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Biology chapter 11
Terms in this set (62)
a special "resting" phase
What step is unique to prophase I?
Recombination is promoted between homologous chromosomes.
What is the mitotic spindle made of?
A diploid organism has 8 chromosomes in G1. How many chromosomes will each of its offspring cells have after meiosis?
When do the sister chromatids separate in meiosis?
What type of cell in the human body is a good example of a haploid cell?
What part of a chromosome do microtubules attach to?
Which of the following is a critical regulator of cell cycle progression?
Cyclin-dependent protein kinases (Cdks)
Which of the following proteins appear in some stages of the cell cycle and are degraded at other stages?
In a healthy human being, which philosophy best describes a cell's life?
As DNA is replicated, the leading strand will have ____________ RNA primer(s) and the lagging strand will have ____________.
In a long DNA molecule, each origin of replication produces a ____________ with a ____________ on each side.
replication bubble; replication fork
The type of genetic engineering that involves isolating genes from one species and introducing them into another is called ____________ technology.
The polymerase chain reaction (PCR) is used to:
generate multiple copies of a targeted region of DNA.
Each DNA parent strand within a replication bubble acts as a template strand that produces:
one leading strand and one lagging strand.
cut double-stranded DNA strands at specific sites.
The enzyme responsible for joining Okazaki fragments together during DNA replication is:
In DNA replication, each individual parent strand acts as a ____________ for the synthesis of a ____________.
template strand; daughter strand
Telomerase is fully active in ____________ and ____________ cells, but almost completely inactive in ____________ cells.
germ; stem; somatic
The enzyme that catalyzes the addition of new nucleotides to a growing DNA strand is:
Tumor suppressors can oppose oncogenes by:
slowing cell division, blocking the action of an oncogene, instructing defective cells to die, and repairing mutations.
During meiosis I:
nonsister chromatids exchange maternal and paternal DNA, chromosomes undergo reductional division, bivalents are formed during prophase I and are taken apart during anaphase I, and sister chromatids are not separated.
Which of the following is NOT true about gametes?
They are genetically identical to other gametes formed during meiosis.
Cell division is regulated by:
growth factor signals, signals that indicate a sufficient size of the cell, signals about the nutritional status of the cell, and signals that indicate that DNA has been replicated.
Reproduction by cell division:
results in two daughter cells that are genetically identical, persists in mature plant cells for continued growth, continues in mature adult humans to replace damaged and worn-out cells, and is asexual reproduction.
The second meiotic division resembles mitosis because:
chromosomes decondense during telophase II, the daughter cells have the same number of chromosomes as the parent cells, sister chromatids are separated during anaphase II to become the chromosomes of the daughter cells, and microtubules attach from opposite directions to the centromere of each sister chromatid pair.
the physical breakage and reunion of non-sister chromatids during prophase I
the region of a chromosome where sister chromatids remain attached
chromatids in a bivalent that do not share a centromere
a four-stranded structure of homologous chromosomes in alignment
the microtubule organizing center
paired chromosomes that share the same set of genes
cross-like structures found in bivalents as a consequence of crossing over
alignment of homologous chromosomes during prophase I
Compare and contrast the ways in which prokaryotic cells and eukaryotic cells divide.
Prokaryotic cells reproduce through a process called binary fission. During this process, the cell replicates its DNA, increases in size, and divides into two daughter cells, each having one copy of the parental DNA. Eukaryotic cells go through a similar process, albeit more complex, called mitotic cell division. In this process, cells first replicate their chromosomes in the nucleus. The nuclear envelop then dissolves and each pair of chromosomes are divided by connecting to the mitotic spindle. Once the two full sets of chromosomes are separated, a nuclear envelope forms around each one. The cell then goes through a process called cytokinesis, where it is split into two new daughter cells.
Describe three situations in which mitotic cell division occurs.
Three situations in which mitotic cell division occurs are in the development of multicellular organisms, maintenance and repair of organs and tissues, and asexual reproduction of unicellular eukaryotes.
Name the five steps of mitosis, and draw the changes in the structure and position of the chromosomes at each step.
