2 Mendelian and Mitochondrial Inheritance

Question 1

what is unit inheritance?

Answer 1

parental phenotypes do not blend

Question 2

segregation?

Answer 2

only one copy of each pair of genes is passed on

Question 3

achondroplasia:
-inheritance?
-symptoms
-

Answer 3

• dominant
• short arms, legs, large head
• intelligence and life span normal

Question 4

what is a tell tale sign of daminant inheritance on a pedigree?

Answer 4

every generation effected

Question 5

what is variable expressivity?

Answer 5

the disease or condition can present with different or varying phenotypes (Marfans)

Question 6

Marfans:

• inheritance
• physiology
• mortality

Answer 6

• mendel dominant
• connective tissue disorder, bone overgrowth and join laxity
• ruptured aorta

Question 7

what is incomplete penetrance?

Answer 7

not everyone with the mutation will produce the phenotype (BRCA, and many other cancer mutations)

Question 8

when are new (de novo) mutations common?

Answer 8

• occur at hot spots in the genome

- more common when the father is older, his sperm will begin to acrew more mutations

Question 9

cystic fibrosis:
-inheritance?
-systems effected?
-reproductive issues?
-

Answer 9

• recessive
• primarily lung and GI
• 95% of males are infertile due to flagella not functioning (Cl channel required)

Question 10

if only one generation is affected on the pedigree, what could this mean?

Answer 10

recessive inheritance

Question 11

recessive traits have less variability than dominant traits T/F

Answer 11

True, and penetrance is usually complete

Question 12

Sickle Cell Anemia:

• inheritance
• ethnic predis
• clinical manifestation

Answer 12

• autosomal recessive
• prominent in african americans
• pain crises, organ damage

Question 13

hemophilia:
-inheritance
-deficiency in what protein
-where does bleeding occur
-

Answer 13

• X linked recessive
• def in factor 8 or 9 depending on type
• internally, in joints or muscles

Question 14

are females or males more likely to be affected by x linked recessive disorders?

Answer 14

males

Question 15

what transmission is not possible in x linked recessive disorders?

Answer 15

male to male

Question 16

what is lyonization?

Answer 16

the inactivation of one x chromosome in female cells

-this could be random (50/50) or skewed, leading to a phenotype in carriers of an x linked recessive condition

Question 17

Duchenne muscular dystrophy:

• inheritance
• symptoms

Answer 17

• x linked recessive

- progressive degen of skeletal muscle, seemingly hypertrophic

Question 18

would a female karyotype of 45, X leave this woman more susceptible to x linked recessive diseases?

Answer 18

yes

Question 19

in what scenarios are females affected by X linked recessive traits?

Answer 19

• has a 45, X karyotype
• skewed X inactivation
• affected father and carrier mother (rare)
• the condition may also have a non-x-linked cause

Question 20

incontinentia pigmenti:

• inheritance
• systems effected
• symptoms

Answer 20

• x linked dominant

- skin, hair, nails, eyes, and CNS. Skin lesions, alopecia, hypodontia, cognitive delays/disabilities

Question 21

are males or females more likely to be affected by x linked dominant inheritance?

Answer 21

Females

-often lethal in males

Question 22

where are the genes for ox phos found?

Answer 22

nuceleus, not the mitochondria

Question 23

where do the mitochondrial genes come from

Answer 23

mother’s oocyte, not father’s sperm

Question 24

what is MELAS?

• inheritance
• features

Answer 24

• mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes
• hearing loss, diabetes, seizures, intellectual disability

Question 25

what is heteroplasmy?

Answer 25

a mixture of normal and abnormal mitochondria in the cytoplasm

Question 26

what is homoplasmy?

Answer 26

all mtDNa is the same (abnormal or normal)

Question 27

how are mitochondria segregated during mitosis?

Answer 27

randomly

Question 28

what is the threshold effect with regard to mitochondrial disorders?

Answer 28

you need a certain number of malfunctioning mitochondria to express a phenotype. this phenotype may also vary depending on the % of abnormal mtDNA

Question 29

how can the percentage of abnormal mtDNA change over time in different tissues?

Answer 29

• random genetic drift

- selective (replicative) advantage

Question 30

how does age affect mitochondria?

Answer 30

• decreases with age thought is that there is oxidative damage from ox phos or an increased mutation rate
• if you have a mitochondrial disease it gets worse with age
• mitochondria might have a large effect on age in general

Question 31

what tissues are effected most by mitochondrial diseases?

Answer 31

• tissues that require a lot of energy

- brain and muscle

Question 32

what might be necessary in order to diagnose mitochondrial disorders?

Answer 32

muscle biopsy

Question 33

if a diagnosis is made prenatally, what is the difficulty with determining prognosis?

Answer 33

heteroplasmy

Question 34

what is nuclear transfrer?

Answer 34

a nucleus is removed from an oocyte with healthy mitochondria and discarded and then the nucleus is removed from an oocyte with abnormal mitochondria and placed inside the oocyte with abnormal mitochondria