Extranuclear Inheritance Flashcards
What is extranuclear inheritance?
Extra DNA found outside the nucleus.
Where is extra nuclear DNA found?
Typically found in organelles
- Mitochondria in eukaryotes
- Chloroplasts in plants
How does extranuclear DNA affect phenotype?
The phenotype of an organism can be influenced by this extranuclear DNA
-Different from Mendelian principles
How is mitochondrial DNA transmitted?
Mitochondrial DNA is transmitted from maternal gamete known as organelle heredity.
-recall secondary oocyte’s and mature ovum get most of the cytoplasm and the polar bodies get very little cytoplasm
Mitochondrial DNA mutations have…
Been linked to human disease affecting mainly energy production
Define extranuclear inheritance
Transmission of genetic information to offspring through the cytoplasm and not the nucleus
-usually from one parent
What is organelle heredity?
DNA from mitochondria or chloroplast determines certain phenotypic characteristics of offspring
What is infectious heredity?
Symbiotic or parasitic association with a microorganism
What is the maternal effect?
- nuclear gene products are stored in egg then transmitted through ooplasm to offspring
- Gene products in ovule distributed to embryo cells can influence phenotype
Describe the mitochondrial genome
Mitochondrial genome is circular with ~16500 bases and 37 genes.
There are hundreds of copies of the mitochondrial genome in each mitochondria and hundreds of mitochondria per cell
What are the abbreviations of mitochondrial and chloroplasmic DNA?
mtDNA and cpDNA
How do chloroplasts and DNA get their needed DNA?
Both chloroplasts and mitochondria also need proteins which were encoded for the on the nuclear DNA
Nuclear proteins are imported into the organelle
Compare and contrast cpDNA with mtDNA in terms of locations and number
Both are mainly circular DNA within non-nuclear organelles
-mtDNA in mitochondrial matrix. Many mtDNA per mitochondria, many mitochondria
-cpDNA in chloroplast stroma. Many chloroplast in the cell, many cpDNA per chloroplast but more in young growing leaves
Compare and contrast cpDNA with mtDNA in terms of their replication
Both are replicated within their particular organelle and use their own DNA to produce RNA and proteins required for their function
-both mitochondria and chloroplasts can divide inside the cell
How did we fund out about organelle inheritance?
1908 a German botanist/scientist , Carl corresponds who followed Mendel’s work was studying four o’ clock plants that had a variety of leaf colors on different branches
Had all white shoots And all green shoots
Main shoot is variegated
Where were the seed(eggs) from in the Crossing experiments with the 4 O’clock plant?
Seeds(eggs) from:
Green branches or white branches
Mixed with pollen from:
Green branches or white branches
Produced plants according to the source of ovule(seeds)
Since leaf coloration is a function of the chloroplast, there must be genetic information in the organelle to influence leaf color
White color resulted from the non-nuclear (cpDNA) genetic information that has a “defect”
What are the 3 types of ovule found in variegated regions ?
Type 1: all chloroplast contains mutated cpDNA
Type 2: all chloroplast contain wild-type cpDNA
Type 3: mixture of chloroplast, some containing wild-type cpDNA and others containing mutated cpDNA
What do seeds from variegated branches produce?
Seeds from variegated branches mixed with pollen from any of the branches STILL produced plants according to the source of ovule
How do organelle DNA contribute to the endosymbiosis theory?
- mtDNA and cpDNA look remarkably similar to bacterial DNA
- mitochondria and chloroplasts replicate their own DNA and contain their own machinery (proteins and RNA) for transcription and translation
- Mitichondria and chloroplasts have a double membrane. (Not seen in other organelles)
How was the endosymbiosis theory proposed?
Dr. Lynn Margulis proposed the theory in 1967:
- Mitochondria and chloroplasts(organelles) arose independently 2 billion years ago from free living bacteria
- Organelles possessed attributes of aerobic respiration and photosynthesis, respectively
- was not believed until genetic evidence substantiated in 1980s
What are the main points of the endosymbiosis theory?
- bacteria were engulfed by larger eukaryotic cells
- beneficial symbiotic relationship developed
- bacteria lost ability to function autonomously
- eukaryotic cells gained oxidative respiration and photosynthesis
How does mtDNA support the endosymbiotic theory?
- Exists in eukaryotes as double-stranded circular DNA
- Smaller than DNA in chloroplasts
How does cpDNA support the endosymbiotic theory?
Genes encode products involved in photosynthesis and translation
How many genes are in human mtDNA?
37
How many RNA in human mtDNA?
Two ribosomal RNAs (rRNA)
22 transfer RNAs (tRNA)
How many polypeptides are essential for oxidative respiration in human mtDNA ?
13 polypeptides are essential for oxidative respiration
-these 13 polypeptides combine with nuclear encoded proteins to make 4 important complexes found in the inner mitochondrial membrane required to make energy for the cell
-ATP is energy for the cell
Which of the DNA encode mitochondrial proteins ?
The majority of proteins for mitochondrial function are encoded by nuclear genes
Include:
DNA polymerase
RNA polymerase
Other tRNAs
Ribosomal proteins
Other respiratory proteins amino acyl tRNA synthases
Initiation and elongation factors of transcription and translation
What are the mitochondrial proteins encoded for by the mtDNA?
Some respiratory proteins
Some tRNAs (comeback to video)