The five steps in mitosis are: (1) Prophase (chromosomes condense, centrosomes radiate microtubules and migrate to opposite poles), (2) Prometaphase (microtubules of the mitotic spindle attach to chromosomes), (3) Metaphase (chromosomes align in center of cell), (4) Anaphase (sister chromatids separate and travel to opposite poles), and (5) Telophase (nuclear envelope re-forms and chromosomes decondense).
Describe how chromosomes behave in meiosis. Be able to state when chromosomes are duplicated (forming sister chromatids) and when they are not duplicated.
Meiosis basically goes through two cell-division cycles called meiosis I and meiosis II. In meiosis I, chromosomes are duplicated in Prophase I forming sister chromatids. In Anaphase I, homologous chromosomes separate into two different daughter cells. During meiosis II, the chromosomes do not duplicate and instead the sister chromatids are separated into two more daughter cells. The end result of this process is four daughter cells, each having unique genetic information.
Compare and contrast mitotic cell division and meiotic cell division in terms of number of products, number of cell divisions, and processes unique to each.
Mitosis goes through one round of DNA synthesis to produce two genetically identical daughter cells, each with 46 chromosomes. Meiosis also goes through one round of DNA synthesis but goes through two rounds of cell division to produce four genetically different daughter cells, with 23 chromosomes each.
Name two ways in which meiotic cell division creates genetic diversity, and explain how each occurs.
Genetic diversity is created in meiotic cell division by the crossing over of chromosomes and random alignment of bivalents in metaphase I. Crossing over occurs when homologous chromosomes of maternal origin and paternal origin undergo an exchange of DNA segments, thus creating genetic diversity. Random alignment of bivalents leads to a chromosome set that is a random mix of maternal and paternal homologs.
Explain how cytokinesis differs between animal and plant cells.
In animal cells, cytokinesis involves a contractile ring made of actin. In plant cells, it involves the growth of a new cell wall called a cell plate.
Describe the roles of cyclins and cyclin-dependent kinases in the cell cycle.
In the cell cycle, cyclins bind to and activate cyclin-dependent kinases (CDKs). Once activated, the CDKs then phosphorylate target proteins involved in promoting cell division. Once activation has occurred, the CDK dissociates from the cyclin and the cyclin degrades.
Give three examples of checkpoints that the cell monitors before proceeding through the cell cycle.
Three examples of checkpoints during the cell cycle are (1) Spindle assembly checkpoint, which happens before anaphase and ensures that all chromosomes are attached to the spindles; (2) DNA damage checkpoint, which happens in the G1 phase and checks for DNA damage; and (3) DNA replication checkpoint, which happens in G2 and makes sure all the DNA is replicated.
Describe the differences among a proto-oncogene, an oncogene, and a tumor suppressor gene.
An oncogene is a gene that causes cancer. A proto-oncogene is a gene that has the potential to cause cancer when mutated. A tumor suppressor gene blocks specific steps in the development of cancer.
Explain how DNA structure relates to DNA replication.
DNA consists of two antiparallel strands, meaning that the 3' hydroxyl end of one strand interacts with the 5' phosphate group of the other strand. In the antiparallel helical coil, a purine base (A or G) of one strand interacts with a pyrimidine base (T or C, respectively) of the other strand. This mechanism allows the two strands to have identical genetic information in the form of nucleotide sequence. When DNA replication occurs, the two strands separate ("unzip") from each other and both are used as a template for the replication of two new DNA strands.
Describe the orientation of the two DNA strands and the direction of DNA synthesis.
The orientation of the two DNA strands is antiparallel. This means that the 3' hydroxyl end of one strand is opposite the 5' phosphate group of the other strand. When the two strands separate and DNA replication begins, nucleotides are added to the 3' end of both strands so DNA replication occurs 5' to 3'.
List the differences and similarities in synthesis of the two daughter strands of DNA.
The similarities of the resulting daughter strands from DNA replication are that they will encode the same genetic information in the form of nucleotide sequence and they will also be paired with one of the original parental DNA strands. The two strands are different in the way that they are replicated although the chemistry of strand elongation is the same for both. On both strands, replication occurs in the 5' to 3' direction.
