Genetics Exam 4 Flashcards

Front 1

Transformation

Back 1

The process by which a cell loses its ability to remain constrained in its growth properties

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Tumor

Back 2

Neoplasm; "New Growth"

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Metastasis

Back 3

The spreading of malignant tumor cells throughout the body
- "Change of State"

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Oncogenesis

Back 4

Initiation of tumors in an organism
- onco- "mass/bulk"; -genesis "birth"

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Cell Cycle Checkpoints

Back 5

Different points in the cell cycle that are control points at which the cell cycle is arrested if there is damage to the genome or cell cycle machinery
- Prevents cells from becoming cancerous

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Cyclins and Cyclin-dependent kinases

Back 6

Key components of the regulatory events that occur at checkpoints

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Cyclins

Back 7

Proteins that regulate events that occur at checkpoints

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Cyclin-dependent kinases

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Enzymes that regulate events that occur at checkpoints

Front 9

2 main ways our cells regulate cell growth

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Cell cycle & growth factors

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Growth Factors

Back 10

Molecules that stimulates cell division of a target cell by binding to specific receptors on their target cells
-- Signal is relayed via a serious of proteins, eventually activating nuclear genes that encode proteins for stimulating cell growth and divisions

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Growth-inhibitory factors

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Lead to inhibition of cell growth and division

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Signal Transduction

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The process of relaying a growth-stimulatory or growth-inhibitory signal after a growth factor binds to a cell
-- proteins involved are called signal transducers

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Neoplastic cell

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Cancer cell; lost control of cell division and reproduces without constraints

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5 ways we know cancer is genetically linked

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1.) Cancer has been known to be passed down through generations
2.) Some viruses cause cancer
3.) Descendents of cancerous cells are all cancerous
4.) Exposures to mutagens increases the chances of cancer
5.) Certain chromosomal mutations are associated with particular forms of cancer (Ex. Burketts Lymphoma, Chronic Myelogenous Leukemia)

Front 15

3 Classes of Genes Mutated in Cancer

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1.) Proto-Oncogenes
2.) Tumor Suppressors
3.) Mutator Genes

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Proto-Oncogenes

Back 16

Normally: Stimulate cell growth/reproduction

Mutant: more active than normal or active at inappropriate times

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Tumor Suppressors

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Normally: Inhibit tumors

Mutant: lost their inhibitory function

Front 18

Mutator Genes

Back 18

Normally: ensure loyalty of replication and maintenance of genome integrity

Mutant: lost their normal function and make cell prone to accumulate mutational errors in gene
- include proto-oncogenes and tumor suppressor genes

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Tumor Virus

Back 19

Induce the cells they infect to proliferate in an uncontrolled fashion and produce a tumor

Front 20

Oncogene

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A gene whose action stimulates unregulated cell proliferation

Front 21

Two types of Tumor Viruses

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1.) RNA Tumor Virus
2.) DNA Tumor Virus

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RNA Tumor Virus

Back 22

All RNA Tumor Viruses are retroviruses, but not all retroviruses are tumor viruses
- When an RNA Tumor Virus infects the cell, the RNA genome is released from the viral particle, and via reverse transcriptase, a cDNA copy of the genome - called the proviral DNA - is synthesized. The proviral DNA integrates into the genome of the host cell. Then, using host transcriptional machinery, viral genes are transcribed, and full length viral RNA's are produced. Progeny viruses assembled within the cell then exit and can infect other cells.

Front 23

Example of an RNA Tumor Virus

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Rous Sarcoma Rivus (RSV)

Front 24

Proto-oncogenes

Back 24

These genes, when introduced into other cells growing in culture, transformed those cells into cancer cells

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What is the role of proto-oncogenes?

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Regulating the cell cycle

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oncogenes (oncs)

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when proto-oncogenes become mutated or translocated so that they contribute to inducing tumor formation
-- this mutation is sufficient enough to caused complete loss of the cell cycle control

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v-oncs

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oncogenes carried by a virus

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cellular oncogenes (c-oncs)

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oncogenes that reside in the host chromosome

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Main difference between cellular proto-oncogene and viral oncogene

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most proto-oncogenes contain introns that are not present in v-oncs. This is because of splicing that occurs in the transcription event that generates rival RNA genomes from proviral DNA

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Examples of Proto-oncogenes

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1.) Growth Factors
2.) Protein Kinases
3.) Membrane Associated G Proteins

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Membrane Associated G Proteins

Back 31

Normally involved in the signalling cascade; the steps from the growth factor receptor to the nucleus
-- Example includes RAS that is involved in the activation of transcription of a cell cycle-specific target gene.

When Ras binds to GTP, it becomes Ras-GTP. Ras-GTP recruits Raf-1 and activates it.

