Genetics of Common Diseases

Question 1

true or false: both genetic and environmental factors are both involved in common disorders.

Answer 1

true

Question 2

synonyms for common diseases

Answer 2

complex

multifactorial chronic

Question 3

common idseases are the result of multiple factors

Answer 3

genetic epigenetic

environmental

Question 4

true or false: common diseases are usually not caused by a single gene.

Answer 4

true

Question 5

do common diseases have a simple medelian pattern of inheritance?

Answer 5

no

Question 6

do common diseases run in families?

Answer 6

yes

Question 7

common diseases are _ both in phenotype and genotype

Answer 7

heterogeneous

Question 8

susceptibility genes

Answer 8

genes involved in common diseases. They contribute to risk of developing a disease but are not enough to cause the disease.

Question 9

complex diseases (genes and frequency)

Answer 9

high frequency, low genetic distribution, variable penetrance

Question 10

mendelian diseases (genes and frequency)

Answer 10

low frequency, high genetic distribution, high penetrance

Question 11

how to distinguish genetic and environmental factors

Answer 11

study concordance and discordance of disease in twins: identical and fraternal
twins: identical - reared together and apart
adopted individuals: birth parents and adopted parents.

Question 12

when both twins in a family have the same disease phenotype, they are _ for the disease.

Answer 12

concordant

Question 13

when only one pair of member of twins is affected and the other is not,, the twins are _ for the disease.

Answer 13

discordant

Question 14

heritability

Answer 14

the proportion of phenotypic variation in a trait that is due to underlying genetic variation.
e.g. The heritability of ADHD is 80% means genetic factors are strongly involved in causing symptoms of ADHD.

Question 15

monozygotic twins

Answer 15

identical twins with identical genotypes, but mitochondrial genomes could be different.

Question 16

dizygotic twins

Answer 16

arise from the simulatneous fertilization of two eggs by two sperm and share 50% of alleles.

Question 17

disease concordance of less than 100% in MZ twins suggests that _ play a role in disease

Answer 17

nongenetic factors play a role in disease.

Question 18

what is discordance usually a result of?

Answer 18

environmental influences

epigenetic differences

Question 19

greater concordance in _ vs. _ twins is strong evidence of a strong genetic component to the disease.

Answer 19

greater concordance in MZ vs DZ twins is strong evidence of a strong genetic component to the disease.

Question 20

what do studies of MZ twin pairs reared apart show?

Answer 20

that shared genetic factors are more important than shared environmental factors for many common diseases.

Question 21

adoption studies

Answer 21

compaire similarity for a trait or disorder in biological versus adoptive rleatives to determine the degree to which genetic and shared environmental factors contibue to a phenotype.

Question 22

common variants

Answer 22

genes involved in a disorder in which the minor allele presents in a frequency of 1 - 5%. They have low penetrance.

Question 23

rare variants

Answer 23

multiple rare DNA variants with high penetrance.

Question 24

Common disease, rare variant

Answer 24

a proportion of inherited susceptibility to relatively common human chronic diseases may be due to the summation of the effects of low frequency and independently acting variants.

They are less than 1% and can be identified only by sequencing.

Question 25

Genome wide association studies

Answer 25

Studies designed to identify the genetic variation in common diseases. It is based on the idea that comon variants are involved. it involves comparing allele frequencies hundreds of thousands of common variants spread across the genome between large samples of patients and control cases.

Question 26

SNP alleles more frequent with people with the disease are said to be _ with the disease.

Answer 26

associated

Question 27

In GWAs, associated SNPs are

Answer 27

considered as pointers to the region of the human genome where the disease causing genes are likely to reside. The SNP itself is not necessarily involved but is close to the loci that are involved.

Question 28

What GWA does not require

Answer 28

any hypothesis about what gene or genes one is looking for. No assumption about the function of the genes are required or its chromosomal location.

Question 29

What the GWA requires

Answer 29

large numbers of affected individuals and control individuals - populations, not families.

Question 30

What is examined in GWA

Answer 30

millions of common SNPs spread across the entire genome using microarray chips.

Question 31

features of common diseases

Answer 31

They are usually not caused by mutations in a single gene. Common diseases tend to run in families, and individuals do not always develop a common disease due to the presence of faulty genes.