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Genetics > Chap 4- Principles of Genetic Variation, DNA damage and repair > Flashcards

Chap 4- Principles of Genetic Variation, DNA damage and repair Flashcards

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Biology 101 flashcards
1
Q

Genetic locus

A

address for variations in DNA

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2
Q

homozygotes

A

identical alleles from mother and father

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3
Q

heterozygotes

A

different alleles from mother and father

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4
Q

p arm

A

short arm of chromosome

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5
Q

q arm

A

long arm of chromosome

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6
Q

how to read chromosome location

A

Chromosome number, which arm, region, band, sub-band

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7
Q

outcome of mutations

A
  • normal phenotype
  • disease phenotype
  • no effect
  • beneficial effect
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8
Q

SNP

A
  • single nucleotide polymorphism
  • one nucleotide replaced by another
  • quantity of DNA remains same
  • do not usually cause a problem, most common type of mutation
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9
Q

trisomy

A

having an extra chromosome

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10
Q

deletion

A

loss of genetic material

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11
Q

point mutation

A

small scale mutation only effecting a few nucleotides, usually don’t cause problem

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12
Q

polymorphism

A

genetic mutation that occurs in greater than 1% of population

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13
Q

rare mutations

A

occur in less than 1% of population

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14
Q

hygiene hypothesis

A

being “dirty” helps to make immune system strong because you are exposed to many more pathogens, able to undergo change

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15
Q

purifying (negative) selection

A
  • when genetic variation is so bad lower survival rate or reproductive capacity
  • harmful mutations will slowly be eliminated over time
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16
Q

positive darwinian selection

A
  • give advantage to people who have good/required mutations

- have higher survival rates and reproductive rates

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17
Q

origins of DNA sequence variation

A
  • DNA replication errors
  • chromosome segregation and recombination errors
  • endogenous chemical damage (most common!)
  • exogenous chemical damage
18
Q

how frequent are DNA replication errors?

A

1 incorrect base for every 1 million nucleotides

19
Q

replication slippage

A
  • certain parts of DNA that have tandem repeat nucleotides do not get replicated
  • reach large area of repeated sequence, skips this area and forms a loop in the DNA, loop in additional replications leads to expansion
20
Q

misaligned cross over

A
  • occurs during meiosis prophase I
  • exchanges unequal amount of genetic material
  • leads to deletions or mutations
21
Q

nondisjuction

A

chromosomes do not separate properly, causes unequal distribution of genetic material

22
Q

is extra genetic info more tolerated in sex chromosomes or somatic chromosomes?

A

sex chromosomes

23
Q

base modification

A

add chemical component to a base i.e. methylation

24
Q

crosslinking

A
  • unwanted connections in DNA

- can sometimes be caused by base modifications

25
Q

hydrolytic DNA damage

A
  • loss of water molecule
  • disrupts bond between base and sugar, leaves abasic site
  • common result is loss of purine or pyrimidine
26
Q

glycolytic bonds

A

connect sugar with base

27
Q

phosphodiester bonds

A

connect sugar with phosphate

28
Q

aberrent DNA methylation

A
  • cytosine commonly gets methylated
  • SAM acts as methyl donor
  • abnormal methylation -> transcription factors cant bind to DNA, DNA replication effected
  • converts euchromatin to heterochromatin
29
Q

oxidative damage

A

damage due to ROS

30
Q

ionizing radiation

A
  • x-rays or gamma rays

- generate ROS and causes double stranded DNA breaks

31
Q

non-ionizing radiation

A
  • can cause cross linking
  • linking between adjacent pyrimidines
  • creates thymine dimers
32
Q

mutagenic chemicals

A
  • cause DNA adducts which are bulky additions to DNA

- distort stability of DNA

33
Q

types of single strand DNA repair

A
  • base excision repair
  • nucleotide excision repair
  • mismatch repair
34
Q

types of double strand DNA repair

A
  • non-homologous end joining

- homologous recombination

35
Q

base excision repair

A
  • occurs when something happens to a single base

- base is cut out and repaired

36
Q

DNA mismatch repair

A
  • repairs errors that occur during replication and recombination
  • identify the area that has mismatch, DNA makes a loop with faulty region that is is then removed and replaced with new nucleotides
  • loop is made with help of mut proteins
37
Q

nucleotide excision repair

A
  • repairs DNA damage caused by UV rays
  • UV rays causes dimers and cross linking
  • uses Uvr proteins to scan for damage, cut out damage, replace nucleotides
38
Q

homologous recombination

A
  • help of homologous DNA as template to repair DNA
  • can lead to loss of particular area in DNA
  • available for cells during G2
39
Q

non-homologous end joining

A
  • usually during G1 phase
  • no template strand needed
  • part of DNA resected, joined together
  • can result in loss of part of DNA
40
Q

C-T mutations

A
  • very common hotspot for mutation
  • cytosine is easily methylated
  • deamination and methylation can cause switch to thymine
  • since thymine normally in DNA can go undetected while checking for errors
41
Q

C-U muations

A
  • c can be deaminated
  • deamination can result in change to Uracil
  • uracil DNA glycolase recognizes U, cuts it out
  • because U isnt normally found in DNA it is commonly fixed

Genetics (8 decks)

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