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Unit 11 > Genetics > Flashcards

Genetics Flashcards

1
Q

Watson and Crick were responsible for what

A

Publishing the structure of DNA

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2
Q

What is the TAT of home genetic tests?

how long did it originally take to sequence the entire human genome in 2003?

A

Turn over time: 12-16 weeks

Originally took 13 years

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3
Q

What is the structure of DNA

A

double helix: two DNA wound around one another

Nucleotides/base pairs: held together w/ hydrogen bonds

Nucleotides and sugar phosphate backbone: they branch out medially and connects strands

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4
Q

Genes, DNA, nucleotides, chromosomes relationship

A

Nucleotides make up DNA

DNA makes up genes

Genes are contained in chromosomes

Chromosomes are contained in the nucleus of all cells

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5
Q

genes are

A

long strands of DNA sequencing

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6
Q

each human cell has _____ chromosomes

A

23 chromosomes

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7
Q

How many nucleotides do humans have?

Genes?

A

3 billion nucleotides making about

20,000 genes

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8
Q

Largest chromosome?

Smallest?

A

Largest: 1 (2,000 bp)
Smallest: 21 (300 bp)

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9
Q

What are the two processes needed to create protein from DNA?

A

Transcription

Translation

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10
Q

Genes tell you…

A

which proteins are made
which cells make them
when they are made

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11
Q

Transcription

A

DNA to mRNA

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12
Q

Does the gene change with transcription

A

no

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13
Q

We are able to modify the mRNA to some extent prior to translation to create ______ via ______

A

create similar but non identical proteins

via selective splicing and 3’end formation

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14
Q

DNA makes ______ makes _____

A

DNA makes RNA, makes proteins

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15
Q

Three ways you control the amount of protein made

A

1) control how much mRNA is made during transcription
2) turning the gene on or off
3) what alternative splicing is being used

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16
Q

In translation what is used as a template to create protein?

A

mRNA

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17
Q

What is mRNA read by to create proteins?

A

ribosomes

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18
Q

Transcription and translation are separated due to what?

A

the nuclear membrane

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19
Q

Where does transcription occur?

Translation?

A

Transcription: nucleus

Translation: cytoplasm

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20
Q

Double helix is held together by what?

A

hydrogen bonds

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21
Q

Hydrogen bonds are what

A

tight, non-covalent connections btwn strands

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22
Q

What molecule uses DNA as a template, opens the double helix and binds to the _______ to start ______

A

RNA polymerase uses DNA as a template, opens the double helix and binds to the PROMOTER region on DNA to start TRANSCRIPTION

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23
Q

What is the base pair rules of mRNA

A

A –> U **instead of T
T –> A
G –> C

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24
Q

Where does RNA polymerase enter the DNA strand?

A

promoter region

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25
Q

Strength of the promoter decides what?

A

How much mRNA you get

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26
Q

Initiation stage of transcription

A

Polymerase attaches to the promoter, it unwinds the DNA at that location, and beings making an RNA transcript from one strand

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27
Q

Elongation stage of transcription

A

RNA polyermase moves across the DNA molecule synthesizing a strand of RNA. It advances through the gene like this

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28
Q

RNA is going to have the same sequence as which strand and a complimentary sequence to which strand

A

Identical sequence to non-template strand

Complementary sequence to template strand

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29
Q

Termination stage of transcription

A

RNA polymerase gets the “stop” signal codon. Polymerase falls off and releases the completed RNA transcript

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30
Q

True or false: in general you’ll have the same completed RNA transcript every time the gene gets copied?

A

true

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31
Q

mRNA processing: We can regulate gene expression by what?

A

choosing which exons to keep and which to remove

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32
Q

mRNA processing: Sequencing elements in the gene direct what?

A

where splicing is going to happen

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33
Q

Introns vs. exons

A

introns: non-coding
exons: coding

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34
Q

Number and size of introns per gene…

A

varies greatly

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35
Q

Do alternations in introns alter protein code sequences?

A

No however they can interfere with how the exons come together therefore indirectly interfering with gene expression

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36
Q

Alternate splicing events allow for what?

A

Creation of isoforms: slightly different versions of the same proteins

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37
Q

What is the function of tRNA

A

bing to particular AA and bring that AA to the ribosome to create protein

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38
Q

What are ribosomes made of

A

RNA and proteins

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39
Q

What is ribosomes job

A

bind to mRNA and synthesize proteins one AA at a time

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40
Q

Different AA gives proteins different what?

