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52 Cards in this Set
- Front
- Back
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How many chromosomes and base pairs in the human genome?
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-23 ch'
-700 million base pairs |
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How much is functional and how much is extragenic DNA?
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Extra: 70%
Genes: 30% |
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Pneumonic for remembering the pieces of a chromosome:
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SPLQ
-SHORT = p -LONG = q |
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What is between the short and long arm of a chromosome?
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The centromere
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What do ALL cancers arise from?
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Genetic alterations
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How much cancer is hereditary?
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5-10%
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The study and understanding of cancer is transitioning from traditional epidemiology to:
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Molecular epidemiology
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What is a codon made up of?
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3 base pairs
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How many codons are there?
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64
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What do codons encode?
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Amino acids
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What is a point mutation?
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A change in a single base pair
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In the original primary sequence of base pairs, what are exons and introns?
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Exons: the nonextra stuff
Introns: the nonimportant stuff OPPOSITE |
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What is a polymorphism?
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A DNA sequence change that does NOT alter protein function.
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What is a sequence variant?
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A base pair change that does not change the amino acid sequence.
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How can there be silent sequence variants?
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Because of the redundancy of the genetic code.
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What is a Missense mutation?
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A change in codon that leads to another amino acid being translated.
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Are missense mutations always harmful?
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No, they can be neutral polymorphisms.
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What is a Nonsense Mutation?
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A change that introduces a stop codon where it shouldnt be, resulting in a shorter protein.
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What is a Frameshift mutation?
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A change that inserts or deletes base pairs and produces a stop codon downstream, with a shorter resulting protein.
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What change results from a Splice-Site mutation?
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An altered RNA sequence
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What are the 3 types of genes associated with cancer predisposition?
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1. Tumor suppressor genes
2. Oncogenes 3. DNA damage-response genes |
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What are tumor suppressor genes?
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The cell's brakes for tumor growth
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What change in tumor suppressors allows for cancer to arise?
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Both brakes fail
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What do oncogenes do?
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Accelerate cell division
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When does cancer arise via oncogene mutations?
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When the gas is stuck on
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What are DNA damage-response genes?
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The repair mechanics for DNA
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When does damage to DNA dmg-response genes allow for cancer to arise?
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When BOTH genes fail, so mutations accumulate at a faster rate in OTHER CRITICAL GENES.
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So what is the hypothesis for how tumor suppressor gene mutations cause cancer?
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The 2 hit hypothesis - BOTH BRAKES HAVE TO FAIL.
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Where is the first hit?
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In the germline dna
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HWhat is the hypothesis for how oncogenes cause cancer?
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Just one gas pedal - only one mutation is needed
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What are the 2 main categories of gene mutations?
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1. Germline mutations
2. Somatic mutations |
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What is a Germline mutation?
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One that is present in egg or sperm and is inherited by all of the cells in the affected offspring.
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What is a Somatic mutation?
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One that occurs in nongermline tissue and is NONinheritable.
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What does heterozygosity refer to?
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Having one normal allele and one mutant allele.
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What are 6 mechanisms that lead to loss of heterozygosity?
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1. Chromosome loss
2. Deletion 3. Loss/reduplication 4. Unbalanced translocation 5. Mitotic recombination 6. Point mutation |
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At what point in the cell cycle do oncogene mutations appear?
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Going from G1 to G0 - they accelerate it.
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At what point in the cell cycle do tumor suppressor gene mutations appear?
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Going from G0 to S phase - they fail to stop it.
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At what point in the cell cycle do DNA repair gene mutations appear?
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Going from S phase to G2 and mitosis - fail to see that synthesized DNA is damaged.
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What do disease-associated mutations result in?
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Altered protein function
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What does the RET gene illustrate?
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That different MUTATIONS in the SAME GENE can cause DIFFERENT SYNDROMES.
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What does the BCRA gene illustrate?
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That mutations in DIFFERENT GENES can cause the SAME SYNDROME.
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What is Carrier frequency?
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The prevalence of an altered disease gene in a given population
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If 2 of 10 people are carriers of a diseased gene, what is the carrier frequency?
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20%
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What does Age-specific penetrance show?
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The % of people with an altered gene, who actually get the disease as they get older.
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What disease shows a substantial increase in age-spcf penetrance as individuals grow older?
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HNPCC - hered nonpolyposis colorectal cancer.
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What are 4 factors that affect the penetrance of disease with age in carriers of gene mutations?
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-Modifier genes
-Responses to DNA damage -Carcinogen exposure -Hormonal/repro factors |
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What factor is associated with increased penetrance of breast cancer?
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Estrogen
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What is important to remember about those people that do carry an altered gene?
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Not everyone with altered genes will develop cancer.
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Who is at high risk for hereditary cancer?
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Only a small porportion; only about 10% of cancer is hereditary.
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What is the key to identifying a hereditary cancer?
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The FAMILY HISTORY
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How do you do an accurate risk assessment?
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By looking as extensively into their pedigree as possible.
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What are 6 things that make you suspect hereditary cancer?
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-Cancer in 2/more close relatives
-Early age of diagnosis -Multiple primary tumors -Bilateral or multiple rare cancers -Constellation of tumors consistent with spcf cancer syndromes (breast/ovary) -Evidence of auto-dom transmission |
