BSC 219
Organelles, Developmental genetics, & immunogenetics
11/13/12
21.1 Mitochondria and Chloroplasts Are Eukaryotic Cytoplasmic Organelles
Mitochondrion
and Chloroplast Structure
DNA
is present as circular chromosome in multiple copies
In
stroma of chloroplasts and matrix of mitochondria
The Genetics of Organelle-Encoded Traits
Uniparental
inheritance
mtDNA is
maternally inherited in animals.
Egg
provides majority of cytoplasm
Paternal
inheritance of organelles is common in gymnosperms.
Heteroplasmy
Distinctive
DNA within the cytoplasm of a single cell
The Genetics of Organelle-Encoded Traits
Homoplasmy
All wild-type or all mutant-type DNA are in the cytoplasm of a
single cell.
May
be separated upon random migration during cell division
The Gene Structure and Organization of mtDNA
Ancestral
and derived mitochondrial genomes
Ancestral:
retain many characteristics of their eubacterial
ancestors
Derived:
differ from eubacterial ancestors
Evolved
to fill certain needs
The Gene Structure and Organization of mtDNA
Human mtDNA
H strand
is template for most genes
L strand
is template for a small number of genes
Nonuniversal codons in mtDNA
Still
utilize AUG for initiation of most genes
The Replication, Transcription, and Translation of mtDNA
Random
replicating and extensive variation among different organisms in transcription
and translation
The Evolution of mtDNA
Common eubacterial origin of all mtDNA
Mitochondrial
DNA variation and human history
Much
of human biological history can be tracked with mitochondrial DNA
Similarity
suggests strong bottleneck event in recent past
Possibly
linked to eruption of Toba supervolcano eruption
Model
genetic organism
The
yeast Saccharomyces cerevisiae
21.3 Chloroplast DNA Exhibits Many Properties of Eubacterial DNA
The gene
structure and organization of cpDNA is similar to
that of eubacterial DNA.
Replication,
transcription, and translation:
Little
is known about cpDNA replication.
Transcription
and translation are similar to those of eubacteria.
The
evolution of cpDNA
Cyanobacteria origin
21.4 Through Evolutionary Time, Genetic Information Has Moved
Between Nuclear, Mitochondrial, and Chloroplast Genomes
Much of
the original genetic material in the endosymbiont has
probably been transferred to the nucleus and from chloroplasts to mitochondria.
21.5 Damage to Mitochondrial DNA Is Associated with Aging
Elevated
levels of mtDNA defects have been observed in some
patients with late-onset degenerative disease.
Great
deal of reactive molecules as a result of electron transport
Damages
DNA
22.1 Developmental Takes Place Through Cell Determination
Totipotent cell:
the cell that has the potential to develop into any cell types
Cloning
experiments with plants
Cloning
experiments with animals
22.2 Pattern Formation in Drosophila Serves as a Model for
the Genetic Control of Development
The
Development of the Fruit Fly
The Development of the Fruit Fly
Egg-polarity
genes:
Maternal
origin: determination of anterior-posterior and dorsal-ventral axes of the
embryo
Morphogen:
protein; its concentration gradient affects the developmental fate of the
surrounding region.
The Development of the Fruit Fly
Determination
of the dorsal-ventral axis
Dorsal
gene
Dorsal
gene in nucleus promotes ventral development
Dorsal
gene in cytoplasm promotes dorsal development
Determination
of the anterior-posterior axis
Bicoid gene (ant), nanos gene (pos), hunchback gene
The Development of the Fruit Fly
Segmentation
genes: control the differentiation of
the embryo into individual segments
Gap
genes: broad region gap differentiation
Hunchback
Pair-rule
genes: affect alternate segments
Segment-polarity
genes: development of individual
segments
The Development of the Fruit Fly
Homeotic Genes:
identity of segments
Homeobox: genes
encoding DNA binding proteins; these proteins usually
play a regulatory rule.
Hox genes: encode
transcription factors that help determine the identity of body regions
22.4 Programmed Cell Death Is an Integral Part of Development
Apoptosis
Controlled,
programmed cell death with no leakage of the cellular content to its
neighboring cells
Necrosis
Injured
cells dying in an uncontrolled manner and spilling their contents over
neighboring cells
Key enzyme in apoptosis: caspases
Cleaver
proteins
22.5 The Study of Development Reveals Patterns and Processes
of Evolution
Evo-Devo
The
study of evolution through the analysis of development
Some
genes in distantly related organisms can shape similar developmental pathways,
but they may exert quite different effects.
Many
major evolutionary adaptations are through changes in the expression of genes
that encode proteins that regulate development.
22.6 The Development of Immunity Is Through Genetic
Rearrangement
The Organization of the Immune System
Antigen:
molecules that elicit an immune reaction
Antibody: proteins that binds to antigens and mark them for
destruction by phagocytic cells
The Organization of the Immune System
Humoral
immunity: the production of antibodies by B
cells
Cellular
immunity: depends on T cells
Major Histocompatibility Complex antigen (MHC antigen)
The Organization of the Immune System
Theory
of clonal selection
Immunoglobulin
Structure
The Organization of the Immune System
The
Generation of Antibody Diversity
Somatic
recombination-recombination of gene cassettes produces a large number of ÒrandomÓ protein structures that
bind unique antigens
Recombination
among gene segments within a single chromosome