Allred 2

Question 1

Phenotype

Answer 1

The observable property of an organism; a trait such as height, weight, medical condition, etc.

Question 2

Genotype

Answer 2

The DNA sequence at a specific, defined location; not necessarily observable; can be expressed in a variety of ways

Question 3

Allele

Answer 3

A DNA sequence at a specific chromosome; the genotype is made up of alleles, one allele per chromosome; all DNA sequences (not just genes) are alleles

Question 4

Homozygous

Answer 4

Two identical alleles at the same locus

Question 5

Heterozygous

Answer 5

Different alleles at the same locus

Question 6

Dominant trait

Answer 6

A single copy of the gene (allele) is sufficient to express phenotype

Question 7

Recessive trait

Answer 7

Two copies of the gene (allele) are necessary to express phenotype

Question 8

Codominant trait

Answer 8

Both alleles are expressed as observable phenotypes

Question 9

Blood Type A

Answer 9

UDP-N-acetylgalactose

Question 10

Blood Type B

Answer 10

UDP-Galactose

Question 11

Blood Type O

Answer 11

No additional sugar attachment

Question 12

Locus

Answer 12

A specific location on the chromosome (plural: loci)

Question 13

ABO Blood Group

Answer 13

Multiple alleles in the population at the ABO locus; there are multiple combinations of alleles to create multiple genotypes/phenotypes

Question 14

Why are mouse models used in genetic studies?

Answer 14

Answers questions that ask if two genetic loci are on the same chromosome

Question 15

Chiasma

Answer 15

INSERT

Question 16

Silent mutation

Answer 16

A change in base pairs that does not lead to a change in amino acid sequence; synonymous change

Question 17

Nonsense mutaion

Answer 17

Premature termination

Question 18

Missense termination

Answer 18

A change in base pairs that leads to a change in amino acid sequence; nonsynonymous change

Question 19

Frameshift mutation

Answer 19

Addition or deletion in nucleotide sequence

Question 20

Autosomal Dominant Disorder

Answer 20

A genetic disorder that requires one copy of the mutated gene to express the disease

Can be caused by new mutation, or due to penetrance and expression variability

Question 21

Penetrance

Answer 21

The likelihood of the presence of a disease when the mutation is present

Question 22

Variability of expression

Answer 22

The disease has a wide range of phenotypic expression

Question 23

Autosomal Recessive Disorder

Answer 23

A genetic disorder that requires two copies of the mutated gene to express the disease

Early onset of disease
Fully penetrant
Found with genes that encode for enzymes

Question 24

X linked disorders

Answer 24

Expressed in males; females with the gene are obligate carriers; all daughters of affected fathers are carriers

Question 25

Mitochondrial disorders

Answer 25

Nonmendalean No transmission from affected males Affected females transmit disease to all of their offspring Disease involve oxidative phosphorylation defects

Question 26

Gene heterogeneity

Answer 26

more than one gene can contribute to phenotype

Question 27

Gene-Gene interaction

Answer 27

both genes combined have an effect

Question 28

Gene-environment interaction

Answer 28

Gene suseptibility only observed in the presence of specific environmental triggers

Question 29

Phenocopies

Answer 29

The same phenotype caused by environmental factors only

Question 30

Epigenetics

Answer 30

Modification of histones or DNA sequence by environmental factors

Question 31

Types of polymorphisms

Answer 31

Microsatellites (SSR) | Single Nucleotide Polymorphisms (SNP)

Question 32

Single nucleotide polymorphism

Answer 32

Single base changes Naturally occuring variants Most do not account for phenotypic variability, no "normal" or "wild-type" allele Used mostly for candidate gene and genome-wide association studies May be slight changes for gene functioni or expression levels Can be in the intron/exon

Question 33

How can a SNP affect susceptibility of a complex disease?

Answer 33

Many complex diseases occur later in life SNPs cause slight changes in gene expression levels or function that take time to lead the clinical phenotype Initially the body will compensate for SNP effects, but will eventually lose the ability to do so

Question 34

Where does the SNP effect?

Answer 34

``` Exons: Protein structure or function Promoter/Enhancer: Expression level Introns: splicing or expression level 5' UTR: ribosome binding, protein level 3' UTR: Transcript stability ```

Question 35

Linkage Disequilibrium (LD)

Answer 35

The non-random association of alleles at two or more loci LD Differs by genomic region LD Differs by genetic ancestry

Question 36

Steps for Disease Gene Identification

Answer 36

``` Is there a genetic component Research subject ascertainment Measurement of phenotype Molecular/Analytical analysis Functional analysis ```

Question 37

Genetic component factors

Answer 37

Twin concordance | Familial aggregaion

Question 38

Genetic subject ascertainment

Answer 38

Sib-pair Families Case-control

Question 39

GWAS

Answer 39

Genome-wide association study Scan the genome using > 1m SNP to search for variants that differ in frequency between cases and controls; identifies common genetic variants with a weak influence on the phenotype