Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Principles > Principles Genetics > Flashcards

Principles Genetics Flashcards

1
Q

What is the difference between DNA and RNA?

A

Sugar: 2-deoxyribose vs 2-ribose (OH)
Base: Thymine vs Uracil
Strand: Double vs Single
Stability: Stable vs Unstable

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the difference between mitosis and meiosis?

A

Mitosis: 1 diploid parent cell gives rise to 2 identical diploid daughter cell

Meiosis: 1 diploid parent cell gives rise to 4 Haploid daughter cells + crossing over, independent segregation of genes, occurs in gamete formation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the central dogma?

A

DNA -> pre mRNA -> processed mRNA -> protein -> modified and transported

*Amt of proteins produced depends on rate of transcription to mRNA, rate of splicing of pre mRNA, half-life of mRNA, rate of polypeptide processing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are polymorphisms?

A

Any variation in human genome that has a population frequency of >1%
OR
Variation in human genome that does not cause disease in its own right but may predispose to common disease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are mutations?

A

Gene change/variation causing a genetic disorder OR any heritable change in human genome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Which phase does DNA replication occur at?

A

S phase. Children can have new variants which parents don’t thus mutations can be acquired from mitosis in somatic cells.
*Variants segregate independently unless they are very close together

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How many % of the genomes are genes?

A

2%.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Nomenclature of chromosome

A

Female: 46, XX
Male: 46, XY

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Recognition of chromosome

A

Banding patterns with specific stains, length and position of chromosome.

Normal chromosome: Telomeres, Short arm (p), Centromere, Long arm (q), Telomeres

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is an acrocentric chromosome?

A

Short arm is not significant.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What kind of chromosomal changes are there?

A

Balanced rearrangement: All c/s material present but in different arrangement

Unbalanced rearrangement: extra/missing c/s material; usually 1 (lack) or 3 (extra) copies of part of genome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is aneuploidy?

A

Whole extra/missing c/s

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is translocation?

A

Rearrangement of c/s

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is insertion/ deletion?

A

Duplicated/ missing material

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are microdeletions?

A

1 -3 Mb long involving several contiguous genes, CANNOT be detected by conventional cytogenetic methods

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is down syndrome?

A

Trisomy 21, 47XY + 21

Extra 21 or translocated c/s14 p arm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is Edwards Syndrome?

A

Trisomy 18, 47XY + 18

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is Patau Syndrome?

A

Trisomy 13, 47XY + 13

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is Klinefelter syndrome?

A

47, XXY

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is turner syndrome?

A

45, X

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Is X chromosome aneuploidy better tolerated?

A

Yes, due to X inactivation. Thus 1 X is enough.

22
Q

What is a Robertsonian Translocation and its consequence?

A

Most common form of translocation; 2 acrocentric c/s stuck end to end (E.g. R(14;21))

  • Increased risk of trisomy in pregnancy
  • If 1 parent is a carrier –> 25% normal, 25% balanced translocation, 25% trisomy 14 (miscarriage), 25% trisomy 21
23
Q

Reproductive risk of translocation

A

~50% will have normal c/s or balanced translocation

Unbalanced c/s will lead to miscarriage (large translocation) or dysmorphic delayed child (small segments; more viable)

24
Q

What is karyotyping?

A

It is a conventional clinical analysis looking at >5 million bases under light microscope.
(FOR BALANCED REARRANGEMENTS ONLY)

25
Q

What is FISH?

A

Probe DNA labelled with fluorescence dye is denatured and hybridized to target sequence.
HAVE TO KNOW TARGET SEQUENCE FIRST

26
Q

What is molecular cytogenetics?

A

Only detects UNBALANCE C/S, small changes which can be polymorphisms

Modern, quick, cheap, sensitive

27
Q

What is aCGH?

A

Uses reference DNA and patient’s DNA in metaphase.
First-line c/s test, genome wide, detects for any size of IMBALANCE and a lot of polymorphisms. DNA-based reflecting underlying c/s.
Mainly for deletions and duplications.
Cannot detect balanced rearrangements.

28
Q

What is Digeorge Syndrome?

A

Deletion of small segment of c/s22

29
Q

What can PCR and Sanger sequence do?

A

They can select 1 small piece of human genome (range 100 - 10,000 bases) and amplify it.
Allele with mutation is not amplified.

30
Q

What is next-generation sequencing?

A

Genomic DNA is extracted and fragmented into library of small segments. Each are sequenced in parallel and individual sequence are re-assembled by aligning to reference genome.
Different bases in alignment of short reads might be from variant allele with either polymorphism or disease causing mutation.
Variant sequences are cataloged.

