dna/cell cycle/cancer

Question 1

term

nucleotides

Answer 1

the monomers that make up nucleic acids

Question 1

term

DNA

Answer 1

• molecule that stores our genetic information
• makes up our genes, which are on our chromosomes
• instructions to make proteins in your body
• instruction book for new cells on how to work properly
• instructions to make an entire organism

Question 2

term

nitrogen base

Answer 2

part of nucleotide (A, T, G, C)

Question 3

term

phosphate

Answer 3

• part of nucleotide
• links nucleotides together

Question 4

term

deoxyribose

Answer 4

• part of nucleotide
• links nucleotides together

Question 5

question

What holds base pairs together?

Answer 5

hydrogen bonds

Question 6

objective

DNA strands are antiparallel to each other. What does that mean?

Answer 6

• each strand has a 5’ end and a 3’ end
• the two strands run in opposite directions

Question 7

objective

How is DNA replicated?

Answer 7

1. During DNA replication, both strands of the double helix act as templates for the formation of new DNA molecules.
2. Copying occurs at a localized region called the replication fork, which is a Y shaped structure where new DNA strands are synthesised by a multi-enzyme complex.
3. One new strand is leaving at the top of frame and the other new strand is leaving at bottom.
4. The first step in DNA replication is the separation of the two strands by an enzyme called helicase.
5. This spins the incoming DNA to unravel it: at ten thousand RPM in the case of bacterial systems.
6. The separated strands are called three prime and five prime, distinguished by the direction in which their component nucleotides join up. .
7. The 3’ DNA strand, also known as the leading strand, is diverted to a DNA polymerase and is used as a continuous template for the synthesis of the first daughter DNA helix.
8. The other half of the DNA double helix, known as the lagging strand, has the opposite 3’ to 5’ orientation and consequently requires a more complicated copying mechanism.
9. As it emerges from the helicase, the lagging strand is organised into sections called Okazaki fragments.
10. These are then presented to a second DNA polymerase enzyme in the preferred 5’ to 3’ orientation.
11. These sections are then effectively synthesised backwards.
12. When the copying is complete, the finished section is released and the next loop is drawn back for replication. I

Question 8

term

helicase

Answer 8

enzyme that separates strands of DNA

Question 9

term

DNA polymerase

Answer 9

• an enzyme that binds to the primer during DNA replication and makes a new strand of DNA
• can only add bases in one directon

Question 10

objective

What is the difference between a leading strand and a lagging strand in semi-conservative DNA replication?

Answer 10

• one of the new strands, a leading strand, is made continuously, from 5’ to 3’
• the lagging strand can’t be made continuously because it’s made in the opposite direction, from 3’ to 5’
• DNA polymerase can only make the lagging strand in a series of small chunks known as Okazaki fragments

Question 11

question

What do 5’ and 3’ refer to?

Answer 11

the carbon atoms on the deoxyribose molecule

Question 12

objective

What is the importance of cell division to an organism?

Answer 12

• growth of organism (adding more cells)
• to replace dead/damaged cells (tissue healing and regeneration)
• stem cells are involved in regenerating and replacing cells throughout the body (blood, bone, skin, muscle, etc.)

Question 13

objective

What are stem cells and why are they important?

Answer 13

• cells that give rise to all the cells in the body
• stem cells can divide to create many different types of cells in the body (or to make new stem cells)
• they are involved in regenerating and replacing cells around the body

Question 14

objective

Why must cells stay small?

Answer 14

to stay efficient

Question 15

term

chromosome

Answer 15

• coiled up DNA wrapped around proteins called histones
• 46 of them in the nucleus
• 23 in nuclei of sex cells
• DNA is in this form 5% of the time

Question 16

term

chromatin

Answer 16

• uncondensed DNA
• in this form 95% of the time

Question 17

term

centromere

Answer 17

narrow region where sister chromatids connect

Question 18

term

sister chromatids

Answer 18

• identical copies of the chromosome’s DNA
• two of them make up a duplicated chromosome

Question 19

objective

Describe each stage of the cell cycle.

