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Principles > Genetics > Flashcards

Genetics Flashcards

1
Q

What percent go the human genome in genes?

A

2-3%

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2
Q

Genotyope

A

Genes you have

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3
Q

Phenotype

A

the manifestation of the genotype

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4
Q

What damage can occur during DNA replication

A

DNA strands can ,break, chemical cross linking or mismatched bases

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5
Q

What is a chromosome made up of

A

DNA that is wrapped round proteins called histones and packaged into a chromosome.

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6
Q

Where is the information held in DNA

A

it’s held in the sequence of bases which are held on a sugar phosphate backbone

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7
Q

What occurs during cell cycle

A

G0 is the rest phase where the cell is a cell, G1 is where it begins to grow, S is where it synthesises another strand of DNA (DNA replication), G2 is another growth phase and M is where Mitosis occurs.

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8
Q

What occurs during DNA replication?

A

DNA is unzipped, on one strand DNA replicates in a straight line from its own 5’ to 3’, on the other strand it has to replicate in fragments

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9
Q

What occurs if the DNA repair mechanisms break?

A

it can cause disease

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10
Q

Mitosis

A

one parent diploid cell becomes two identical diploid daughter cells

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11
Q

Meiosis

A

One diploid parent cell becomes four haploid daughter cells

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12
Q

What is different about meiosis than mitosis

A
  • crossing over occurs
  • occurs in gamete formation
  • diploid cell becomes four haploid cells
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13
Q

How is RNA different than DNA?

A
  • single stranded
  • ribose in backbone not deoxyribose
  • uracil is used instead of thymine
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14
Q

Amount of protein produced is determined by

A

rate of transcription, rate of splicing mRNA, half life of mRNA, rate of processing polypeptide

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15
Q

briefly describe how is a gene turned into a protein

A

DNA is transcribed and spliced into mature mRNA and then it is translated into a protein

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16
Q

Promotor

A

identify translation start sites on mRNA

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17
Q

Start codon

A

regions of DNA where translation starts

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18
Q

stop codon

A

signal the end of polypeptide chain during translation

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19
Q

Stop codon bases

A

UAG, UAA, UGA

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20
Q

Start codon bases

A

AUG

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21
Q

Polymorphism

A

any variation in the human genome that has a population frequency of 1% or any variation in the human genome that does not cause disease

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22
Q

Mutation

A

A change that causes a genetic disorder or any heritable change in the human genome

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23
Q

How is a chromosome identified?

A

by its banding pattern, length and position of centromere

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24
Q

How many chromosomes do we have

A

46

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25
Q

What does the karyotype include?

A

number of chromosomes and sex chromosome complement

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26
Q

What do the lighter parts of the chromosome suggest?

A

they have more genes and are more transcriptionally active

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27
Q

Why do chromosomes look stripy?

A

they are looked at during metaphase

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28
Q

What does balanced chromosomal rearrangement mean?

A

all chromosomal material is present

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29
Q

What does unbalanced chromosomal rearrangement mean?

A

extra or missing chromosomal material, usually either 1 or 3 copies of some of the genome which can lead to disease

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30
Q

Aneuploidy

A

extra or missing chromosome

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31
Q

Translocation

A

rearrangement of chromosomes

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32
Q

Insertions and deletions

A

missing or duplicate material

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33
Q

Microdeletions

A

small parts of genetic material that are too small to be seen down a microscope

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34
Q

Name the parts of a chromosome

A

Telomere (top) Short arm (top arm) centromere (middle) long arm (bottom arm) telomere (bottom arm)

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35
Q

Acrocentric

A

the short arm of the chromosome doesn’t matter

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36
Q

What does having missing bits of a chromosome lead to

A

human disease

37
Q

Trisomy 21

A

downsyndrome, caused by extra chromosome on chromosome 21 (47XY + 21)

38
Q

Robertsonian Translocation

A

two acrocentric chromosomes stuck end to end

39
Q

What does robertsonian translocation do?

A

increases risk of trisomy 21 in pregnancy.

40
Q

why is X chromosome aneuploidy better tolerated?

A

because of x inactivation

41
Q

reciprocal translocation productive risks

A

miscarriage (large segments), dysmorphic delayed Childs (small segments)

42
Q

What does FISH allow you to do?

