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BIO 111 > Chapter 14 > Flashcards

Chapter 14 Flashcards

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Biology 101 flashcards
1
Q

mutations

A
  • gene mutation: a small change in the structure of a single gene
  • essential to the continuity of life
  • source of variation for natural selection
  • one way NEW genes can be created!
  • -new mutations more likely to be harmful than beneficial
  • and are usually random events
  • DNA repair systems reverse DNA damage
  • cause of many inherited or genetic disorders- cystic fibrosis
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2
Q

gene mutations alter DNA sequence

A
  • point mutations affect only a single base pari
  • 2 basic alterations
    1. base substitution
    2. add or remove nucleotides
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3
Q

silent mutations (point mutations)

A
  • do not alter AA sequence
  • in coding or non-coding region
  • genetic code is degenerate (Codon table)
  • third base of a codon
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4
Q

missense mutation (point mutation)

A

changes a single amino acid in a polypeptide

  • may not alter protein function
  • may be neutral if substituted amino acid chemically similar
    ex: glutamic acid substituted for aspartic acid
  • sickle cell anemia
  • Glu is hydrophilic, Val is hydrophobic
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5
Q

nonsense mutation (point mutation)

A

a normal codon to a stop codon

  • shorter polypeptide
  • usually bad
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6
Q

frameshift mutation (point mutation)

A
  • addition or deletion of nucleotides that are not multiples of 3
  • completely different amino acid sequence
  • usually VERY BAD; e.g Tay-Sachs disease
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7
Q

Promoter mutations

mutation outside coding sequence

A

-may affect level of transcription

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8
Q

Transcriptional response element/ operator site

mutation outside sequence

A

-may alter regulation of transcription

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9
Q

intergenic regions (mutation outside sequence)

A

typically has little effect on gene expression

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10
Q

splice junction (mutation outside sequence)

A

mutations of intron/ exon boundaries can prevent proper splicing

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11
Q

time and location of mutation

A

determines severity and heritability

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12
Q

germ-line cells

A
  • gives rise to gametes

- if a mutated egg or sperm cell participates in fertilization, every cell in the organisms carries the mutation

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13
Q

somatic cells

A
  • all other body cells
  • skin, muscle, nerve etc
  • mutations can occur early or late in development
  • genetic mosaic- patches of mutated tissue
  • earlier mutation -> larger affected area
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14
Q

spontaneous mutations

A
  • from abnormal biological process
  • rates vary by gene and species
  • 1/million genes
  • results from:
  • erros in DNA replication
  • toxic metabolic products
  • e.g free radicals
  • changes in nucleotide structure
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15
Q

induced mutations

A
  • caused by environmental agent
  • mutagens
  • higher rate than spontaneous
  • brought on by environmental agents
  • mutation rate higher than spontaneous mutation rate
  • can be both chemical and physical
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16
Q

chemical mutagens

A
  • disrupts DNA base pairing
  • modifying nucleotide structure
  • nitrous acid (HNO2) deaminates bases by replacing amino groups (-NH2) with keto groups (=O)
  • changes C to U and A to hypoxanthine
  • bases do not pair correctly; results in leads to point mutations
17
Q

physical mutagens

A
  • ionizing radiation has high energy and can penetrate deeply into biological materials to create free radicals
  • X rays and gamma rays
  • base deletions, breaks DNA strands, free radical generation
  • non ionizing radiation has less energy and can only penetrate the surface (skin-deep)
  • UV rays can cause formation of thymine dimers
18
Q

Thymine dimers (Physical mutagens)

A
  • can result in replication issues:
  • DNA polymerase misreads
  • proper nucleotides are NOT added to the new DNA strand
  • can cause gaps in the new DNA
  • can cause wrong bases to be incorporated
19
Q

Ames test

A
  • to determine mutagenicity of chemicals
  • uses a mutant strain of the bacterium of Salmonella typhimurium
  • this strain cannot synthesize histidine
  • a SECOND mutation in the cell can correct the FIRST
  • test monitors the rate at which second mutation occurs
  • does an agent increase mutation rate above the spontaneous rate?
20
Q

DNA repair; two steps

A
  1. proteins detect an irregularity in DNA structure

2. the abnormality is repaired

21
Q

nucleotide excision repair

A
  • referred to as the NER system
  • a region of several nucleotides around damaged base is removed and replaced
  • deficiency in NER system can have serious consequences
22
Q

cancer

A
  • uncontrolled cell division
  • 10% inherited; germ-line mutation
  • 90%- spontaneous somatic cell mutation
23
Q

carcinogens

A
  • mutagens that increase likelihood of cancer
  • 80% of cancers related to mutagens exposure
  • change gene expression -> uncontrolled cell division
24
Q

cancer is a series of changes

A
  • usually requires multiple genetic changes

- initially benign tumor, can become malignant with accumulation of more mutations

25
Q

cancer progression

A
  • if additional mutations occur in a benign tumor -> cancer
  • malignant-lost normal growth regulation
  • invasive- can invade healthy tissue
  • metastaic- can migrate to other body parts (via blood vessels)
  • left untreated, malignant cells will cause the death of the organism
26
Q

molecules regulate cell division

A
  • growth factors bind to receptors on the cell wall
  • activate signal transducers to relay information
  • activate transcription factors to regulate gene activity
27
Q

in cancer cells..

A
  • receptors may be permanently activated
  • signal transducers may be stuck in an activated state
  • transcription factors may be produced, even if preceding steps are absent
  • apoptosis signals ignored
28
Q

proto-oncogenes

A
  • regulate cell division by growth factors

- get stuck “on” =ONCOGENE

29
Q

tumor supressor genes

A
  • stop cell division
  • get stuck “off”
  • “the accelerator must get stuck and the brakes must fail”
  • cancer- from an accumulation of mutations
30
Q

negative regulator -protein p53

A
  • G1 checkpoint protein
  • 50% cancers associated with defect in p53
  • p53 expression when DNA is damaged
  • resulting protein STOPS cell cycle and REPAIRS damage
  • if damage is severe, p53 will activate apoptosis genes
31
Q

checkpoint genes

A
  • are broken by mutation, the division of normal healthy cells may not be activated
  • ex: mice that missing p53 gene born healthy
  • cell division leading to normal growth is regulated properly
  • checkpoint proteins such as p53 are not necessary for normal cell growth and division
  • BUT, highly sensitive to mutagens, easily develop cancer
  • loss of checkpoint protein function makes it more likely that genetic changes will occur that could cause cancerous growth
32
Q

why is cancer rarer among children/ teens/young adults?

A

??

33
Q

malignant

A

(after benign growth) lost normal growth regulation

34
Q

invasive

A

can invade healthy tissue

35
Q

metastatic

A

can migrate to other body parts

36
Q

translational response elements (outside gene mutation)

A

may prevent proper translational regulation

BIO 111 (17 decks)

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