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BIOL1020 Lecture Notes - Lecture 8: Sister Chromatids, Dna Replication, Eukaryote

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blueclam798
20 May 2018
School
UQ
Department
Biology
Course
BIOL1020
Professor
Dr Paul Ebert

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L8 - cell division and cell cycle !
•Cell division results in genetically identical daughter cells. !
•Cells duplicate their genetic material before they divide, ensuring that each daughter cell
receives an exact copy of the genetic material, DNA !
•The DNA molecules in a eukaryotic cell are packaged into #
chromosomes !
•Eukaryotic chromosomes consist of chromatin; a complex of DNA and protein that condenses
during cell division !
•In animals!
•Somatic cells have two sets of chromosomes (one set from #
each parent). They all have the SAME chromosomes. They divide through mitosis. !
•Gametes (germ cells/ova + sperm) have only one set of chromosomes. These are
produced by a special type of cell division called meiosis. #
Prokaryotic cell division
•Binary fission: asexual reproduction where a cell expands and then divides in two. !
•In Bacteria, DNA is free-floating in the cytoplasm, and does not have membrane-bound
organelles. !
•Very important to replicate the DNA so that daughter cells have identical genetic information. #
Eukaryotic cell division
•the cell division is more controlled because eukaryotic cells have more DNA !
•DNA needs to be packed Into chromosomes !
•Cell division then happens through a carefully coordinated cell cycle and mitosis !
Chromosome
!
One single arm is the chromosome from one parent. For each
chromosome, we have two arms (one from each parent).!
Preparing for cell division, each chromosome is then replicated
into two. If both of arms come from the same chromosome
they are called sister chromatids. Each arm in the sister
chromatid pair, is called a chromatid. !
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!
The cell cycle
•The cell is not often in the division process. !
•Cell division also depends on which type of cell it is
because skin cells divide more than brain cells. !
•The eukaryotic cell cycle consists of two phases: !
•Interphase (G1, S and G2) !
•Mitotic phase (M) !
Interphase!
• Interphase consists of: !
•Gap 1 (G1) phase: normal cell metabolism !
$ $ glucose oxidisation, synthesis of macromolecules !
•S phase: when DNA replication occurs !
•Gap 2 (G2) phase – preparation for cell division (prep for mitosis)!
•Most cells spend most of their time in this phase because they are not always preparing for
mitosis. It may last for hours, days, weeks or longer.!
•During this phase, cells grow to their mature size !
•The metabolism is not active during mitosis because the all the cell compartments are broken
up and rearranging each other. !
Mitotic phase!
The mitotic phase of the eukaryotic cell cycle consists of: !
•Mitosis, the division of the nucleus !
•Cytokinesis, the division of the cytoplasm !
•Typically lasts only 30-60 min. (depending on the cell type) !
•Is the period where cells are overtly dividing. !
•All other activities are put on hold. This is because the normal internal organisation of the cell is
disrupted in this stage. #
5 stages of Mitosis
Interphase (G2)!
•the cell is preparing for mitosis !
•DNA has been duplicated in the previous S phase !
•Duplicated DNA still in form of Chromatin !
•the nuclear envelope is still attached !
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Document Summary

They divide through mitosis: gametes (germ cells/ova + sperm) have only one set of chromosomes. These are produced by a special type of cell division called meiosis. Eukaryotic cell division: the cell division is more controlled because eukaryotic cells have more dna, dna needs to be packed into chromosomes, cell division then happens through a carefully coordinated cell cycle and mitosis. One single arm is the chromosome from one parent. For each chromosome, we have two arms (one from each parent). Preparing for cell division, each chromosome is then replicated into two. If both of arms come from the same chromosome they are called sister chromatids. Each arm in the sister chromatid pair, is called a chromatid. It may last for hours, days, weeks or longer: during this phase, cells grow to their mature size, the metabolism is not active during mitosis because the all the cell compartments are broken up and rearranging each other.

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Related Questions

M2A1 Worksheet: Mitosis and Meiosis

A dog is a diploid organisms and has 39 pairs of chromosomes (2n = 78), where n = 39 chromosomes from each parent. Use this example to answer the following question regarding chromosomal number.

INTERPHASE

How many chromosomes are present in the somatic cell?

What do they look like?

What are they “doing” in G1 of this phase?

What is happening in the S phase?

What is happening in the G2 phase?

What follows G2 phase in a somatic cell?

What follows G2 phase in a gamete cell?

MITOSIS

Number of chromosomes in the parent cell.

Number of chromatids in the parent cell.

Number of chromosomes in the daughter cell.

Number of chromatids in the daughter cell.

How many daughter cells are produced?

Are the daughter cells haploid or diploid?

How many cell divisions take place?

In what type of cell does this division occur?

