Homework #4 - Ch's 12, 13, 16, 17
A particular triplet of bases in the template strand of DNA is 5' AGT 3'. The corresponding codon for the mRNA transcribed is _____.
3' UCA 5'
Which of the following is true of a species that has a chromosome number of 2n = 16?
Each diploid cell has eight homologous pairs.
DNA replication is said to be semiconservative. What does this mean?
Each new double helix consists of one old and one new strand. (This is the meaning of the term "semiconservative.")
Which of the following DNA mutations is most likely to damage the protein it specifies?
a base-pair deletion
At the end of _____ and cytokinesis there are four haploid cells.
telophase II (At the end of telophase II and cytokinesis there are four haploid cells.)
An old DNA strand is used as a _____ for the assembly of a new DNA strand.
template (An old DNA strand is used as a template for the synthesis of a complementary new strand.)
The following question refer to this table of codons. https://session.masteringbiology.com/problemAsset/1835118/1/0314.jpg A possible sequence of nucleotides in the template strand of DNA that would code for the polypeptide sequence phe-leu-ile-val would be _____.
3' AAA-GAA-TAA-CAA 5'
The direction of synthesis of an RNA transcript is _____.
5' → 3' (Nucleotides are added to the 3' end of RNA.)
The role of DNA polymerase III In DNA replication in bacteria, the enzyme DNA polymerase III (abbreviated DNA pol III) adds nucleotides to a template strand of DNA. But DNA pol III cannot start a new strand from scratch. Instead, a primer must pair with the template strand, and DNA pol III then adds nucleotides to the primer, complementary to the template strand. Each of the four images below shows a strand of template DNA (dark blue) with an RNA primer (red) to which DNA pol III will add nucleotides. In which image will adenine (A) be the next nucleotide to be added to the primer?
Option 3) TCGGCCGA https://session.masteringbiology.com/problemAsset/1108497/37/1108497_010.jpg (In the example above, DNA pol III would add an adenine nucleotide to the 3' end of the primer, where the template strand has thymine as the next available base. You can tell which end is the 3' end by the presence of a hydroxyl (-OH) group. The structure of DNA polymerase III is such that it can only add new nucleotides to the 3' end of a primer or growing DNA strand (as shown here). This is because the phosphate group at the 5' end of the new strand and the 3' -OH group on the nucleoside triphosphate will not both fit in the active site of the polymerase. https://session.masteringbiology.com/problemAsset/1108497/37/1108497_029.jpg)
The initiator tRNA attaches at the ribosome's _____ site.
P (The initiator tRNA attaches to the ribosome's P site.)
Which part of a deoxynucleoside triphosphate (dNTP) molecule provides the energy for DNA synthesis?
Phosphate groups (The potential energy stored in the bonds of the phosphates provides the energy for DNA synthesis.)
How is plant cell cytokinesis different from animal cell cytokinesis?
Plant cells deposit vesicles containing cell-wall building blocks on the metaphase plate; animal cells form a cleavage furrow.
Which of the following enzymes creates a primer for DNA polymerase?
Primase (This RNA polymerase synthesizes an RNA primer antiparallel to the template DNA strand.)
Which of the following statements about DNA synthesis is true?
Primers are short sequences that allow the initiation of DNA synthesis. (When a primer is added to a single strand of DNA, DNA polymerase can start adding nucleotides to synthesize a complementary strand.)
In the process of transcription, _____.
RNA is synthesized
In the diagram below, the gray unit represents _____. https://session.masteringbiology.com/problemAsset/1100612/8/Part_ABC.jpg
RNA polymerase (RNA polymerase untwists a portion of the DNA double helix.)
The synthesis of a new strand begins with the synthesis of a(n) _____.
RNA primer complementary to a preexisting DNA strand (The synthesis of a DNA strand begins with the formation of an RNA primer.)
What is meant by the description "antiparallel" regarding the strands that make up DNA?
The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand.
After DNA replication is completed, _____.
each new DNA double helix consists of one old DNA strand and one new DNA strand (DNA replication is semiconservative.)
The RNA segments joined to one another by spliceosomes are _____.
exons (Exons are expressed regions.)
