Chap 5- single gene disorders

Question 1

phenotype

Answer 1

observable characteristics of person, organ, or cell

Question 2

genotype

Answer 2

combination of alleles that a person possesses at a single locus (genetic make up)

Question 3

disease phenotype

Answer 3

specific manifestations that arise in response to differential expression of just one or a small number of genes that may be harmful

Question 4

character or trait

Answer 4

observable manifestations that are not disease associated

Question 5

genetic variation

Answer 5

changes in the base sequence of our DNA -> changes in phenotype

Question 6

pedigree

Answer 6

graphical representation of a family tree that uses standard symbols

Question 7

proband

Answer 7

first member in a family to be evaluated by physiciain

Question 8

square symbol

Answer 8

male

Question 9

circle symbol

Answer 9

female

Question 10

diamond symbol

Answer 10

sex unstated

Question 11

dark symbol

Answer 11

affected person

Question 12

symbol with dot in the middle

Answer 12

carrier who will not manifest disease

Question 13

symbol with line through middle

Answer 13

carrier who may go on to manifest disease

Question 14

symbol with diagonal line

Answer 14

deceased

Question 15

dominant trait

Answer 15

gene is expressed with single copy

Question 16

recessive trait

Answer 16

will need two copies of gene to be expressed (only if both alleles have mutations)

Question 17

incomplete penetrance

Answer 17

just because someone has faulty gene does not always mean they will develop the disease

Question 18

male sex chromosomes

Answer 18

X and Y, hemizygous

Question 19

female sex chromosomes

Answer 19

X and X

Question 20

types of inheritance patterns

Answer 20

• autosomal dominant
• autosomal recessive
• y linked
• x linked dominant
• x linked recessive

Question 21

autosomal dominant inheritance

Answer 21

• only one copy required to be affected
• males and females equally affected and can transmit disease
• offspring have 50% chance of dev disease

Question 22

autosomal recessive

Answer 22

• need affected genes from both parents
• both parents are carriers
• chance that each offspring has disease is 25%

Question 23

compound heterozygote

Answer 23

affected child born to parents who have different mutations for same gene

Question 24

consanguineous

Answer 24

• autosomal recessive diseases can skip generations

Question 25

symbol with two lines in middle

Answer 25

- consanguineous mating

Question 26

Y chromosome

Answer 26

- has very few genes - genes have male specific function - helps to maintain balance between males and females

Question 27

X- chromosome inactivation

Answer 27

- compensate for having different number of X chromosomes in males and females - initiated after fertilization - forms barr body

Question 28

pseudoautosomal regions

Answer 28

- regions in both X and Y chromosomes that have genes similar to autosomes - no X and Y recombination outside of this region

Question 29

how does X-chromosome inactivation occur?

Answer 29

marked by long ncRNA and whatever is marked is silenced

Question 30

X-linked dominant inheritance

Answer 30

- affected individuals can be either sex - significantly more females than males - affected females have milder symptoms - no male to male transmission - children have 50% chance of being affected

Question 31

X-linked recessive inheritance

Answer 31

- mostly males - no male to male transmission - male cannot be carrier

Question 32

four rules of inheritance

Answer 32

- dominant diseases- chance offspring can get disease is 50% - recessive diseases- chance offspring can get disease is 25% - carrier refers to recessive diease - no male to male transmission in X linked diseases

Question 33

matrilineal inheritance

Answer 33

- mitochondrial DNA only comes from mother - more prone to mutation due to proximity to ROS - mitochondrial DNA disorders can be of either sex but males dont transmit

Question 34

modifier gene

Answer 34

- gene that modifies another gene | - modifies effects of disease producing gene

Question 35

locus heterogeneity

Answer 35

- mutations causing same disease come from two totally different mutations - people who have same disease can produce normal offspring

Question 36

penetrance

Answer 36

probability that a person who has a mutant allele will express disease phenotype

Question 37

imprinting

Answer 37

- mutant allele is not expressed - silencing - for most genes you have two working copies from mom and dad - with imprinting will only have one working copy

Question 38

Angelman

Answer 38

- maternal deletion in Ch 15 q11-13 - effects ubiquitin pathway - learning difficulties, speech problems, seizures, jerky movements, and unusually happy

Question 39

Parder- Willi

Answer 39

- paternal deletion of Ch 15 q11-13 - gene involved in mRNA splicing - learning difficulties, short stature, compulsive eating

Question 40

anticipation

Answer 40

- mutation can expand from generation to generation - phenotype varies in a directional way - can be expressed at earlier age and become increasingly severe

Question 41

allele frequency

Answer 41

- measure of relative frequency of allele on a genetic locus in a population expressed as a percentage - frequency of allele can vary widely from one population to another

Question 42

nonrandom mating

Answer 42

- humans select mate and prefer phenotypes like themselves - causes allele frequency to skew to one direction - helps to spread disease phenotype

Question 43

forces that lead to evolutionary change

Answer 43

- negative/purifying selection - new mutations - influx of immigrants - genetic drift

Question 44

genetic drift

Answer 44

out of all alleles in population, only those present in people who reproduce can be transmitted

Question 45

population bottleneck

Answer 45

- population becomes very small and then expands - removes all species not fit to survive - due to natural disaster

Question 46

founder effect

Answer 46

- when group emigrate to form separate colony they represent a subset of genetic variation in original population - expansion leads to new genetic pool

Question 47

balancing selection

Answer 47

- evolution throws in mutant gene if it is favorable | - i.e. sickle- cell anemia causing malaria resistance