Lecture 3: Genetic Inheritance

Question 1

What is Leber’s hereditary optic neuropathy?

Answer 1

Mitochondrial inherited disease -degeneration of retinal ganglion cells -loss of vision by teens or early 20s

Question 2

What is myoclonic epilepsy and ragged red fibers?

Answer 2

Mitochondrial inherited disease -affects muscle and nerves –> ataxia and seizures

Question 3

What is MELAS?

Answer 3

Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes -most common mitochondrial inherited disease -affects many body systems -stroke and dementia

Question 4

What is threshold?

Answer 4

When there are enough mutations in mitochondrial DNA to make an individual symptomatic

Question 5

What is polyploidy?

Answer 5

When cells contain a complete set of extra chromosome in cells

Question 6

What is aneuploidy?

Answer 6

When cells contain a missing or additional individual chromosomes -Monosomy, trisomy

Question 7

What is nondisjunction?

Answer 7

When chromosomes fail to properly separate in either meiosis I or II -results in monosomy or trisomy in offspring

Question 8

What is uniparental disomy?

Answer 8

Two chromosomes are inherited from same parent -results from nondisjunction

Question 9

What is genomic imprinting?

Answer 9

Certain genes only expressed from mother or father -other gene is silenced via methylation and histone modification

Question 10

What is a reciprocal translocation?

Answer 10

Exchange of material between non homologous chromosomes -Philadelphia chromosome: t(9:22)

Question 11

What is a Robertsonian translocation?

Answer 11

Long arm crosses with short arm -short arm is typically lost

Question 12

What is Turner Syndrome?

Answer 12

45, XO (Monosomy X) -Short female -Ovarian failure and doesn’t undergo puberty -Infertile (most) -30% webbed neck -CV defects

Question 13

What is Prader-Willi and Angelman Syndrome?

Answer 13

Deletion of a region in chromosome 15 Paternal deletion: Prader Willi -short, obese, hyptonia, small hands/feet Maternal deletion: Angelman -Severe intellectual disability, seizures, ataxic gait

Question 14

What is Kilinefelter Syndrome

Answer 14

47, XXY -Primary hypogonadism -Small/undescended testes -Infertility -Tall -Varying degrees of cognitive, social, behavioral, and learning difficulties

Question 15

What is Down’s Syndrome?

Answer 15

Trisomy 21 (47, XX+21) -Maternal meiotic nondisjunction or unbalanced translocation -Increased nuchal translucency -Cardiac defects -Duodenal atresia -Absent nasal bone

Question 16

What is Edwards Syndrome?

Answer 16

Trisomy 18 (47, XX+18) -Intrauterine growth restriction (most die in utero) or live up to a year -Microencephaly -Prominent occiput -Malformed and low-set ears -small mouth and jaw

Question 17

What is Patau Syndrome?

Answer 17

Trisomy 13 (47, XX+13) -Severe developmental abnormalities -most die before birth -Cleft lip/palate -Heart abnormalities, kidney malformations, CNS dysfunction

Question 18

What is penetrance?

Answer 18

Frequency a gene manifests itself

Question 19

What is expressivity?

Answer 19

Range of phenotypes vary with specific genotype *Example: NF can differ among family

Question 20

What is locus heterogeneity?

Answer 20

single disorder, trait, or pattern caused by mutations -only one mutant locus needed for phenotype to manifest -Example: Osteogenesis Imperfecta (brittle bone disease)

Question 21

What are polygenic traits?

Answer 21

Variations of traits due to combined effects

Question 22

Multifactorial Inheritance

Answer 22

Environmental factors can cause variation -Pyloric Stenosis: males needs less risk genes to show disease

Question 23

In Hardy Weinberg Principle, what does each variable mean?

p²+2pq+q²=1

p + q = 1

Answer 23

Genotype frequencies: p², 2pq, q²

Allele frequencies: p and q