Meiosis II typically produces _____ cells, each of which is _____.
four ... haploid (At the end of meiosis II there are typically 4 haploid cells.)
What is the final result of mitosis in a human?
genetically identical somatic cells containing 46 chromosomes
The first step in the replication of DNA is catalyzed by _____.
helicase (The first step of DNA replication is unwinding the DNA double helix.)
According to the central dogma, what molecule should go in the blank?DNA → _____ → Proteins
mRNA
Crossing over normally takes place during which of the following processes?
meiosis I
True or false? Single-stranded DNA molecules are said to be antiparallel when they are lined up next to each other but oriented in opposite directions.
True (When the 3' end of one DNA strand points in the same direction as the 5' end of the other DNA strand, the strands are said to be antiparallel.)
The following question refer to this table of codons. https://session.masteringbiology.com/problemAsset/1835119/1/0314.jpg What amino acid sequence will be generated, based on the following mRNA codon sequence?5' AUG-UCU-UCG-UUA-UCC-UUG 3'
met-ser-ser-leu-ser-leu
During _____ chromosomes align single file along the equator of a haploid cell.
metaphase II (Metaphase II is essentially the same as mitotic metaphase except that the cell is haploid.)
During RNA processing a(n) _____ is added to the 5' end of the RNA.
modified guanine nucleotide (The 5' cap consists of a modified guanine nucleotide.)
In nucleotide excision repair, damaged DNA is excised by what enzyme(s)?
nuclease (Nucleases are enzymes that cut DNA.)
Which of the following represents the order of increasingly higher levels of organization of chromatin?
nucleosome, 30-nm chromatin fiber, looped domain
Synapsis occurs during _____.
prophase I (Synapsis, the pairing of homologous chromosomes, occurs during prophase I.)
During _____ a spindle forms in a haploid cell.
prophase II (Prophase II is essentially the same as mitotic prophase except that the cells are haploid.)
The action of helicase creates _____.
replication forks and replication bubbles (A replication fork is the transition region between paired and unpaired DNA strands.)
Which of the following does NOT occur during mitosis?
replication of the DNA
Meiosis II is similar to mitosis in that
sister chromatids separate during anaphase.
Spliceosomes are composed of _____.
small RNAs and proteins (Spliceosomes are complexes composed of small RNAs and proteins.)
What are the repetitive DNA sequences present at the ends of eukaryotic chromosomes called?
telomeres (Telomeres consist of many copies of a short DNA sequence that is bound by specific proteins.)
At the end of _____ and cytokinesis, haploid cells contain chromosomes that each consist of two sister chromatids.
telophase I (At the end of telophase I and cytokinesis, there are two haploid cells with chromosomes that consist of two sister chromatids each.)
What is crossing over?
the exchange of homologous portions of nonsister chromatids (The result is new combinations of genetic material (genetic recombination).)
The leading and the lagging strands differ in that _____.
the leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction
In the diagram below, the green unit represents _____. https://session.masteringbiology.com/problemAsset/1100612/8/Part_ABC.jpg
the promoter (The promoter is the region of DNA at which the process of transcription begins.)
Independent assortment of chromosomes is a result of _____.
the random way each pair of homologous chromosomes lines up at the metaphase plate during meiosis I
There are sixty-one mRNA codons that specify an amino acid, but only forty-five tRNAs. This is best explained by the fact that _____.
the rules for base pairing between the third base of a codon and tRNA are flexible
Taxol is an anticancer drug extracted from the Pacific yew tree. In animal cells, Taxol disrupts microtubule formation. Surprisingly, this stops mitosis. Specifically, Taxol must affect _____.
the structure of the mitotic spindle
In a DNA double helix an adenine of one strand always pairs with a(n) _____ of the complementary strand, and a guanine of one strand always pairs with a(n) _____ of the complementary strand.
thymine ... cytosine (This is referred to as specific base pairing.)
Translation occurs in the _____.
cytoplasm (Ribosomes, the sites of translation, are found in the cytoplasm.)
Mitosis and cell cycle terminology As in most areas of biology, the study of mitosis and the cell cycle involves a lot of new terminology. Knowing what the different terms mean is essential to understanding and describing the processes occurring in the cell. Drag the terms on the left to correctly complete these sentences. Not all the terms will be used.