31
Q

What could genetic change identified from NGS be?

A

3,00,000 polymorphisms identified ->could be disease causing mutation, polymorphism or variant of unknown significance

32
Q

How is filtering done for NGS?

A

It is to find the mutation that matters.
3,000,000 genetic variants -> exclude known polymorphisms -> keep if variant affects gene function (e.g. stop/ splice) -> see if gene can explain the phenotype -> single down to 1 or some variants that may be causative

33
Q

What is the Philadelphia chromosome and its treatment?

A

t(9;22) where 22q has bcr-abl gene fusion producing p210 protein that increases proliferation, decrease apoptosis, and disturb interaction with extracellular matrix.
Tx
- HER2 amplification (malignant): Trastuzumab
- Ph C/s: Imatinib (Tyrosine kinase inhibitor)

34
Q

Where can mutations act?

A
  1. Promoter mutation (reduce/stop transcription)
  2. Splice consensus altered (mutation occur where intron splicing occur, directly next to exon -> abnormal splicing/ absent protein)
  3. Early stop (short/ absent protein)
  4. aa seq changed (different/ non-functioning protein)
35
Q

Types of mutation in DNA seq

A

Nonsense (premature stop), Missense (aa change), Insertion (in/out of frame), Deletion (in/out of frame), Triplet expansion

36
Q

What is penetrance?

A

Extent at which a certain gene is expressed in phenotype
Measured by proportion of carriers showing the phenotype (E.g. 3 out of 10 people with the gene) or likelihood of having disease if gene is present

37
Q

What disease has 100% penetrance?

A

Huntington’s Disease

38
Q

What are Mendelian disorders?

A

Disease predominantly caused by change in single gene (high penetrance, small environmental influence, low mutation/polymorphism frequency)

39
Q

What is Autosomal Dominant?

A

Seen in every generation, 1 copy of defective gene needed
- 50% risk if 1 parent affect and 75% if both
- Disease severity can vary (Penetrance)
- Male and female equally likely to be affected
E.g. Achondroplasia, Huntington’s Disease

40
Q

What is Autosomal Recessive?

A

Usually skips generation, 2 copies of defective gene needed
- 25% risk if both parents are carriers
- Increased likelihood in consanguineous families
E.g. Cystic Fibrosis

41
Q

What is X-linked recessive?

A

Passed from mother to son, daughters usually carriers.

  • Females carry mutation but will not show MAJOR features of disease -> 50% of son will be affected and 50% daughters will be carriers
  • Affected father -> ALL sons will be normal (inherits Y c/s) and ALL daughters are carriers
  • Female carriers can show mild features due to random X inactivation thus 50% of cells have the working gene of average
42
Q

Relevance of Y chromosome in disease causing genes

A

Almost irrelevant (very little gene contact)

43
Q

When does X inactivation occur?

A

Early embryo stage to prevent double dose of X-linked genes but inactivation is not absolute; can still be leaky

44
Q

What are some non-mendelian inheritance?

A
  1. Methylation/ Imprinting
  2. Mitochondrial Inheritance
  3. Mosaicism
  4. Multifactorial inheritance
45
Q

What is multifactorial inheritance?

A

High mutation/polymorphism frequency ( a lot of SNPs involved)
Individual genetic factors are treated the same way as environmental factors.
Genetic change is just another risk factor.
Low penetrance for any one mutation.

46
Q

What is mosaicism and somatic mosaicism?

A

Mosaicism: Different cells have different genetic constitution -> could arise from mosaic c/s abnormality or from point mutation

Somatic mosaicism: All cells can acquire mutation from mitosis/ meiosis

47
Q

What are SNPs?

A

Not likely to exert effects of causing disease by themselves but effects can still show through gene function -> can increase predisposition.

Some SNPs can completely destroy gene without causing disease.
Question: Where, What, Effect of SNP and population frequency

48
Q

What is Copy number variation?

A

Extra/missing stretches of DNA (size range widely varied)

Highly prevalent in genome and at least 12% of human genome can be variable.

49
Q

How can low penetrance risk polymorphism be investigated?

A

Via case-control study to see if variant is found more in affected people.
Within normal distribution: Proportion of population vs risk of disease is classified by sum of different risk factors involved which can be genetic or environmental.

50
Q

What is Spinomuscular atrophy type 1?

A

Babies with SMN1 gene deletion (loss of function) can undergo RNA targeted therapy (Spinraza tx via alternate splicing of SMN2 to SMN1)
Route of Administration: Intrathecal
*targeting mRNA is currently the most effective method to control the central dogma

Principles (14 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions