Da Cell Flashcards
How do Prokaryotic cells divide?
Binary Fission.
What are homologs?
Chromosome pairs, these may carry different alleles of the same gene.
What is the interphase of Mitosis, what are it’s parts.
The interphase is the biggest phase of cellular life during which the cell functions and grows and prepares for replication.
G1, S, G2
What is interphase G1
G1 is the first phase and this is where the cell grows and synthesizes enzymes and proteins necessary to replicate DNA. The cell will either then go into phase S or G0 ( Where it will not divide, this can be temporary or permanent.)
What is interphase S
S phase is after G1 and is when the cell is committed to divide but must duplicate it’s chromosomes before mitosis, the chromosomes will now have duplicate sister chromatids.
What is the G1/S checkpoint.
A check point before entering cell division that ensure the cell has all enzymes and proteins for replication of DNA.
What is G2
G2 is after S phase has some more chemical components prepping for cell division.
What is the G2/M Checkpoint
This check point ensures all the DNA has been duplicated without any errors or damage.
What is the M phase?
The M phase is the Cell Division phase and incudes all of Mitosis.
What are the stages of mitosis in order?
Prophase, Pro-metaphase, Metaphase, Anaphase, Telophase, Cytokinesis.
PPMATC.
Prophase?
Chromosome condense and the mitotic spindle forms.
What is the mitotic spindle?
Forms in Prophase and is an array of microtubules that move the chromosomes. In animal cells these form from the centrosomes which split at opposite ends of the cell.
Prometaphase?
Disintegration of the nuclear membrane, spindle microtubules enter the nuclear region and attach to the sides of the kinetochore on the chromosome, this is two tubules per kinetochore, or one per sister chromatid. This is called Bi-Orientation.
Metaphase?
The chromosomes will arrange in a single file line at the center metaphase plate and the microtubules begin to have tension on the kinetochores.
What is the spindle assembly checkpoint?
Occurs during metaphase and ensures each chromosome is aligned on the metaphase plate, and Bi-orientation is achieved and tension is required to pass this checkpoint.
Anaphase?
This is when the Sister Chromatids split.
Telophase
Marked by when the sister chromatids meet at opposite ends of the cell at the spindle poles. The nuclear membrane will reform, one at each end, around these now chromosomes. The chromosomes then relax.
Cytokinesis
This is when the cytoplasm splits (cell wall forms in plant cells) and the cell officially divides into two genetically identical daughter cells, however they may not be identical in cytoplasm/ organelle content.
Name two points of Mitosis
Produces two genetically identical daughter cells.
Asexual cell type.
Name three points on Sexual reproduction
Combines genetic material from parents for variable offspring.
Uses Meiosis
Fertilization: two haploid gametes forming a Diploid Zygote.
What kind of cells are formed from meiosis?
Genetically variable haploid gametes.
What are some things in common between meiosis and mitosis?
They both have interphase G1, S, G2. Where the DNA is duplicated and goes through the same checkpoints.
Prophase 1 Meiosis
Chromosomes (2 chromatids) condense, form homologous pairs, synapses form, recombination happens and centromeres start to move away from each other but remain attached at chiasmata. nuclear membrane breaks down and spindle fibers start to appear.
What are Homologous pairs of chromosomes?
Chromosomes that are the same shape, size and have genes at the same locus’s. One is generally from each parent.
After this the nuclear membranes disintegrate.
Metaphase 1 Meiosis
The homologous chromosome pairs align in the center of the cell (no specific oder to which side each chromosome is on creates independent variation.) and spindle fibers begin to attach to the kinetochore of the chromosome on it’s corresponding side.
What are the Five Stages of Prophase 1 Meiosis?
Leptotene: Chromosomes Condense.
Zygotene: Continue to condense and start synapsis, each of these pairs is bivalent or tetrad.
Pachytene: Chromosome becomes shorter and thicker and form a synaptonemal complex and then recombinate.
Diplotene: The synapse complex breaks down and the centromeres of the pairs will move apart but remain attached at the now formed chiasmata where cross overs occurred.
Diakinesis: Chromosomes finish condensing , the nuclear membrane disintegrates, and spindles start to form.
What is the synaptonemal complex?
A protein complex that forms “Railroad track-like fibers” between homologous chromosomes and is thought to assist in recombination.
Anaphase 1 Meiosis
Spindle fibers pull apart the homologous chromosomes to each pole of the cell. (The sister chromatids remain attached.)
Telophase 1 Meiosis
When the chromosomes (sister chromatids attached.) reach the poles on each side of the cell. The cytokinesis then occurs.
What is Interkinesis?
The period between Meiosis 1 and 2 where The nuclear membrane reforms, spindle disappears, and chromosome relax.
Prophase 2 Meiosis?
The chromosome re-condense, nuclear membrane disintegrates and the spindle reforms.
Do all cells go through interkinesis?
No, in some cells the chromosomes will remain condensed, no nuclear membrane reformation, still have spindles and go right from cytokinesis into metaphase 2 meiosis.
Metaphase 2 Meiosis?
The chromosome single file line up at the center metaphase plate and the spindle fibers attach at the kinetochore.
Anaphase 2 Meiosis?
