Chapter 17: cytoplasmic inheritance and the evolution of organelle genomes

Question 1

What does mtDNA stand for

Answer 1

mitochondrial dna

Question 2

what does cpDNA stand for

Answer 2

chloroplast dna

Question 3

What does uniparental inheritance mean?

Answer 3

often female gamete, all DNA from one parent

Question 4

WHat does Biparental inheritance mean?

Answer 4

maternal + parental

Question 5

Describe the four o’clock plant experiment

Answer 5

Plant can have variegated, green or white branches

doesnt matter the stem that pollen came from, all depends on the color of the leaves of the female parent

Question 6

What are homoplasmic cells?

Answer 6

-contain organelles with the same genotype

ex: all green or all white chloroplasts

Question 7

What are heteroplasmic cells?

Answer 7

-contain a mixture of alleles
ex: mutant (white) + green (wild) chloroplasts

Question 8

in maternal inheritance, What does the phenotype of offspring depend on?

Answer 8

It depends entirely on the genotype of the maternal parent

ex: green –> green
white –> white
variegates –> green, white OR variegated

Question 9

describe the process of chloroplasts becoming mutant?

Answer 9

1. nucleiods contain several copies of organelle genome, where DNA replication occurs. contains a single mutated genome
2. Nucleoids divide within each organelle, mutant gene is replicated, creates a nucleoid containing ONLY mutation
3. organelle divides, creates an organelle with mutant and a wild type organelle

Question 10

What is replicative segregation?

Answer 10

When a daughter cell randomly receives a chloroplast that may be homozygous (wild/mutant) or heterozygous

Question 11

True or false genetic code is univeral

Answer 11

FALSE it is almost universal… there can be differences in the mitochondrial genetic code amongst organisms

Question 12

Describe the characteristics of maternal inheritance?

Answer 12

• predictions of inheritance based solely on genotype of mother

-maternal lineage : can trace lineage through mitochondrial line

-phylogenetic trees:
—–mtDNA&raquo_space;> maternal genealogies
—–maternal history of species

Question 13

Will offspring inherit a mitochondrial disease if it the father is a carrier and the mother is wild type?

Answer 13

NO, only mother can pass down mitochondrial disease

Question 14

What are the three functions that are affected by mitochondrial mutations?

Answer 14

functions that require energy….
-muscle function
-hearing
-vision

Question 15

What is incomplete penetrance?

Answer 15

• when every offspring is expected to inherit the disease, but some don’t

Question 16

What is homoplasmic segregation?

Answer 16

• all progeny are homo plasmic… ex: mother and children 100%

Question 17

What is heteroplasmic segregation?

Answer 17

Each progeny may differ depending on replicative segregation during egg production… ex: mother 50%, children: 10%, 100%, 50%, 70%, 30%

Question 18

WHat is variable expressivity?

Answer 18

within a given disease, severity will vary on the # of mutant/wild type mitochondria

Question 19

How does variable expressivity occur?

Answer 19

1 - mother’s cell has a low proportion of mutant mitochondria

2 - restriction in mitochondrial numbers occur in egg production (bottleneck effect)

3 - mitochondrial number amplified as oocytes mature

4 - heteroplasmic females can produce eggs with a greater/lesser proportion of mutant mitochondria

Question 20

What are the three outcomes of variable expressivity?

Answer 20

1 - low proportion of mutant mitochondria (unaffected)

2 - intermediate (mildly affected)

3 - high (affected individuals)