Transcript Cell Reproduction

Cell Reproduction
3.02
Chromosomes
• Rod shaped structures
in the nucleus that
only appear right
before cell division
Chromosomes Cont.
• Types:
– Autosomes
• Not involved in sex
determination
– Sex Chromosomes
• Determine sex
– Female: XX
– Male: XY
• Numbers
– Diploid: 2 of each
• Body Cells
• For humans 46
– Haploid: 1 of each
• Gametes (sex cells)
• For humans 23
Karyotype: chart of
chromosome pairs
used to detect
abnormalities in
chromosome number
Cell Cycle
• The regular cycle of grow, development, and reproduction.
• Why?
– To Grow
– To Repair
– To Replace
Mitosis
• A period of nuclear division in which 2
daughter cells are formed from 1 parent
cell.
– Each daughter cell contains a complete set of
chromosomes
– This produces more body cells
Mitosis
• Can you put these images in order?
4
1
1
2
3
Mitosis Cont.
• Paired chromosomes
are visible
• Spindle fibers appear
• Nucleolus and
nuclear envelope
breakdown
Mitosis Cont.
• Paired chromosomes
line up along the cells
middle
Mitosis Cont.
• Paired Chromosomes
separate and move
toward the opposite
pole of the cell guided
by the spindle fibers
Mitosis cont.
• Chromosomes reach
opposite poles of the
cell
• Begin to uncoil into
chromatin
• Nuclear envelope and
nucleolus begin to
reform
Asexual Reproduction
• Some organisms use mitosis to reproduce.
– All offspring are genetically identical to the
parent.
– Forms of asexual reproduction
Budding
Meiosis
• The process of cell division in which
haploid gametes are produced from diploid
cells
– Occurs in 2 stages
23
46
46
23
92
Meiosis I
Meiosis II
23
– Allows for genetic recombination
46
23
Genetic Recombination: Shuffling
genes from parents to get new combinations
• Crossing Over
– Exchanging equivalent
information from
homologous chromosomes
• Random Assortment of
Chromosomes
– Independent Assortment
– Chance distributes maternal
and paternal chromosomes
to gametes
Fertilization
• The fusion of 2 haploid gametes to produces a diploid
zygote.
• Fertilization is random.
– Adds to genetic variation.
Possible
sperm
Possible
eggs
How many different zygote
combinations can these
make?
Other Sources of Variation
• Gene Mutation
– A change in the
sequences
– Types
DNA
• Point mutations
• Frameshift mutations
– Effects
• Advantagous: produces a phenotype that is more suited to the
environment
• Neutral: does not help or hurt survival
• Lethal: produces a phenotype that is less suited to the
environment or causes a disease
Mistakes in Meiosis
• Nondisjunction: The failure of homologous
chromosomes to separate properly.
– Trisomy
• Down’s Syndrome
What gender is this person?
Comparing Mitosis & Meiosis
Mitosis
Number of divisions?
DNA replicated before each division?
Homologous chromosomes
separated?
How many cells are produced?
Cells all the same?
Used for asexual or sexual
reproduction?
Meiosis
Comparing Mitosis & Meiosis
Mitosis
Meiosis
1
2
DNA replicated before each division?
Yes
No
Homologous chromosomes
separated?
No
Yes
2
4
Yes
No
Asexual
Sexual
Number of divisions?
How many cells are produced?
Cells all the same?
Used for asexual or sexual
reproduction?