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Genetics > Chap 7- Genetic variation causing disease > Flashcards

Chap 7- Genetic variation causing disease Flashcards

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Biology 101 flashcards
1
Q

pathogenic mutation

A
  • changes function of gene
  • usually do not randomly occur, we have “hot spots” for mutations
  • i.e. CpG islands
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2
Q

male germ line and mutations

A
  • has higher probability of getting mutated
  • with each cell division there is increased risk of mutation
  • sperm cells continuously undergo division
  • likelihood of mutation increases with males age
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3
Q

degeneracy of genetic code

A
  • most AA have more than one codon to specify them for protein synthesis
  • change in nucleotide does not always result in new codon
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4
Q

synonymous/ silent mutation

A
  • result of redundancy of genetic code

- mutated codon often specifies same AA so no phenotype change

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5
Q

nonsynonymous substitution

A
  • causes change in AA
  • replace purine with pyrimidine or vice versa
  • aka missense mutation
  • severity of mutation ranges
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6
Q

stop-gain mutation

A
  • AKA nonsense mutation

- mutation makes premature stop codon

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7
Q

stop- loss mutation

A
  • stop codon is lost due to mutation

- results in translation of untranslated regions

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8
Q

what is the stop codon?

A
  • UAG
  • UAA
  • UGA
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9
Q

frameshift mutation

A
  • when nucleotide is inserted or deleted that is not a multiple of 3
  • frame completely changes
  • can indirectly cause nonsense mutation
  • can also occur from some mutations that produce altered splicing
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10
Q

what is the usual result of a frameshift mutation?

A

nonfunctional protein

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11
Q

karyotyping

A
  • staining of chromosomes
  • usually occurs and metaphase or prometaphase
  • examined to identify chromosome abnormalities
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12
Q

germ cell abnormality

A
  • aka constitutional abnormality
  • present in all nucleated cels
  • present very early in development
  • earlier a mutation starts the more severe consequences
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13
Q

somatic abnormalities

A
  • aka acquired abnormalities
  • present in only certain cells or tissues
  • acquired after child is born or anytime during their life
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14
Q

structural abnormality

A
  • problem with structure of chromosome

- i.e. breakage or new parts added

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15
Q

numerical abnormalities

A
  • change in number of chromosomes

- usually due to errors in chromosome segregation

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16
Q

inversion

A
  • deletion happens in just one arm

- material switched around in reverse direction

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17
Q

paracentric inversion

A
  • double break in just one arm of chromosome

- does not involve centromere

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18
Q

pericentric inversion

A
  • involves centromere which connects both arms
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19
Q

ring chromosome

A
  • occurs when both ends/ arms of chromosome are broken
  • ends become sticky
  • stick together to form ring
  • rare
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20
Q

role of centromere in mitosis and meiosis

A
  • mitosis looks for one centromere, even if rest of chromosome is mutated
  • if there is a dicentric or acentric centromere will not undergo mitosis
  • meiosis cannot handle translocation
21
Q

translocation

A
  • two different chromosomes each sustain a single break
  • incorrect joining of broekn ends -> chromosome material exchange
  • must occur between two close chromosomes
  • can include the centromere but does not always
22
Q

euploid

A
  • normal chromosomal makeup of individual
23
Q

aneuploid

A
  • loss or gain of one or more chromosomes (not entire set)
  • often in cancers
  • i.e. trisomy 21
24
Q

polyploid

A
  • extra set of chromosomes

- i.e. 3n or 4n rather than the normal 2n

25
Q

trisomy

A
  • three copies of a particular chromosome are present

- usually autosomal changes are less tolerated than sex chromosome changes

26
Q

monosomy

A
  • chromosome is lacking
  • i.e. turner syndrome
  • autosomal monosomies are more severe than trisomies
27
Q

how can aneuploid cells arise?

A
  • nondisjunction

- anaphase lag

28
Q

what is nondisjunction?

A
  • failure to separate paired chromosomes during meiosis anaphase I
  • sister chromatids fail to disjoin at meiosis II or mitosis
29
Q

what is anaphase lag?

