Genetics, ecology and
evolution
Lecture 1, Introduction to genetics:
Genetics is a study of how certain qualities or traits are passed from parent to
offspring as a result of changes in the DNA.
Some traits are coded by a single gene, and some by multiple gene (which is called
polygenetic). These genes are written in DNA. The DNA gets duplicated and is
packed into the reproductive cell as gametes. The gametes of the parents unite
during fertilization, this way the offspring has genetic material from both parents.
Animals and plants reproduce sexual. Which means the offspring varies genetically
from the parents.
Microbes reproduce asexual, which makes it make common because there are way
more microbes then other organisms. Asexual reproduction means that the offspring
are genetic clones of the parents, and there is no genetic variation except for
mutations.
There are some organisms besides microbes who do reproduce asexual, then it is
called parthenogenesis. So the unfertilized egg develops into a new individual. This
can either happen by accident, and most of the time the organism reproduces
sexually, but due to lack of males the female fertilizes herself (facultative) or this is
the only way an animal can reproduce (obligate).
Facultative parthenogenesis: during meiosis the sex chromosomes divide from XX
into XXXX. One X-cell becomes the egg, while the others become polar cells. During
this time the female waits for the male to fertilize the egg, but if there are none
around one of the polar cells can fertilize the egg. New shark embryos developed, but
these can only ever be female.
Obligate parthenogenesis: this kind of parthenogenesis mostly only occurs in
reptiles like snakes and lizards. But all species are exclusively female. The number of
chromosomes are usually double that of the sexually reproductive organisms.
Asexual reproduction:
In bacteria. Step one the replication of the DNA, then the two are separated by the
septum. The cell splits into two identical daughter cells. There is not an original cell,
both are equal.
In yeast. A bud forms on the outside of the parent cell, then the nucleus moves
towards the bud to devide itself during mitosis. The daughter cell separates from the
parent cell. Both are not equal. This is called budding.
In plants. It is called apoximis, they reproduce without fertilization, this is always
facultative.
Sexual reproduction:
In animals. This is the fusion of the male and female gamete in the process of
fertilization. A complex cycle of meiotic and mitotic cell devisions.
In humans the mother gives 23 chromosomes in her gamete and the father also. The
embryo will have 23 pairs and thus 46 chromosomes in total.
In plants. The plants produce flowers with stamen. In these stamen meiosis occurs and
produces eggs and sperm. During pollination, a pollen with sperm cells connect to the
,stigma and gives off it’s sperm nuclei. The fertilized egg becomes an embryo of a
seed.
The plant can also self-fertilize. So the stamen produces the pollen and fertilizes its
own stigma with pollen.
In bacteria. They don’t sexually reproduce!
But they can exchange genetic information through conjugation. The donor cell
connects a conjugation bridge to the recipient cell and through this bridge it
exchanges a duplicate of the plasmid. They do this because this way they can
exchange share their antibiotic resistance.
Why sexual reproduction:
The main advantage is because it results in genetic diversity. This is a good thing
because they are more prone to survive environmental changes. It contributes greatly
to the evolution of a species.
Some disadvantages are that it costs way more energy then asexual reproduction. It is
also very easy to make mistakes, which would cause birth defects or otherwise
unhealthy offspring.
Chromosomes:
They are only visible under a microscope during cell devision, because then the DNA in
the cell is doubled through meiosis. An ordered display of chromosome pairs in a cell,
lined up in order of biggest to smallest, is called a karyotype.
There are four types chromosome pairs:
Metacentric: the centromere is located around but close to the middle.
Sub-metacentric: the centromere is a big further from the middle.
Acrocentric: the centromere is located near the end of chromosome.
Telocentric: the centromere is at the telomere, aka the end of the chromosome. This
one does not occur in humans.
Two duplicates of one chromosome, next to each other are sister chromosomes. Two
non-sister chromosomes in a homologous pair, only takes place in diploid cells. That
means the chromosomes in cells come in pairs. Haploid means the chromosomes
don’t come in pairs.
The number of chromosomes an organism has does not equal to the complexity of the
organism.
The lifecycle of an organism means from conception until the production of their own
offspring. Not to be mistaken for the life span which is from birth until death.
Meiosis:
The goal of meiosis is the reduction in the number of chromosomes in a cell.
The first step of meiosis in the interphase, here the two parent chromosomes are
duplicated. So there arise two pairs of sister chromosomes.
The second step is meiosis I, the two homologous chromosomes pairs are separated.
The final step is meiosis II, now the two sister chromosomes are separated. In the end
the cells either have one chromosome from the mother or from the father, but not
both. They turned from a diploid parent cell into a haploid cell.
Difference between mitosis and meiosis:
Occurrence, mitosis can occur in either haploid or diploid cells, while meiosis can only
occur in diploid cells.
Number of devisions, mitosis only has one devision, while meiosis has two (meiosis I
and meiosis II).
