BY 30 – Fall 2001
7.1. The Nucleus
and Cell Division
a. Most cells have __________________ nucleus. Cells that contain more than one nucleus are called __________________________. An example of a cell that has no nucleus is the _____________________________.
b. Within the nucleus, the genetic material is stored in the form of ___________. This genetic material is passed to the cytoplasm in the form of _____________________, where it is used to make ___________________.
c. The nucleus of the cell has three components: ________________________, ___________________________ and _______________________________.
d. The nuclear envelope is a double membrane in which the outer membrane is continuous with the ____________________________. The two membranes fuse to form _________________________ through which substances pass to and from the nucleus and ________________________.
e. ____________________ are spherical bodies within the nucleus consisting of _______________________ and ___________________________. These represent the site of _________________________ subunit formation.
f. The material located between nucleoli and chromatin is called _____________________________.
g. A single chromatin strand consists of a single ______________________ that wraps twice around a cluster of eight proteins called ____________________ forming a compact structure called a ____________________________. The entire structure is known as beads (= ___________________________) on a ___________________________ (= DNA molecule).
h. Just before a cell divides, the chromatin condenses to form ______________. In humans there are ____________________ chromosomes, of which 44 are called ____________________ and 2 are called _______________________. The chromosomes form ________________ pairs of ___________________ chromosomes. Each member of a pair of homologous chromosomes contains similar ___________________________.
i. There are two types of cell division called __________________ cell division and ___________________ cell division. In ______________________ cell division, the result is two identical daughter cells while the result of reproductive cell division is _____________________, cells which have only 23 chromosomes. Another name for reproductive cell division is _________________________.
7.2. Somatic Cell
Division
a. The cell cycle consists of two major phases called ______________________ and the __________________________ phase.
b. Interphase is subdivided into the ___________________________________, __________________________, and __________________________ phases. In the ______________________ phase, cells synthesize proteins and grow rapidly, and duplicate their ________________________. Some cells never divide again, and are said to be in the __________________________ phase, an example being ____________________________ cells.
c. The S phase is where ____________________________ occurs. During the _____________________ phase, enzymes and other proteins needed for cell division are synthesized. Also ____________________ replication, begun during the G1 phase, is completed during the G2 phase.
d. DNA ____________________ begins with an untwisting and separation of the two strands through the enzymatic action of a ______________________. To each of the old strands, new strands are added by a __________________. This enzyme joins DNA ______________________ via complementary base pairing [Note, a nucleoside is a nucleotide with _______________ phosphate groups.] As each is added, the terminal __________________________ are cleaved off, providing energy to drive the process.
e. As soon as replication ends, ______________________ associate with DNA comprising chromatin strands.
f. The mitotic phase has two distinct events: ___________________________ (= division of the nucleus); and cytokinesis (= division of the ____________________________). Mitosis in turn has four phases called _____________________________, ______________________________, ____________________________, and_____________________________.
g. ______________________________ is first indicated as chromatin starts to condense to form chromosomes. Each chromosome consists of two __________________________ joined by the _______________________. When chromatids separate, each is considered to be a new __________________________________.
h. Another event that takes place within prophase is _______________________ formation, which begins with migration of the _________________________ from the _____________________________ to the opposite poles of the cell. The mitotic spindle is composed of _________________________, composed of the protein ___________________________. Some microtubules attach to centromeres at their outer portion, called the __________________________, forming _______________________ microtubules. Microtubules that do not attach to chromosomes are called ________________________ microtubules, and those that radiate outward from centrioles are called __________________________________ microtubules.
i. Other events of prophase involve disappearance of _____________________ and the disintegration of the ______________________________.
j. At ___________________________, the chromosomes cluster at the center of the cell with their _________________ aligned at the ___________________. The plane located halfway between the cell poles is called the __________________________________.
k. At anaphase, the __________________________ split and each chromatid is pulled by the _________________ microtubules toward each pole of the cell.
l. ____________________ is sometimes called prophase in reverse because _______________________ uncoil; a new _________________________ develops; __________________________ reappear; and the mitotic spindle ____________________________.
m. During cytokinesis, a ring of __________________________ contracts at the ______________________ splitting the cell in half. Microfilaments are solid strands made up of the protein __________________________. The cellular ________________________ are divided between the two daughter cells.
7.3. Protein
Synthesis
a. A segment of DNA responsible for coding a particular protein is called a ____________________. This information is ___________________ to form a mRNA molecule which is then ___________________ into a corresponding amino acid sequence. Information is stored in DNA in the form of a set of three nucleotides called a ______________________, which will specify the particular amino acid to be added. Each triplet is transcribed as a complementary sequence of three RNA nucleotides on a mRNA molecule called a _________________________.
b. ______________________ are sites of protein synthesis composed of proteins and ___________________________. These can be either free or attached to ______________________. In general, free ribosomes make soluble proteins that stay in the _______________________________, while proteins made on _____________________________ are destined for insertion into the plasma membrane or ______________________________ from the cell.
c. The _____________________ is a network of membranes that are continuous with the nuclear membrane and is subdivided into ______________________ (has ribosomes) and _____________________________ (no ribosomes). The _____________________________ functions in the synthesis of lipids and in detoxification. By contrast, the __________________________ is a series of flattened sacs which modifies, concentrates, and packages proteins into either ____________________________ or ______________________________.
d. Transcription takes place within the ______________________ and involves an enzyme called a _____________________________ binding to DNA and opening it up at a location called the _____________________ which acts as a _____________________________ sequence. One DNA strand, called the ____________________________ serves as a template forming mRNA. The other DNA strand is called the _______________________________ strand.
e. Transcription ends when the _____________________ codon is reached. The result of transcription is called a ___________________ molecule consisting of _________________________ and ______________________________. The __________________ are spliced out, leaving the __________________, which contain coded information. The final mRNA molecule leaves the nucleus to enter the __________________________ of the cell.
f. ___________________________ begins with the mRNA binding to the small subunit of the ribosome. ________________ molecules transport amino acids to the ribosome for assembly. Each tRNA molecule has an amino acid at its tail and a three base sequence called the _________________________ that is complementary to the mRNA ______________________________.
g. When the protein contains a ____________________________ sequence, the ribosome attaches to the membrane of the ______________________ and the protein is inserted into the cisterna where the leader sequence is clipped off. From the RER, ______________________ coated vesicles pinch off the RER and travel to the ___________________________ side of the Golgi.
h. Within the ____________________________, the protein is further modified by clipping off proteins and adding or modifying ______________________. Proteins are concentrated and packaged into vesicles that leave the ____________ side, which have various fates: ________________________ which migrate to the plasma membrane and discharge their contents by _____________________; vesicles which migrate to the _________________ and insert their proteins into it; and vesicles which contain ____________________________ which pH optimas aroung pH 5 that form _____________________. Lysosomes fuse with ______________________ allowing the digestion of their contents.
i. _____________________ technology is a technique for inserting genes into a host organism causing it to make proteins it normally does not synthesize. The organism is called the __________________________; and their DNA is called _____________________________. In this method, the mRNA of the desired protein is isolated and a reverse transcriptase is used to make _____________________________, which is inserted into the host (usually _____________________) to make recombinant DNA. This method allows production of large amounts of therapeutic substances such as _____________________________, _______________________________, ____________________________, and _____________________________.