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LC Principles Genetics > Genetics > Flashcards

Genetics Flashcards

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Biology 101 flashcards
1
Q

What is the cell cycle, and what is the sequence of it?

A

An active period of growth and metabolism.
G0 = cell is being a cell
(GI,S,G2,M)
G1 = first growth stage, the cell makes new proteins and copies the organelles
S = DNA replication happens
G2 = Second part of growth, cell makes more proteins and copies the organelles in preparation for mitosis
M = mitosis

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2
Q

What is mitosis?

A

One diploid parent cell , two identical diploid daughter cells.
Interphase, prophase, metaphase, anaphase, telophase, cytokinesis

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3
Q

Describe Interphase

A

Active period of growth GI, S, G2

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4
Q

Describe prophase?

A

The chromosomes condense (coil up) and become visible as two joined chromatids. Spindle fibres attach to the chromosomes at the centromeres. The nuclear membrane disintegrates

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5
Q

Describe metaphase?

A

Spindle fibres move the chromosome so that they line up on the metaphase plate at the equator of the cell

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6
Q

Describe anaphase?

A

The spindle fibres pull the sister chromosomes apart. Once they are separated the chromatids are called chromosomes in their own right

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7
Q

Describe telophase?

A

The separated chromosomes are pulled by the spindle fibres to opposite poles to form daughter nuclei. the chromosomes start to uncoil and a nuclear membrane is made again

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8
Q

Describe cytokinesis?

A

The membrane is pulled in by part of the cytoskeleton to divide the cytoplasm to form two daughter cells.

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9
Q

What is meiosis?

A

One diploid parent cell becomes 4 haploid daughter cells. Takes place in meiosis 1 and 2.

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10
Q

What takes place in meiosis and what is one of the key features?

A

Crossing over occurs here

Key feature - formation of chiasmata between homologous chromosomes during meiosis 1.

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11
Q

Describe transcription?

A

A transcription factor binds to the promoter and a single RNA strand is synthesised using the DNA sequence as a template.

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12
Q

Describe Splicing?

A

The primary messenger RNA (mRNA) that is synthesised undergoes splicing to remove the introns. This creates mature mRNA. (Each intron starts with a GT sequence and ends with an AG sequence)

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13
Q

describe translation?

A

The mRNA is moved up to the ribosome in the cytoplasm where it is translated into a polypeptide.
Evert 3 bases (codons) of the mRNA encode an amino acid or a stop.
tRNA transport the amino acids to the assembling peptide.
The polypeptide then undergoes post - translational modification and is transport to its place of function as a mature protein.

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14
Q

In translation what is the start codon? And what is the stop codon?

A

AUG encoding methionine.

Stop - UAA, UAG, UGA.

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15
Q

What is the amount of protein produced determined by?

A

Rate of transcription
Rate of splicing to mRNA
Half life of mRNA
Rate of processing of polypeptide

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16
Q

What is a polymorphism?

A

Any variation in the human genome that has a population frequency of greater than 1%.
Any variation in the human genome that does not cause a disease in its own right, maybe however predispose to a common disease

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17
Q

What is a mutation?

A

A gene change that causes a genetic disorder

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18
Q

Describe a chromosome?

A

Consists of a DNA strand wound around histones and packages with other proteins into a compact structure.
Has a long arm (q), short arm (p), 2 tellers and a centromere.

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19
Q

Describe acrocentric chromosome?

A

When the P arm is so short its too hard to observe.

The p arm contains genetic material that can be translocated without significant harm.

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20
Q

Describe balance chromosomal change?

A

Chromosome rearrangement. All the chromosomal material is present

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21
Q

Describe unbalanced chromosomal change?

A

Chromosome rearrangement. Extra or missing chromosomal material. Usually 1 or 3 copies of the same genome. (bad news)

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22
Q

Describe aneuploidy?

A

Whole extra or missing chromosomes

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23
Q

Describe translocation?

A

rearrangement of chromosomes

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24
Q

Describe insertions and deletions?