Meiosis 1:

Number of chromosomes in the parent cell.

Number of chromatids in the parent cell.

Number of chromosomes in each Meiosis I daughter cell.

Number of chromatids in each Meiosis I daughter cell.

Are the daughter cells haploid or diploid at the end of Meiosis 1?

Meiosis II:

Number of chromosomes in the “parent” cell (which is a daughter cell from Meiosis I).

Number of chromatids in the “parent” cell.

Number of chromosomes in each Meiosis II daughter cell.

Number of chromatids in each Meiosis II daughter cell.

Are the daughter cells haploid or diploid at the end of Meiosis II?

Which phase or phases of Meiosis account for the genetic variability among the daughter cells? How… what happens in this phase to create the diversity?

Comparing Mitosis and Meiosis…..

How many daughter cells result from Mitosis? Are they diploid or haploid?

How many daughter cells result from Meiosis? Are they diploid or Haploid?

Cell structures and function: Match each organelle to its function:

Organelle Function

Lysosome 1. Lipid synthesis

Rough ER 2. Houses DNA

Nucleus 3. Energy extraction

Smooth ER 4. Dismantles debris

Golgi apparatus 5. detoxification

Mitochondria 6. Protein synthesis

Peroxisome 7. Processes secretions

What is the function of checkpoint proteins in the cell cycle?

How can all of a person’s cells contain exactly the same genetic material, yet specialize as bone cells, nerve cells, muscle cells and connective tissues?

What are the 3 primary germ layers?

Briefly, in one or two sentences, distinguish between

a bacterial cell and a eukaryotic cell

interphase and mitosis

mitosis and apoptosis

an autosome and a sex chromosome

homologous pair of chromosomes and a sister chromatid

centromere and centriole

chromosome and chromatid

monozygotic and dizygotic twins

allele and gene

What is the difference between chromatin and chromosomes?

Question options:

chromatin is one of two identical strands of DNA.

chromosomes are chromatin that has been tightly packed and coiled.

chromosomes are composed of nucleosomes and chromatin is composed of sister chromatids.

chromosomes are important in mitosis and chromatin is essential to meiosis.

Bacterial cells only reproduce asexually and cannot exchange genetic material.

Question options:

True, because they undergo binary fission.

False, because they transfer genetic material with other bacterial cells.

True, because they have a cell wall that prevents sharing of genetic material.

After a visit to a specialist, Dan was diagnosed with liver cancer. Six months later additional tumors were found in his stomach and small intestine. This is an example of

Question options:

malignant tumors.

benign tumors.

Both malignant tumors and metastasis are correct.

Which of the following does NOT occur during mitosis?

Question options:

DNA is replicated.

Replicated chromosomes divide.

Cells line up along the equator of the cell.

Which of the following is INCORRECTLY matched?

Question options:

prophase -- mitotic spindle forms

metaphase -- chromosomes line up along the equator

telophase -- cytoplasm divides



Why is hair loss a common side effect of cancer treatments?

Question options:

Hair cells are at the surface of the body so die easily.

Hair cells divide rapidly and so are targeted by the cancer drugs.

Cancer drugs often target and kill random cells within the body.

From "Investigating Life: Cutting Off a Tumor's Supply Lines in the War on Cancer," how are endostatins used to treat cancerous cells?

Question options:

They prevent angiogenesis by cancerous cells.

They promote growth of new blood vessels to feed cells.

They bind to receptors on cancerous cells and prevent cells from reproducing.

1. In addition to identifying the genetic material, the experiments of Avery, MacLeod, and McCarty with different strains of Streptococcus pneumoniae demonstrated that
DNA is a double helix.
DNA may be taken up by bacterial cells and be active.
DNA is present in bacteriophage T2.
eukaryotic cells may be genetically transformed.
DNA binds to the cell wall of the bacterium.
2. In order to show that DNA in cell extracts is responsible for genetic transformation in Streptococcus pneumoniae, important corroborating evidence should indicate that _______ also destroy transforming activity.
temperatures high enough to kill cells
enzymes that hydrolyze proteins
enzymes that hydrolyze DNA
enzymes that hydrolyze polysaccharides
enzymes that hydrolyze RNA
3. Based on what you have learned about the experiments conducted by Griffith and Avery and colleagues with bacteria, which of the following would result in transformation of living R cells?
Pure RNA from S cells
Cell-membrane extracts from S cells
A mixture of pure RNA and protein from S cells
Cell-free extracts from S cells
Pure protein from S cells
4. A-T base pairs in a DNA double helix
form three hydrogen bonds with each other.
are more heat-stable than G-C base pairs.
are of a substantially different length than G-C base pairs.
are not accessible to DNA binding proteins.
are chemically distinct from G-C base pairs.
5. If 23 percent of the bases in a sample of double-stranded DNA are adenine, what percentage of the bases are uracil?
27
50
0
73
23
6. The uniform diameter of the DNA structure provides evidence for
antiparallel DNA strands.
a right-handed helix.
a double-stranded helix.
3′ end phosphorylation.
purine–pyrimidine pairing.
7. If a sequence of one strand of DNA is 5′-TGACTATC-3′, what is the complementary strand?
5′-ACTGATAG-3′
3′-TGACTATC-5′
3′-ACTGATAG-5′
3′-ACTGATAG-3′
5′-TGACTATC-3′
8. What structural aspect of the DNA facilitates dissociation of the two DNA strands for replication?
3′ end phosphorylation
Purine–pyrimidine pairing
Antiparallel DNA strands
Covalent bonds between sugars and phosphate groups
Hydrogen bonding between paired bases
9. If the Meselson–Stahl density gradient experiment had resulted in two bands of DNA molecules after only one round of replication, one containing only 15N and the second only 14N, this result would have indicated that replication was
unidirectional.
dispersive.
conservative.
bidirectional.