A

shape and function

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41
Q

What makes up AA’s

A

amino group, central carbon group, carboxyl R group (what makes aa different from one another)

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42
Q

How are amino acids encoded

A

non overlapping triplets of nucleotides = codons in mRNA

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43
Q

True or false: there is only one triplet codon combination for each protein

A

False: the genetic code is redundant. Some aa’s are encoded by more than one triplet

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44
Q

How many aa do we have

A

20

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45
Q

What is the start codon

A

AUG

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46
Q

How many stop codons are there

A

3

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47
Q

Where do ribosomes bind to begin translation, scanning for what?

A

5’ end scanning, scanning for the AUG start signal

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48
Q

What is the relevance of methionine

A

Always the first tRNA in translation has methionine as it’s aa

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49
Q

once the first tRNA leaves what happens?

A

the ribosome steps one codon over, the new tRNA

50
Q

When does translation end?

And what happens to the protein at this point

A

When ribosome encounters a stop signal

The full length protein is released

51
Q

What is a peptide bonds job

A

bonding one aa to another aa during translation/within the protein

52
Q

Ribosome carries its own enzyme that catalyzes what?

A

peptide bond formation (bonds aa’s to another to create protein during translation)

53
Q

When are introns removed in the whole process?

A

during mRNA splicing

54
Q

Changes in DNA affect proteins by changing what three things

A

Amount
Timing
Function

55
Q

insertions or deletions of thousands of nucleotides is also called what

A

Copy number variants (CNV)

56
Q

True or false CNV are not pathogenic

A

false they can be but most are not

57
Q

What is a translocation

A

rearrangement iwithin a choromosome; there is a piece where they are not supposed to be

58
Q

Point mutation is a single gene level change or a chromosomal change?

A

Gene level

59
Q

sex specific chromosomes generally severe or not?

A

Not severe in general

60
Q

Williams DiGeorge syndome is what kind of variant?

A

chromosomal microdeletion syndrome (thousands of base pairs lost)

61
Q

Duchenne muscular dystrophy often caused by what?

A

deletions or duplications that affect one or more exons - single gene change

62
Q

single base insertion generally causes what

A

stop to come early

63
Q

single base deletion generally causes what

A

extensive aa changes down the line

64
Q

Single gene changes may cause what type of mutation?

A

frameshift

65
Q

What does an in-frame deletion mean

what is an example of one

A

multiple of three deletions

cystic fibrosis - affects protein folding, wrong shape of protein and it gets stuck

66
Q

what kind of mutation is cystic fibrosis?

A

single gene in frame deletion

67
Q

3 possible consequences of point mutations

A

silent, nonsense, missense

68
Q

Silent point mutations

A

there is genetic variation so sometimes the deletion does not change anything

69
Q

nonsense point mutation

A

changes a codon from coding an aa to a STOP codon

Can produce shortened proteins
mRNA often unstable so no protein is made

OFTEN SEVERE consequences bc there is no protein being made when there should be

70
Q

missense point mutation

Dangerous?

Example?

A

changes one aa to another

Can be silent or damaging

Ex: sickle cell

71
Q

Why do missense variants cause problems?

A

protein function is dependent on their shape - enzymes don’t fit

72
Q

True or false: genetic diseases are always inherited

A

False! new mutation/varients exist

In fact most cases of cancer are sporadic

73
Q

Pairs of chromosomes mean what for genes? Except for what?

A

that every gene comes in two copies

Except for sex genes

74
Q

Autosomal dominant: what does an affected individual look like chromosome wise

A

affected individuals will have one copy with a variant, one copy that is unaffected

75
Q

What is the chance of an autosomal dominant individual passing it onto their children?

A

50%

76
Q

Do autosomal dominant disorders impact relatives?

A

Yes!

77
Q

Achondroplaisa (dwarfism) and familial hypercholesterolemia are what kind of genetic conditions?

A

autosomal dominant

78
Q

Autosomal recessive: what does an affected individual look like chromosome wise

A

both copies of the gene have varients

79
Q

Typically what do the parents of a child with an autosomal recessive phenotype look like

A

unaffected carrier parents

80
Q

What is the risk of siblings in an autosomal recessive situation?

Other relatives?

Men or women?

A

25% to an unborn sibling

Rare for other relatives to have the same condition

Men and women have same risk

81
Q

Which autosomal pattern has “horizontal transmission”

A

recessive

82
Q

Albinism and Spinal muscular atrophy are what kind of genetic conditions?

A

autosomal recessive

83
Q

X- linked recessive disorders

boys risk vs girls if mother is a carrier

A

boys have 50% chance of being affected if their mother is a carrier

50% chance daughter is A CARRIER
50% chance they are nothing

84
Q

X- linked recessive disorders

boys risk vs girls if father is affected

A

no chance the son is affected

100% chance daughter will be affected

85
Q

name x-linked conditions

A

color blindness, hemoophilia

86
Q

general thoughts for x linked genes

A

boys are more likely affected than girls

mothers are often carriers: sons have a 50% chance of being affected

87
Q

True or false, the majority of CA is hereditary

A

False!!! only 10-15% majority of cases are sporadic

88
Q

If the CA is hereditary are most dominant or recessive?

