Chapter 9 Conceps of genetics

-Extranuclear inheritance = transmission of genetic information to offspring trough cytoplasm (not

nucleus).

Varieties:

1. Organelle heredity: DNA in mitochondria determines certain phenotypic characteristics of

offspring.

2. Infectious heredity: results from symbiotic or parasitic association with microorganisms.

3. Maternal effect: nuclear gene products stored in the egg, then transmitted trough ooplasm to

offspring.

-Endosymbiotic theory:

Mitochondria en chloroplast arose independently about 2 billion years ago from free-living

protobacteria.

mtDNA particularly vulnerable to mutations:

1. mtDNA doesn’t have structural protection from mutations provided by histone proteins in

nuclear DNA.

2. DNA repair systems are limited.

3. High concentrations of ROS (reactive oxygen species) generated by cell respiration.

-Heteroplasmy: variation in genetic content of organelles, because zygote receives large number of

organelles through egg.

-Disorders mt DNA:

MERF (myclonic epilypsy and ragged-red fiber disease) > neurological symptoms

LHON (Leber’s hereditary optic neuropathy) > sudden bilateral blindness

KSS (kears-sayre syndrome) > lose vision, hearing loss and heart conditions

-Mitochondrial dysfunction implicated in most human diseases

-Maternal effect:

-an offspring’s phenotype for a particular trait is under the control of nuclear gene products present

in the egg.

-Nuclear genes of female gamete transcribed: genetic products accumulate in egg’s cytoplasm.

-Products distributed among newly formed cells influencing patters/traits established early in

development.

Summary chapter 9 concepts of genetics

Genetics (WPFA16005)