Genetics Refresher

Question 1

What determines the individual’s risk for a disease?

Answer 1

The interactions between genetic risk factors (predisposition) and environmental risk factors.

Question 2

Define a TRAIT.

Answer 2

Describes a characteristic BUT also used to describe a group of symptoms of a disease or disorder.

Question 3

Define a DISEASE.

Answer 3

Refers to an illness which produces specific symptoms or affects a specific body function/structure.

Question 4

Define a DISORDER.

Answer 4

Disruption to regular bodily structure/function usually causing a disease.

Question 5

Define a CONDITION.

Answer 5

An abnormal state of health that interferes with normal wellbeing.

Question 6

Define a SYNDROME.

Answer 6

A collection of symptoms associated with a specific disease (usually affect multiple organs).

Question 7

Define a COMPLEX DISEASE.

Answer 7

A disease where one or more alleles, acting alone or in concert increase or reduce the risk of developing a trait.

Question 8

What kinds of alterations can genetic disorders make?

Answer 8

1 gene

Multiple genes.

Chromosomes.

Question 9

What types of genetic disorders are there?

Answer 9

Monogenic (mendelian) disorders.

Polygenic (multifactorial) complex disorders.

Chromosomal disorders.

Question 10

What are monogenic (mendelian) disorders?

Answer 10

Mutations which occur due to singular gene mutation which can be transferred from parent to offspring.

Question 11

What are some examples of monogenic/mendelian disorders?

Answer 11

Cystic fibrosis

Sickle cell anaemia

Some cancers

Question 12

What are polygenic (multifactorial) complex disorders?

Answer 12

Common disorders which occur due to multiple risk alleles along with environmental risk increasing risk.

Question 13

What are some examples of polygenetic (multifactorial) complex disorders?

Answer 13

Most cancers

Type 2 Diabetes

Cardiovascular Disease

Arthritis

Question 14

What are chromosomal disorders?

Answer 14

Very rare diseases which are caused by a structural or numerical abnormality on the chromosome.

Question 15

When does the risk of chromosomal disorders increase?

Answer 15

When the mother gets older.

Question 16

What kinds of disorders are chromosomal?

Answer 16

Trisomy (3 types of a chromosome rather than 2)

Monosomy ( 1Chromosome rather than 2)

Question 17

What does DE NOVO mean?

Answer 17

Not inherited, occurring new inside the body.

Question 18

What kind of disorders are cancer?

Answer 18

Mostly complex diseases and may also involve de novo/somatic mutations.

Question 19

What are mitochondrial disorders?

Answer 19

Very rare disorder caused by mutations in mitochondrial DNA or nuclear DNA.

Question 20

What are chromosome abnormalities?

Answer 20

Changes resulting in visible alteration of the chromosomes.

An abnormality produced by chromosomal mechanisms.

Question 20

What happens when a chromosomal abnormality occurs in a gamete cells?

Answer 20

Results in constitutional abnormalities which affect all cells.

Question 21

What happens when chromosomal abnormalities occur later in life?

Answer 21

Results in somatic abnormalities (not all cells) which results in mosaicism.

Question 22

What types of chromosome abnormalities are there?

Answer 22

Numerical or Structual.

Question 23

What kinds of numerical chromosome abnormalities exist?

Answer 23

Triploid

Aneuploidy

Question 24

What is triploid?

Answer 24

Containing homologous sets of chromosomes, it is lethal.

Question 25

What is aneuploidy?

Answer 25

Loss or extra copy of one/more chromosomes, can be lived with.

Question 26

What kinds of structural chromosome abnormalities exist?

Answer 26

Deletion Duplication Translocation Inversion

Question 27

What are monogenic disorders caused by?

Answer 27

A rare mutation at a single locus.

Question 28

What kinds of gene mutations cause mendelian disorders?

Answer 28

Point mutations Deletion Insertion

Question 29

What is a point mutation?

Answer 29

Replace 1 base with another.

Question 30

What kind of mutation is sickle cell anemia?

Answer 30

Point mutation.

Question 31

What kinds of point mutations are there?

Answer 31

Silent Missense Nonsense Other regulatory regions.

Question 32

What is a silent point mutation?

Answer 32

No change in the protein sequence (change for a pair).

Question 33

What is a missense point mutation?

Answer 33

A change in an AA sequence, causes a codon to code for a different amino acid. (sickle cell anaemia)

Question 34

What is a nonsense point mutation?

Answer 34

Creates a STOP codon.

Question 35

What is a STOP codon?

Answer 35

Signals the termination of the translation process.

Question 36

What kind of mutation is cystic fibrosis?

Answer 36

Deletion

Question 37

What kind of mutation is Huntington's Disease?

Answer 37

Insertion

Question 38

What is include in Mendel's Law?

Answer 38

Law of segregation Law of independent assortment Law of dominance

Question 39

What is the Law of Segregation?

Answer 39

During gamete formation, the 2 alleles for each gene (locus) segregate from each other so that each gamete carries only one allele for each gene (locus).

Question 40

What is the Law of Independent Assortment?

Answer 40

Alleles for different traits segregate independently during the formation of gametes.

Question 41

What is the Law of Dominance?

Answer 41

An organism with at least one dominant allele will display (phenotype) the effect of the dominant allele.

Question 42

What is penetrance?

Answer 42

The proportion of individuals carrying a particular genetic variant that also expresses an associated trait.

Question 43

What does high penetrance mean?

Answer 43

More space for prophylactic intervention.

Question 44

What is the impact of environmental factors on mendelian (monogenic)?

Answer 44

Weak but can impact progression.

Question 45

What kind of penetrance do Mendelian disorders have?

Answer 45

HIGH

Question 46

What kinds of cells undergo mutations?

Answer 46

Somatic (body) cells Gamete cells.

Question 47

What does a mutation in a somatic cell lead to?

Answer 47

Can cause malignant transformation and some congenital diseases.

Question 48

What does a mutation in a gamete cell lead to?

Answer 48

Can give rise to inherited disease.

Question 49

Where do inherited mutation come from?

Answer 49

Passed from one or both parents. De novo mutations in gametes.

Question 50

When are inherited mutations present?

Answer 50

All through life and in ALL cells.

Question 51

Are inherited mutations passed?

Answer 51

YES

Question 52

When do Somatic (de novo) mutations occur?

Answer 52

Very early stages of development mean they are present through life but can also occur later in life.

Question 53

What are mosaics?

Answer 53

Somatic mutations which occur later in life, are only present in some cells resulting in a mosaic of affected and unaffected cells.

Question 54

Are somatic mutations passed?

Answer 54

NO

Question 55

What are multifactorial disorders?

Answer 55

Common disorders caused by the combined effects of multiple genetic variants interacting with environmental factors.

Question 56

What does polygenetic mean?

Answer 56

Multiple SNPs

Question 57

What is the impact of environment on Multifactorial Complex disorders?

Answer 57

A very strong effect works alongside the genetic aspect.

Question 58

What is the penetrance of Multifactorial Complex disorders?

Answer 58

Very low so no prophylactic approaches available.

Question 59

What is the individual risk for a multifactorial disease determined by?

Answer 59

The combination of the genetic + Environmental risk portfolio for this individual

Question 60

Define AETIOLOGY.

Answer 60

Cause or set of causes of a condition.

Question 61

What does it mean to have a genetic susceptibility to a complex disease?

Answer 61

The likelihood of developing disease increases but doesn't always directly cause it.