A

Dominant

89
Q

What does hereditary CA syndroms not being fully penetrant mean

A

people can have the mutation and NOT get CA however their risk for developing it is high

90
Q

BRCA1 and 2 account for what % of all cases of breast CA

A

5%

91
Q

HBOC

recessive or dominant

A

Hereditary breast and ovarian CA

Dominant

92
Q

What does a BRCA 1 or 2 mutation mean for an individual

A

they have an increased lifetime risk of breast cancer (85% instead of average 12% risk)

93
Q

Cystic fibrosis recessive or dominant?

A

recessive

94
Q

Mutation in CFTR gene causes what

A

Cystic fibrosis

95
Q

two symptoms of cystic fibrosis you wouldn’t have thought of

A

Pancreatic insufficeincey, male infertility

96
Q

PT implications for cystic fibrosis

A

chest PT, reduced bone density, kyphosis (due to barrel chest), muscle atrophy, myalgia, OA

97
Q

Mitral valve prolapse plus retinal detachment plus disproportionately long arms/legs could mean what?

A

Marfan syndrome

98
Q

What are some things that would signal HBOC

A

HBOC: hereditary breast and ovarian cancer

Premenopausal breast cancer

Multiple individuals w/ breast or ovarian in the same blood lineage over generations

Someone with multiple primary CA’s

Man with breast CA

99
Q

If you suspect HBOC what should you do

A

refer patient to genetic counselor

100
Q

Value of genetic testing

A

determine risk

offer genetic testing

identify other at risk family members who should be aware of their risk

Offer info, surveillance or treatment if positive

101
Q

The kind of genetic testing you get depends on what?

A

what variant is suspected

Ex: chromosomal vs. gene sequencing

102
Q

What is gene sequencing

A

reading the nucleotides in a gene to determine if there are variants

103
Q

Sanger vs. Next gen sequencing

A

Sanger: slow (one gene at a time) gold standard, high cost

Nex Gen: rapid, multiple genes simultaneously “shot gun/masively parallel”

104
Q

What is next gen sequencing used in

A

Whole exome sequencing (WES) and whole genome sequencing WGS

105
Q

Pathogenic or likely pathogenic variant (LPV) gives what result

A

positive

106
Q

No faimilial vairant, a benign variant, or likely benign variant gives what result

A

negative

107
Q

What is a true negative result in regards to a mutation found in family

A

you have the gene your sister does not, she has the same risk as the general population NOT zero

108
Q

What does a benign variant tell you about risk

A

not harmful, risk is not increase, no altered management/screening

109
Q

What does a LBV tell you

A

likely benign variant: no risk, no alternation in management/screening

110
Q

What do you do with a variant of uncertain significance treatment wise

A

hardest to counsel on we don’t act on knowing this: no testing other people, does not reduce or increase risk

111
Q

Different labs still “weigh” evidence somewhat differently

Leads to potentially different classification for the same variant

A

Multigene testing is much more common than single: looks at a set of genes most likely to be involved in the condition

Ex: familial CA, autism, intellectual disabilities

112
Q

What does WES stand for

A

Whole exome sequencing

113
Q

Sequences all of the protein-coding regions (1.5%) of the human genome

A

Whole exome sequencing (WES)

114
Q

True or false: WES has a low diagnosis yield

A

false: very high diagnostic yield because the WES looks at the coding regions of the human genome and 85% of pathogenic variants are in exons

115
Q

limitations of NGS therefore WES or WGS (whole genome sequencing)

A

does not detect all types of variant bc some are found in the non-coding regions, not all exons are targeted, carrier status not reported, incidental findings common

116
Q

Labs are required to report certain findings in WES

A

you look at WGS if WES is uninformative

117
Q

Limitations of WGS

A

tons of variation, which ones are important? Will find variations of unknown significance, unexpected/didn’t want to know disease

118
Q

Not all insurance companies cover WGS, its hard to say you got consent to test for EVERY genetic disorder

A

Some information is not reported when its not interpreted to affect the pts health

119
Q

Benefits of WGS

A

identify new mutations, carrier screening, pharmacogenomics, disease identification possibly before symptoms, more cost effective than one gene at a time

120
Q

Genetic information non-disrimination act

A

protects insurance from discriminating based on genetic info

but there are limitations

121
Q

Is hereditary cancer a single gene disorder

A

yes!

122
Q

is DMD chromosomal change or single gene disorder?

A

single gene disorder

Unit 11 (5 decks)

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