack of food

spermatogenesis

Meiosis begins with a cell called a primary spermatocyte. At the end of the first meiotic division, a haploid cell called a secondary spermatocyte is produced. This haploid cell must go through another meiotic cell division. When the spermatid (cell produced at the end of meiosis) reaches the lumen of the tubule and grows a flagellum (or "tail"), it is called a sperm cell. Four sperms result from each primary spermatocyte that goes through meiosis.

metaphase

Mitotic spindle fully developed Chromosomes line up in the middle of the cell Centromeres attach to the spindle fibers originating at opposite poles

p21

Production of p21 is triggered by p53; p21 prevents the cycle by binding to and inhibiting the activity of the Cdk/cyclin complex.

proto-oncogenes

Proto-oncogenes normally regulate cell division but can be changed into oncogenes through mutation, which may cause cancers to form. Proto-oncogenes positively regulate the cell cycle, whereas oncogenes disrupt normal cell division and cause cancers to form.

Range of reaction

Range of reaction asserts that our genes set the boundaries within which we can operate, and our environment interacts with the genes to determine where in that range we will fall.

Negative regulator molecules of the cell cycle

Rb, p53, and p21 act primarily at the G1 checkpoint and prevent the cell from moving forward to division until damaged DNA is repaired.

when can gene regulation in development occur?

Regulation may occur when: the DNA is uncoiled and loosened from nucleosomes to bind transcription factors (epigenetics); the RNA is transcribed (transcriptional level); the RNA is processed and exported to the cytoplasm after it is transcribed (post-transcriptional level); the RNA is translated into protein (translational level); or after the protein has been made (post-translational level).

Senescence

Senescence is the failure of cells to divide due to shortened telomeres that result in aging.

cytokinesis

Separation of the cytoplasm into 2 new daughter cells Animal cells divide when proteins pinch in the center of the cell until it separates into 2 (cleavage furrow) Plant cells divide when new cell wall components lay down in the center of the cell (cell plate)

S phase

The synthesis phase of interphase takes the longest because of the complexity of the duplicated genetic material. The S phase is where DNA replication occurs, and centrioles replicate. The two centrosomes give rise to the mitotic spindle, the apparatus that orchestrates the movement of chromosomes during mitosis. At the center of each animal cell, the centrosomes of animal cells associate with a pair of rod-like objects, the centrioles, which are at right angles to each other.

Tumor suppressor genes

Tumor suppressor genes are segments of DNA that code for negative regulator proteins, which keep the cell from undergoing uncontrolled division. One of the most important tumor suppressors is tumor protein p53, which plays a vital role in the cellular response to DNA damage. The role of normal p53 is to monitor DNA and the supply of oxygen (hypoxia is a condition of reduced oxygen supply). If damage is detected, p53 triggers repair mechanisms. If repairs are unsuccessful, p53 signals apoptosis. A cell with an abnormal p53 protein cannot repair damaged DNA and thus cannot signal apoptosis.

determination vs differentiation

determination - commitment differentiation - final realization of that commitment ex. determined to become neural cell, differentiates into a neuron or neuroganglia

Where does fertilization of the ovum typically happen?

fallopian tubes

ectoderm

outermost germ layer; produces sense organs, nerves, and outer layer of skin

cell migration

prokaryotic --> flagella or cilia eukaryotic --> involve drastic changes in cell shape, which are driven by the cytoskeleton, motor proteins, blebbing, and cytoplasmic displacement neural crest cells --> form at the edge of the neural folds during neurulation and then migrate throughout the body to form many different structures

Nervous tissue function

provides a means of rapid internal communication by transmitting electrical impulses

cyclins and cyclin-dependent kinases (Cdks)

responsible for promoting the cell cycle Cyclins regulate the cell cycle only when they are bound to Cdks. To be activated, the Cdk/cyclin complex must be phosphorylated, which allows it to phosphorylate other proteins that advance the cell cycle.

connective tissue function

supports and protects body organs