semiconservative.
10. The nucleoside analogue acyclovir, which is used to treat herpes simplex virus (HSV) infections, lacks a 3′ hydroxyl group (–OH). Predict what will happen if the host cell DNA polymerase incorporates a molecule of acyclovir into an elongating strand of HSV DNA.
The replication complex will no longer bind to origins of replication.
The DNA polymerase will only incorporate acyclovir molecules.
Acyclovir will bind single-strand binding proteins.
DNA polymerase will not be able to link a successive nucleotide.
Acyclovir will block the activity of the DNA helicase.
11. Which of the following does not demonstrate the stability of the DNA double helix?
Single-strand binding proteins are required to keep the strands apart.
Paired bases form hydrogen bonds.
High temperatures are required to denature it.
DNA synthesis requires energy.
DNA helicases require ATP.
12. What effect would a primase inhibitor have on DNA replication?
DNA polymerase would not be able to add bases to the DNA.
Primase would be blocked from joining the DNA replication complex.
Primase would not be able to provide primers for DNA polymerases.
DNA polymerase would not be able to use DNA as a template.
There would be no effect on DNA replication.
13. To replicate their DNA in a timely manner, most eukaryotic chromosomes
normally have uncoiled DNA.
have multiple origins of replication.
contain linear molecules of single-stranded DNA.
have two replication forks that move in the same direction.
are composed entirely of DNA.
14. Which statement about DNA replication is false?
Okazaki fragments are synthesized as parts of the leading strand.
Error rates for DNA replication are reduced by proofreading of the DNA polymerase.
The sliding clamp increases the rate of DNA synthesis.
Replication forks represent areas of active DNA synthesis on the chromosomes.
Ligases and polymerases function in the vicinity of replication forks.
15. In many eukaryotes, there are repetitive sequences called telomeres at the ends of chromosomes. After successive rounds of DNA replication, the _______ strand becomes shorter. In some cells, an enzyme called _______ repairs the shortened strand.
leading; telomerase
lagging; telomerase
lagging; DNA polymerase I
leading; DNA polymerase I
leading; replicase
16. A researcher studies normal human fibroblast cells. They can be maintained in culture but die off after about 30 cell generations. Unexpectedly, a colony of cells continues to survive and divide past 30 generations. Which scenario is most likely true for these cells?
DNA polymerase is constantly active.
Primase is able to extend the telomeres.
The mismatch repair system is extra efficient.
The telomerase gene is being expressed.
The cells do not need the ends of their chromosomes.
17. If DNA polymerase III introduces an incorrect nucleotide, what is the first corrective action made by the DNA repair system?
The replication complex excises the incorrect nucleotide.
The excision repair proteins remove the incorrect nucleotide.
The mismatch repair system scans for base-pairing mismatches.
There is no correction, because nucleotide errors by DNA polymerases are not repaired.
DNA ligase connects the correct nucleotide.
18. Choose the correct order of the following four events in the excision repair of DNA:
(1) Base-paired DNA is made complementary to the template.
(2) Damaged bases are recognized.
(3) DNA ligase seals the new strand to existing DNA.
(4) Part of a single strand is excised.
1, 2, 3, 4
2, 1, 3, 4
3, 4, 2, 1
2, 4, 1, 3
4, 2, 3, 1
19. Six complete cycles of PCR should result in a _______-fold increase in the amount of DNA.
64
32
12
128
6
20. When double-stranded DNA is heated to temperatures above 90°C, it denatures. Denaturation is a process that
breaks covalent bonds.
hydrolyzes DNA.
separates double-stranded DNA into two single strands.
causes new hydrogen bonds to form.
irreversibly destroys the double helical structure.