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BIOL243 > Theme 2D > Flashcards

Theme 2D Flashcards

Changes in DNA Sequences & Spontaneous Mutations

1
Q

What does germine mean

A

inherited

mutation

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2
Q

What does somatic mean?

A

not inherited

mutation

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3
Q

What are mutations

A
  • changes to nucleic acid sequence (DNA & RNA)
  • can be germine or somatic
  • changes can be small (gene level) or large (chromosomal)
  • altered gene sequence can change the amino acid sequence of polypeptide resulting in variation of phenotype
  • effect on phenotype can be harmful, neutral, or beneficial
  • primary force in evolution (beneficial mutations are favored)
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4
Q

Germline mutations

A

mutation originally occured in gametes and become heritable

example: sex-influenced trait - autosomal dominant trait that is dependant on sex

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5
Q

Somatic Mutations

A

can occur in all other cell types except gametes and are not heritable

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6
Q

Where does a somatic mutation occur? What are they expressed as?

A

occurs in a progenitor cell and all other daughter cells will express mutations; they are expressed as sectors (size depends on time of mutation)

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7
Q

Small Scale Mutations

Base Substituation

A

single nucleotide change as a result of point nutations

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8
Q

Small Scale Mutations

Insertion

A

one or more base pairs added in sequence during DNA replication usually resulting in frameshift mutation

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9
Q

Small Scale Mutations

Deletion

A

one or more base pairs skipped during DNA replication usually resulting in frameshift mutations

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10
Q

Small Scale Mutations

Transition

A

purine-to-purine or pyrimidine-to-pyrimidine changes

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11
Q

Small Scale Mutations

Transversions

A

purine-to-pyrimidine or pyrimidine-to-purine changes

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12
Q

Effect of point mutations on amino acid sequence

Missense mutation (nonsynonymous)

A

codon change causes change in amino acid

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13
Q

Effect of point mutations on amino acid sequence

Nonsense mutation (premature stop)

A

sense codon change into a stop codon (truncated polypeptide)

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14
Q

Effect of point mutations on amino acid sequence

Silent mutation (synonymous)

A

codon change does not change the amino acid due to degeneracy of the genetic code

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15
Q

Effect of point mutations on amino acid sequence

Frameshift Mutation

A

insertion or deletion of a small number of base pairs that alter the reading frame

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16
Q

Effect of point mutations on amino acid sequence

Which type of mutation would have most effect on the function of the polypeptide?

A

frameshift but depends where
or early premature stop

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17
Q

Sickle Cell Anemia (missense mutation)

A

single missense mutation in the entire genome and a resulting single amino acid change can have effect on phenotype

  • missense mutation in the beta hemoglobin gene causes 6th amino acid to change from glutamic acid to valine
  • Red blood cells: defficient in oxygen exchange, clogged arteries, circulatory problems, higher risk of heart attack and stroke
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18
Q

Large scale chromosomal mutations

Deletion

A

loss of genes

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19
Q

Large scale chromosomal mutations

Duplication/amplification

A

increasing dosage of genes

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20
Q

Large scale chromosomal mutations

Translocation

A

interchange of genetic parts from nonhomologous chromosomes

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21
Q

Large scale chromosomal mutations

Inversion

A

reversing orientation of a segment of the chromosome

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22
Q

Spontaneous Mutation

A

naturally occuring mutations mainly caused by replication errors and spontaneous lesions

a low rate (freuquency) of mutation - usually during replication

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23
Q

Induced Mutation

A
  • natural/environmental or artificial agent or mutagen that causes mutation at a rate much higher than spontaneous mutagens
  • mutagens induce mutations by replacing base, alter a base so it mispairs with another base, or damage base so it can no longer pair up
  • base analogs mimic bases and incorporates into DNA
  • chemicals that alter base structure to cause mispairing
  • damage to bases
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24
Q

Allele

A

one or different forms of a gene (sequence variation) which can cause different phenotypes

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25
Q

Wild-type allele

A

normal form of the gene found in nature or the standard laboratory strain of a model organism

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26
Q

Loss-of-function alleles

A

mutations that reduce/eliminate gene function/expression

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27
Q

Gain-of-function alleles

A

mutations that enhance gene function/expression

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28
Q

The eukaryotic cell cycle

A
  • cell cycle is ordered set of processes by which one cell grows and divides into two daughter cells
  • need to fully replicate DNA and organelles and properly segregate them to daughter cells
  • G1 & G2 (gap phases)’
  • S phase
  • M phase
  • Cytokinesis
  • G0 (most adult human cells are here)
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29
Q

Eukaryotic Cell Cycle

G1 & G2 (gap phases)

A

synthesis of proteins, RNA, metabolites, and other DNA

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30
Q

Eukaryotic Cell Cycle

S phase

A

DNA replication

31
Q

Eukaryotic Cell Cycle

M phase (mitosis)

A

nuclear division

32
Q

Eukaryotic Cell Cycle

Cytokinesis

A

cell division

33
Q

Eukaryotic Cell Cycle

G0

A

resting phase or quiescence

34
Q

Regulation of the eukaryotic cell cycle

Progression of the cell cylce depends upon activities of a __________________________ bound to its regulatory _________ subunit in each phase of the cell cycle

A

cyclind-dependant kinase (CDK); cyclin

35
Q

Regulation of the eukaryotic cell cycle

Cyclin-dependant kinase (CDK)

A

protein/enzyme that phosphorylates other proteins

36
Q

Regulation of the eukaryotic cell cycle

3 checkpoints

A
  1. DNA Damage (G1/S) Checkpoint
    (is DNA ok for replication?)
  2. DNA Replication (G2/M) Checkpoint
    (is DNA fully replicated before mitosis?)
  3. Mitotic Spindle Checkpoint
    (Are chromosomes aligned properly in metaphase?)

checkpoints will not stop cycle permenantly

important b/c cells will die if they proceed w/ incomplete steps

37
Q

What happens when cell cycle regulation goes wrong?

