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Question 1

Circumstantial evidence for DNA as the hereditary material found via cell staining techniques?

Answer 1

DNA was in the nuclei
DNA was present in the correct amounts
Cells from different species had their own specific amount of DNA

Question 2

Explain the procedure in which Frederick Griffith discovered that DNA from one bacterium transforms another type

Answer 2

2 strains of bacterium Streptococcus pneumoniae (virulent and non-virulent) were introduced to mice
virulent bacteria killed the mice
non-virulent bacteria didn’t kill the mice
The virulent bacteria was then boiled, and it didn’t kill the mice
However, when the boiled virulent bacteria was mixed with the non-virulent bacteria, it killed the mice

Question 3

Explain the bacteriophage replication process

Answer 3

Bacteriophage attaches to the surface of a bacterium and injects its genetic material.
Viral genes then take over the host’s machinery, which synthesizes new viruses.
The bacterium bursts, releasing about 200 viruses

Question 4

Why is the double-helix structure essential to DNA function:

Answer 4

Precise replication of DNA can be carried out via complementary base pairing.
Genomes contain millions of nucleotides, therefore allowing the base sequences to store a huge amount of genetic information.
DNA is susceptible to mutations (alterations in base sequences), allowing natural selection to occur
Genetic information is expressed as the phenotype—nucleotide sequence determines the sequence of amino acids in proteins

Question 5

How is DNA replicated?

Answer 5

semi-conservatively ( in which each parent strand serves as a template for a new strand, and the two new DNA molecules each have one old and one new strand )

Question 6

Name the 2 steps of DNA replication

Answer 6

The DNA double helix is unwound to separate the two template strands and make them available for new base pairing
New nucleotides form complementary base pairs with template DNA, which are covalently linked together by phosphodiester bonds, forming a polymer whose base sequence is complementary to the bases in the template strand.

Question 7

Where does DNA replication start

Answer 7

At the origin of replication

Question 8

Why do eukaryotic chromosomes have multiple origins

Answer 8

because they are much longer than prokaryotic chromosomes

Question 9

Which end of DNA can DNA polymerase add to

Answer 9

3” (That’s why a primer is needed)

Question 10

How is DNA unwound?

Answer 10

by DNA helicase (uses ATP hydrolysis to break the hydrogen bonds)

Question 11

Explain DNA proofreading

Answer 11

3’-5’ exonuclease is activated to remove the incorrect nucleotide, which allows DNA replication to proceed

Question 12

Explain mismatch repair

Answer 12

A nucleotide is mismatched, and mismatch repair proteins remove the mismatched nucleotide and a couple adjacent nucleotides, and DNA polymerase adds the correct nucleotides, and DNA ligase fixes the gap

Question 13

Explain excision repair

Answer 13

A nucleotide is damaged, and excision repair proteins excise the damaged nucleotide and a couple adjacent nucleotides, and DNA polymerase adds the correct nucleotides, and DNA ligase fixes the gap

Question 14

Name the 3 events that are required before a cell can divide

Answer 14

DNA replication
Growth
Chromosome segregation

Question 15

Name and describe the type of division that occurs in prokaryotic cells

Answer 15

binary fission, this process is the simplest mechanism of cell division, and is a type of asexual reproduction, this is so simple due to DNA replication, cell growth, & division occur simultaneously.

Question 16

Name each stage of the Eukaryotic Cell Division Cycle in order

Answer 16

G1 phase(Cells must double in size and prepare for DNA replication)
S phase(DNA replication begins at origins of replication and continues until all DNA has completed a single round of replication)
G2 phase(Second growth phase: organelles are duplicated and cell prepares for mitosis)
Mitosis(Segregation of sister chromatids to form two identical sets of chromosomes)
Cytokinesis(two new cells are formed, each carrying an identical set of chromosomes)

Question 17

Name and describe the asexual reproduction method in eukaryotic Cells

Answer 17

Budding- the process in which a new organism develops from an outgrowth or bud due to cell division at one particular site.

Question 18

How does a cell ‘know’ when to divide?

Answer 18

Either via external (attaches to receptor outside cell-hydrophilic) or internal stimuli (attaches to receptor inside nucleus-hydrophobic)

Question 19

What is the role of growth factors

Answer 19

To promote cell growth

Question 20

What is the role of mitogen

Answer 20

To promote cell division

Question 21

What is the difference between an allele and a gene?

Answer 21

A gene is a distinct sequence of nucleotides which is transferred from a parent to an offspring (1 gene from each parent, both are the same), and an allele is when the copy of the gene from each parent differs

Question 22

What is the difference between a centromere and a centrosome

Answer 22

a centromere is a structure in a chromosome that holds together the 2 sister chromatids, and a centrosome (made from 2 centrioles) is an organelle where microtubules are organised

Question 23

Explain the term “homologous chromosomes”

Answer 23

homologous chromosomes are chromosome pairs that are the same (one from each parent)

Question 24

What is a kinetichore

Answer 24

a structure that is formed on chromatids that attach to the spindle fibres

Question 25

What are the 2 mendel laws

Answer 25

The principle of segregation (First Law): The two members of a gene pair (alleles) segregate (separate) from each other in the formation of gametes. Half the gametes carry one allele, and the other half carry the other allele.
The principle of independent assortment (Second Law): Genes for different traits assort independently of one another in the formation of gametes.

Question 26

What is a test cross?

Answer 26

When an unknown allele and homozygous recessive allele are crossed

Question 27

What determines gamete variability?

Answer 27

The heterozygous allele

Question 28

What is an oncogene

Answer 28

A gene which in certain circumstances can transform a cell into a tumour cell.

Question 29

What is a proto-oncogene

Answer 29

A normal gene which, when altered by mutation, becomes an oncogene that can contribute to cancer.

Question 30

What is a tumor suppressor genes

Answer 30

A type of gene that makes a protein called a tumor suppressor protein that helps control cell growth.

Question 31

What does a kinase do?

Answer 31

Adds a phosphate (catalyses phosphorylation)

Question 32

What does a phosphatase do?

Answer 32

Removes a phosphate (catalyses dephosphorylation)

Question 33

Explain how a CDK is activated

Answer 33

It binds to a cyclin, which then causes it to undergo phosphorylation and activates

Question 34

What is a CDI

Answer 34

a Cylcin Dependent Inhibitor, this joins to a cyclin-CDK complex and inactivates it

Question 35

What does a CDK do?

Answer 35

arrests the cell cycle to allow allow certain checkpoints to be satisfied, these checkpoints fixes cell damage or causes the cell to undergo apoptosis

Question 36

What does the G1/S checkpoint check for? and what activates it

Answer 36

Damage toDNA?
Presence of Growth factors/mitogens? (activates checkpoint)
Correct size?
Adequate energy reserves?

Question 37

What does the G2/M checkpoint check for? and what activates it

Answer 37

Has DNA synthesis occurred correctly?
Is DNA damaged? (activates checkpoint)
Are preparations for M phase complete?
Is the cell big enough?

Question 38

What does the Metaphase-Anaphase checkpoint (Spindle Assembly Checkpoint (SAC)) check for? and what activates it

Answer 38

Are all chromosomes attached to the mitotic spindle?(activates checkpoint)
Can sister chromatids separate correctly?