, Resulting daughter cells, mitosis has 2 who are generally identical to the parent
cell, while meiosis results in four daughter cell who are generally different from the
parent cell due to crossing over.
Function, for mitosis it is to form multi cellular organisms from a single cell, while for
meiosis it ice to produce gametes (for reproduction) or to produce spores.
Both mitosis and meiosis occur in animals, plants, fungi but not in prokaryotes.
Meiosis causes genetic variation in two ways:
Through the independent assortment of chromosomes during meiosis I, which results
in a 50% chance to get either the paternal or maternal genetic maternal
chromosomes. This means you can get one of each, but also only maternal or
paternal chromosomes.
Genetic variation van also happen due to crossing over. During prophase when the
chromosomes are stuck together, they can lap over each other. The point where this
happens is called the chiasma. Because of crossing over the telomeres switch places,
usually this happens to only one telomere, but it can also occur twice, which is called a
double crossing over, this is very rare though.
Lecture 2, Mendelian genetics:
George Mendel is the founder of modern genetics.
He started working with peas in monastery garden, because peas come in multiple
varieties, have short generation time and have a large number of offspring. The large
number of offspring gives lots of statistics to work with.
To ensure the peas don’t self-fertilize and thus wouldn’t create genetically variable
offspring, Mendel but out every stamen. This way the plant can only be fertilized by
another plant.
He crossed a plant with purple flowers with a plant with white flowers, the filial
generation (aka the F1 generation) only existed of purple flowers. Mendel decided to
cross the F1 generation, either through self-pollination or cross-pollination. The F2
generation contained the white flowers again. In a 3:1 ratio. So for each white flower
plant, there were 3 purple flower plant.
In this example the purple color is the dominant trait and the white color is the
recessive trait. In the F1 generation the white color was hidden because the parent
were both homozygous.
When two homozygous parents cross, the F1 generation all has the same genotype.
This is called true breeding.
Mendel’s model:
Because of his experiments, Mendel came to three conclusions.
1. Alleles account for variation of inherited characters
2. One allele is inherited from each parent
3. The dominant allele determines the organism’s appearance, where as recessive
allele has no noticeable effect on an organisms phenotype.
4. Two alleles for a heritable character separate from each other during gamete
forming. This is the law of segregation.
In inheritance of characters by a single gene may deviate from the simple Mendelian
patterns in the following situations:
- if the alleles are not completely dominant or recessive
evolution
Lecture 1, Introduction to genetics:
Genetics is a study of how certain qualities or traits are passed from parent to
offspring as a result of changes in the DNA.
Some traits are coded by a single gene, and some by multiple gene (which is called
polygenetic). These genes are written in DNA. The DNA gets duplicated and is
packed into the reproductive cell as gametes. The gametes of the parents unite
during fertilization, this way the offspring has genetic material from both parents.
Animals and plants reproduce sexual. Which means the offspring varies genetically
from the parents.
Microbes reproduce asexual, which makes it make common because there are way
more microbes then other organisms. Asexual reproduction means that the offspring
are genetic clones of the parents, and there is no genetic variation except for
mutations.
There are some organisms besides microbes who do reproduce asexual, then it is
called parthenogenesis. So the unfertilized egg develops into a new individual. This
can either happen by accident, and most of the time the organism reproduces
sexually, but due to lack of males the female fertilizes herself (facultative) or this is
the only way an animal can reproduce (obligate).
Facultative parthenogenesis: during meiosis the sex chromosomes divide from XX
into XXXX. One X-cell becomes the egg, while the others become polar cells. During
this time the female waits for the male to fertilize the egg, but if there are none
around one of the polar cells can fertilize the egg. New shark embryos developed, but
these can only ever be female.
Obligate parthenogenesis: this kind of parthenogenesis mostly only occurs in
reptiles like snakes and lizards. But all species are exclusively female. The number of
chromosomes are usually double that of the sexually reproductive organisms.
Asexual reproduction:
In bacteria. Step one the replication of the DNA, then the two are separated by the
septum. The cell splits into two identical daughter cells. There is not an original cell,
both are equal.
In yeast. A bud forms on the outside of the parent cell, then the nucleus moves
towards the bud to devide itself during mitosis. The daughter cell separates from the
parent cell. Both are not equal. This is called budding.
In plants. It is called apoximis, they reproduce without fertilization, this is always
facultative.
Sexual reproduction:
In animals. This is the fusion of the male and female gamete in the process of
fertilization. A complex cycle of meiotic and mitotic cell devisions.
In humans the mother gives 23 chromosomes in her gamete and the father also. The
embryo will have 23 pairs and thus 46 chromosomes in total.
In plants. The plants produce flowers with stamen. In these stamen meiosis occurs and
produces eggs and sperm. During pollination, a pollen with sperm cells connect to the
,stigma and gives off it’s sperm nuclei. The fertilized egg becomes an embryo of a
seed.
