non mendelian inheritance extra nuclear inheritance

1. Extranuclear
Inheritance

2. Extranuclear Inheritance
Commonly defined as transmission through the
cytoplasm (or things in the cytoplasm, including
organelles) rather than the nucleus
Generally only one parent contribute
RULES:
1. Ratio typical of Mendelian not found
2. Mitochondrial and chloroplast genes show
biparental inheritance.
3. Cytoplasmic inheritance is maternal as zygote
receives most of cytoplasm from female parent.

3. types of extranuclear
inheritance
 Organelle Heredity - mitochondria and
chloroplast have their own genetic material. The
offspring get their organelles from the mother
through the egg when fertilization is with sperm
 Biparental inheritance in fruit flies and honey
bees; yeast and Saccharomyces
 Maternal/Cytoplasmic - Genotype of the mother
determines the phenotype of the offspring. mRNA or
protein from the mother gets stored in the cytoplasm
of the egg for the zygote to use.
 the sperm donates only genetic material (DNA) while
the egg donates both genetic material (DNA) and
cytoplasm with the accompanying organelles.

4. Mitochondria have their own DNA and Ribosomes
Mitochondria have some of their own DNA, ribosomes, and can
make many of their own proteins. The DNA is circular and lies
in the matrix in structures called "nucleoids". Each nucleoid
may contain 4-5 copies of the mitochondrial DNA (mtDNA).
mitochondrial
DNA- organelle
heriditary

5. Human mtDNA
• small, double stranded
circular chromosome
• 16,569 bp in total
. Encodes 13 proteins, 22
tRNAs and 2 rRNAs
• no non-coding DNA
• no introns
• polycistronic replication
which is initiated from
the D (displacement)- loop
region
Organisation of the
mitochondrial chromosome

6. Chloroplast
 Chlamydomonas Chloroplast
 Unicellular alga : 2 flagella and single chloroplast (50
copies cpDNA)
 2 mating types :mt+ and mt-
 Mating gives diploid cell that immediately undergoes
meiosis to form haploid cells
 Mendelian ratio – 2:2 (mt+: mt-)
 Streptomycin or erythromycin resistance: chloroplast
trait
 strS and strR strains (streptomycin resistance)

7. strS and strR
Crosses
Offsring always have str phenotype of
mt+ parent

8. Offspring of strS and strR Crosses
mt+(eryr) x mt-(erys)
all resistant (uniparental)
Mendelian : 2:2(mt+ : mt-)
50% of offspring mt+ and 50% mt-
5% - encoded by nuclear gene (biparental)
Zygote : cytohet
95%- chloroplast (uniparental)
Only mt+ parent donates cytoplasm

9. Uniparental Inheritance of
Streptomycin resistance

10. Maternal Effect
 called uniparental inheritance- The phenotype of the
offspring is dependent on the genotype of only one
parent (in this case the mother).
 During fertilization the sperm donates only nuclear DNA
to the egg. The egg donates both DNA and cytoplasm.
In this cytoplasm are many things including:
1. mRNA which can be translated into protein. This mRNA
was transcribed from the DNA from the mother (not
DNA from the zygote).
2. Protein that has already been translated. Again, the
information to make this protein came from the mother’s
DNA.

11. Maternal Effect
 Shoot variegation in four o’clock (Mirabilis jalapa)

12. Model for the inheritance of shoot color in the four o’clock
Chapter 15 slide 12

13. Shell coiling in snails (Limnaea peregra)
 Snails can have either right-handed or left-handed coils.
 D = Right-handed coil ; d = left-handed coil
 Coiling in the offspring is dependent upon the genotype of the mother (NOT
dependent on her phenotype)
 DD and Dd mothers -> Right-handed offspring
 dd mothers -> Left-handed offspring

14.  If the mother has the “D” allele then she produces an active gene product
that directs the formation of right-handed coils in the offspring, regardless
of the offspring’s genotype.
 If the mother is “dd” then no active gene product is produced and the
default, left-handed coils result, even if the offspring has a “D” allele.
 Interpretation :
i. The D allele produces a cytoplasmic product that causes
dextral coiling.
ii. The d allele does not produce this product, and sinistral
coiling is produced by default.

15. Fig. 8.9
Maternal Effect: shell coiling in snails
Uniparental
inheritance
DD and Dd mothers
right-handed offspring
dd mothers
left-handed offspring

16. Inheritance in Paramecium
 Kappa bodies are elements
within Paramecium that cause
them to be killers
 Killer Paramecium kill other
Paramecium in the immediate
environment
 Kappa bodies are inherited
through the cytoplasm and not
through chromosomes
 Ciliates contain at least 2 nuclei

17.  Killer Paramecium Uses a Bacterial Toxin
 (A) The kappa particles are found in the cytoplasm of the
Paramecium. (B) Kappa particles are symbiotic Caedibacter that are
found in many strains of Paramecium, yet they have their own DNA
and divide like typical bacteria.

18. Kappa in Paramecium
Certain strains are called killer strains because
they release paramecin, a substance toxic to
sensitive strains
Kappa particles contain DNA and protein and
require a nuclear gene (K)
Kappa particles are bacteria like

19. Kappa in Paramecium
During this cytoplasmic exchange, the
kappa particles present in the cytoplasm
of the killer type enter the non-killer type
and convert it into a killer type.
 Paramecium becomes a killer when it
receives kappa particles and it becomes a
sensitive when it does not receive kappa
particles.