Lecture 28

Question 1

what is cytoplasmic inheritance?

Answer 1

when sperm fertilizes egg, offspring inherits many things from mother thru oocyte cytoplasm

Question 2

what does the offspring inherit from oocyte cytoplasm? (3)

Answer 2

1. proteins
2. mRNAs
3. organelles

Question 3

2 other names for cytoplasmic inheritance

Answer 3

1. maternal inheritance
2. extranuclear inheritance

Question 4

where do offpsring acquire their mitochondria?

Answer 4

from the mother

Question 5

describe the mt genome?

Answer 5

> 16,000 nt circular DNA

Question 6

how many mt are in a cell? what does each have?

Answer 6

dozens-hundreds of mt per cell, each with multiple mtDNA copies

Question 7

what % of cellular DNA is made of mtDNA

Answer 7

1%

Question 8

what does mtDNA encode? is this cytoplasmic or mendelian inheritance?

Answer 8

mtDNA encodes 13 proteins and 24 rRNAs/tRNAs –> CYTOPLASMIC INHERITANCE

Question 9

the proteins that mtDNA itself encodes are involved in what?

Answer 9

involved in ETC

Question 10

how many proteins are in a mt?

Answer 10

> 1000

Question 11

if mt only encodes 13 proteins, how are there >1000 proteins in mt?

Answer 11

encoded in nuclear genome: produced in cytoplasm then imported to nucleus

Question 12

3 factors that affect mt genome replication

Answer 12

1. many mtDNA are replicated within nucleoids
2. nucleoids divide within a mt
3. mt divide within a cell

Question 13

what is a nucleoid?

Answer 13

protein particle that holds mtDNA

Question 14

how does mtDNA relate to nuclear DNA?

Answer 14

INDEPENDENT

Question 15

how many mitochondria are in oocyte vs sperm?

Answer 15

oocyte: >100,000 mt

sperm: ~100 mt

Question 16

if sperm have mt, why are mt only inherited from the oocyte?

Answer 16

upon fertilization, all sperm mt are destroyed/consumed by oocyte via autophagy

Question 17

why are mt DNA are helpful research tool?

Answer 17

can be used as a tool to trace maternal heritage

Question 18

what is poky gene?

Answer 18

slow growth mutant when mutation in mtDNA –> maternally inherited

Question 19

what is ad gene?

Answer 19

nuclear gene –> mendelian inheritance

Question 20

what are the offspring if poky female with ad+ is crossed with WT male with ad-?

Answer 20

poky is maternally inherited, half offspring are ad+, half are ad-

Question 21

what are the offspring if WT female with ad- is crossed with poky male with ad+?

Answer 21

poky cannot be inherited bc in male, so they are WT with half ad+ and half ad-

Question 22

is maternal inheritance independent or dependent of mendelian inheritance?

Answer 22

maternal inheritance is INDEPENDENT of mendelian inheritance

Question 23

rate of mutation in mt genes vs nuclear genes

Answer 23

mt genes have 1000x greater mutation rate than nuclear genes

Question 24

2 reasons why mt genes have greater mutation rate than nuclear genes

Answer 24

1. more frequent DNA replication
2. no DNA repair

Question 25

what is heteroplasmy?

Answer 25

spontaneous mtDNA mutations can make WT and mutant mt populations in a cell

Question 26

what is homoplasmy?

Answer 26

cell has only WT or mutant mt population

Question 27

what proportion of ppl have disease caused by mt dysfunction?

Answer 27

1/5000 people

Question 28

describe diseases caused by mt dysfunction

Answer 28

progressive and multi-system diseases

Question 29

describe the 2 possible causes of mt dysfunction diseases

Answer 29

1. some are autosomally inherited
2. some are due to mtDNA mutation

Question 30

will children of an affected mother have mt disease? why?

Answer 30

ALL children of affected mother will have disease bc of maternal inheritance

(but if mother heteroplasmic, children may be normal)

Question 31

will children of an affected father have mt disease?

Answer 31

children of affected father will NEVER have disease

Question 32

how to prevent mt disease with 3-parent fertilization?

Answer 32

offspring has mother’s nuclear material and donor’s mt material