A

choose one chromosome segment and light it up with fluorescent dye

43
Q

When is FISH useful

A

as some defects in chromosomes are so small that FISH has to be used, used widely in molecular analysis of cancers

44
Q

What is array CGH

A

first line chromosome testing kit, it is genome wide and finds lots of polymorphisms but it’s technique is ‘DNA based’ and so reflects on underlying chromosomes.

45
Q

Where does mutation come from

A

new mutations can happen in gametogenesis

46
Q

Mosaicism

A

when a person has multiple genetically different cells

47
Q

Somatic Mosaicism

A

genetic variation within the body of an individual

48
Q

Why is every cell a mosaicism

A

because all cells suffer mutations as they divide

49
Q

What can chromosome change lead to ?

A

activation of an oncogene (a gene that has the potential to cause cancer) or deletion of a tumour suppressor

50
Q

HER2 gene

A

growth gene, found in breast cancer

51
Q

Why is it important to identify chromosome change?

A

specific chromosome change can indicate treatment in cancer

52
Q

ACGH

A

is used to analyse DNA, used for deletions, duplications for imbalance.

53
Q

PCR

A

allows us to select one small piece of human genome from a patient and amplify it

54
Q

disadvantage of PCR

A

can only sequence a bit of DNA at a time

55
Q

Whats better than PCR?

A

Next generation sequencing

56
Q

What does NGS allow

A

large scale sequencing, can sequence all exons or whole genome cheaply

57
Q

Mutation

A

a genetic variation that causes disease

58
Q

Polymorphism

A

a genetic variation that is prevalent in the population and not disease causing

59
Q

promotor mutation

A

no or reduced transcription, no or reduced protein

60
Q

what does altering splice consensus lead to

A

mRNA decay, abnormal or absent proteins

61
Q

What does a base change that leads to a new stop codon lead to?

A

mRNA decay, short or absent proteins

62
Q

What happens if a base change alters the amino acid sequence?

A

Different or non functioning protein

63
Q

Missense

A

a base is replaced

64
Q

Insertion

A

a base is inserted

65
Q

Deletion (out of frame)

A

an amino acid is deleted, completely non functioning

66
Q

deletion (in frame)

A

shorter than normal protein but still functioning

67
Q

triplet expansion

A

one, three base codon repeats itself leaving you with multiple copies of amino acid

68
Q

What his considered a normal sequence?

A

The most common sequence in USA

69
Q

Wild Type

A

most common sequence

70
Q

c.

A

change in mRNA sequence

71
Q

p.

A

change in peptide sequence

72
Q

Del

A

deletion

73
Q

Ter/ *

A

stop and for peptide may be a nonsense

74
Q

Ins

A

insertion

75
Q

Val

A

Missense

76
Q

Fs

A

frameshift

77
Q

what do promoter and splice site sequence change do?

A

stop transcription or cause abnormal splicing

78
Q

What does a base change causing an amino acid change do?

A

change in protein sequence, not every base change causes disease, this may or may not reduce protein function, some missense mutations make proteins work faster.

79
Q

Trinucleotide repeat expansion

A

replicate of trinulcleotide

80
Q

Advantages and disadvantages of next generation sequencing

A

advantages, higher sensitivity and cheaper disadvantages , don’t know what the genetic change actually is, it may be a disease causing mutation, a polymorphism or a variant of unknown significance

81
Q

How to tell if it’s a polymorphism or disease causing mutation

A

does it match expected inheritance, is it in the right gene, has it been reported before and what does it do to the protein.

82
Q

How many chromosomes do you have in each cell?

A

22 pairs of chromosomes and the sex chromosomes

83
Q

difference between mosaicism and somatic mosaicism

A

somatic mosaicism can be present in gonadal cells

84
Q

What things may a variant may be?

A

a disease causing variant, a variant of uncertain significance and polymorphism

85
Q

What’s the variant classification

A

Class 1 is definitely a polymorphism, class 2 is probably s polymorphism, class 3 is unclassifiable, class 4 probably pathogenic and class 5 is definitely pathogenic

86
Q

Penetrance

A

the likelihood of having a disease if you have a gene mutation

87
Q

Mendelian disorders

A

a disease that is predominantly caused by a change in a single gene

88
Q

What characteristic of a cancer cell is central allowing it to acquire further new characteristics?

A

Genomic instability

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