Normal: Turning the Ras signal off in normal genes involves GAP making Ras hydrolyze the GTP bound to it back to GDP. This inactivates Ras and cancels the cell cycle stimulatory signal

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How does Ras become an oncogene?

Back 32

Via mutation
-- Abolishes its ability to hydrolize GTP to GDP.
-- Even with GAP, the Ras-GTP complex remains and the signal is continuously on.

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3 ways a proto-oncogene can turn into an oncogene

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1.) Point mutation; via base-pair substitutions
2.) Deletions
3.) Gene amplifications; increased number of copies of a gene

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Point Mutation of Proto-oncogene

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- Base-pair substitution
- in the coding region or in the controlling sequences
- cause an increase in either the activity of the gene product, or the expression of the gene

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Deletion mutation of a Proto-Oncogene

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occur on part of the coding region or part of the regulatory regions
- cause changes in the amount of growth stimulatory protein, resulting in unprogrammed proliferation of the cell

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Gene Amplification of Proto-Oncogenes

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- Over replication of small segments of DNA make extra copies of genes
- Extra copies of genes result in extra gene expression

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Transducing Retrovirus

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Retrovirus carrying an oncogene

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Normal Cellular Genes that are similar to those of viral oncogenes and encode proteins that stimulate cell growht and division

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Proto-oncogenes

Front 39

Retroviral Oncogenes

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modified copies of the cellular proto-oncogenes that have been picked up by the retrovirus

Front 40

2 Hit Model for Cancer

Back 40

explains the difference between familial and sproradic cancers
-- In familial cancers, one mutation is inherited. A second mutation occurs later in somatic cells, and cancer may then develop.
- In sporadic cancers, both mutations occur in somatic cells.

Front 41

DNA Tumor Viruses

Back 41

Transform host cells into cancerous cells through action of genes within the viral genome
-- ex.: papovavirus, hepatitis B, herpes, adenovirus, pox virus

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How do DNA Tumor Viruses Work?

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1.) Virus activates viral protein
2.) Protein results in excess replication of viral DNA
3.) Viral progeny lyse cell and infect other cells

Front 43

normal p53

Back 43

Tumor suppressor protein.
Normal cell: unphosphorylated, and binds with the unphosphorylated Mdm2, which degrades p53.

Cell w/ DNA damage: Mdm2 and p53 are phosphorylated, and cannot bind. p53 accumulates, and WAF1 is activated by p53 which encodes for p21 protein that binds to the G1-S checkpoint. Cdk3-cyclin D complexes, and inhibits their activity. As a result pRB in the pRB-E2F complex doesn't become phosphorylated and E2F is kept inhibited. Entry into S is blocked, and the cell arrests in G1 of the cell cycle

Front 44

TP53

Back 44

Tumor suppressor that encodes for p53

Front 45

p53 causing cancer

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When both alleles of TP53 carry loss of function mutations, no active p53 can be produces. Through the cascade of events, the cell is unable to arrest in G1 and the cell can proceed into S phase of the cell cycle.

Front 46

Carcinogens

Back 46

Natural and artificial agents that increase the frequency with which cells become cancerous.
-- mostly chemicals and types of radiation
-- cause genomic changes in the cell
-- act directly on the genome or indirectly on the genome
-- typically point mutations

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Direct-acting carcinogens

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chemicals that bind to DNA and act as mutagens

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Procarcinogens/Indirect carcinogens

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must be converted metabolically to become active carcinogens called ultimate carcinogens most of which bind to DNA and act as mutagens

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Gene pool

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Genes shared by the individuals of a Mendelian population

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Mendelian population

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a group of interbreeding individuals who share a common set of genes

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Goal of population genetics

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Understand the genetics of evolution

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Questions frequently studied by population geneticists

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1.) How much genetic variation is found in natural opulations and what processes control the amount of variation observed
2.) What processes are responsible for producing genetic divergence among populations
3.) How do biological characteristics of a population, such as mating system, fecundity, and age structure, influence the genetic structure of the population

Front 53

Hardy-Weinberg law

Back 53

Set of equations that describe the influence of random mating on the allele and genotype frequencies of an infinitely large population

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5 assumptions of Hardy-Weinberg

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1.) Large population
2.) No mutation
3.) No natural selection
4.) No migration
5.) Random Mating

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Hardy-Weinberg Results (2)

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1.) The frequencies of the alleles do not change over time, where p is the allele frequency of A and q is the allele frequency of a
2.) Genotypic frequencies remain in the proportions p^2, 2pq, and q^2. The sum of the genotype frequencies equals 1
-- 1 = p^2 + 2pq + q^2

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Discontinuous Traits

Back 56

Traits that show an exact phenotype
-- Ex.: Seed color, pea shape, pod color, etc.

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Continuous traits

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Traits which show great variation in phenotype
-- Ex.: body weight or height