A

ones you can see

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25
Q

Describe micro deletions?

A

ones you can’t see

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26
Q

What is robertsonain translocation?

A

Where two acrocentric chromosomes are stuck end to end.

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27
Q

Edward Syndrome - Trisomy 18?

A

Extra chromosome 18

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28
Q

Turner syndrome - 45X

A

There is only one X chromosome. Not a problem, boys only have one X and girls only need one functioning X anyways. (milk clinical phenotype)

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29
Q

Klinefelter syndrome?

Triple x?

A

47 XXY

47 XXX

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30
Q

What is reciprocal translocation?

A

Where one arm has a bit of another arm attached to it.

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31
Q

Describe alternate and adjacent segregation in terms of reciprocal translocation?

A

Alternate - normal and balance

adjacent - unbalanced

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32
Q

what may unbalanced products result in?

A

Miscarriage (large segments)

Dysmorphic delayed child (small segments)

33
Q

What is FISH?

A

a technique used to look rapidly for micro deletions and subtelomere deletions and also for gross alterations in chromosomal number.

34
Q

How does FISH work?

A

Fluorescent dye is attached to a probe DNA that attaches to the chromosomal region of interest. If the specific genetic sequence you probed for is present the dye fluoresces.

35
Q

DiGeorge syndrome?

A

Characterised by low copy repeats and the deletion occurs near the middle of the chromosome. Missing genes on chromosome 22. Can see it when you use FISH.

36
Q

PCR?

A

Allows dosage analysis of polymorphic repeat sequences at several loci on the target chromosome.
Allows us to select one small piece of the human genome from a patient and amplify it.
PCR products from the repeats are amplified and fluroescently labelled.

37
Q

Microarray CGH?

A

Detects any missing or duplicated piece of chromosome.

38
Q

Array CGH?

A

Now the first line chromosome test. Genome wise. Can find polymorphisms.

39
Q

What is mosaicism?

A

The term “mosaicism” describes a situation in which different cells in the same individual have different numbers or arrangements of chromosomes.

40
Q

Describe somatic mosaicism?

A

Somatic mosaicism occurs when the somatic cells of the body are of more than one genotype.

41
Q

Describe gonadal mosaicism?

A

A condition in which the precursor (gremlin) cells to ova and spermatozoa are a mixture (mosaic) of two or more genetically different cell lines.
E.g. - duchenne muscular dystrophy

42
Q

What could chromosomal changes do?

A

Activate an oncogene, delete a tumour suppressor

43
Q

Treatment of HER2 amplification?

A

Monoclonal antibody

44
Q 
Describe the mutation effect;
Promotor mutation
Splice consensus altered
Base change makes a new stop
Base change alters amino acid sequence
A

Promotor = no transcription, no protein
Splice = mRNA decay, abnormal or absent protein
New stop = mRNA decay, short or absent protein
amino acid = different or non functioning protein

45
Q

What are the different types of mutation in DNA sequence?

A 
Wild type
Stop
Missense
Insertion 
Deletion (in and out of frame)
Triplet expansion
46
Q

What is penetrance?

A

The likelihood of having a disease if you have a gene mutation
e.g. 100% penetrance means you will always get the disease if you have the mutation

47
Q

What are mendelian disorders?

A

Diseases that segregate in families in the manner predicted by mender’s laws
A disease that is predominantly cause by a change in a single gene (high penetrance)

48
Q

FGFR3 gene?

A

Provides instructions for making a protein. Plays a role in several important cellular processes.

49
Q

Describe X inactivation?

A

In female cells only one X chromosome is active.

In a female half of the X chromosomes will be randomly turned off.

50
Q

What happens in a carrier female in terms of X inactivation?

A

If you have a mutation then in every cell one X will be normal and one will be mutated. Half the cells will be turned off, this means there will be less of an impact as only half the cells have the mutation. Causing an impact, just not as bad. Half the cells have working gene on average.

51
Q

Describe skewing of X inactivation?

