Test 2 (chp 9-15) Flashcards
Mitosis
A process of nuclear division in eukaryotic cells conventionally divided into five stages: prophase, prometaphase, metaphase,anaphase, and telophase. Mitosis conserves chromosome number by allocating replicated chromosomes equally to each of the daughter nuclei.
Meiosis
A modified type of cell division in sexually reproducing organisms consisting of two rounds of cell division but only one round of DNA replication. It results in cells with half the number of chromosome sets as the original cell.
DNA replication
The process by which a DNA molecule is copied; also called DNA synthesis.
Protein synthesis
The process by which amino acids are linearly arranged into proteins through the involvement of ribosomal RNA, transfer RNA, messenger RNA, and various enzymes during transcription and translation to link together into polypeptide chains.
Operons
A unit of genetic function found in bacteria and phages, consisting of a promoter, an operator, and a coordinately regulated cluster of genes whose products function in a common pathway.
Cell cycle
interphase prophase pro metaphase metaphase anaphase telophase cytokinesis
Interphase
Can be divided into the G1 phase (“first gap”) where the cell grows, the S phase (“synthesis”) where the cell continues to grow and copies its chromosomes, and the G2 phase (second gap”) where the cell grows more as it completes preparations for cell division.
During all three subphases, a cell that will eventually divide grows by producing proteins and cytoplasmic organelles such as mitochondria and endoplasmic reticulum.
G0 phase is a nondividing stage the cell goes in when the cell does not receive the go-ahead signal.
Prophase:
The mitotic spindle forms from the centrioles in the centrosome area starting to create spindle fibers made out of microtubules
Chromosomes start to coil and condense
Prometaphase:
Nuclear envelope disappears
Nucleolus disappears
Centrosomes are on opposite poles of the cells
Spindle fibers attach to the sister chromatids
Metaphase:
The sister chromatids line up on the metaphase plate (invisible line in the center of the cell)
Anaphase:
Sister chromatids are pulled apart towards opposite ends of the cell using the shortening of the spindle fibers
The cell is starting to elongate
Telophase:
(opposite of prophase)
Nuclear envelope returns
Nucleolus returns
Spindle fibers are broken down
Cytokinesis:
Dividing of the cytoplasm to form two new cells
Cleavage furrow in animal cell
Golgi apparatus puts down vesicles that build the plate in plant cell
Make sure you are able to recognize crossing over. What should you see happening?
In Meiosis, Prophase 1
A genetic rearrangement between nonsister chromatids involving the exchange of corresponding segments of DNA molecules, begins during pairing and synaptonemal complex formation and is completed while homologs are in synapsis.
Potentially can switch ends of their chromosomes of the non-sister chromatids (in the middle)
Know the process of DNA replication: molecules involved, how leading strand/lagging strand copied.
Begins at the origin of replication which are short stretches of DNA having a specific sequence of nucleotides. Proteins that initiate DNA replication recognize this specific sequence and attach to the DNA, causing the two strands to separate and open a replication “bubble”. At the end of the bubble is the replication fork, a Y-shaped region where the parental strands of DNA are being unwound. To unwind the DNA, several kinds of proteins help. Helicase is an enzyme that untwists the double helix at the replication fork by breaking the hydrogen bonds, separating the two parental strands and making them available as template strands. After the parental strands separate, single-strand binding proteins bind to the unpaired DNA strands, keeping them open and preventing them from re-pairing. Topoisomerase helps relieve the strain of the tighter twisting ahead of the replication fork by breaking, swiveling, and rejoining DNA strands (aka reliefs tension of the supercoiling of the DNA behind replicating fork due to the unwinding). Replication then proceeds on the leading and lagging strands, but only in the 5’3’ direction. The enzyme primase puts an RNA nucleotide (5-10 nucleotides long) primer down on the strands for the DNA polymerase to start synthesizing a new DNA strand by adding nucleotides. DNA polymerase 3 synthesises the complementary strand in the 5’3’ direction by adding nucleotides to the new complementary strand as the fork progresses. DNA polymerase 3 is also working on the lagging strand in the 5’3’ direction away from the replication fork with multiple primers that were put down by primase. The lagging strand is synthesized discontinuously with those primers (put down by primase), DNA polymerase 3 attaches and lays down opposite nucleotides until it reaches a primer, then it jumps backwards to the next primer. These series of segments called Okazaki fragments. Once the one long leading strand is synthesized and the all of the Okazaki fragments are synthesized DNA polymerase 1 replaces the RNA primer with DNA nucleotides. Then, an enzymes called DNA ligase joins the sugar-phosphate backbones of all the Okazaki fragments into a continuous strand by joining the 3’ ends to the 5’ ends.
If no DNA ligase those fragments will stay as fragments so the next replication will be problematic
When is DNA replication needed?
In a favorable environment the cell can copy all of the DNA and divide to form two genetically identical daughter cells.
