Killer notes! I'm stoked I can finally just pay attention in class!!!
Control of Gene Expression in Eukaryotes
● Differential Genes Expression: considering why we see RNA in certain ways and how genes are expressed
○ Central Dogma: DNA > RNA>mRNA> protein
■ replication: DNA makes more DNA
■ transcription: DNA make RNA
■ translation: mRNA makes protein
Principles of Development
What are the five essential developmental processes?
● Cell Proliferation
● Programmed Cell Death
● Move and Change Shape
● Cell Differentiation
● CellCell Interactions
What is the effect of cell proliferation and death on development?
● Cell Proliferation: divide and replicate
○ replication is highly regulated: controlled by mitosis promoting factor
○ uncontrolled cell replication: leads to tumors and cancer
○ without it, humans would remain a single cell
○ have to maintain a high amount of undifferentiated cells to replace other such as blood, skin, immune and gut.
When is cell movement important?
● Gastrulation: the cells are rearranged into the correct places (forms different tissue layers) ● Highly migratory cells:
○ Gametes, nerve cells, blood cells, and pigment cells We also discuss several other topics like What are considered the best practices or legal codes, classifies crime according to the victim of the crime such as?
What is cellular differentiation?
● Cells are able to go through a process to become specialized
● Animal cells: most of the time (99%) cells that are already differentiated cannot undifferentiate itself to become another type of specialized cell
What are cellcell interactions?
● cells produces signals to other cells, which are critical for the early stages of development ● one cell may produce a protein that will not affect that cell, but it will affect the cells around it. ○ cells receive signals at the membrane and then processes it
What is differential gene expression?
● all cells have the same genes but different types of cells express different genes What is nuclear transfer?
● Also known as cloning, is a process of taking a nucleus from a differentiated cell and placing it into an enucleated egg cell to produce an offspring identical to the nucleus donor. How do nuclear transfer experiments demonstrate the genetic information is the same in every cell in the body? If you want to learn more check out What if you leave out an important category?
● Cloning provides evidence that a differentiated cell has to have all of the genes of an undifferentiated cell
What is a clone? If you want to learn more check out When did certain things occur?
● A clone is an exact replica (genetic replica) of an parent and offspring.
What is the most important level of control of gene expression?
● Transcriptional control: DNA to RNA, transcription factors decide which genes are being transcribed, in transplantation the rate of translation is effected, and in post translational modification protein folding.
What are the main body axes?
● Anterior (head) and Posterior (Tail) We also discuss several other topics like How do you identify secondary amines?
● Right and Left from point of view of organism
● Dorsal (back) and Ventral (Belly)
Why is it important to know “where” in the body a cell is?
● It is important for a cell to know its location it will know what to differentiate it into. This sets up the axis.
○ Example: A cell in the anterior region needs to know it will look like the head of an organism. Don't forget about the age old question of What is done on a given job and what should be done on that job?
● Cells have to “know” where they are development organized by signals cells send and receive; these; cells send and receive transcription factors that tell which specific genes to turn on and off What is a master regulator?
● Master Regulator: gives a cell precise coordinates where it is located in the embryo What is the difference between a zygotic effect and a maternal effect gene?
● Zygotic effect: any genes expressed in early embryo (its own genotype determine its own phenotype)
● Maternal Effect Inheritance: mother’s genotype determines offspring’s phenotype. What is the difference between in situ hybridization and antibody staining?
● In situ hybridization pinpoints the location of specific RNA
● Antibody staining to look to see where a protein is and where the gene is actually working (or being expressed) or testing for presence of a gene
How does bicoid work?
● Concentration gradient: cells will get information based on how concentrated the bicoid is in its vicinity
○ high concentration: high levels of transcription
○ medium concentration: medium levels of transcription
○ low concentration: low levels of transcription Don't forget about the age old question of Who created the swan neck flask?
Where are the segmentation genes expressed and what do their mutants look like? ● Segment: small region in the body
○ contains distinct structures and repeated down the link
● Gap Genes: Organize cells into groups of segments along anteriorposterior axis. ○ A mutant will be missing groups of segments.
● Pair Rule Genes: Expressed in every other segment.
○ A mutant will be missing alternate segments, therefore missing half of segments. ● Segment Polarity Genes:expressed in a section of every segment, giving every segment an anteriorposterior axis.
○ Mutant will be missing parts of every segment (shorter), impaired anterior posterior polarity
What are homeotic genes?
● Homeotic Genes: One phenotyped structure replaces another structure; trigger development of structures
○ Example: Fruit Flies found with legs in place of antenna.
Introduction to Animal Development
general life cycle of animals.
● 1. Gametogenesis
● 2. Fertilization
● 3. Cleavage
● 4. Gastrulation
● 5. Organogenesis
What are the different parts of sperm and why are they important for successful fertilization? ● Head: Nucleus (genetic information) that is given to egg later on.
● Neck: Centriole (mitosis)
● Mid Piece : Mitochondria (movement/energy)
● Tail : Flagellum propeller; push sperm to egg
What are the major differences between eggs and sperm?
● An egg after undergoing meiosis II will produce 4 haploid cells, one of which will be the egg and the other three will be the polar bodies. The cell that becomes the egg has more cytoplasm, protein, and mRNA than the polar bodies. Sperm on the other hand will produce four haploid cells which are equivalent to each other.
