Genetics (Week 1) Flashcards

Define and describe some common genetic terms

1
Q

Define Mendelian inheritance

A

Disorder of a single gene (Autosomal recessive, dominant or X-linked)

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2
Q

Define variable expression

A

When the same genetic condition affects members of the same family to different extents

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3
Q

Define incomplete penetrance

A

A mutation is inherited but the disease does not develop at all

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4
Q

Define complete penetrance

A

A mutation is inherited by an individual and the disease develops to some extent

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5
Q

Describe the term “double homozygous”

A

When a fault occurs in two separate genes meaning an individual is a carrier of two different conditions

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6
Q

Define the term consanguinity

A

This occurs when a mother and father are related to each other and is important in autosomal recessive conditions

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7
Q

Define the term “obligate carrier”

A

These are family members who must be carriers (this can be worked out from the pedigree)

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8
Q

Describe the concept of X inactivation

A

This occurs in females in utero where some X chromosome are inactivated, meaning females can suffer from X-linked recessive conditions but to a lesser extend than males

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9
Q

Define the term “genetic anticipation”

A

Moving down the pedigree chart means the condition gets worse and has an earlier onset age due to more and more repeat sequences being passed onto offspring down the generations

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10
Q

Describe the pattern of mitochondrial inheritance in offspring from a mother compared to a father

A

A father never passes on a mitochondrial condition to offspring whereas all children of an affected mother will inherit the disease to some extent

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11
Q

Define the term “manifesting carrier”

A

A female carrier who may show symptoms of the disease she carries to some extent

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12
Q

Define the term “heteroplasmy”

A

A feature of mitochondrial DNA inheritance where a % of DNA is mutant and reaches a threshold to cause disease

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13
Q

Which gene is specifically associated with male breast cancer?

A

BRCA 2 gene

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14
Q

Which two types of cancer are BRCA 1 and BRCA 2 associated with?

A

Breast and ovarian cancer

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15
Q

Which two tumour suppressor genes are known to contribute to bowel cancer?

A

MSH2 and MLH1

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16
Q

A mutation in which gene causes Cowden syndrome?

A

PTEN gene

17
Q

Describe Li Fraumeni syndrome

A

A rare autosomal dominant cancer predisposition syndrome

18
Q

Name 4 common genes which when mutated cause ovarian cancer

A

BRCA 1, BRCA 2, MLH1, MSH2

19
Q

What is Lynch syndrome (HNPCC)?

A

Autosomal dominant condition causing an increased risk of colon cancer

20
Q

Name 4 causative genes involved in Lynch syndrome

A

MLH1, MSH2, MSH6, PMS2

21
Q

What does to term syndactyly mean?

A

Fingers and/or toes are joined together

22
Q

On average, what percentage of genes in common do siblings have?

A

50% on average

23
Q

Define “intergenic regions”

A

Non-coding areas between genes