Transcript Genetics 3.3 and 3.4

Jeans to Genes
and
Asexual vs. Sexual
Reproduction
Vocabulary
• Chromosomes- condensed chromatin,
contains DNA that carries genetic
information
• Genes- a segment of DNA that codes for a
specific trait (which are instructions for
making a specific protein)
• Alleles- alternate forms of a gene that
code for a single trait at the same location
on a homologous chromosome
Genes control….
the production of proteins (or other
materials) made by the cell.
Where are proteins made in the cell……
ribosomes
History of Chromosome Research
Walter Sutton- an American geneticist
(1903) who studied grasshoppers.
He was trying to figure out how sex cells
were formed (the movement of
chromosomes from parents to offspring)
He observed that the egg and sperm have
half the number of chromosomes as the
body cells
Theory of Inheritance
Genes are carried from parents to
their offspring on chromosomes.
Previous thought……
Father contribute all of the
information for the child, mother
only contributed nutrition.
Mitosis vs. Meiosis
What happens to the number of
chromosomes in a cell before mitosis
begins? When does this happen?
The number of chromosomes double (each
is copied) during the S-phase of the cell
cycle.
Mitosis
Part of the cell cycle in which the doubled
chromosomes separate into two sets, in
order to produce daughter cells that are
exact copies of the parent cell.
Meiosis
• The doubled chromosomes divide twice to
produce four daughter cells that have half
the number of chromosomes as the parent
cell.
Comparing the two processes…
# of chromosomes in
each cell at the end of
the process
# of cells at the
end of the
process
haploid/diploid
Mitosis
Full set
2
diploid
Meiosis
Half of the set
4
haploid
Haploid: contain half of the complete set of chromosomes
(sex cells- gametes)
Diploid: contain a complete set of chromosomes
(body cells- somatic cells)
Gametes different than somatic
Gametes (sex cells) have half the number of
chromosomes as body cells, so during
fertilization two gametes combine to form
one offspring with a full set of
chromosomes.
Reproduction
Asexual vs. Sexual
What is reproduction?
Reproduction is the process by which
organisms produce more of their own kind.
•
Think about it – Without reproduction, all
life on earth would no longer exist.
Reproduction:
The Continuity of Life
Reproduction
Sexual
Reproduction
Asexual
Reproduction
What is Asexual Reproduction?
• Only one parent is involved.
• Offspring are genetically identical to their
parents.
• All cells that come from a single cell are
genetically identical to it and to each other;
they are all clones.
Types of Asexual Reproduction
1. Binary Fission occurs in one-celled
organisms such as the
ameoba and
paramecium.
The nucleus divides by
mitosis and the
cytoplasm divides,
forming 2 new
daughter cells of equal
size.
Types of Asexual Reproduction
2. Conjugation- occurs
in one-celled
organisms such as the
paramecium.
Here the organisms
exchange genetic
material prior to
reproducing by
binary fission.
Types of Asexual Reproduction
3. Budding - Occurs in Hydra
and yeast.
Buds (daughter cells) form on the
side of parent. The daughter
cells can separate or remain
attached.
More examples
of budding
include:
Sponges,
Corals and
Jellyfish…
Types of Asexual Reproduction
4.Fragmentation –
occurs in flatworms
(Planaria)
Refers to the
replacement or
regrowth of lost or
damaged body
parts
Some of these
animals can also
grow new
organisms from
the severed
pieces
(Segmented
Worms and Sea
Stars)
Types of Asexual Reproduction
5. Parthenogenesis
• Occurs in some Fish,
Reptiles, Amphibians
and Aphids.
• Offspring can arise from
unfertilized eggs.
• Most of these species
can switch between
sexual and asexual
reproduction.
(depending on conditions)
• Example:
Bees – unfertilized eggs become
male drones
- fertilized eggs – female
workers or queens
Types of Asexual Reproduction
6. Vegetative Propagationoffspring are produced
from plant parts.
Advantages:
•
clones of parents
(helpful when trying to
produce more of a
desirable plant)
•
plants bypass
immature seedling stage
Organism
Description of Sexual Form of
Reproduction
Paramecium
Description of Asexual Form of
Reproduction
Binary Fission- splits in half
to form two
Conjugation- exchange of
genetic material between
two, before binary fission
Hydras
One forms testes, the other
forms ovaries.
Budding- offspring forms on
body of parent, separates
eventually
Planaria
Hermaphrodites- each
animal possesses complete
male and female organs.
Fragmentation- organism
splits in the middle, and
grows new halves.
Komodo Dragon
Male and female KDs.
Parthenogenesis- eggs
becomes embryos without
male fertilization.
Potato
Strawberry
Vegetative Propagationoffspring produced from plant
parts
Sexual Reproduction
What are the differences between the two types of reproduction?
# parents
Offspring produced compared to the
parent
Asexual
Reproduction
1 parent
exact copies (except
parthenogenesis)
Sexual
Reproduction
2 parents
unique combination of genesproduce variation in the species
Compare the result of mitosis and meiosis in
dog cells that have 78 chromosomes.
HINT: How many daughter cells are produced?
How many chromosomes are in each daughter cell?
Mitosis
Meiosis