Question

2. Explain why the replication of one of the DNA strands is continuous while the other...

2. Explain why the replication of one of the DNA strands is continuous while the other strand is discontinuous. What causes this difference? 3. A) What are telomeres? B) Are telomeres present in both Prokaryotes and Eukaryotes? Explain why some cells have telomeres and others don't. 4. A) Draw a cell with 2 pairs chromosomes as it goes through the cell cycle and indicate the main things that happen to its chromosomes at each stage (label: sister chromatids, homologous chromosomes, G1, S, G2, Prophase, metaphase, anaphase, telophase, citokinesis, indicate the 3 checkpoints). Draw it in paper and upload a photo or scanned. B) Assuming the life of a cell starts as soon as cell division is completed and ends when the cell starts a new process of cellular division, how many times in a cell’s life does it replicate its DNA? Explain. 5. A) Draw the phases of mitosis and indicate the main events that occur in each. B) When does a multicellular organism undergo mitosis (when it wants to reproduce, all the time, only when injured, when it’s growing, or when)? 6. Discuss A) why cell division requires multiple checkpoints and B) what is the role of proto-oncogenes and tumor suppressor genes in normal cells and C) why are proto-oncogenes and tumor suppressor genes related to cancer?


0 0
Add a comment Improve this question Transcribed image text
Answer #1

2.

  • The two strands of the DNA run antiparallel. The polymerase enzymes that add nucleotides to the primer, during replication, can add only in one direction, that is in the 3’to 5’direction. To the 3’- OH of the leading strand, new nucleotides are added.

  • The energy required for phosphodiester bond formation is derived from hydrolysis of the phosphates in the NTP that is added to the existing chain. This ensures that if there is any mismatch, the nucleotide phosphate can be excised and correct nucleotide is added.

  • If nucleotides can be added to the 5’end of a growing chain, the energy required for bond formation must be derived by hydrolysis of the phosphates at the 5’end. If there is any mismatch, there is no chance of repair, since the energy is derived from the existing strand and not from the in coming nucleotide. This poses a problem.

  • Due to this limitation, the replication of DNA is unidirectional. But since the two strands of the DNA run antiparallel, a different strategy is adapted in replication of the lagging strand. It is discontinuous replication; okazaki fragments are added, and from the 3’end of this fragments, polymerization occurs. Technically, a large number of primers are required for lagging strand replication, each okazaki fragment acts as a primer.

3.

Telomeres are self replicating entities that are present at the ends of eukaryotic chromosomes. They are present only in eukaryotes, but not in prokaryotes. Prokaryotes have circular chromosomes and do not face the problem of end replication, of their chromosomes

Eukaryotes have linear chromosomes. DNA replication requires a primer, which is RNA in nature. To this RNA primer, nucleotides are added during replication, in 3’to 5’direction. Once the replication is over, the RNA primer is degraded. However, the polymerases are unable to add nucleotides to the 5’end. Thus, with each round of replication, eukaryotic chromosomes fall short of a small segment of DNA. To solve this problem, they have self replicating entities called Telomeres.

Add a comment
Know the answer?
Add Answer to:
2. Explain why the replication of one of the DNA strands is continuous while the other...
Your Answer:

Post as a guest

Your Name:

What's your source?

Earn Coins

Coins can be redeemed for fabulous gifts.

Not the answer you're looking for? Ask your own homework help question. Our experts will answer your question WITHIN MINUTES for Free.
Similar Homework Help Questions
  • Cancer and Gene Regulation Why is a cell cycle control system needed for cell division? What...

    Cancer and Gene Regulation Why is a cell cycle control system needed for cell division? What happens when cells do NOT respond to the cell cycle control system and divide excessively? Tumor Proto-oncogeno (for protein that stimulates coll division) 6 Y DNA Benign Tumor= Mutation withln a control region of DNA Malignant Tumor Mutated promoter Metastasis Normal growth-stimulating protein in excess Oncogene Tumor-Suppressor Genes Proto-oncogene utled tara gese Samor-auppresr gane Many proto-oncogenes code for growth factors /Deletive nonimenig Normel grewt...

  • There are two main types of cells in the human brain, neurons (nerve cells) and glial...

    There are two main types of cells in the human brain, neurons (nerve cells) and glial cells (supporting cells). Once neurons fully mature, these nerve cells no longer divide. Glial cells, however, continue to divide over a person’s entire lifetime. GDNF (glial cell line-derived neurotrophic factor) is a small protein that stimulates growth in glial cells. What kind of signal molecule is this protein? How does GDNF likely promote cell division? After the glial cell receives GDNF, what will happen...

