Extranuclear inheritance

Question 1

Organelle definition

Answer 1

Organelle is a specialized structure of the cell (such as a mitochondrion, chloroplast, or nucleus) that has a specific function and is considered analogous to an organ inside the cell.

Question 2

What is the law of segregation (separation)?

Answer 2

Law of segregation: the two alleles for each trait separate (segregate) during gamete formation, and then they unite at random, one from each parent, at fertilization

Question 3

What are the 3 ways that mitochondrial and chloroplast DNA differ from the DNA found in the nucleus?

Answer 3

1. Random segregation (separation of organelles). Mitochondria and chloroplasts (and the genes they carry) are randomly distributed to daughter cells during mitosis and meiosis. For example, somatic mutation (body cells).
2. High copy number. Each organelle has multiple copies of its DNA, and a typical cell has many mitochondria (and in plants, chloroplasts).
3. Single-parent inheritance. The offspring gets non-nuclear DNA only from the male or the female parent. In humans, mitochondrial DNA is only inherited from the mother. For example, gametic mutation.

Question 4

What is the main function of mitochondria?

Answer 4

Cellular respiration

Question 5

What is cristae?

Answer 5

A cristae is a fold in the inner membrane of a mitochondrion

Question 6

What is the s-re of the mitochondria?

Answer 6

a. outer/inner membrane

b. cristae and matrix

Question 7

Most mitochondrial proteins are encoded by?

Answer 7

Most mitochondrial proteins are encoded by genes in the nucleus, which are made in the cytoplasm, and then transported into the mitochondria.
It carries relatively few genes; rRNA and tRNA genes
some genes (13) that function in oxidative phosphorylation

Question 8

Somatic vs Gametic mutation

Which mutations mtDNA are prone to?

Answer 8

mtDNA are prone to non-inherited (somatic) mutations. Somatic mutations occur during a person’s lifetime, and typically are not passed to future generations.

Question 9

Definition of free radicals??

Answer 9

Free radicals are unstable atoms that can damage cells, causing illness and aging. For example, tobacco, fried food, alcohol, air pollutants, pesticides etc.

Question 10

Why is mtDNA is particular vulnerable to mutation? (2 reasons)

Answer 10

a. mtDNA have different ability to repair comparing with nuclear DNA
b. A high concentration of mutagenic free radicals from cellular respiration accumulate in small confined (closed) space (inside mitochondria), which raises the mutation rate

Question 11

What is the main function of chloroplast and where it occurs?

Answer 11

The main function of chloroplast is photosynthesis, which occurs on surface of the thylakoid membrane.

Question 12

What is the s-re of the chloroplast?

Answer 12

a. outer/inner membrane

b. Granum (green stacks of disks) and thylakoid (each individual disk)

Question 13

What is the function of thylakoid?

Answer 13

Thylakoids capture solar energy and store it in the form of chemical energy

Question 14

Homoplasmy vs heteroplasmy

Answer 14

Heteroplasmy is the presence of more than one cpDNA type per cell (for example mixed green and white). Heteroplasmy is defined as the existence of both normal and mutated cpDNA in a single cell (humans).
Homoplasmy is the presence of only one type of cpDNA in each eukaryotic cell (for example only white).
All parents on the photo, no offspring.

Question 15

What is Endosymbiont theory?

Answer 15

Endosymbiont theory states that mitochondria and chloroplasts are descended from bacteria (prokaryotic cells) that fused with nucleated cells (any cell with a nucleus).

Question 16

What are the 3 reasons for evidence of endosymbiont theory for mitochondria and chloroplasts?

Answer 16

1. They have their own DNA
2. Like in bacteria, mtDNA (mitochondrial DNA) and cpDNA (chloroplast DNA) are not arranged into nucleosomes
3. Comparisons of rRNA gene sequences suggest mitochondrial and chloroplast genomes derive from a common ancestor of nonsulfur and cyanobacteria (types of ancient bacteria – prokaryotic cell),

Question 17

Mutations (mitochondrial) are passed from parent to children in one of two ways:

Answer 17

(1) A person (mother) with a disease caused by a mitochondrial mutation may lack normal mitochondria (and have only abnormal, mutation-bearing ones). In this case: an affected mother will always pass on mutation-bearing mitochondria to her children.
(2) A mitochondrial disorder may occur when a person has a mix of normal and abnormal mitochondria in her body. In this case: normal and mutation-bearing mitochondria may go randomly into eggs during meiosis. As a result, children who get a large proportion of mutant mitochondria may have severe disease, while those with few mutant mitochondria may have mild or no disease. Symptoms vary due to heteroplasmy.

Question 18

Oxidative phosphorylation system in the mitochondria generates??

Answer 18

Oxidative phosphorylation system (it’s a part of respiration) in the mitochondria generates
_free radicals_which can damage DNA

Question 19

Evidence in support of role of mtDNA and aging:

Answer 19

• Brain cells of people with Alzheimer’s disease (AD) have abnormally low energy metabolism
• 20% to 35% of mitochondria in brain cells of most AD patients have mutations in cytochrome c oxidase genes (located in mtDNA), which may explain the low energy metabolism (hypothesis).

Question 20

Cytochrome oxidase c (enzyme): functions in?

Answer 20

ETC (Electron Transport Chain)

Question 21

ETC (Electron Transport Chain) consists of ?

Answer 21

7 subunits (proteins): 3 encoded by mitochondrial genome (genes) and 
4 by nuclear genes (comes from the nucleus).

Question 22

Accumulation of mtDNA mutations over time may result in??

Answer 22

Accumulation of mtDNA mutations over time may result in age-related decline in process of oxidative phosphorylation (respiration). This means that because of mutation, the respiration will be inhibited, so that less energy can be produced.

Question 23

Organellar definition

Answer 23

Organellar: all organelles that has it’s own DNA, such as chloroplast, mitochondria etc.

Question 24

What is the DNA form of mtDNA/cpDNA VS nuclear DNA

Answer 24

mtDNA/cpDNA have circular double stranded DNA, while nuclear DNA is linear double stranded DNA

Question 25

Do we have maternal or paternal inheritance of mitochondria in humans? Explain.

Answer 25

We have maternal Inheritance of mitochondria in humans, which develops from the original small amount of mtDNA in the original egg cell. The mitochondrial DNA is passed only from mother to offspring.

Question 26

What is the arrangement of chloroplast genome?

Answer 26

Compact gene arrangement (includes introns and exons), have more genes than mitochondria.
* rRNA and tRNA genes
* Many genes that are required for photosynthesis
Many chloroplast proteins are also encoded by genes in the nucleus

Question 27

Do we get the maternal or the paternal inheritance in leaf pigmentation?

Answer 27

Leaves could be green, white or multi-colored: pigmentation of the offspring depended solely on the maternal parent and not at all on the paternal parent.
The phenotype is only passed from mother to offspring, but not father based on pic in plants. All parents on the photo, no offspring.

Question 28

What kind of procedure can sidestep (bypass) transmission of mitochondrial disease?

Answer 28

Oocyte nuclear transplantation can sidestep (bypass) transmission of mitochondrial disease.

Question 29

Organellar vs Organelle

Answer 29

Organellar: all organelles that has it’s own DNA, such as chloroplast, mitochondria etc.
Organelle is a specialized structure of the cell (such as a mitochondrion, chloroplast, or nucleus) that has a specific function and is considered analogous to an organ inside the cell.