A

Occurs when one X chromosome carries a cell-lethal mutation.

52
Q

What are single nucleotide polymorphisms? SNPs?

A

Alterations in DNA sequence. Genetically determined differences.

53
Q

What is non-mendelian inheritance?

A

A general terms that refers to ay pattern of inheritance in which traits do not segregate in accordance with Mendels lows. These laws describe the inheritance of traits linked to single genes on chromosomes in the nucleus.

54
Q

What are Copy Number Variations? CNVs?

A

Extra or missing stretches of DNA

You can have 2,1 or 0 copies of a stretch of DNA that has a deletion polymorphism.

55
Q

What is a risk model?

A

An equation that ties together different risk factors and gives you a risk prediction for your patient

56
Q

Name other non-mendelian inheritance patterns?

A

Epigenetic modification of DNA
Mitochondrial inheritance
Somatic mosaicism

57
Q

Describe DNA methylation?

A

Methylation usually occurs on the cytosine bases just before guanine bases. This changes DNA from easy to transcribe to hard to transcribe.

58
Q

When does DNA methylation matter?

A

Only matters if the methylation is at the promoter - prevents transcription

59
Q

What is the clinical importance of methylation?

A

Abnormalities of methylation can cause genetic disease. Causes gene silencing in cancer.

60
Q

What is imprinting?

A

the epigenetic phenomenon by which certain genes are expressed in a parent of origin specific manner. if the alley inherited from the father is imprinted, it is thereby silenced and only the allele from the mother is expressed.

61
Q

Angolan syndrome?

A

Near genetic disorder - developmental delay, intellectual disability etc

62
Q

What is imprinting controlled by?

A

Imprinting is controlled by methylation.

63
Q

Where else do you keep DNA?

A

Mitochondria

64
Q

What is heteroplasmy?

A

Different daughter cells contain different proportions of mutant mitochondria.

65
Q

Symptoms of mitochondrial disease?

A

Myopathy, diabetes, deafness, optic atrophy, encephalitis

66
Q

Describe mitochondrial inheritance

A

Rare. Maternal transmission only, sons and daughters equally effected.

67
Q

What are oncogenes?

A

a gene which in certain circumstances can transform a cell into a tumour cell.

68
Q

What are tumour suppressors?

A

is a gene that protects a cell from one step on the path to cancer. When this gene mutates to cause a loss or reduction in its function, the cell can progress to cancer, usually in combination with other genetic changes.

69
Q

What are the mechanisms of gene activation?

A

Duplication of the gene, activation of the gene promotor, change in the amino acid sequence.

70
Q

Describe Knudosons 2 hit hypothesis?

A

Inherit first mutation from parent (first hit)
Aquire the second mutation later on (second hit)

Or acquire both mutations later on in life (first and second hit)

71
Q

What is retinoblastoma?

A

Classical tumour suppressor gene.Need to lose two copies for tumour to develop, both copies can be lost by somatic mosaicism.

72
Q

What are some of the fates of a cell that had accumulated DNA damage?

A

Repair
Senescence - cell is not functioning and diving anymore
Apoptosis - cell death
tumour

73
Q

What are some of the mechanisms of DNA repair?

A 
Cell cycle checkpoints 
Direct repair 
Base excision 
Nucleotide excision 
Mis-match repair complex
74
Q

Describe mis-match repair?

A

Mis match (e.g. A and C) is recognised and excised by mis match repair complex

75
Q

What is P53?

A

Important tumour suppressor cell
Activates DNA repair proteins
Arrest cell growth at the GI/S cell cycle checkpoint
Initiates apoptosis if DNA damage is irreparable.

76
Q

BRCA1/2?

A

Breast cancer genes

77
Q

What is symptomatic testing?

A

Test to find the cause of disease in a person. Find mutation - allows to test other family members. No mutation - patient still has disease.

78
Q

Pre-symomatic testing?

A

If a family member have the disease.

LC Principles Genetics (3 decks)

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