  • Write the letter of the correct answer on the first page. Control of entry into the...

    Write the letter of the correct answer on the first page. Control of entry into the cell cycle is essential. Unicellular eukaryotes that enter into it too soonyw have the necessary energy to complete it, leading to their demise, whereas in multicellular eukaryotes usually leads to cycle are controlled by proteins, problems with the genes that code for these proteins are a commorn source of error. These genes fall into two broad groups: 33 uncontrolled cellular division 32 Since the...

  • Quession 14 Which statement about mitosis is true? Select one a. DNA replication is completed in...

    Quession 14 Which statement about mitosis is true? Select one a. DNA replication is completed in prophase. b. The chromosome number in the resulting cells is halved c. Two genetically identical daughter cells are formed. d Crossing over occurs during prophase e. It consists of two nuclear divisions. Quession 15 How does a nucleus in G2 difler from a nucleus in G17 Select one a. DNA synthesis occurs only in G1 phase. b Inactive cells are arrested only in G2...

  • please help me with these quetions DNA replication is checked G1 for accuracy Cells no longer divide GO DNA is cop...

    please help me with these quetions DNA replication is checked G1 for accuracy Cells no longer divide GO DNA is copied or replicated Cells synthesize proteins G1 needed for the process of mitosis Cell doing its normal 'job GO 30 Crossing over between non Meiosis sister chromosomes Spindle formation complete Prophase I Nuclear membrane reforms Metaphase Chromosomes line up at Metaphase midline Spindle fibers shorten Telophase 13. Cell |Туре Normal Mitotic Index C A E 3% 5% 8% 12% 15%...

  • Please help with answers to these questions answer the ones that are straightforward like this one...

    Please help with answers to these questions answer the ones that are straightforward like this one Question 24 5 pts 1. Beta-catenin is classified as a proto-oncogene and APC is classified as a tumor suppressor gene. Both are important parts of the Wnt signaling pathway. Describe the relationship between beta-catenin and APC. Explain in detail why they are classified as a proto-oncogene or tumor suppressor gene. 2. Suppose you're working in a cancer research lab and discover a small molecule...

  • Binary Fission and Mitosis are similar processes. One way they are different is that: . A....

    Binary Fission and Mitosis are similar processes. One way they are different is that: . A. In Mitosis, the DNA does not form into chromosomes. • • • B. In Binary Fission, the DNA does not form into chromosomes. C. Binary Fission only occurs in Eukaryotes. D. They both split by growing a new cell wall. What phase is the indicated cell currently in? D A. Anaphase B. Telophase C. Metaphase D. Prophase • 10 PUNTS When DNA condenses in...

  • Part C: Mitosis the body nceds more cells (for growth or repair), the way to produce...

    Part C: Mitosis the body nceds more cells (for growth or repair), the way to produce new ones is for existing cells to divide. The series of events that leads to cell division is called the cell cycle. The cell cycle has distinct phases-most of the time, a cell is in itself is divided into three phases: Gl, in which a cell is engaged in the normal activity of thar cell making protcin, gencrating ATT, etc.l; S, the phase when...

  • Please help me with this. I'm so lost. If you could be detailed/help explain, I would...

    Please help me with this. I'm so lost. If you could be detailed/help explain, I would appreciate it a lot. Thank you. Topic: Onions, Lily Anther, Mitosis and Meiosis!: Prophase I, Prometaphase I, Metaphase I, Anaphase I, Telophase I, Cytokinesis Prophase II, Metaphase II, Anaphase II, Telophase II, Cytokinesis II Tetrads Intro Pretend you were in the lab and you took some onion root tips and some lily and viewed them under the lab in a microscope. We are Concerned...

  • The picture below represents a cell during metaphase of mitosis. The chromosomes are represented in red...

    The picture below represents a cell during metaphase of mitosis. The chromosomes are represented in red and the mitotic spindle is represented in green. BO ! A. The cell is stuck in metaphase because a checkpoint has been activated. Why was the checkpoint triggered? B. What could have happened to this cell without this checkpoint? There are three main checkpoints during the cell cycle. One checkpoint occurs at the end of G1 phase and involves the protein p53. If p53...

ADVERTISEMENT
Free Homework Help App
Download From Google Play
Scan Your Homework
to Get Instant Free Answers
Need Online Homework Help?
Ask a Question
Get Answers For Free
Most questions answered within 3 hours.
ADVERTISEMENT
ADVERTISEMENT
ADVERTISEMENT