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Genetics > Lecture 4 - Genetic Variation > Flashcards

Lecture 4 - Genetic Variation Flashcards

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Biology 101 flashcards
1
Q

Significance of Genetic Variability

A

-provides raw material for evolution - allowing species to adapt to the environment

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2
Q

What causes Genetic Variability

A

1) Sexual Reproduction:
- meiosis
- crossing over
- independent assortment of Homologues chromosomes
- Fertilization

2) Mutation (new variations produced)

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3
Q

Mutation

A

-allele of DNA sequence which yield a slightly modified mmolecule

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4
Q

Polymorphism

A

-allele of DNA sequence which has no effect on the Phenotype and it’s frequency > 1% in a population

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5
Q

Classification of Mutation

A

1) Cause
2) Site
3) Size
4) Function
5) Fitness

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6
Q

What can the Causes be for Mutation

A

1) Spontaneous:
- Chem Rxns:
> Tautomerization
> Depurination
> Deamination

-Error withDNA Proccessing:
> Replication + Repair
> Recombination

2) Induced:
- physical
- chemical

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7
Q

Tautomerization

A
  • usually DNA in Keto form -> can be enol/imino form

- spont A becomes A* -> pairs up with G -> next cycle returns to Keto –> the C would persist in daughter DNA

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8
Q

Other causes of Tautomerization

A

Induced mutation:

-> by mutagenic source

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9
Q

Depurination

A
  • base loses Purine
  • during DNA replication -> apurinic site cannot be used a template
  • thus by default A is added (serves in next cycle as template)
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10
Q

Deamination

A

C -> U (repaired)

5-methyl-C –> Thymidine (not recognised)

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11
Q

Causes of Induced

A

1) Physical (radiation):
- Heat
- Ionization
- UV

2) Chemical:
- Natural Toxic Mutagen
- Lab Chem
- Pollutants
- Biowarfare

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12
Q

Definition of Mutagen

A

Mutagen = Environmental agent capable of causing mutation

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13
Q

Natural Toxic Mutagen

A
  • Psoralen
  • Aflatoxin
  • Aspergillen
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14
Q

Lab Chemical

A
  • Arcidine Orange
  • Ethidium Bromide
  • Acrylamide
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15
Q

Pollutants

A

-Benzpyrine:

> metabolized in Liver to epoxides -> DNA Adduct

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16
Q

Biwarfare

A

-Mustard Gas

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17
Q

DNA Adduct

A
  • piece of DNA covalently bound to Cancer-Causing Chemical

- initial step of carcinogenesis

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18
Q

Direct Repair vs Excision Repair

A

DIRECT REPAIR:
-change is reversed w/o a template
> DNA Photolysase: repair thymi dimers by photoactivation
> DNA Methyltransferase

INDIRECT REPAIR
-template needed

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19
Q

Mismatch Repair

A

-defective in Hereditory Non-Polyposis Colon Cancer

  • adenosines of the 5’GATC sequence methylated on template strand is methylated
  • -> endonuclease cleaves at palindromic sequences –> exonuclease degrades liberated strand –> Dna Pol I fills in + DNA ligase closes nick
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20
Q

Base Exision repair

A

-problem in Deamination (Cys –> Uracil)

  • DNA glycolyase + Endonuclease cuts out the Uracil
  • -> replaced by DNA pol
21
Q

Nucleotide Exision Repair

A
  • defective in Xeroderma Pigmentosum
  • fixes thymidine dimers

-Endonuclease cleaves at 2 spots –> removed –> DNA Pol I fills in segment –> Ligase closes nick

22
Q

Diseases caused by Nucleotide Excision Repair

A

-coded by 11 genes

  • > Xeroderma pignmentosum
  • > Cockanye Syndrome
  • > Trichothiodystrophy
23
Q

Types of ds DNA repair

A

1) Homologous Recombination

2) Non-Homologous Recombination

24
Q

Homologous Recombination

A
  • seen in Meiosis

- restricted to: S or G2 Phase

25
Q

Non-Homologous Recombination

A
  • occur throughout the cell cycle
  • works well against: oxidative damage + ionizing rad
  • does not return amended DNA to the original sequence
26
Q

