10.1 Meiosis
Click for Meiosis Animation
MeiosisSection 10.1
Body Cells & Gametes· somatic cells = body cells
do NOT pass on DNA to offspring46 chromosomes (23 pairs)
· gametes = sex cellseggs (females) and sperm (males)pass on DNA to offspring23 chromosomes, NO pairs
· a.k.a. homologues· matching chromosomes (same length and genes)· 1 from mom and 1 from dad· carry genes that control the same inherited traits· duplicated during "S" phase of interphase
Homologous Chromosomes
To see what the homologous pairs look like after the "S" stage.
Homologous Chromosomes and Chromatids
How many chromatids in a pair of duplicated homologous chromosomes?
(instant math question)
· autosomeschromosome pairs 1 - 22
· sex chromosomeschromosomes pair 23X + X = femaleX + Y = malecontrols the development
of sexual characteristics
Autosomes & Sex Chromosomes
10.1 Meiosis
1 MATA: Cells in your stomach, liver, or heart are considered
A sex cells
B body cells
C somatic cells
D gametes
2 Which of the following describes gametes?
A sperm and egg
B sex cells
Chave 23 chromosomes to pass on to offspring
D all of the above describe gametes
3 Homologous chromosomes contain genes for the same traits. You get one from mom and one from dad. After the "S" phase they contain only 2 sister chromatids.
True False
4 The first 22 pairs of chromosomes are called ______, pair 23 are called ______ chromosomes. (separate terms with a space)
5 What is the sex/gender of this person? · fusion of 2 gametes (egg and sperm)· results in offspring that are genetic combinations of mom and dad (genetically unique)· fertilization - fusion of egg and sperm
Sexual Reproduction
10.1 Meiosis
Diploid and Haploid
DIPLOID· diploid = 2n· 2 copies of each chromosome
1 from mom1 from dad
· body cells
HAPLOID· haploid = n· 1 copy of each chromosome· gametes (sex cells)
egg & sperm
6 MATA: Fertilization
A is the fusion of egg and sperm
B results in genetically unique offspring
C requires 2 gametes
D can happen sexually or asexually
7 Diploids cells (n) contain 2 copies of each chromosome and are found in gametes.
True False
My, oh my, Meiosis· form of nuclear division that creates 4 haploid (n) cells from one diploid cell (2n)· "reduction division"
reduces the number of chromosomes (2n to n) then divides into 4 cells (1 cell becomes 4)· essential for sexual reproduction
ensures the same # of chromosomes in each generation
creates genetic diversity· requires 2 rounds of cell division
meiosis I and meiosis II· GOAL: to produce 4 genetically unique daughter cells
gametes (egg & sperm)
body cells
n + n = 2N
Mitosis Vs. MeiosisMitosis
1 cell becomes 2 cells
genetically identical
two set of chromosomes
diploid (2n)
Meiosis1 cells becomes 4 cells
genetically unique
one set of chromosomes
haploid (n)
10.1 Meiosis
· PURPOSE: homologous chromosomes separate creating 2 cells each with duplicated chromosomes #1-23 (haploid)· Interphase - 46 chromosomes replicate
Meiosis I Prophase I· homologous chromosomes find each other (synapsis)· tetrads form
tetra = four4 chromatids
· crossing over occursportions of chromatids
break and change placeslike wearing two different socks
· tetrads line up in the center of the cell· spindle fibers attach to chromosomes· independent assortment occurs
homologous chromosomes line up randomly8,388,608 possibiliites
Metaphase I Anaphase I & telophase I· Anaphase I
homologous chromosomes separate
· Telophase Iresults in 2 cells each with
chromosomes #1-23 (haploid)
8 What is the purpose of MEIOSIS?
Ato produce 4 genetically unique daughter cells
B to separate homologous chromosomes
C to separate sister chromatids
Dto produce 4 genetically identical daughter cells
9 What is the purpose of MEIOSIS I?
Ato produce 4 genetically unique daughter cells
B to separate homologous chromosomes
C to separate sister chromatids
Dto produce 4 genetically identical daughter cells
10.1 Meiosis
10 MATA: What happens during Prophase 1?
A independent assortment
B synapsis
C triplets form
D crossing over
11 Homologous chromosomes separate during _______________
12 At the end of meiosis I, chromosomes are __________ (diploid or haploid).
Meiosis II· PURPOSE: sister chromatids separate creating 4 unique cells· no Interphase between meiosis I and meiosis II
PMAT II· Prophase II
chromosomes still replicated
· Metaphase IIsister chromatids line up in
the center of the cell
· Anaphase IIsister chromatids separate
· Telophase II4 haploid daughter cells
13 What is the purpose of MEIOSIS II?
A to create 4 genetically unique daughter cells
B to separate homologous chromosomes
C to separate sister chromatids
D to create 4 genetically identical cells