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Principles SOH > Genetics > Flashcards

Genetics Flashcards

1
Q

DNA strand is read in which direction?

A

From 5’ -> 3’ end

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2
Q

DNA features (4)

A

Double stranded
Sugar/phosphate backbone
Sugar backbone is 2-deoxyribose
Pairs up in an antiparallel fashion

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3
Q

DNA base pairing

A

A binds with T (double hydrogen bond)

C binds with G (triple hydrogen bond)

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4
Q

Which type of bonds are formed between bases in DNA?

A

Hydrogen bonds

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5
Q

Mitosis

A

Production of 2 daughter cells

  • identical to each other
  • identical to the original parent cell
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6
Q

Mitosis phases (6)

A
  1. S phase - duplicate genetic material
  2. Metaphase - chromosomes align at equator
  3. Anaphase - centromeres divide and chromatids move towards corresponding poles
  4. Telophase - nucelar envelope appears which separates duplicated material into 2 identical daughter cells
  5. Cytokinesis - cytoplasm divides, 2 identical daughter cells produced
  6. Interphase - cell rests and produces new proteins
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7
Q

Meiosis

A

One diploid parent cell produces 4 haploid daughter cells

Genetic makeup is re-shuffled by crossing over

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8
Q

Meiosis phases (9)

A
  1. Genetic material duplicated
  2. Prophase 1 - crossing over occurs
  3. Metaphase 1 - homologous chromosomes line up at equator
  4. Anaphase 1 - homologous pairs separate
  5. Telophase 1 - 2 daughter cells formed, each with only 1 chromosome
  6. Prophase 2 - DNA does not replicate
  7. Metaphase 2 - Chromosomes line up at equator
  8. Anaphase 2 - chromosomes separate to each pole
  9. Telophase 2 - cell division complete producing 4 haploid daughter cells
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9
Q

Cell cycle - G1

A

Growth phase

  • cells increase in size
  • cells produce RNA
  • protein synthesis
  • checkpoint at end of G1
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10
Q

Cell cycle - S phase

A

DNA replication

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11
Q

Cell cycle - G2

A

Growth phase 2

  • cells further increase in size
  • new proteins produced
  • checkpoint at end of G2
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12
Q

Cell cycle - M phase

A

Mitosis occurs

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13
Q

DNA replication - what is needed to initiate DNA replication?

A

RNA primer (synthesised by primase)

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14
Q

DNA replication - leading strand

A

Always has a free 3’ end for next nucleotide to join

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15
Q

DNA replication - lagging strand

A

Replicated in short segments (okazaki fragments)

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16
Q

DNA replication - what joins the lagging strand fragments together?

A

Ligase

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17
Q

DNA replication - what catalyses the reaction?

A

DNA polymerase

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18
Q

RNA features (3)

A

Single stranded
Ribose backbone
Uracil is used instead of thymine

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19
Q

Protein synthesis

A

DNA is transcribed to pre-mRNA
pre-mRNA is spliced to mRNA
mRNA is translated to a protein

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20
Q

DNA replication - What is used to unwind the DNA double helix?

A

Helicase

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21
Q

Exons

A

Coding regions

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22
Q

Introns

A

Non-coding regions

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23
Q

Splicing

A

Removes all introns and joins the eons together to form mRNA

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24
Q

DNA replication - where does transcription occur?

A

Nucleus

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25
Q

DNA replication - where does translation occur?

A

Ribosome

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26
Q

Polymorphism

A

Any variation in the human genome that does NOT cause disease in it’s own right

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27
Q

Mutation

A

A genetic variation that can cause:

  • a genetic disorder (disease)
  • any change in the genome
28
Q

Balanced chromosomal rearrangement

A

All chromosomal material is present

Chromosomal material is just switched around and not in the same order

29
Q

Unbalanced chromosomal rearrangement

A

Extra/missing chromosomal material

eg: miscarriage, trisomy 14

30
Q

Aneuploidy

A

A whole extra or missing chromosome

X chromosome aneuploidy is better tolerated (due to X-inactivation)

31
Q

FISH

A

Fluorescently tagged copy of a specific genetic sequence

Useful to identify where a particular gene falls within an individuals chromosomes

32
Q

Microarray CGH

A

Detects missing or duplicated pieces of chromosomes

33
Q

Array CGH

A

Searches the whole of the genome
Can find polymorphisms
For deletions/duplications of DNA