1. DNA replication produces two identical DNA molecules, called SISTER CHROMATID(S), which separate during mitosis. 2. After chromosomes condense, the CENTROMERE(S) is the region where the identical DNA molecules are most tightly attached to each other. 3. During mitosis, microtubules attach to chromosomes at the KINETOCHORE(S) 4. In dividing cells, most of the cell's growth occurs during INTERPHASE 5. The MITOTIC SPINDLE(S) is a cell structure consisting of microtubules, which forms during early mitosis and plays a role in cell division. 6. During interphase, most of the nucleus is filled with a complex of DNA and protein in a dispersed form called CHROMATIN 7. In most eukaryotes, division of the nucleus is followed by CYTOKINESIS, when the rest of the cell divides. 8. The CENTROSOME(S) are the organizing centers for microtubules involved in separating chromosomes during mitosis. (The key structures involved in mitosis are labeled in this diagram of an animal cell that shows the two sister chromatids of each duplicated chromosome beginning to attach to the mitotic spindle by means of their kinetochores. The centrosomes anchor the mitotic spindle at opposite ends of the cell. https://session.masteringbiology.com/problemAsset/1095526/57/1095526_011.jpg)
Synthesis of the lagging strand In contrast to the leading strand, the lagging strand is synthesized as a series of segments called Okazaki fragments. The diagram below illustrates a lagging strand with the replication fork off-screen to the right. Fragment A is the most recently synthesized Okazaki fragment. Fragment B will be synthesized next in the space between primers A and B. https://session.masteringbiology.com/problemAsset/1108498/34/1108498_008.jpg Drag the labels to their appropriate locations in the flowchart below, indicating the sequence of events in the production of fragment B. (Note that pol I stands for DNA polymerase I, and pol III stands for DNA polymerase III.)
1. pol III binds to 3' end of primer B 2. pol III moves 5' to 3', adding DNA nucleotides to primer B 3. pol I binds to 5' end of primer A4. pol I replaces primer A with DNA5. DNA ligase links fragments A and B (https://session.masteringbiology.com/problemAsset/1108498/34/1108498_009.jpg Synthesis of the lagging strand is accomplished through the repetition of the following steps. - Step 1: A new fragment begins with DNA polymerase III binding to the 3' end of the most recently produced RNA primer, primer B in this case, which is closest to the replication fork. DNA pol III then adds DNA nucleotides in the 5' to 3' direction until it encounters the previous RNA primer, primer A. - Step 2: DNA pol III falls off and is replaced by DNA pol I. Starting at the 5' end of primer A, DNA pol I removes each RNA nucleotide and replaces it with the corresponding DNA nucleotide. (DNA pol I adds the nucleotides to the 3' end of fragment B.) When it encounters the 5' end of fragment A, DNA pol I falls off, leaving a gap in the sugar-phosphate backbone between fragments A and B. - Step 3: DNA ligase closes the gap between fragments A and B. These steps will be repeated as the replication fork opens up. Try to visualize primer C being produced to the right (closest to the replication fork). Fragment C would be synthesized and joined to fragment B following the steps described here.)
If there are 20 duplicated chromosomes in a cell, how many centromeres are there?
20
Which of the following is an example of alternation of generations?
A diploid plant (sporophyte) produces, by meiosis, a spore that gives rise to a multicellular, haploid pollen grain (gametophyte).
During elongation, which site in the ribosome represents the location where a codon is being read?
A site
https://session.masteringbiology.com/problemAsset/1835093/2/0330.jpg Refer to the figure above. What bases will be added to the primer as DNA synthesis proceeds? The bases should appear in the new strand in the order that they will be added starting at the 3' end of the primer. (Note that the primer shown is composed of DNA, not RNA, nucleotides which is often the case in test-tube DNA synthesis such as PCR.)
A, G, A, C, G, A, C
Independent assortment and genetic variation Consider a diploid cell where 2n = 6. During metaphase I of meiosis, as the pairs of homologous chromosomes line up on the metaphase plate, each pair may orient with its maternal or paternal homolog closer to a given pole. There are four equally probable arrangements of the homologous pairs at metaphase I. (Note that this problem assumes that no crossing over has occurred.) https://session.masteringbiology.com/problemAsset/1073306/45/1073306_002.jpg The cells below show the eight possible combinations of chromosomes that the daughter cells of meiosis II can receive. Sort each daughter cell into the appropriate bin depending on which arrangement at metaphase I would create it.
ARRANGEMENT 1: 3 & 8 ARRANGEMENT 2: 1 & 5 ARRANGEMENT 3: 6 & 2 ARRANGEMENT 4: 4 & 7 (One aspect of meiosis that generates genetic variation is the random orientation of homologous pairs of chromosomes at metaphase I. Each pair can orient with either its maternal or paternal homolog closer to a given pole; as a result, each pair sorts into daughter cells independently of every other pair. Due to independent assortment alone, a diploid cell with 2n chromosomes can produce 2 n possible combinations of maternal and paternal chromosomes in its daughter cells. For the cell in this problem (n = 3), there are 23, or 8, possible combinations; for humans (n = 23), there are 223, or 8.4 million, possible combinations. Note that when crossing over occurs, the number of possible combinations is even greater.)
Changes in DNA structure during the cell cycle As the chromosomes of a parent cell are duplicated and distributed to the two daughter cells during cell division, the structure of the chromosomes changes. Answer the three questions for each phase of the cell cycle by dragging the yes and no labels to the appropriate locations in the table. Note: Assume that by the end of the M phase, the parent cell has not yet divided to form two daughter cells.
Are sister chromatid present in all or part of this phase? G1-no S-yes G2-yes Beginning of M-yes End of M-no Is the DNA condensed in all or part of this phase? G1- no S-no G2-no Beginning of M-yes End of M-yes Does the cell contain twice as much DNA in this phase as it did in the G1 phase? G1- no S-yes G2-yes Beginning of M- yes End of M-yes (Sister chromatids form when DNA replicates in the S phase. The sister chromatids become individual chromosomes once they separate in early anaphase. Similarly, the cellular DNA content doubles in the S phase when the DNA replicates. However, the cell's DNA content does not return to its normal (undoubled) levels until after cytokinesis is complete and two daughter cells have formed. The condensation state of the DNA is not related to the presence or absence of sister chromatids. The DNA condenses in prophase and remains condensed until after the sister chromatids separate and the new daughter cells begin to form. In late telophase/cytokinesis, the emphasis shifts to cell growth and DNA replication for the next cell cycle. For these processes to occur, the DNA needs to be de-condensed so it is accessible to the cellular machinery involved in transcription.)
Density-dependent inhibition is explained by which of the following?
As cells become more numerous, the cell surface proteins of one cell contact the adjoining cells and they stop dividing.
Use the following information to answer the questions below. The unlettered circle at the top of the figure shows a diploid nucleus with four chromosomes that have not yet replicated. There are two pairs of homologous chromosomes, one long and the other short. One haploid set is black, and the other is gray. The circles labeled A to E show various combinations of these chromosomes. https://session.masteringbiology.com/problemAsset/1834836/1/0217.jpg
B
Which of these is a tRNA? https://session.masteringbiology.com/problemAsset/1100614/8/1716q.jpg
B (This is a tRNA.)
The tRNA anticodon, GAC, is complementary to the mRNA codon with the sequence _____.
CUG (In RNA uracil replaces thymine.)
Hershey and Chase set out to determine what molecule served as the unit of inheritance. They completed a series of experiments in which E. coli was infected by a T2 virus. Which molecular component of the T2 virus actually ended up inside the cell?
DNA
In the diagram below, the two blue strands represent _____. https://session.masteringbiology.com/problemAsset/1100612/8/Part_ABC.jpg
DNA (DNA is a double helix.)
What catalyzes DNA synthesis?
DNA polymerase (This enzyme catalyzes DNA synthesis.)
Why is the new DNA strand complementary to the 3' to 5' strands assembled in short segments?
