1 Flashcards
Circumstantial evidence for DNA as the hereditary material found via cell staining techniques?
DNA was in the nuclei
DNA was present in the correct amounts
Cells from different species had their own specific amount of DNA
Explain the procedure in which Frederick Griffith discovered that DNA from one bacterium transforms another type
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
Explain the bacteriophage replication process
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
Why is the double-helix structure essential to DNA function:
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
How is DNA replicated?
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 )
Name the 2 steps of DNA replication
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.
Where does DNA replication start
At the origin of replication
Why do eukaryotic chromosomes have multiple origins
because they are much longer than prokaryotic chromosomes
Which end of DNA can DNA polymerase add to
3” (That’s why a primer is needed)
How is DNA unwound?
by DNA helicase (uses ATP hydrolysis to break the hydrogen bonds)
Explain DNA proofreading
3’-5’ exonuclease is activated to remove the incorrect nucleotide, which allows DNA replication to proceed
Explain mismatch repair
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
Explain excision repair
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
Name the 3 events that are required before a cell can divide
DNA replication
Growth
Chromosome segregation
Name and describe the type of division that occurs in prokaryotic cells
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.
Name each stage of the Eukaryotic Cell Division Cycle in order
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)
Name and describe the asexual reproduction method in eukaryotic Cells
Budding- the process in which a new organism develops from an outgrowth or bud due to cell division at one particular site.
How does a cell ‘know’ when to divide?
Either via external (attaches to receptor outside cell-hydrophilic) or internal stimuli (attaches to receptor inside nucleus-hydrophobic)
What is the role of growth factors
To promote cell growth
What is the role of mitogen
To promote cell division
What is the difference between an allele and a gene?
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
What is the difference between a centromere and a centrosome
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
Explain the term “homologous chromosomes”
homologous chromosomes are chromosome pairs that are the same (one from each parent)
What is a kinetichore
a structure that is formed on chromatids that attach to the spindle fibres
What are the 2 mendel laws
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.
What is a test cross?
When an unknown allele and homozygous recessive allele are crossed
What determines gamete variability?
The heterozygous allele
What is an oncogene
A gene which in certain circumstances can transform a cell into a tumour cell.
What is a proto-oncogene
A normal gene which, when altered by mutation, becomes an oncogene that can contribute to cancer.
What is a tumor suppressor genes
A type of gene that makes a protein called a tumor suppressor protein that helps control cell growth.
What does a kinase do?
Adds a phosphate (catalyses phosphorylation)
What does a phosphatase do?
Removes a phosphate (catalyses dephosphorylation)
Explain how a CDK is activated
It binds to a cyclin, which then causes it to undergo phosphorylation and activates
What is a CDI
a Cylcin Dependent Inhibitor, this joins to a cyclin-CDK complex and inactivates it
What does a CDK do?
arrests the cell cycle to allow allow certain checkpoints to be satisfied, these checkpoints fixes cell damage or causes the cell to undergo apoptosis
What does the G1/S checkpoint check for? and what activates it
Damage toDNA?
Presence of Growth factors/mitogens? (activates checkpoint)
Correct size?
Adequate energy reserves?
What does the G2/M checkpoint check for? and what activates it
Has DNA synthesis occurred correctly?
Is DNA damaged? (activates checkpoint)
Are preparations for M phase complete?
Is the cell big enough?
What does the Metaphase-Anaphase checkpoint (Spindle Assembly Checkpoint (SAC)) check for? and what activates it
Are all chromosomes attached to the mitotic spindle?(activates checkpoint)
Can sister chromatids separate correctly?