This DNA Replication is needed to replace cells(mitosis), growth and repair (mitosis) and for production of gametes (meiosis) (replicate own cells) and meiosis (reproduction)
Know the chromosome numbers throughout the mitotic process.
Mitosis: Interphase G1 is c, Interphase G2 through Telophase is 2c, Cytokinesis c.
Meiosis 1: Interphase G1 is c, Interphase G2 through Telophase is 2c, Cytokinesis c.
Meiosis 2: (no interphase in M2) All phases c, Cytokinesis 1/2c.
How does the replicated DNA stay protected?
Telomerase puts down Telomeres that do not contain genes; instead, the DNA typically consists of multiple repetitions of one short nucleotide sequence. Telomeric DNA acts as a buffer zone that protects the organism’s genes.
Prevents the DNA from getting shorter and shorter because of its buffer area
Extra strand of unneeded DNA that protects the needed genes of the cell
Be able to calculate the A/T, C/G percentages.
Chargaff’s Rule (Out of 100%) Only with double stranded DNA-not single strand
Number of T=Number of A
Number of C=Number of G
EX: if you have 15% A then you have 15% T. Then you add those percentages (you get 30%) and then subtract from 100% (70%)
Why are we able to insert genes of one organism into another organism?
Using plasmids (a plasmid is a small circular DNA molecules that replicate separately from the bacterial chromosome).
A gene of interest is inserted into a plasmid which is now recombinant DNA (a DNA molecules formed when segments of DNA from two different sources are combined in vitro-in a test tube). That plasmid is now put into a bacterial cell, producing a recombinant bacterium. This single cell reproduces through repeated cell divisions to form a clone of cells,a population of genetically identical cells. The production of multiple copies of a signal gene is gene cloning.
Gene cloning is used for two basic purposes:
To make many copies of a particular gene
To produce a protein product
the second reason we are able to insert a gene of one organism into another organism is because DNA is the universal code. All organisms have the same nitrogen bases-A,T,C,G
Understand how restriction enzymes work to cut DNA
Restriction enzymes protect the bacterial cell by cutting up foreign DNA from other organisms or phages. Each restriction enzyme is very specific, recognizing a particular short DNA sequence-or restriction site- and cutting both DNA strands at precise points within this restriction site.
EX: The sequence of nucleotides is the same on both strands when read in the 5’3’ direction. A restriction enzyme will make cuts in a DNA molecule, yielding a set of restriction fragments. One of these fragments has a sticky end (one single-stranded end) that can form hydrogen -bonded base pairs (hybridize) with complementary sticky ends on any other DNA molecules cut with the same enzyme. This is temporary but can be made permanent by DNA ligase by joining the sugar-phosphate backbones. The ligase-catalyzed joining of DNA from two different sources produces a stable recombinant DNA molecule.
There are some restriction enzymes that cut straight through the DNA molecule not producing sticky ends. When doing recombinant DNA it is preferred to use the ones that cut into sticky ends.
The DNA of a bacterial cell is protected from the cell’s own restriction enzymes by the addition of methyl groups (-CH3) to adenines or cytosines within the sequences recognized by the enzymes
Be able to interpret a karyotype
A karyotype is a display of the chromosome pairs of a cell arranged by size and shape.
Shows the two chromosomes of each of the 23 types. When looking at it you can see if nondisjunction has occurred causing there to be extra chromosomes in a pair or causing missing chromosomes in a pair. It is also looked at to see the sex of the child
understand the steps of protein synthesis
protein synthesis consists of transcription and translation
Aka: Gene expression the process by which DNA directs the synthesis of proteins
transcription
The synthesis of RNA using information in the DNA
The two nucleic acids are written in different forms and the information is simply transcribed (“rewritten”) from DNA to RNA. A DNA strand provides a template for making a new complementary strand during RNA replication, it also may serve as a template for assembling a complementary sequence of RNA nucleotides. This starts at the promoter’s TATA box region that helps to bind RNA polymerase along with the help of transcription factors. Then replication begins by then unwinding the DNA and reading the template strand DNA and adding corresponding complementary RNA nucleotides. It stops once it reaches the terminator sequence and will stop right after this sequence. The pre-mRNA is the result of this replication. For the pre-mRNA to become mRNA a process called RNA splicing occurs. During RNA splicing it cuts out the unneeded noncoding stretches of DNA called the introns so only the needed introns (which will vary) and exons are left in the RNA strand and are spliced together. The resulting RNA molecule is a transcript of the gene’s protein-building instructions called a messenger RNA (mRNA) because it carries a genetic message from the DNA to the protein-synthesizing “machinery” of the cell. The 5’ cap (a bunch of Guanisines) and the poly-A tail (a bunch of Adenines) are added and then it is ready to leave the nucleus for translation to start in the cytoplasm.
Occurs inside the nucleus