What are the different parts of eggs and why are each important for fertilization? ● Jelly Layer: provides protection in sea urchin (zona pellucida in humans)
● Vitelline Envelope: connected to plasma membrane
● Plasma Membrane: contains yolk, nucleus and cortical granules that contain enzymes. Fertilization:
How do sperm fertilize eggs?
● The sperm will penetrate the egg and release its nucleus in order to fuse their membrane. As the nuclei come together, the chromosomes line up which will allow cell division.
How do eggs and sperm of the same species recognize one another?
● Organisms have species specific receptors called bindin.
What is polyspermy and why is it detrimental? How can polyspermy be prevented? ● Polyspermy: egg is fertilized by more than one sperm
● It is detrimental because it can result in an zygote with one or more copies of the chromosome thus making unviable
● Polyspermy prevention: a Ca2+ based signal is induced; influx of water die due to osmosis which causes the vitelline envelop matris to lift away from the cell and form a fertilization envelope. Cleavage:
What is cleavage?
● Cleavage is the first step in embryogenesis, where rapid cell division occurs. NO CELL GROWTH. Each cell is called a blastomere, and a the end of cleavage we have a blastula. What is a blastomere?
● A cell during cleavage. At the end of cleavage we have a mass of blastomeres called blastula. What are the differences between radial, spiral, discoidal, and superficial cleavage? ● Radial: Cells divide at right angles.
● Spiral: Cells divide at oblique angles
● Discoidal: Cells divide on top
● Superficial:Cell division of mitosis is not followed by cytokinesis.
What does gastrulation result in?
● Gastrulation occurs right after cleavage in which pattern formation and the germ layers develop. The cells move into their correct positions.
what types of adult tissues come from which germ layer?
● Ectoderm: gives rise to the outer layer (nervous system, epidermis of skin, epithelial lining of mouth and rectum, cornea and lens of eye)
● Mesoderm: gives rise to the muscle, most internal organs, connective tissues such as bone and cartilage (skeletal system, circulatory system, lymphatic system, muscular system, excretory system, reproductive system, dermis of skin, lining of body cavity)
● Endoderm: gives rise to the interior (digestive tract, respiratory tract, reproductive tract, urinary tract, liver, pancreas, thyroid, parathyroid, thymus)
What is organogenesis?
● It is the process in which tissue and organ formation begins.
What is the notochord?
● It is a key organizing element which sends signals to the ectoderm, telling it to fold. How does the neural tube form?
● 1. Notochord form
● 2. Notochord signals ectoderm to fold
● 3. Neuraltube formation is complete
● 4. Somites form
● acts as a major signaling center (which sends out signals to tell the ectoderm cells to fold up) What are somites?
● Found on either side of the neural tube. It gives rise to muscle on the back, connective tissue in skin, limbs, and bone.
● blocks of mesoderm tissues
Asexual and sexual reproduction:
What differs between asexual and sexual reproduction?
● A sexual reprodction requires one parent in which the offspring is identical. Sexual reproduction involves two parents in which the offspring is the result of egg and sperm fusing.
What are the different types of asexual reproduction?
● Budding: Begin growing on parent until it breaks off
● Fission: Organism splits into two
● Parthenogenesis: Female will develop from an unfertilized egg.
Can organisms switch between asexual and sexual reproduction? How?
● Yes, organisms can switch throughout the year depending or favorable and unfavorable environments. This is mostly seen with Parthenogenesis, where a female can produce off springs from unfertilized eggs.
Why would this be beneficial?
● Asexual: only one organism is necessary for reproduction; happens fast and quickly ● Sexual: organisms can adapt and acquire new traits die to genetic variability (since individuals are not genetically identical, there is a variety of traits change in environments, individuals have more traits that can help them survive in a different environment)
Describe gametogenesis in male and female mammals.
● Spermatogenesis: process by which sperm are made [occurs continuously throughout male’s life] ○ 1. In the male gonad, diploid cells (spermatogonia) divide by mitosis to generate the cells that undergo meiosis (2n)
○ 2. Spermatogonia divide by mitosis to produce primary spermatocytes (2n)
○ 3. Primary spermatocytes undergo meiosis I to produce secondary spermatocytes (2n) ○ 4. Secondary spermatocytes undergo meiosis II; result is four haploid cells called spermatids. (n)
○ 5. Each spermatids matures into a sperm (n)
● Oogenesis: process by which eggs are made [occurs before birth of humans] ○ 1. Diploid cells called oogonia divide by mitosis to form primary oocytes
○ 2. When these cells undergo meiosis, only one of the four haploid products, known as an ovum, matures into an egg
○ 3. The other cells do not mature into eggs which are called polar bodies
Fertilization and Egg Development:
What is the major difference between external and internal fertilization?
● External fertilization occurs when sperm and egg meet outside the body while internal occurs when sperm enters the body to meet the egg.
What is sperm competition?
● Sperm Competition occurs when a female mates twice where in most cases the female will choose the second male’s sperm over the primary.
Describe several unusual mating behaviors.
● Female spiders will often eat the head of the male after copulating.
● Penis will break off in female to form a plug and prevent second male.
● Some flies can produce giant sperms in which they will clog up the female and prevent second male.
● Hermaphrodites will shoot love darts into their partner.
What is the difference between oviparity, viviparity, and ovoviviparity?
● Oviparity: Lay Eggs
● Viviparity: Live Birth, nutrients from mother’s circulatory system
● Ovoviviparity: Offspring receives nutrients from yolk, hatches within the body but released as live birth.