Transcript Reproduction

Reproduction
An quick over view
Asexual Reproduction
• Many organisms reproduce asexually
– Bacteria DNA replicates and cell divides =
Binary Fission
– Budding as in Yeast and sponges
– Vegetative propagation- take a cutting or
spreads from root.
– Parthenogenesis- in some lizards, fish and
insects females can produce offspring from an
unfertilized egg.
– Spores- Fungus, Ferns and some mosses
produce asexual spores.
Binary Fission
•
•
•
•
•
DNA Replicates
Chromosomes split
Cytokinesis
Two smaller cells
Genetically Identical
Asexual reproduction
• There is no genetic change from generation
to generation.
• Offspring are basically clones of parent
(genetically identical)
• No need to mate
• Single individual may reproduce…even if
they are stuck on a island alone…
• Population may be more susceptible to
disease, environmental change or other
problems
Sexual Reproduction
• 2 haploid (1n)
gametes (Such
as Sperm and
Egg) unite to
form a diploid
(2n) Zygote
Diploid vs Haploid
• These terms refer to the number of sets of
chromosomes and organism has.
• Humans are Diploid, we have two sets of
chromosomes 46 total or 23 Pairs of
“Homologous” chromosomes
• Sperm and eggs are haploid they only
have 23 chromosomes each.
• When sperm and egg join the resulting
zygote will have 46 chromosomes
Homologous Chromosomes
• Homologous means “Like” or “Same”
• Homologous chromosomes are
chromosomes that code for the same
genes. Remember that a gene codes for
a protein that may result in a trait.
• The homologous chromosomes may have
different version of the genes called
“Alleles” They code for the same trait but
may have different forms or colors.
Meiosis
• The process of making a haploid cell
• Also known as a reduction division
because the number of chromosomes is
reduced in this process.
• Two stages
– Meiosis I
– Meiosis II
– Results in 4 haploid (1N) Gamates
– Meiosis I –DNA is Replicated Homologous
chromosomes line up in metaphase. This is
when genetic recombination can occur… so
not all offspring from the same pair will be
identical! Very important for variation within a
population and for the rise of new species.
-Results in 2 hapliod cells
– Meiosis II –DNA in NOT replicated in the two
haploid cells, chromatids separate and divide,
results in 4 hapliod (1n) cells.
Meiosis I
Meiosis II
Prophase II
Metaphase II
Meiosis II
Anaphase II
Meiosis I results in two
The chromosomes line up in a The sister chromatids
haploid (N) daughter cells,
similar way to the metaphase separate and move toward
each with half the number of stage of mitosis.
opposite ends of the cell.
chromosomes as the original.
Telophase II
Meiosis II results in four
haploid (N) daughter cells.