Zusammenfassung der Ressource
Genetics
- The study of heredity and variation of inherited
characteristics
- Gene
- Unit of heredity that is
transferred from a parent to
offspring and is held to
determine some characteristics
of the offspring
- DNA
- Molecule of life
- Shape
- DNA is made up of
two strands that are
bonded together in a
double helix shape
- Each strand of DNA consist of
nucleotides. Each nucleotide is
composed of a sugar, a
phosphate and a nitrogenous
base.
- Sugar and phosphate
form backbone of the
two strands.
- Nitrogenous base pairing
- Guanine-Cytosine
- Adenine-Thymine
- Replication
- 1. DNA is replicated during
Interphase, the double helix
unwinds into two seperate strands
- 2. After unwinding a
complimentary strand is created
for each split strand
- 3. Final step is the bonding of the
bases. Then two new daughter
DNA molecules are formed.
- Chromosomes
- a threadlike structure of nucleic acids
and protein found in the nucleus of
most living cells, carrying genetic
information in the form of genes
- Most species that reproduce sexually have
23 chromosomes from their mother and 23
chromosomes from their father
- Sex chromosomes
are the chromosomes
in the egg and sperm.
(23 each)
- All other
chromosomes are
autosomes
- Sexual reproduction
- Production of new living organisms by
combining genetic information from two
individuals of different sexes
- Asexual reproduction
- Mode of reproduction by which offspring arise
from a single organism and inherit the genes of
that parent only
- Humans has 2 sets
of 23 chromosomes
- Each species has
its own number of
chromosomes
- Karyotype
- Photograph of an individual's
chromosomes lined up from longest
to shortest with sex chromosomes last
- Used to study genetic diseases,
taxonomy, evolutionary
relationships etc.
- Chromatin
- The tangled fibrous complex of
DNA and protein within a
eukaryotic nucleus
- Chromatid
- either of the two
strands into which a
chromosome divides
during mitosis
- Centromere
- The structure that
holds chromatids
together
- Sister Chromatids
- A chromosome strand
and its duplicate
attached to each other
by a centromere
- Homologous
- Pairs of chromosome
that appear similar
but are not identical
- One chromosome
comes from the
mother and the
other from the
father
- They carry genes for
the same trait
- They can carry different forms
of the same gene, called alleles
- Cell cycle
- Life cycle of a cell
- 1. Interphase
- A cell most of its life in
interphase, during this stage
they will prepare for cell division
- Cells grow
- Make structural
proteins that repair
damaged parts
- Transport nutrients to where they are needed
- Eliminate waste
- Prepare for mitosis by creating proteins
- DNA will replicate during interphase
- 2. Cell division
- Mitosis
- Cell division in which the
daughter cells receive the
same number of
chromosomes as the parent
cell
- Prophase
- Metaphase
- Anaphase
- Telophase
- Cytokinesis
- Pinching off the cell
into two parts and
cytoplasm divides
- New nuclear membrane forms
around each set of chromatids
- Chromosomes spilt up and
chromatids are pulled to
opposite ends of the cell
- Chromosomes line up
along the center axis of
the cell
- Nucleolus disappears
- Chromatin condenses into chromosomes
- Spindle fibres are formed by centrosomes
- Centrosomes
- Small protein bodies that are found in
cytoplasm of animal cells, helps during
mitosis
- Spindle fibres
- Protein structures that guide
chromosomes during cell division
- Meiosis
- Two stage cell division in which the
chormosome number of the parental
cell is reduced by half, process by
which gametes are formed
- Gametes
- Sex cells that have haploid
chromosome number
- Haploid
- refers to number
of chromosomes in
a gamete. ( 23
chromosomes)
- Diploid
- refers to twice the
number of
chromosomes in a
gamete. Evert cell in the
body contains diploid
chromosomes except
the sex cells, ( 46
chromosomes)
- During fertilization, sperm cell ( haploid- n=23)
unites with egg cell (haploid - n=23) to produce a
diploid (2n=46) zygote
- zygote
- a cell resulting from the union of a male and
female sex cell, until it divides and then is called
an embryo
- Prophase 1
- Homologous chromosomes
come together
- Synapsis
- Pairing of homologous chromosomes
- Each pair is made up of 4 chromatids
- Tetrad
- Pair of homologous
chromosomes, each with two
chromatids
- Recombination shuffles the allele
content between homologous
chromosomes ( Increasing genetic
diversity)
- Crossing over
- Exchange of genetic
material between
homologous chromosomes
- Metaphase
1
- Spindle fibres attached line up
the homologous pairs at the
equatorial plate
- Anaphase 1
& Telophase
1
- Homologous chromosomes
are moved to opposite ends
- One member of each
homologous pair will be
found in each daughter cell
- Meiosis 2
- Pairs of chromatids separate
and move to opposite poles
- There is no replication
of chromosomes before
meiosis 2
- Each cell has half the
number of chromosomes as
the parent cell
- Oogenesis
- In female animals , meiosis takes
place in the ovaries
- Starts during embryonic
development with diploid cells called
oogonia
- These cells divide by mitosis, becoming
primary oocytes which are diploid
- The primary oocyte begin the process
of meiosis but they stop at prophase
and remain in this stage until puberty
- After puberty is reached, every month one of the
oocytes will continue through the process of meiosis
- Division of the cytoplasm happens
unevenly during cell division that takes
place at the end of meiosis 1
- The cell that receives the most
cytoplasm, now called a
secondary oocyte, will continue
with meiosis
- One a month the secondary oocyte will
burst out the ovary and travel down the
fallopian tube to the uterus
- If oocyte is penetrated by sperm
the second cell division of meiosis
will take place
- Most of the cytoplasm will go to one of the
daughter cells, called the ovum, and a
smaller polar body will be formed
- after fertilization, as soon as meiosis is complete, the
chromosomes of the haploid sperm cell will fuse with those
of the haploid egg cell
- The resulting diploid cell is called a zygote, the zygote will
attach itself to the lining of the uterus and pregnancy begins
- Number of chromosomes
- 46
- 23
- 23
- polar
body
- polar
body
- polar
body
- polar
body
- The cell that receives less
cytoplasm is called a polar body, it
usually degenerates
- Spermatogenesis
- In male animals, meiosis
takes place in the testes
- Starts with diploid cell called a
spermatagonia
- When boy reached puberty , spermatogonia reproduces by
mitosis. The resulting cells then undergo meiosis to form four
haploid cells
- After meiosis 2, the haploid cells, called spermatids, undergo several additional changed:
- 1. Development of the head
section, which contains nucleus
- 2. Development of middle section which contains a
lot of mitrochondria which provides energy for
swimming
- 3. Development of a tail, called a
flagellum, which is used for
swimming
- Number of chromosomes
- 46
- 23
- 23
- 23
- 23
- 23
- 23
- Number of
chromosomes
- Mitosis
- 46
- 46
- 46
- Meiosis
- 46
- 23
- 23
- 23
- 23
- 23
- 23
- Somatic cell
- Any cell of a living organism other than reproductive cells