DNA polymerase can assemble DNA only in the 5' to 3' direction (Since DNA polymerase can assemble DNA only in the 5' to 3' direction, the new strand complementary to the 3' to 5' strand must be assembled either in short 5' to 3' segments, which are later joined together by ligase, or be assembled continuously.)
Cells will usually divide if they receive the proper signal at a checkpoint in which phase of the cell cycle?
G1 (In mammalian cells, this checkpoint is termed the restriction point.)
Which of these correctly illustrates the pairing of DNA and RNA nucleotides?
GTTACG CAAUGC (In RNA, uracil takes the place of thymine.)
As DNA replication continues and the replication bubble expands, the parental double helix is unwound and separated into its two component strands. This unwinding and separating of the DNA requires three different types of proteins: helicase, topoisomerase, and single-strand binding proteins. Sort the phrases into the appropriate bins depending on which protein they describe.
HELICASE -binds at the replication fork -breaks H-bonds between bases TOPOISOMERASE -binds ahead of the replication fork -breaks covalent bonds in DNA backbone SINGLE-STRAND BINDING PROTEIN -binds AFTER the replication fork -prevents H-bonds between bases (At each replication fork, helicase moves along the parental DNA, separating the two strands by breaking the hydrogen bonds between the base pairs. (This makes the two parental DNA strands available to the DNA polymerases for replication.) As soon as the base pairs separate at the replication fork, single-strand binding proteins attach to the separated strands and prevent the parental strands from rejoining. As helicase separates the two parental strands, the parental DNA ahead of the replication fork becomes more tightly coiled. To relieve strain ahead of the replication fork, topoisomerase breaks a covalent bond in the sugar-phosphate backbone of one of the two parental strands. Breaking this bond allows the DNA to swivel around the corresponding bond in the other strand and relieves the strain caused by the unwinding of the DNA at the helicase. https://session.masteringbiology.com/problemAsset/1108497/37/1108497_025.jpg)
Processes that determine heredity and contribute to genetic variation Meiosis guarantees that in a sexual life cycle, offspring will inherit one complete set of chromosomes (and their associated genes and traits) from each parent. The transmission of traits from parents to offspring is called heredity. Another important aspect of meiosis and the sexual life cycle is the role these processes play in contributing to genetic variation. Although offspring often resemble their parents, they are genetically different from both of their parents and from one another. The degree of variation may be tremendous. The following processes are associated with meiosis and the sexual life cycle: - DNA replication before meiosis - crossing over - chromosome alignment in metaphase I and separation in anaphase I - chromosome alignment in metaphase II and separation in anaphase II - fertilization Sort each process into the appropriate bin according to whether it contributes to heredity only, genetic variation only, or both. (Note that a bin may be left empty.)
HEREDITY ONLY: none GENETIC VARIATION ONLY: none BOTH: all -fertilization -metaphase 1→anaphase 1 -metaphase 2→anaphase 2 -crossing over -DNA replication (In organisms that reproduce sexually, the processes of DNA replication, the precise pairing of homologs during crossing over, chromosome alignment and separation in meiosis I and II, and fertilization ensure that traits pass from one generation to the next. Unlike with asexual reproduction, offspring of sexual reproduction are genetically different from each other and from both of their parents. Mechanisms that contribute to genetic variation include - errors (mutations) that occur during DNA replication - the production of recombinant chromosomes due to crossing over - the independent assortment of homologous chromosomes in meiosis I - the separation of sister chromatids (which are no longer identical due to crossing over) in meiosis II - the random fusion of male and female gametes during fertilization)
How are sister chromatids and homologous chromosomes different from each other?
Homologous chromosomes contain the same gene loci but may have different alleles of a particular gene. Sister chromatids are identical copies of each other produced during DNA replication. (One homologous chromosome comes from the father, and the other comes from the mother. Sister chromatids are identical copies of each other.)
Refer to the drawings in the figure below of a single pair of homologous chromosomes as they might appear during various stages of either mitosis or meiosis, and answer the following question. https://session.masteringbiology.com/problemAsset/1834904/1/0302.jpg Which diagram represents anaphase I of meiosis?
