Genetics, Ecology and Evolution
Evolution Lecture 1:
Genetics: A study of heredity and the variation of inherited characteristics. The study of how certain
qualities or traits are passed from parents of offspring as a result of changes in DNA sequence.
Branch of biology concerned with the study of genes, genetic variation and heredity in organism.
Ecology: Organisms and their distribution through time and space. The study of the environment.
The study of the relationships between living organisms and their physical environment.
Evolution: Change in the heritable characteristics of biological populations over successive
generations. The theory that organisms have grown and developed from past organisms. The process
by which different kinds of living organism are believed to have developed from earlier fornms during
the history of the earth.
Evolution is not linear, it has a lot of branching events. Evolution is never finished. Some genes evolve
faster than others:
- Smell
- Reproduction
- Brain development
- Skin pigmentation → we still get exposed to new environments
- Immunity against pathogens → new pathogens that we get exposed to
Applications
- Helping identifying genes important for vision by blind fishes comparing to the same that
aren’t blind
- Gene therapy for genetic disorders
- Dog breeding
Genetics
Multi-gene traits → polygenetic
Sexual reproduction → offspring varies genetically from parents → genetic variation
Asexual reproduction → offspring are genetic clones of parents → no genetic variation (unless you
have mutations)
Asexual reproduction
- in animals = parthenogenesis → unfertilized egg
o facultative parthenogenesis for example sharks, they can fertilize their own eggs if
necessary
o Obligate parthenogenesis
, ▪ 50 species of lizard an 1 species of snake
▪ Number of chromosomes is usually double that of sexually reproducing
species
▪ Either through full or half-cloning
▪ Species are all females
- In bacteria → through binary fission
o Prokaryotes (bacteria and archaea) can undergo a
type of reproduction in which the cell grows to
roughly double its size and then divides to form
two cells
o No mitosis
- In Yeast → through budding (vegetative reproduction)
- In plants
o apomixis: reproduction without fertilization, always
facultative
o Vegetative reproduction: any form of asexual reproduction occurring in plants in
which a new plant grows from a fragment of the parent plant or grows from a
specialized reproductive structure (tillering)
Sexual reproduction
- In animals
o Fusion of male and female gametes in the process of fertilization
o Complex cycle consisting of mitotic an meiotic cell division
- In plants
o Similar to animals
o Occurs after pollination: The transfer of pollen
to the part of a seed plant that contains the
ovules
o Either self-fertilization of cross-fertilization →
some plants have female AND male parts
- In bacteria
o Not possible
o But: they can exchange genetic information
through conjugation. A donor cell can
give information to a recipient cell.
There will form a bridge, the
information will be copied and
duplicated.
Why sexual reproduction
- Disadvantages:
o Easy to make ‘mistakes’
o More expensive energetically
- Advantages:
o Generation of genetic diversity
,Centromere in chromosomes
- Metacentric → Centromere in the
center
- Sub-metacentric
- Acrocentric
- Telocentric → humans don’t have
this
Lifecycle → from conception until production of their own offspring
It is not the same as a lifespan → birth to death
In plants and some algae: Gametophyte and sporophyte
The multicellular diploid stage is called the sporophyte. Meiosis in the sporophyte produces haploid
cells called spores. Unlike a gamete, a haploid spore doesn’t fuse with another cell but divides
mitotically, generating a multicellular haploid stage called the gametophyte. Cells of the
gametophyte give rise to gametes by mitosis. Fusion of two haploid gametes at fertilization results in
a diploid zygote, which develops into the next sporophyte generation. Therefore, in this type of life
cycle, the sporophyte generation produces a gametophyte as its offspring, and the gametophyte
generation produces the next sporophyte generation.
A third type of life cycle occurs in most fungi and some protists, including some algae. After gametes
fuse and form a diploid zygote, meiosis occurs without a multicellular diploid offspring developing.
Meiosis produces not gametes but haploid cells that then divide by mitosis and give rise to either
unicellular
descendants or a
haploid multicellular
adult organism.
Subsequently, the
haploid organism
carries out further
mitoses, producing
the cells that develop
into gametes. The
only diploid stage is
the single-celled
zygote.
Mitosis → form multicellular organisms from single cell
Meiosis → production of gametes/ spores
Crossing over → pieces of the chromosomes are exchanged during the meiosis, so you have a
mixture. This is very common and leads to more genetic diversity.
,
,
, Genetics Lecture 1:
Mendel → the founder of modern genetics. He was a monk. He worked with peas.
He cut of the stamen to prevent peas from self-fertilizing. He wanted
cross-pollination of two contrasting varieties (parental generation). He
started with purple and white flowers → everything became purple. In
the F2 generation ¼ was white. He did this with a lot of traits. It was 3:1
everywhere. Dominant: recessive.
Mendel’s experimental setup
- Naturally, pollen from stamen lands on carpel of same flower
and fertilizes eggs
- To prevent peas from serf-fertilizing stamen were removed (1)
- Pollen from another plant were dusted onto flowers (2)
- A new seed (pea) develops (3,4)
Typical experiment:
cross-pollination of two contrasting varieties (parental
generation) offspring (called filial generation) showed purple
trait self- or cross-pollination of F1 plants brings white coloration
back in F2 plants overall ratio = 3 purple : 1 white plants.
Dominant: recessive.
Mendel’s model
1. Alleles account for variation of inherited characters
a. Variation of DNA leads to different function of
protein → Variation of inherited trait
2. One allele is inherited from each parent
a. Two copies of each gene
3. The dominant allele determines the organisms appearance
a. Recessive allele has no noticeable effect on the organism’s phenotype
4. Two alleles for a heritable character separate from each other during gamete formation (law
of segregation)
a. Only one of the two gene copies is distributed to each gamete (egg or sperm cell)
and the allocation of the gene copies is random
Genotype → complete set of genetic material
Phenotype → organisms appearance
Homozygous → 2 same alleles
Heterozygous → 2 different alleles
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