Answer 19

gap1 (11 hrs)
* cell grows bigger and functions normally
* has checkpoints (is the cell big enough? are there enough energy and other reserves? is the DNA damaged?)
gap0
* cell stops dividing
synthesis (8 hrs)
* cell copies DNA
gap2 (4 hrs)
* cell makes more organelles and proteins for division
* has checkpoints (did all our DNA get replicated together? is the DNA damaged?)
mitosis (1 hr)
* cell divides duplicated chromosomes/DNA evenly
* cell divides cytoplasm and organelles (cytokinesis)

Question 20

objective

Describe each stage of mitosis.

Answer 20

prophase
* nuclear membrane breaks down
* spindle fibers made of microtubules begin to lengthen as centrioles move apart
* chromatin coils into visible chromosomes

metaphase
* spindle fibers are attached to the centromeres of the chromatids
* chromosomes are pulled to the equator (or middle) of the cell)
* nucleus is gone btw

anaphase
* sister chromatids of duplicated chromosomes are pulled apart as spindle fibers shorten and move to opposite ends of the cell

telophase
* new nucleus forms around each set of chromosomes
* cell membrane pinches inward at center
* chromosomes unwind into chromatin
* spindle fibers break down

cytokinesis
* division of the cytoplasm

Question 21

objective

How is cytokinesis different in animal and plant cells?

Answer 21

• plant cells: cell plate forms (new cell wall)
• animal cells: cleavage furrow forms (indentation in the cell membrane)

Question 22

term

cleavage furrow

Answer 22

indentation in the cell membrane of an animal cell during cytokinesis

Question 23

term

cell plate

Answer 23

new cell wall formed during a plant cell’s cytokinesis

Question 24

# term cancer

Answer 24

* uncontrolled growth of abnormal cells * shortens the cell cycle and affects gap1 and mitosis the most * since the cell cycle is shortened, doctors have to act quickly

Question 25

# term tumor

Answer 25

mass of abnormal cells

Question 26

# term benign vs. malignant

Answer 26

**benign** * confined to one area; slow growing * stage 0 tumors are benign **malignant** * can spread to other areas; fast growing * stages I, II, III, and IV tumors are malignant

Question 27

# term metastasis

Answer 27

spreading of cancer cells | stage IV tumor is metastastized

Question 28

# term apoptosis

Answer 28

* programmed cell death * happens for damaged cells * does NOT happen much with cancerous cells

Question 29

# question Why are cancer cells harmful?

Answer 29

* they take nutrients from healthy cells * they can't perform the tasks that healthy cells need to do * they crowd out healthy cells

Question 30

# term angiogenesis

Answer 30

when cancer cells release chemicals that cause bloood vessels to grow towards the tumor to supply it with nutrients and allow it to metastasize (spread

Question 31

# term mutations

Answer 31

* mistakes in genes * can lead to cancer * can be caused by radiation (UV and x-rays), chemicals (carcinogens like cigarettes, processed foods and preservatives, and cosmetics and cleaning products), and infectious agents (viruses and bacteria) * can also be spontaneous * a cell needs multiple mutations for cancer to develop (most have at least 60)

Question 32

# question How does semi-conservative replication help prevent mutations during DNA replication?

Answer 32

half of the original molecule is already there to serve as a template for the new strand

Question 33

# question What phase of the cell cycle is most affected by radiation?

Answer 33

gap1

Question 34

# question Why would radiation help combat cancer?

Answer 34

* it damages cancer cells * interferes with uncontrolled cell division

Question 35

# question What happened during the Hershey Chase experiment?

Answer 35

**first phase** * phage was produced in a medium that also contained S-35 amino acids * this led to a phage population with S-35 labeled proteins, but no label in DNA * phage infected the bacteria by attaching to the outside of the cell and injected the DNA into the cell, but the protein coat stayed on the outside of the cell * phage in these cells were not radioactive * when intense shaking occurred, protein coat shook off, but phage production in the cell was unaffected **second phase** * phage were produced in a medium that had P-32 nucleotides * this led to a population with P-32 labeled nucleotides, but no label in the protein * when the phage infected the bacteria, radioactive DNA entered the cell and was found in phage that was later produced in the bacteria