Patient DNA is dyed red
Control DNA (perfect DNA) is dyed green
Place these both in wells and there should be an equal amount of red and green

34
Q

Mosaicism

A

Different cells have different genetic constritution

35
Q

Result of changes of chromosomes

A

Activate an oncogene

Delete a tumour supressor gene

36
Q

Translocation

A

Section of one chromosome is attached to another chromosome

37
Q

How to search for deletions of chromosomes

+ e.g. of disease

A

FISH

di George syndrome

38
Q

Trisomy 21

A

Downs syndrome

39
Q

PCR

A

Select one small section of the human genome and amplify it
Focussed test
Detect pathogenic material

72c - select target DNA
100c - denature DNA causes strands to separate
50c - primers anneal (starting point)
72c - optimum temp for taq polymerase to copy DNA

40
Q

Next Generation Sequencing

A

Sequence entire genome of a person

41
Q

Point mutation

A

Single base change

Not every base change causes a change in amino acid

42
Q

Penetrance

A

Likelihood of having the disease if you have the mutation

43
Q

Monozygotic twins

A

Share all genes

Predispose to disease

44
Q

Dizygotic twins

A

Share 50% of genes

45
Q

High penetrance disease e.g.

Low penetrance disease e.g.

A

High - Mendelian disorders (eg achondroplasia)

Low - multifactorial disease

46
Q

Autosomal dominant

A

Only need 1 faulty copy of the gene to cause disease
Affects males and females equally
Disease is seen in every generation
If parent is affected, 50% risk that child will be affected

47
Q

Autosomal recessive

A

Need 2 faulty copies of the gene to cause disease
Affects men and women equally
Disease is usually one seen in 1 generation
1 in 4 risk of child being affected if parents are carriers
Occurs if related family members (e.g. cousins) have kids

48
Q

X-linked recessive

A

Gene fault on the X chromosome
Males (XY) will be affected
Females (XX) will be carriers
No male-male transmission

If a male is affected:

  • all daughters will be carriers
  • no sons will be affected

If a female is a carrier:

  • 50% of sons will be affected
  • 50% of daughters will be carriers
49
Q

X inactivation

A

In females only 1 X chromosome is active

Methylation is one mechanism of X inactivation

50
Q

SNP

A

Alterations in DNA sequence every 100-300 base pairs

Most have no effects

51
Q

Copy number variation (CNV)

A

Extra/missing stretches of DNA

Deletions/duplications

52
Q

Methylation

A

Occurs on C bases just before G bases
No transcription occurs
Makes the mutation “C” to “T” more likely

53
Q

Imprinting

A

Differences in gene expression depends on whether a gene was maternally or paternally inherited

54
Q

Mitochondrial DNA

A

Inherited maternally

Affects sons and daughters equally

55
Q

How a cell becomes cancerous

A

Mutation makes happy cells -> unhappy cells
Body kills off unhappy cells (apoptosis)
- if body doesn’t kill off unhappy cells then the cells become even more unhappy and starts to proliferate, invade and metastasise

56
Q

2 hit hypothesis

A

If you inherit a mutation (e.g. from a relative) then you only need 1 more mutation to cause cancer

If you don’t inherit a mutation then you need to inherit 2 mutations before it causes cancer

57
Q

Breast cancer and ovarian cancer mutations

A

BRCA 1 and BRCA 2

58
Q

Testing for mutations

A

Test an affected (symptomatic) individual first and if there is a mutation then test other family members (pre-symptomatic)

59
Q

High medium or low risk?

Mother with cancer at 70

A

Low

60
Q

High medium or low risk?

People with some FHx: (mother and sister with cancer at 45)

A

Medium

61
Q

High medium or low risk?

Lots of FHx, known BRCA 1 mutation

A

High

62
Q

Symptomatic testing

A

Find the cause of the disease in a person with a disease

  • finding a mutation: confirms diagnosis and allows testing of family members
  • not finding a mutation: treatment based on clinical parameters
63
Q

Pre-symptomatic testing

A

Patient has a relative with a KNOWN mutation and wants to find out if they have it

64
Q

Turner’s syndrome

A

Only occurs in females

Individual with normal number of autosomes but only one X chromosome

65
Q

Inheritance pattern for CF

A

Autosomal recessive

Principles SOH (5 decks)

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