I
Comparing the leading and lagging strands As the two parental (template) DNA strands separate at a replication fork, each of the strands is separately copied by a DNA polymerase III (orange), producing two new daughter strands (light blue), each complementary to its respective parental strand. Because the two parental strands are antiparallel, the two new strands (the leading and lagging strands) cannot be synthesized in the same way. https://session.masteringbiology.com/problemAsset/1108498/34/1108498_001.jpg Drag each phrase to the appropriate bin depending on whether it describes the synthesis of the leading strand, the synthesis of the lagging strand, or the synthesis of both strands.
LEADING STRAND: -made continuously -daughter strand elongates toward replication fork -only one primer needed LAGGING STRAND: - multiple primers needed -daughter strand elongates away from replication fork -made in segments BOTH STRANDS: -synthesized 5' to 3' (Because DNA polymerase III can only add nucleotides to the 3' end of a new DNA strand and because the two parental DNA strands are antiparallel, synthesis of the leading strand differs from synthesis of the lagging strand. -The leading strand is made continuously from a single RNA primer located at the origin of replication. DNA pol III adds nucleotides to the 3' end of the leading strand so that it elongates toward the replication fork. -In contrast, the lagging strand is made in segments, each with its own RNA primer. DNA pol III adds nucleotides to the 3' end of the lagging strand so that it elongates away from the replication fork. In the image below, you can see that on one side of the origin of replication, a new strand is synthesized as the leading strand, and on the other side of the origin of replication, that same new strand is synthesized as the lagging strand. The leading and lagging strands built on the same template strand will eventually be joined, forming a continuous daughter strand. https://session.masteringbiology.com/problemAsset/1108498/34/1108498_002.jpg)
How is translation initiated?
The small ribosomal subunit binds to the mRNA. The tRNA bearing methionine binds to the start codon. The large ribosomal subunit binds to the small one. The start codon signals the start of translation. (All of these processes occur at the initiation of translation.)
Crossing over and genetic variation Assume that an organism exists in which crossing over does not occur, but that all other processes associated with meiosis occur normally. Consider how the absence of crossing over would affect the outcome of meiosis. If crossing over did not occur, which of the following statements about meiosis would be true? Select all that apply.
There would be less genetic variation among gametes. (Crossing over contributes significantly to the genetic variation seen in gametes. This is because the exchange of maternal and paternal genes between the nonsister chromatids of a homologous chromosome pair creates recombinant chromosomes with unique combinations of alleles. However, crossing over is not the only process that introduces genetic variation in meiosis I. The independent assortment of homologous chromosomes (which are never identical) in meiosis I produces daughter cells that differ from each other. The effect of crossing over on genetic variation is shown below. Without crossing over, sister chromatids remain identical and thus, pairs of daughter cells would be identical. With crossing over, however, all four daughter cells are genetically unique. https://session.masteringbiology.com/problemAsset/1073306/45/1073306_027.jpg)
Which of the following statements about Okazaki fragments in E. coli is true?
They are formed on the lagging strand of DNA. (While DNA is synthesized continuously on the leading strand, Okazaki fragments are formed on the lagging strand because DNA synthesis always proceeds in the 5' to 3' direction.)
Which of the following enzymes is important for relieving the tension in a helix as it unwinds during DNA synthesis?
Topoisomerase (This enzyme untwists the coils that occur in the DNA as it is being unwound into a single-stranded template.)
RNA primers on the leading and lagging strands The diagram below shows a replication bubble with synthesis of the leading and lagging strands on both sides of the bubble. The parental DNA is shown in dark blue, the newly synthesized DNA is light blue, and the RNA primers associated with each strand are red. The origin of replication is indicated by the black dots on the parental strands. https://session.masteringbiology.com/problemAsset/1108498/34/1108498_006.jpg Rank the primers in the order they were produced. If two primers were produced at the same time, overlap them.
a b c d h g f e *In this format of left to right, top to bottom* (As soon as the replication bubble opens and the replication machinery is assembled at the two replication forks, the two primers for the leading strands (primers a and h) are produced. The production of the first primers on the lagging strands (those closest to the origin of replication, b and g) is delayed slightly because the replication forks must open up further to expose the template DNA for the lagging strands. After completion of the first segments of the lagging strands, additional template DNA must be exposed before the second primers (c and f) can be produced. And after completion of the second segments, additional template DNA must be exposed before the third primers (d and e) can be produced. In summary, because of the way the replication bubble expands, the lagging strand primers near the origin of replication were produced before the primers near the replication forks.)
During RNA processing a(n) _____ is added to the 3' end of the RNA.
a long string of adenine nucleotides (A poly-A tail is added to the 3' end of the RNA.)
A human cell containing 22 autosomes and a Y chromosome is
a sperm
Animal life cycles In the life cycle of an organism, meiosis is paired with the process of fertilization. Understanding the life cycle of an organism is the key to understanding how sexual reproduction ensures the inheritance of traits from both parents and also introduces genetic variation. Complete the diagram to show the life cycle of a typical animal. Follow these steps: 1. Drag labels of Group 1 to identify each stage of the life cycle. 2. Drag labels of Group 2 to identify the ploidy level at each stage. 3. Drag labels of Group 3 to identify the process by which each stage occurs. Labels can be used once, more than once, or not at all.
a) 2n b) 2n c) meiosis d) meiosis e) n f) egg g) sperm h) n i) fertilization j) 2n k) zygote l) mitosis m) 2n n) meiosis o) n p) egg (Meiosis creates gametes (eggs and sperm) with only a single chromosome set (haploid or n) from parental cells with two chromosome sets (diploid or 2n). During fertilization, the haploid sperm (n) and egg (n) fuse, producing a diploid zygote (2n). The cells of the zygote then divide by mitosis (which does not change the ploidy level) to produce an adult organism (still 2n) of the next generation. In sexual life cycles, meiosis and fertilization keep the number of chromosomes constant from generation to generation.)
The chemical structure of DNA and its nucleotides The DNA double helix is composed of two strands of DNA; each strand is a polymer of DNA nucleotides. Each nucleotide consists of a sugar, a phosphate group, and one of four nitrogenous bases. The structure and orientation of the two strands are important to understanding DNA replication. Drag the labels to their appropriate locations on the diagram below. Targets of Group 1 can be used more than once.
a) 5' end b) hydrogen bond c) 3' end d) deoxyribose sugar e)nitrogenous base f)phosphate group g)3' end h)5' end (The DNA double helix is constructed from two strands of DNA, each with a sugar-phosphate backbone and nitrogenous bases that form hydrogen bonds, holding the two strands together. Each DNA strand has two unique ends. The 3' end has a hydroxyl (-OH) group on the deoxyribose sugar, whereas the 5' end has a phosphate group. In the double helix, the two strands are antiparallel, that is, they run in opposite directions such that the 3' end of one strand is adjacent to the 5' end of the other strand.)
Meiosis terminology Drag the labels from the left to their correct locations in the concept map on the right.
a) chromatin b) genes c) chromosomes d) genome e) traits f) locus g) gametes (Knowing the terms and relationships shown in this concept map will help you understand the role that meiosis plays in heredity, sexual reproduction, and genetic variability.)
Interactions among chromosomes This diagram shows a diploid nucleus (2n=8) in which chromosome replication has occurred in preparation for mitosis (top) and meiosis (bottom). The nucleus at top right is now in prophase of mitosis; the nucleus at bottom right is now in prophase I of meiosis. Drag the labels to their appropriate targets to correctly identify the various chromosome structures. Labels can be used more than once.
a) non-homologous chromosomes b) sister chromatids c) homologous chromosomes d) centromere e) nonsister chromatids f) homologous chromosomes g)sister chromatids (To understand the process of meiosis, it is essential that you can differentiate between sister chromatids, nonsister chromatids, homologous chromosomes, and non-homologous chromosomes. https://session.masteringbiology.com/problemAsset/1071684/64/1071684_016.jpg)
The replication bubble and antiparallel elongation DNA replication always begins at an origin of replication. In bacteria, there is a single origin of replication on the circular chromosome, as shown in the image here. Beginning at the origin of replication, the two parental strands (dark blue) separate, forming a replication bubble. At each end of the replication bubble is a replication fork where the parental strands are unwound and new daughter strands (light blue) are synthesized. Movement of the replication forks away from the origin expands the replication bubble until two identical chromosomes are ultimately produced. https://session.masteringbiology.com/problemAsset/1108497/37/1108497_016.jpg In this activity, you will demonstrate your understanding of antiparallel elongation at the replication forks. Keep in mind that the two strands in a double helix are oriented in opposite directions, that is, they are antiparallel. Drag the arrows onto the diagram below to indicate the direction that DNA polymerase III moves along the parental (template) DNA strands at each of the two replication forks. Arrows can be used once, more than once, or not at all.
