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What are the mistakes made in DNA replication?
Nucleotides bases are mismatched into DNA strand incorrectly (proofreading, mismatch repair, and nucleotide excision repair typically fixes the mismatches); DNA not fixed in time become mutated
What typically makes the mistake of DNA replication?
DNA polymerase
What are the mistakes made in cell division?
Nondisjunction (spindle fibers form incorrectly) & aneuploidy (wrong # of chromosomes)
What are the mistakes made in transcription and translation?
Wrong protein brought in
Where do the mistakes in transcription and translation typically occur?
tRNA
What are mutations?
Spontaneous or induced permanent changes in DNA
What are germline mutations?
-Present in egg or sperm
-can be inherited
-cause cancer family syndrome
What are somatic mutations?
-occur in nongermline tissues
-cannot be inherited
What are point mutations?
Mutations with one or two nucleotides
What are the types of point mutations?
Substitutions
Additions
Deletions
Describe the first type of point mutation.
Substitution: replace a nucleotide w/ another nucleotide
Describe the second type of point mutation.
Addition (insertion): add an extra nucleotide
Describe the third type of point mutation.
Deletion: take out a nucleotide
Mutations can also be...
Large scale chromosomal arrangements
Do all mutations affect protein structure and function?
No, most don't
If a mutation has an effect on protein structure/function (mutation affects the phenotype), it is called a...
Genetic disorder (inherited) or heritable disease
What are the three types of small scale mutations?
Silent mutation
Missense mutation
Nonsense mutation
Describe the first type of small scale mutations (point mutations).
Silent mutation: mutation that has no effect on the polypeptide sequence (most occur in the third base position); majority of mutations in humans are silent
Why do silent mutations not have an effect on the DNA?
Nucleotide-pair substitution results in the same amino acid as the wild type (AKA the normal strands before substitution)
Describe the second type of small scale mutations (point mutations).
Missense mutation:
-exchanges one amino acid for another
-typically substitutes a nucleotide at the first or second base position
-may have an effect (depending on the amino acid)
Describe the third type of small scale mutations (point mutations).
Nonsense mutation:
-exchanges on amino acid for a stop sequence
-will affect the protein b/c of termination
What are frameshift mutations?
Insertion or deletion of 1-2 nucleotides; will affect a protein
What is a sickle-cell anemia mutation?
Single base pair mutation in the sixth codon of B-globin gene results in a different protein
What type of mutation is sickle-cell?
Germline (inherited), missense, and substitution mutation
How does the sixth codon substitution of sickle-cell affect RBCs structure?
Polar (glutamate)-> Nonpolar (valine) affects how protein folds which creates divets in RBCs
What are large scale mutations?
Extensive changes in chromosomal structure; whole chromosomes can break and grossly misjoin through deletion, duplication (in replication), inversion, translocation (between two separate chromosomes)
Do large mutations survive?
In most cases, no, but they do survive in cancer
Define endogenous.
Inside of you
Define exogenous.
From environment
What causes mutations?
-enzyme mistakes while replication DNA
-mistakes during cell cycle, cell division
-mutagens
DNA mutations may lead to...
Uncontrolled growth or new species
Define mutagens.
Causes a DNA mutation (depend where mutation occurs)
Define carcinogens.
A mutagen that causes cancer
Define cancer.
Uncontrolled growth of abnormal cells (lead to tumors)
Define tumor.
Growing mass of cells
What tumors are invasive?
Malignant
Define metastasis.
Cells from a malignant tumor leave and spread to different areas of the body to from new tumors
Why are cancer cells considered immortal?
They are not recognized as problematic by the immune system and can grow unchecked
Define differentiation.
Zygote (stem cell) can turn into any of the adult cells
Does cancer undergo differentiation?
No, it undergoes __de__differentiation (e.g. WBC->stem cell->invades body)
What are the four hallmarks of cancer?
Dedifferentiation
Unrecognized by the immune system
Metastatic
Loss of cell cycle, or contact inhibition control (bypass the cell division checkpoints)
What do most cells exhibit?
Anchorage dependence
Density dependent inhibition
What do cancer cells lack?
Anchorage dependence and density dependent inhibition (continue to grow on top of each other-> tumor)
When a tumor develops, what can it prevent?
It prevents healthy cells from dividing due to cell density (lack of space)
Define oncogenes.
Cancer-causing genes (results in hyperactive/degradation-resistant protein)
Define proto-oncogenes (normal gene).
Corresponding normal cellular genes that are responsible for normal cell growth and division
What can happen to the proto-oncogenes?
Translocation, Gene amplification, and point mutation (can change promoter)
Define translocation.
Gene moved to new locus, under new controls
Define tumor-suppressor gene.
Normally prevent uncontrolled cell growth (e.g. CDKs [cyclin-dependent kinase] stop the cell from growing at checkpoints)
What is the main mutation that causes cancer?
Defective/missing p53-> cannot pause the cell cycle when there is damage in the DNA
How does cancer relate to age?
Older cells-> more cancer signifying cancer results from multiple mutations; a single mutation would be less dependent on age
What are the most fatal cancers?
Lung and pancreatic cancer
What are viruses composed of?
A genome (DNA or RNA) surrounded by a protein capsid
Viruses are ________
Acellular
How do viruses work?
Phage genome “hijacks” the host system
Do antibiotics kill viruses?
No
What do vaccines do?
Stimulate immune system to fight the disease-causing organism
Note
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