Where is Non-Homologous Recombination useful for

A

-benefit in generating AG-Rec diversity (as it does not return amended DNA to original sequence)

27
Q

ATM

A
  • Ser/Thr Protein Kinase –> serves as a sensor for DNA damage (dsdmg)
  • activates several proteins to initiate cell cycle arrest/DNA repair/apoptosis
28
Q

Targets of ATM

A
  • p53
  • CHK2
  • TSG (BRCA)
29
Q

When ATM is mutated what is affect

A

-Neurogenerative disease

30
Q

BRCA

A
  • the effect in repair of DSB
  • mut -> incr probability of Chrom Repairr problem/Aneuploidy/Malformation
  • ovarian + breast cancer
31
Q

Classification by Site (in orgnaism)

A

1) Somatic:
- inherited by Cells in the organism

2) Generative:
- inherited by the next generation

32
Q

Classification by Site (in a gene)

A

1) Promotor -> Decr. Transcription
2) Exon -> Change in AA seq/ formation of Truncated protein
3) Intron -> error in splicing
4) Polyadenylation site -> reduced mRNA stability
5) 5’UTR -> Disturbed ribosome binding

33
Q

Classification by Function

A
  • loss of function
  • gain of function
  • back mutation (point mut reverses back to orig seq)
  • Lethal
34
Q

Classificaion by Size

A

1) Genome Mut -> change in Chromo number
2) Chromo Mut -> Change in Chromo Structure
3) Gene Mut

35
Q

Types of Repeats

A
  • Interspersed repeats

- Tandem Repeats

36
Q

Types of Tandem Repeats

A
  • Satellite DNA
  • MiniSatellite (VNTR)
  • Microsatellite (STR)
37
Q

Satellite Repeats

A
  • large arrays of tandem repeats of non-coding DNA
  • produce different frequency of NT -> lower density than normal DNA
  • Satellite Band -> as it has G+C content
38
Q

Where are Satellite Repeats

A

1) Functional Component of Centromere

2) Structura Component of hetereochromatin

39
Q

Minisatellite Repeats (VNTR)

A
  • 10-60 BP

- Telomere = Minisatellite with thousands of repeating TTAGGG

40
Q

Significance of VNTR

A

-amount of repeats at various locations -> varies amongst people –> banding pattern of VNTR used in DNA fingerprinting

41
Q

Microsatellite Repeats (STR)

A
  • 2-4BP
  • Tripet repeats are frequent
  • marker of Kinship
42
Q

Triple Repeats Disease

A

Fragile X:
->non-coding CGG

Spinobulbar Muscular Atrophy:
-> coding repeats of CAG

Huntington’s Disease:
-> coding repeats of CAG in Huntington gene -> yields Glu residues

43
Q

Polyalanine Disorders

A

1) Synpolydactylia Type 2:
- HOXD13 issue

2) Holoprosencepthaly:
- issue with ZIC2

44
Q

Types of Deletion and Insertions

A

1) Point Mutation: one NT changed
2) Frame-shift:
- gain/loss NT -> fucks reading frame

3) In-frame mutation:
- > deletion/gain of triplet doesnt fuck the reading frame

45
Q

Tay Sachs

A

Frameshift Mutation -> addition of 4 BP in region of Hexosaminodase gene

46
Q

Types of Point Mutation

A

1) Transition (pyr -> Pyr or Pur ->ur)
2) Transversion (pyr -> pur)
3) Silient -> mut doesnt cause chara change in AA
4) Misense
5) non-sense

47
Q

Sickle Cell Anemia

A
  • mis-sense mut

- GAG -> GTG (Glu - Val)

48
Q

Duchenne

A
  • deletion leading to -> non-sense mut

- exon 45-54 deleted

49
Q

hBecker

A

-deletion -> in-frame transcript

Genetics (9 decks)

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