A

cancer! - malignant growth caused by uncontrolled cell division and is caused by altered expression of multiple genes as a result of mutations (polygenic disease)

38
Q

Which mutated genes are implicated in cancers?

A
  1. Oncogenes
  2. Tumor Supressor Genes
  3. Inactivated p53 gene (in 50% of tumors) & cyclin D and E are often highly expressed in breast cancer carcinomas
39
Q

Why is it difficult to find universal cure for cancer?

A

each cancer is caused by different gene mutations

40
Q

Oncogenes

A

positive regulators of the cell cycle (gain-of-function) including cyclin D/E (gene amp.), cdk4 alleles (insensitive to inhibition)

41
Q

Tumor Suppressor Genes

A

negative regulators of the cell cycle (loss of function) including checkpoint genes p53 and RB

42
Q

Homologous Chromosomes

n

A

haploid number of chromosomes

43
Q

Homologous chromosomes

2n

A

diploid number of chromosomes

44
Q

Homologous chromosomes have _________________ and _______________ pair of chromosomes

A

maternal and paternal

45
Q

Homologous Chromosomes

the ___________ & ___________ of genes are the same between homologous chromosomes but alleles could be different

A

number and order

46
Q

Events of the mitotic cell cycle I

Events in order

A

G1
G2
Prophase

47
Q

Review diagram on slide 4

A
48
Q

G1

A

(2n)
4 chromosomes
1 chromatid/chromosome

49
Q

G2

A

2n
4 chromosomes
2 chromatic/chromosome

50
Q

Prophase

A

2n
4 chromosomes
2 chromatids/chromosome

51
Q

A human is diploid with 2n = 46. A cell in G2 would contain:

A

46 chromosomes
23 homologous pairs
92 chromatids

52
Q

Why should all genes on sister chromatids be the same allele

A

DNA replication; multiple forms of gene

53
Q

Why should some genes on non-sister chromatids or homologous chromosomes have different alleles?

A

b/c one comes from mom and one from dad

54
Q

Events of the mitotic cell cycle II

A

prometaphase
metaphase
anaphase

55
Q

Events of the mitotic cell cycle II

prometaphase

A

2n
4 chromosomes
2 chromatids/chromosome

56
Q

Events of the mitotic cell cycle II

metaphase

A

2n
4 chromosomes
2 chromatids/chromosome

57
Q

Events of the mitotic cell cycle II

anaphase

A

4n
8 chromosomes
1 chromatid/chromosome

58
Q

Evenets of the mitotic cell cycle III

A

telophase
G1

59
Q

Events of the mitotic cell cycle III

telophase

A

4n
8 chromosomes
1 chromatid/chromosome

60
Q

Events of the mitotic cell cycle III

G1

A

2n
4 chromosome
1 chromatid/chromosome

61
Q

Cell cylcle in prokaryotes

A

binary fission

62
Q

binary fission

A
  • replication begins at origin
  • bacterial chromosome is attached to the inner membrane
  • cell elongates and chromosomes seperate
  • inward growth of plasma membrane and partition assembly of new cell wall, dividing replicated DNA
  • two daughter cells produced
  • effective bc only 1 chromosome
  • mitosis evolved from this
63
Q

Meiosis I

A
  • creation of gametes
  • germ cell (2n, 4 chromosomes 1 chromatid/chromosome) –> germ cell (2n, 4 chromosomes, 2 chromatid/chromosome)
  • non-sister chromatids from 2 homologous chromosomes are attached by protein structure called synaptonemal complex
  • pieces of non-sister chromatids are exchanged by recombination
64
Q

Recombination in Eukaryotes

  1. _______________ align with each other during prophase I and exchange of sections of non-sister chromatids occur by crossing over
A

homologous chromosomes

65
Q

Recombination in Eukaryotes

  1. _________________________ occurs of each strand
A

precise breakage

66
Q

Recombination in Eukaryotes

  1. __________- of non-sister chromatids
A

equal exchange

67
Q

Recombination in Eukaryotes

  1. ______________ after genetic exchange
A

repair of breakage

68
Q

Recombination in Eukaryotes

  1. genetic exchange can involve large sections of homologous chromosomes creating __________________ with various combinations of 100s of genes/alleles
A

new chromatids

69
Q

Recombination in Eukaryotes

Why is it important for perfect exchange of genetic material between non-sister chromatids during recombination?

A

because if it wasn’t perfect, there would be loss or gain of genetic mutation

70
Q

Meiosis I (reductional division)

Diploid - haploid

A
  • the number of homologous pair of chromosomes is reduced from 2 in parental to 1 in daughter cell
  • chromosome number is haploid, but there are still 2 chromatids/chromosome
  • sister chromatids no longer identical due to crossing over
71
Q

Meiosis II

A
  • process between MI & MII is similar but no DNA replication
  • centromeres & sister chromatids separate during anaphase II
  • at the end: 4 cells are produced with haploid number of chromosomes (1 chromatid/chromosome) that are not identical due to crossing over and random assortment
72
Q

If a human is diploid with 2n=46. A cell after meiosis I would contain:

A

46 chromosomes
23 homologous pairs
46 chromatids

73
Q

If a human is diploid with 2n=46. A cell after mitosis II would contain:

A

23 chromosomes
0 homologous pairs
23 chromatids

BIOL243 (7 decks)

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