Module 5

Question 1

A. Quadripartite
B. Numt
C. Nupt
D. Endosymbiosis
E. Rubisco
F. Haploid
G. Maternal inheritance
H. Paternal inheritance
I. Biparental inheritance

1. The enzyme responsible for CO₂ fixation.
2. The process where one organism engulfs another, leading to a symbiotic relationship.
3. A nuclear sequence originating from mitochondrial DNA.
4. A nuclear sequence originating from chloroplast DNA.
5. The four-part structure of most plant chloroplast genomes.
6. Having a single set of unpaired chromosomes.
7. Organelles inherited exclusively from the mother.
8. Organelles inherited exclusively from the father.
9. Organelles inherited from both parents.

Answer 1

A. Quadripartite → The four-part structure of most plant chloroplast genomes.

B. Numt → A nuclear sequence originating from mitochondrial DNA.

C. Nupt → A nuclear sequence originating from chloroplast DNA.

D. Endosymbiosis → The process where one organism engulfs another, leading to a symbiotic relationship.

E. Rubisco → The enzyme responsible for CO₂ fixation.

F. Haploid → Having a single set of unpaired chromosomes.

G. Maternal inheritance → Organelles inherited exclusively
from the mother.

H. Paternal inheritance → Organelles inherited exclusively from the father.

I. Biparental inheritance → Organelles inherited from both parents.

Question 2

What is the most common mode of inheritance for both chloroplasts and mitochondria?

Answer 2

Maternal inheritance.

Question 3

Name an exception to maternal inheritance for mitochondria.

Answer 3

Paternal inheritance in some plants and algae.

Question 4

Name an exception to maternal inheritance for chloroplasts.

Answer 4

Biparental inheritance in some algae and gymnosperms.

Question 5

What does quadripartite mean in the context of chloroplast genomes?

Answer 5

It refers to a four-part structure with two single-copy regions (LSC and SSC) and two inverted repeats (IRA and IRB).

Question 6

Which came first, the mitochondrion or the chloroplast?

Answer 6

The mitochondrion.

Question 7

How many times did mitochondria evolve?

Answer 7

Once, from a single endosymbiotic event.

Question 8

How many times did chloroplasts evolve?

Answer 8

At least three times, through primary, secondary, and tertiary endosymbiosis.

Question 9

Why might PCR of a mitochondrial gene from human muscle show two different sequences?

Answer 9

Due to nuclear mitochondrial DNA sequences (numts).

Mitochondrial DNA fragments can transfer to the nuclear genome, creating non-functional copies. PCR may amplify both authentic mtDNA and nuclear-integrated numts, leading to different sequences.

Question 10

What are numts and nupts?

Answer 10

Numt (Nuclear Mitochondrial DNA): mtDNA fragments inserted into the nuclear genome.

Nupt (Nuclear Plastid DNA): cpDNA fragments inserted into the nuclear genome.

Question 11

How many numts are in the human genome. What is the largest one?

Answer 11

Human Genome: Contains 755 numts; the largest is 16,106 bp, nearly an entire mt genome!

Question 12

How many times did chloroplasts and mitochondria evolve?

Answer 12

Chloroplasts evolved once through primary endosymbiosis (cyanobacteria engulfed by eukaryotic cells).

🔹 Mitochondria evolved once through endosymbiosis of an α-proteobacterium, present in all eukaryotes.