The leading strand has the 3' end of its DNA pointed toward the replication fork and thus will be synthesized as one long, continuous polymer. The replication of the other strand, or lagging strand, is a little more complex due to its 5' end pointing toward the replication fork. Since DNA can only be replicated in the direction of 5' to 3', the lagging strand is synthesized in short, discontinuous pieces. Each new piece, or Okazaki fragment, is elongated at its 3' end until it reaches the piece in front of it.
Explain why replicating the tips of linear chromosomes is problematic and how the cell overcomes this challenge.
Replicating the tips of linear chromosomes is problematic because during the synthesis of the lagging strand, about 100 base pairs at the 3' end are not replicated. This is due to the fact that the sequence of the last RNA primer binding site is not replicated because the primer is bound at the time of replication and then removed when replication is finished. This results in about 100 base pair gap in sequence This loss of sequence is restored through an enzyme called telomerase, which is most active in germ and stem cells. Eukaryotic chromosomes are capped by a repeating sequence called the telomere, which does not encode any genes. When 100 nucleotides of the telomere are lost, the telomerase replaces them. This shortening and lengthening of the chromosome is not detrimental to the cell because there are no coded genes in this region.
Name the three steps of PCR and at least two uses for the PCR technique.
The three steps of PCR are (1) denaturation of the double-stranded DNA into two individual strands, (2) annealing of the two primers to their complementary sequence on the DNA template strands, and (3) extension of the parental DNA strands through elongation (5' to 3') by DNA polymerase (by extending the primers). PCR can be used in a variety of ways such as DNA fingerprinting, where a person's DNA is sequenced and potentially matched to evidence found at a crime scene (paternity tests are performed in a similar way). PCR can also be used to identify an organism based on a known conserved region of their DNA, and it can also be used to mass-produce certain sequences of DNA for DNA-based vaccines.
Explain how the properties of DNA determine how it moves through a gel, is cut by restriction enzymes, and hybridizes to other DNA strands
Since fragments of DNA are negatively charged, pieces will move through a porous gel when an electric current is passed through it. The distance the DNA pieces move through the gel is based on their size, with larger fragments moving more slowly and smaller fragments moving through the gel quickly. To get these fragments of DNA, restriction enzymes, which each recognize a particular sequence of DNA (the restriction site), cleave the DNA at its specified site. DNA can also hybridize to other DNA strands if their nucleotide sequences are complementary to each other.
Describe how DNA molecules are sequenced.
In Sanger sequencing, the sequence of a template DNA strand is unknown. This DNA is used as the template for replication by DNA polymerase. A DNA primer, polymerase, normal nucleotides and chain terminating nucleotides are all added to the template and replication of the unknown strand begins. Elongation of this strand stops whenever a dideoxynucleotide terminator (a nucleotide in which the 3' hydroxyl group on the sugar ring is absent) is incorporated at the 3' end. The four altered nucleotides are chain terminators, each labeled with a different fluorescent dye, so the result of Sanger sequencing is a tube filled with different length fragments of the same DNA sequence. The mixture is then run on a gel and "read" by looking at the fluorescent pattern of the dideoxynucleotides incorporated into the sequence. For example, a sequence of 5'-ATGC-3' would be "read" as green-red-blue- purple (for the fluorescent dyes).
Describe how recombinant DNA techniques can be used to express a mammalian gene in bacteria.
The mammalian gene (donor DNA) can be expressed in a bacterium through its insertion into a vector DNA that can be replicated in the bacterium. The same restriction enzymes are used to cut the donor DNA and the vector DNA so that they now have complementary ends. A ligation reaction is then performed to insert the donor DNA into the vector DNA. The vector DNA is then inserted into the bacterium and replicated through the normal method which also replicates the donor, mammalian gene, at the same time.
______ forms genetically identical daughter cells
______ forms genetically unique daughter cells
______ forms four daughter cells
______ parent cell undergoes two rounds of cell division
______ homologous chromosomes exchange DNA prior to dividing
______ forms diploid daughter cells
______ divides after a single round of DNA replication
______ homologous chromosomes undergo synapsis
______ follows a single round of replication
a. mitosis b. meiosis c. both mitosis and meiosis
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