The plant can also self-fertilize. So the stamen produces the pollen and fertilizes its
own stigma with pollen.
In bacteria. They don’t sexually reproduce!
But they can exchange genetic information through conjugation. The donor cell
connects a conjugation bridge to the recipient cell and through this bridge it
exchanges a duplicate of the plasmid. They do this because this way they can
exchange share their antibiotic resistance.
Why sexual reproduction:
The main advantage is because it results in genetic diversity. This is a good thing
because they are more prone to survive environmental changes. It contributes greatly
to the evolution of a species.
Some disadvantages are that it costs way more energy then asexual reproduction. It is
also very easy to make mistakes, which would cause birth defects or otherwise
unhealthy offspring.
Chromosomes:
They are only visible under a microscope during cell devision, because then the DNA in
the cell is doubled through meiosis. An ordered display of chromosome pairs in a cell,
lined up in order of biggest to smallest, is called a karyotype.
There are four types chromosome pairs:
Metacentric: the centromere is located around but close to the middle.
Sub-metacentric: the centromere is a big further from the middle.
Acrocentric: the centromere is located near the end of chromosome.
Telocentric: the centromere is at the telomere, aka the end of the chromosome. This
one does not occur in humans.
Two duplicates of one chromosome, next to each other are sister chromosomes. Two
non-sister chromosomes in a homologous pair, only takes place in diploid cells. That
means the chromosomes in cells come in pairs. Haploid means the chromosomes
don’t come in pairs.
The number of chromosomes an organism has does not equal to the complexity of the
organism.
The lifecycle of an organism means from conception until the production of their own
offspring. Not to be mistaken for the life span which is from birth until death.
Meiosis:
The goal of meiosis is the reduction in the number of chromosomes in a cell.
The first step of meiosis in the interphase, here the two parent chromosomes are
duplicated. So there arise two pairs of sister chromosomes.
The second step is meiosis I, the two homologous chromosomes pairs are separated.
The final step is meiosis II, now the two sister chromosomes are separated. In the end
the cells either have one chromosome from the mother or from the father, but not
both. They turned from a diploid parent cell into a haploid cell.
Difference between mitosis and meiosis:
Occurrence, mitosis can occur in either haploid or diploid cells, while meiosis can only
occur in diploid cells.
Number of devisions, mitosis only has one devision, while meiosis has two (meiosis I
and meiosis II).
, Resulting daughter cells, mitosis has 2 who are generally identical to the parent
cell, while meiosis results in four daughter cell who are generally different from the
parent cell due to crossing over.
Function, for mitosis it is to form multi cellular organisms from a single cell, while for
meiosis it ice to produce gametes (for reproduction) or to produce spores.
Both mitosis and meiosis occur in animals, plants, fungi but not in prokaryotes.
Meiosis causes genetic variation in two ways:
Through the independent assortment of chromosomes during meiosis I, which results
in a 50% chance to get either the paternal or maternal genetic maternal
chromosomes. This means you can get one of each, but also only maternal or
paternal chromosomes.
Genetic variation van also happen due to crossing over. During prophase when the
chromosomes are stuck together, they can lap over each other. The point where this
happens is called the chiasma. Because of crossing over the telomeres switch places,
usually this happens to only one telomere, but it can also occur twice, which is called a
double crossing over, this is very rare though.
Lecture 2, Mendelian genetics:
George Mendel is the founder of modern genetics.
He started working with peas in monastery garden, because peas come in multiple
varieties, have short generation time and have a large number of offspring. The large
number of offspring gives lots of statistics to work with.
To ensure the peas don’t self-fertilize and thus wouldn’t create genetically variable
offspring, Mendel but out every stamen. This way the plant can only be fertilized by
another plant.
He crossed a plant with purple flowers with a plant with white flowers, the filial
generation (aka the F1 generation) only existed of purple flowers. Mendel decided to
cross the F1 generation, either through self-pollination or cross-pollination. The F2
generation contained the white flowers again. In a 3:1 ratio. So for each white flower
plant, there were 3 purple flower plant.
In this example the purple color is the dominant trait and the white color is the
recessive trait. In the F1 generation the white color was hidden because the parent
were both homozygous.
When two homozygous parents cross, the F1 generation all has the same genotype.
This is called true breeding.
Mendel’s model:
Because of his experiments, Mendel came to three conclusions.
1. Alleles account for variation of inherited characters
2. One allele is inherited from each parent
3. The dominant allele determines the organism’s appearance, where as recessive
allele has no noticeable effect on an organisms phenotype.
4. Two alleles for a heritable character separate from each other during gamete
forming. This is the law of segregation.
In inheritance of characters by a single gene may deviate from the simple Mendelian
patterns in the following situations:
- if the alleles are not completely dominant or recessive