a) → b) → c) ← d) ← (DNA polymerase III can only add nucleotides to the 3' end of a new DNA strand. Because the two parental DNA strands of a double helix are antiparallel (go from 3' to 5' in opposite directions), the direction that DNA pol III moves on each strand emerging from a single replication fork must also be opposite. For example, in the replication fork on the left, the new strand on top is being synthesized from 5' to 3', and therefore DNA pol III moves away from the replication fork. Similarly, the new strand on the bottom of that same replication fork is being synthesized from 5' to 3'. But because the bottom parental strand is running in the opposite direction of the top parental strand, DNA pol III moves toward the replication fork. In summary, at a single replication fork, one strand is synthesized away from the replication fork, and one strand is synthesized toward the replication fork. When you look at both replication forks, note that a single new strand is built in the same direction on both sides of the replication bubble.)
Can you match these prefixes, suffixes, and word roots with their definitions? against: to love: with or together: difficult, painful: from, out of, remove: change, turn, move: of neither gender or type: to: not: many:
anti- -phil (or philo-) co- dys- de- trop- (or -tropic) neutr- ad- non- poly-
Phases of the cell cycle The cell cycle represents the coordinated sequence of events in the life of a cell from its formation to its division into two daughter cells. Most of the key events of the cell cycle are restricted to a specific time within the cycle. In this exercise, you will identify when various events occur during the cell cycle. Recall that interphase consists of the G1, S, and G2 subphases, and that the M phase consists of mitosis and cytokinesis. Drag each label to the appropriate target.
a. Non-dividing cells exit cell cycle. b. At this point, cell commits to go through the cycle. c. DNA replicates. d. Two centrosomes have formed. e. Mitotic spindle begins to form. f. Cell divides, forming two daughter cells. (Many organisms contain cells that do not normally divide. These cells exit the cell cycle before the G1 checkpoint. Once a cell passes the G1 checkpoint, it usually completes the cell cycle--that is, it divides. - The first step in preparing for division is to replicate the cell's DNA in the S phase. - In the G2 phase, the centrosome replicates. - In early M phase, the centrosomes move away from each other toward the poles of the cell, in the process organizing the formation of the mitotic spindle. - At the end of the M phase when mitosis is complete, the cell divides (cytokinesis), forming two genetically identical daughter cells.)
What enzyme catalyzes the attachment of an amino acid to tRNA?
aminoacyl-tRNA synthetase (This enzyme matches a particular tRNA with a particular amino acid.)
During which phase of mitosis do the chromatids become chromosomes?
anaphase
Homologous chromosomes migrate to opposite poles during _____.
anaphase I (During anaphase I sister chromatids remain attached at their centromeres, and homologous chromosomes move to opposite poles.)
During _____ sister chromatids separate.
anaphase II (Anaphase II is essentially the same as mitotic anaphase except that the cell is haploid.)
Alternative RNA splicing _____.
can allow the production of proteins of different sizes and functions from a single gene
What is the name of the process shown in the diagram? https://session.masteringbiology.com/problemAsset/1100614/8/Part_D_translation.jpg
initiation (of translation) (The diagram illustrates the initiation of translation.)
Can you match these prefixes, suffixes, and word roots with their definitions? within: different, other: change, after: milk: three: blood: one-half: enzyme: across:
intra- hetero- meta- lact- tri- hem- (or hemato-) semi- -ase trans-
Once a peptide bond has been formed between the amino acid attached to the tRNA in the P site and the amino acid associated with the tRNA in the A site, what occurs next?
translocation
Meiosis I produces _____ cells, each of which is _____.
two ... haploid (At the end of meiosis I there are two haploid cells.)