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Principles > Genetics > Flashcards

Genetics Flashcards

1
Q

When does DNA replication occur?

A

During the S phase of mitosis

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2
Q

Why are DNA repair mechanisms required?

A

DNA can be damaged during replication

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3
Q

What happens if there are defects in DNA repair mechanisms?

A

This may lead to the development of specific human diseases

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4
Q

How is a protein produced from DNA?

A

1) DNA is transcribed to RNA
2) Primary mRNA is spliced to mature mRNA
3) mRNA leaves the cell and is translated to proteins at ribosomes
4) The protein is modified and moved around the cell

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5
Q

How is the amount of protein produced determined?

A
  • Rate of transcription
  • Rate of splicing to mRNA
  • Half life of mRNA
  • Rate of processing of polypeptide
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6
Q

What is a polymorphism?

A

Any variation in the human genome which does not cause a disease in its own right, but may predispose to a common disease

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7
Q

What is a mutation?

A

A gene change that is heritable and causes a genetic disorder

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8
Q

What are the two types of sequence variations within a gene?

A

1) Changes in the promotor sequence

2) Changes in the exon sequence (may or may not change an amino acid)

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9
Q

What is an acrocentric chromosome?

A

A chromosome in which the centromere is located quite near one end of the chromosome

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10
Q

What are the two types of chromosomal rearrangement?

A

1) Balanced chromosomal rearrangement

2) Unbalanced chromosomal rearrangement

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11
Q

What is aneuploidy?

A

A whole extra or missing chromosome

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12
Q

What is a Robertsonian translocation?

A

Two acrocentric chromosomes stuck end to end

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13
Q

Why is X chromosome aneuploidy better tolerated?

A

Due to X inactivation

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14
Q

What are possible effects of an unbalanced chromosomal rearrangement?

A
  • Miscarriage
  • Multiple malformations
  • Dysmorphic delayed child
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15
Q

How can chromosome changes contribute to the development of cancer?

A
  • Activation of an oncogene

- Deletion of a tumour suppressor

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16
Q

What is somatic mosaicism?

A

Occurrence of two genetically distinct populations of cells within an individual, derived from a post-zygotic mutation

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17
Q

What is a germ line mutation?

A

A mutation which comes from the parent’s genome

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18
Q

What is array-based comparative genomic hybridisation? (aCGH)

A

A genome-wide chromosome test, which can detect polymorphisms

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19
Q

What are the limits of aCGH?

A

It can not detect balanced chromosomal rearrangements

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20
Q

What is FISH?

A

A technique which allows visualisation of specific genes or portions of genes to understand chromosomal abnormalities and other genetic mutations

21
Q

What are the functions of introns?

A
  • Control regulation of genes
  • Space genes out, insulate genes from promoters
  • Provide substrate to expand the genome/add genes
22
Q

What is the significance of p. when describing a mutation?

A

The change in the peptide sequence

23
Q

What is the significance of c. when describing a mutation?

A

The change in the mature mRNA sequence

24
Q

What is next generation sequencing (NGS)?

A

An available method for quickly sequencing whole genomes or just all known exons

25
Q

What is the issue with NGS?

A

Humans have approximately 3 million polymorphisms (changes from the ‘normal’ sequence) and if there is a mutation causing a genetic disease, it is only one polymorphism

26
Q

What is filtering?

A

A method of finding the mutation which is causing the abnormal phenotype

27
Q

What is penetrance?

A

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

28
Q

What are Mendelian Disorders?

A

Diseases that segregate in families in the manner predicted by Mendel’s laws i.e. a disease predominantly caused by a change in a single gene

29
Q

What are Mendel’s laws?

A

1) Law of segregation
2) Law of independent assortment
3) Law of dominance

30
Q

What are the different types of Mendelian inheritance?

A
  • Autosomal dominant
  • Autosomal recessive
  • X-linked
31
Q

What is multi-factorial inheritance?

A

When many factors are involved in causing a birth defect

32
Q

What is Polymerase Chain Reaction (PCR)?

A

A method which allows the amplification of one small piece of the human genome

33
Q

What is Sanger sequencing?

A

A laboratory method used to determine the sequence of a DNA molecule

34
Q

What are some factors involved in mitochondrial inheritance?

A
  • Methylation/imprinting
  • Mitochondrial inheritance
  • Mosaicism
35
Q

What are single nucleotide polymorphisms (SNPs)?

A

Alterations in DNA sequence which exert effects which may make you more prone to disease or have no effect

36
Q

What are copy number variations (CNVs)?

A

Extra or missing stretches (deletions or duplications) of DNA which are highly prevalent in the genome.

37
Q

What are the Hallmarks of Cancer?

A

Characteristics that a cell needs to acquire to be able to develop as a cancer

38
Q

What are the different types of cancerous mutations?

A

+ Driver mutations - drive carcinogenesis
+ Passenger mutations - incidental mutations that happen due to instability of cancer
+ Germline mutations - inherited, 5-10% of cancer cases
+ Somatic mutations - not inherited, caused by carcinogens

39
Q

What is epigenetics?

A

The study of changes in gene expression without a change in DNA sequence

40
Q

What are oncogenes?

A

A gene that has the potential to cause cancer

41
Q

How are oncogenes activated?

A

+ Point mutations - signal for protein is always switched on -> hyperactive protein
+ New promoter/chromosome rearrangement - translocation produces a hyperactive fusion protein -> excess amount of protein
+ Amplification - excess production of protein

42
Q

What are tumour suppressors?

A

A gene that regulates a cell during cell division and replication and whose loss results in carcinogenesis

43
Q

What is the two hit hypothesis?

A

The hypothesis that most genes require two mutations to cause a phenotypic change:

1) susceptible carrier
2) leads to cancer

44
Q

Are cancers homogenous or heterogenous?

A

Heterogenous i.e. they have multiple different mutations (e.g. evade apoptosis, hypoxia resistant, drug resistance etc)

45
Q

What is the difference between sporadic and hereditary mutations?

A 
Sporadic = multifactorial, slightly older children
Hereditary = Mendelian inheritance, babies with family history
46
Q

What is retinoblastoma?

A

A mutation in the Rb gene resulting in cancer

47
Q

What are some features suggestive of inherited cancer susceptibility?

A
  • Several first or second degree relatives with cancer
  • Several close relatives with related cancers
  • An unusually early age of onset
  • Bilateral tumours in paired organs
  • Tumours in two organ systems in one individual
48
Q

What is genetic counselling?

A

The process of advising individuals and families affected by or at risk of genetic disorders to help them understand and adapt to the medical, psychological and familial implications of genetic contributions to disease

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