The sister chromatids are pulled apart towards the poles of the cell.
Telophase
The Chromosomes (sister chromatids.) reach the poles of the cell. The nuclear membrane reforms, the chromosomes relax and cytokinesis occurs.
What is the protein cohesin responsible for?
Cohesin is responsible for holding together the sister chromatids along their entire length during mitosis and meiosis. Additionally in meiosis Cohesin holds the homologous chromosomes together at the chiasmata.
What is the protein shugosin responsible for?
Shugosin means “guardian spirit in japanese” it guards the cohesin from separase at the centromere keeping sister chromatids together during meiosis 1 and degrades after.
What does separase do?
breaks down cohesin causing separation of the homologous chromosomes (shugosin) in anaphase 1 and then separation of chromatids in anaphase 2.
It also breaks down cohesin in mitosis anaphase so the sister chromatids separate.
What is non disjunction of meiosis?
A problem with chromosome separation that occurs during metaphase 1 and/ or 2 and will affect the number of chromosomes in the daughter cells.
How many sperm are produced from meiosis in mammals?
4 this is called spermatogenesis.
how many ovum are produced from meiosis in mammals?
1
How does oogenesis occur?
Oogonium enter prophase 1 and become primary oocytes they will stay at this stage until puberty start becoming secondary oocytes (this can span 30-40 yrs) after finishing meiosis 1 there will be a secondary oocyte and a polar body. The oocyte will stay at this stage until fertilization, and then will complete meiosis 2 producing an ovum and a second polar body. The new ovum will then fuse with the sperm and form a zygote.
What are the four points of Cell Theory?
- All living organisms are made of cells.
- The cell is the fundamental unit of structure and function in living organisms.
- All cells are essentially the same in chemical composition.
- All cells come from other cells.
Are viruses Alive?
No! They cannot reproduce on their own.
They also don’t have growth.
DNA to RNA?
Transcription!!!
RNA to Protein?
Translation!!
What molecule was likely not present on earth at first?
When was it produced?
Primitive earth likely lacked O2 and started with anaerobic organisms. It wasn’t until photosynthesis that earth became abundant in O2 primarily from cyanobacteria.
What were the three processes of early earth allowing for production of organic molecules?
- Heat (sun)
- Electric Discharge (lightning)
- Cooling System (Molecules to liquid form.)
What four molecules were produced by “Early Earth Experiments”
- Aldehydes
- Simple Acids (ammonium NH4+)
- Complex Acids (amino acids)
- Long Hydrocarbon Chains. (Fatty Acids.)
After organic molecules were produced by the earths atmosphere what likely came next?
Abiotic Earth self replicating macromolecules. RNA world hypothesis. Discovered certain RNA could self replicate.
RNA molecule that can also act as an enzyme (usually folded in some way.)
Ribozyme.
What are three activities of ribozymes?
- RNA splicing
- Ligation
- Polymerization.
What is a ribosome composed of?
rRNA and rProteins.
What are the types and functions of RNA?
mRNA- Messenger transcribed RNA that leaves the nucleus with code for proteins.
tRNA- Transfers amino acids to ribosome during translation.
rRNA- Ribosomal RNA, main component of ribosome. in combination with proteins forms large and small sub units that build polypeptide chains.
What ribozyme is part of the large ribosomal subunit and assists in forming peptide bonds?
peptidyl transferase.
how might ribozymes interact with other RNA molecules?
Ribozymes can cleave RNA (if mRNA, this stops production of that protein.)
Ribozymes can also base pair, and this allows for cleavage at specific sites of the substrate.
How did DNA come about?
Hypothesis: Some RNA can self replicate using ribozymes. These RNA’s eventually became able to produce proteins. DNA is more stable than RNA but requires many proteins to replicate.
What limits the size of cells? excluding frog eggs.
The size of a cell requires more membrane to be produced per unit of volume.
Three characteristics of smaller cells in relation to larger cells.
- Smaller cells can interact with surroundings more efficiently.
- Smaller cells lose more heart/ energy to surroundings.
- Smaller cells have higher metabolic rate.
Three things prokaryotes lack?
- Cytoskeleton
- Nuclear envelope
- Membrane bound organelles
Distinguishing feature of eukaryotes?
Nuclear envelope.
What happens when two monosaccharides go through a condensation RXN?
Dehydration reaction, will combine the monosaccharides and have H2O by product, builds a Disaccharide bonded via Glycosidic (covalent) bond.
Amino Acid.
In the body a (+) on the Amine (NH2) and a (-) on the Carboxylic Acid (COOH)
The R-group Defines the type of amino acid.
The carbon the R-group is attached to is the alpha carbon.
How are amino acids bonded?
Through (covalent) peptide bonds, usually formed via condensation (Dehydration).
The blue is by product H20
The Carbon will attach to the Nitrogen.
This creates a Carbon nitrogen backbone with a C and N terminus. (N-C-C)
Name and why special?
Cysteine, non-polar. The H-S
What is exon shuffling?
Usually occurs during a crossing over event where an exon is involved and can lead to new functions of proteins once made into mRNA. Since introns are removed the crossing over does not have to be precise, more likely to occur when there are longer introns involved.
