meiosis chapter 10.1 and 11.3. do now how is a baby made? on the cellular level, draw how a baby is...
TRANSCRIPT
Meiosis
Chapter 10.1 and 11.3
Do Now
How is a baby made? On the cellular level, draw how a baby is
made. (NO PHALLIC SYMBOLS PLEASE!)
Why does sex exist?
Sexual reproduction creates genetic variability
Let’s Brainstorm…
How do we get our different traits?
What is the difference between fraternal and identical twins?
Let’s define the following words…
Meiosis:Sexual reproduction-production of gametes
Gamete:Sex Cells (egg and sperm) haploid
Somatic Cells:Body Cells - diploid
Haploid:Half the chromosome number (n) 1 of each pair of chromosomes (23)
Diploid:2 of each type of chromosome (2n)Twice the haploid number
Fertilization:Sperm enters egg
Zygote:Fertilized egg (diploid)
Chromosomes and Chromosome Number Human body cells have 46 chromosomes Each parent contributes 23 chromosomes Homologous chromosomes —one of
two paired chromosomes, one from each parent
Karyotype
Homologous Chromosomes
Same length Same centromere position Carry genes that control
the same inherited traits
Meiosis
The sexual life cycle in animals involves meiosis
Meiosis produces gametes.
When gametes combine in fertilization, the number of chromosomes is restored.
DNA Replication
PrepareGrowth
Division
Cell Cycle
Mitosis
Meiosis
2N
2N
N NNN
2N
Do Now
Label A, B, and C
(Hint same size, same shape…)
Meiosis
2 DivisionMeiosis I (separation of homologous
chromosomes)Meiosis II (separation of sister chromatids)
Interphase Same as Mitosis (G1, S, G2) DNA- Chromatin Centrioles- located near the nucleus
Prophase I Pairing of homologous chromosomes
occurs. (Synapsis) Each chromosome consists of two
chromatids. The nuclear envelope breaks down. Spindles form
Prophase I (cont.) Crossing over produces exchange
of genetic information. Crossing over —chromosomal
segments are exchanged between a pair of homologous chromosomes.
Metaphase I
Chromosome centromeres attach to spindle fibers
Homologous chromosomes line up at the equator.
Anaphase I
Homologous chromosomes separate and move to opposite poles
Telophase I
The spindles break down. Chromosomes uncoil and form two nuclei. The cell divides.
Prophase II
A second set of phases begins as the spindle apparatus forms and the chromosomes condense.
Metaphase II
A haploid number of chromosomes line of at the equator
Sister chromatids line up
Anaphase II The sister chromatids are pulled
apart at the centromere by spindle fibers
Move toward the opposite poles of the cell.
Telophase II The chromosomes reach the poles, and the
nuclear membrane and nuclei reform.
Cytokinesis
Cytokinesis results in four haploid cells Each with n number of chromosomes.
Genetic Variability Depending on how the
chromosomes line up at the equator, four gametes with four different combinations of chromosomes can result.
Genetic variation also is produced during crossing over and during fertilization, when gametes randomly combine.
Genetic Variability Animation
http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter12/animations.html#
Do Now: Label the phases of meiosis
Do Now – Period 3
How many autosomes?
How many sex chromosomes?
What is the sex of this patient?
Monosomy, Trisomy?
Is this individual normal?
Think – Pair - Share Draw out the stages of meiosis using the
following cell. Make sure you draw the cell with crossing over of only one pair of homologous chromosomes! (use colored pencils)
Do Now: Label the phases of meiosis
Do Now Match the description to the phase of meiosis.
1. Sister Chromatids are pulled apart. _____
A. Prophase I
2. Homologous chromosomes line up in the middle of the cell._____
B. Metaphase I
3. 2 daughter cells are formed ____ C. Telophase I
4. Nuclear membrane disappears__ D. Anaphase II
5. Nuclear membrane reforms around 4 cells ____
E. Anaphase I
6. Homologous chromosomes are pulled apart ____
F. Telophase II
Review
How does meiosis promote genetic variability? List 3 reasons why.
Review Spermatogenesis and oogenesis
Do Now
If a hamster has 44 chromosomes in G1 phase of the cell cycle, then…How many chromatids are in G2 Phase?How many chromosomes are in the G2
Phase?How many chromosomes will be in each cell
after it has gone through mitosis?
Do Now
What two divisions do your cells undergo? What are the differences between the
two?
Animations on Meiosis
http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter12/animations.html#