A
  • “lazy chromosome”
  • all sisters have already crossed line
  • nuclear division will not wait for lagging chromosome to get to opposite pole
  • can result in abnormal distribution of chromosomes
30
Q

what happens if there is a chromosome in cytoplasm?

A
  • it gets degraded

- can happen with anaphase lag

31
Q

hypomorph

A
  • mutant gene is incapable of carrying normal function
  • can be reduced function or total loss of function
  • usually involve change in protein structure
32
Q

neomorph

A
  • mutant gene has new acquired function that is toxic to cells
  • usually involve change in protein structure
33
Q

loss-of-function mutations

A
  • severe mutation leads to deletion of an entire gene
  • can lead to complete degradation of mRNA so no protein is produced
  • includes nonsense mutations, frameshift mutations, and RNA splicing mutations
34
Q

gain of function mutation

A
  • common in cancer

- many arise from chromosomal translocations and other rearrangements that make chimeric genes

35
Q

chimeric genes

A
  • due to translocation
  • can have genes that are partly one gene and partly other gene
  • can cause many problems
36
Q

what is the result of a mutation in a regulatory gene?

A
  • indirectly effects expression of many target genes controlled by the regulator
  • genes themselves will not be mutated
37
Q

what happens in a mutation in the enhancer?

A

get too much gene product

38
Q

what happens in a mutation in the silencer?

A

not enough gene product

39
Q

point mutation

A
  • due to protein misfolding
  • protein should be degraded
  • in some diseases misfolded proteins are not degraded
  • hydrophilic side must be outside, hydrophobic side must be inside
40
Q

beta- thalassemia

A
  • problem with adult Hb
  • Hb normally has two alpha chains and two beta chains
  • when balance is skewed, leads to aggregation of Hb in cell
  • reduced beta production -> more alpha production -> cells aggregate and are lysed
41
Q

environmental factors and phenotype

A
  • environmental factors can sometimes influence phenotype
  • exposure can be at various levels: at a distance, direct exposure, or contact with microbes/toxins
  • especially important in triggering cancers
42
Q

neurofibromatosis type 1

A
  • autosomal dominant
  • mutation in gene neurofibromin
  • orginate from nonmyelinating schwann cells
  • normal gene is tumor supressing gene
43
Q

duchenne muscular dystrophy

A
  • caused by mutation in dystrophin gene
  • x linked recessive
  • dystrophin gene should normally repair plasma membrane damage
  • in DMD muscle membrane is progressively damaged and not repaired
  • marked elevation of serum CK
44
Q

what is turner syndrome?

A
  • females lose one X chromosome
  • 45 X, is a form of monosomy
  • many live normal life with no signs showing until puberty
45
Q

what are clinical features of Turner Syndrome?

A
  • short stature
  • primary ovarian failure
  • cubitus valgus
  • webbed neck
  • broad chest with wide spaced nipples
  • coartication of aorta *
  • horseshoe kidney *
  • does not affect intelligence
46
Q

what is Klinefelter syndrome?

A
  • when males have an extra X chromosome

- 47 XXY

47
Q

what are clinical features of Klinefelter syndrome?

A
  • primary testicular failure
  • gynecomastia, infertility, smaller testicles
  • lower IQ
  • tall stature
  • poor muscle tone
  • reduced secondary sex characteristics
48
Q

down syndrome

A
  • extra chromosome 21 aka trisomy 21
  • flattened facial profile
  • small nose
  • epicanthal folds and bushfield spots
  • short fifth fingers, wide gap between 1st and 2nd toes
  • transverse palmar creases
  • low IQ*
  • hypotonia, vision and hearing problems
  • Congenital heart malformations*
  • increased risk for leukemia
49
Q

how does maternal age effect down syndrome?

A
  • 70% of down syndrome cases are due to issues at meiosis I in mother
  • due to increased maternal age
  • the longer the egg is at rest, the “lazier” it becomes, result is nondisjunction

Genetics (8 decks)

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