6.1 Chromosomes and Meiosis
REVIEW OF MITOSIS.
•
•
•
•
Mitosis is _____________________________________
CELL DIVISION/REPRODUCTION
It refers to the process of replication of ___________
cells.
BODY
Two purposes of mitosis: ____________
and __________
REPAIR
GROWTH
It results in __________________________________
TWO IDENTICAL DAUGHTER CELLS
(_______________________________________)
2 CELLS WITH THE SAME DNA AS ORIGINAL CELL
Meiosis - Chapter 3
6.1 Chromosomes and Meiosis
You have body cells and gametes.
somatic
• Body cells are also called _________________
cells.
• Germ cells develop into ______________.
gametes
ovaries
testes
– Germ cells are located in the _________
and ________.
Egg and sperm
– Gametes are sex cells: ______________________.
DNA that can be passed to offspring.
– Gametes have _______
body cells
sex cells (sperm)
sex cells (egg)
6.1 Chromosomes and Meiosis
KEY CONCEPT
the number
Gametes have ______________________
of
chromosomes
______________________
that body cells have.
½
6.1 Chromosomes and Meiosis
2
1. Your cells have __________ different type of
chromosomes:
AUTOSOMES
- ___________________
- Chromosomes that carry
ONLY
_____________
body traits
-SEX
________________
CHROMOSOMES- chromosomes that carry
SEX/GENDERof an organism
genes specific to the ___________
EXAMPLES OF
AUTOSOMAL TRAITS
EXAMPLES OF SEX
CHROMOSOME TRAITS
6.1 Chromosomes and Meiosis
Your cells have autosomes and sex chromosomes.
• Your body cells have
23
_______
pairs of
chromosomes.
- Chromosome pairs
# 1-22 are
Homologous pairs
________________.
• Sex chromosomes,
23
# ______determine
gender in humans.
They are referred to as
X and Y
_________________
6.1 Chromosomes and Meiosis
Understanding Homologous Chromosomes
AUTOSOMES
– ____________________of
chromosomes have the
same structure.
– For each homologous pair, one chromosome comes
from each parent
_____________________.
Allele for straight hair
From
Mom
Gene for
hair texture
From
Dad
Allele for curly hair
6.1 Chromosomes and Meiosis
Understanding Sex Chromosomes
– ____________________do
_________
always have
Sex Chromosomes
NOT
the same structure.
– Each parent still contributes one sex cell, BUT
depending upon the parent, they can give either an
X or a Y
_____________________.
6.1 Chromosomes and Meiosis
Body cells are diploid; gametes are haploid.
• Fertilization between egg and sperm occurs in sexual reproduction.
• Diploid (2n) cells have two copies of every chromosome.
– n represents the “pairs of chromosomes”
Human = 2n = __46___________________________
Goldfish = 2 n = _96___________________________
Pea = 2n = __18______________________________
– Body cells are diploid.
– Half the chromosomes __haploid_______________________.
6.1 Chromosomes and Meiosis
GAMETES
Sex cells, (______________)
are haploid.
ONLY ONE
• Haploid (n) cells have ________________
of every
chromosome.
ONLY ONE PARENT
– Only contain DNA from ______________________
22 autosomes and __
1 sex chromosome.
- Gametes have ___
6.1 Chromosomes and Meiosis
MAINTAINED in animals.
• Chromosome number must be _____________
• Many plants have more than two copies of each chromosome.
• Mitosis and meiosis are types of nuclear division that make
2 DIFFERENT
_________________
types of cells.
SOMATIC/BODY cells. (____________)
DIPLOID
• Mitosis makes more _________________
GAMETES/SEX
HAPLOID
• Meiosis makes more __________________
cells.(____________)
6.1 Chromosomes and Meiosis
HAPLOID
• Meiosis makes _______________
cells from diploid cells.
SEX
– Meiosis occurs in _______________
cells.
GAMETES
SPERM & EGG
– Meiosis produces _______________.
(_________________)
6.1 Chromosomes and Meiosis
PROPHASE 1
____________________________________
METAPHASE 1
____________________________________
ANAPHASE 1
____________________________________
TELOPHASE 1 / PROPHASE 2
____________________________________
METAPHASE 2
____________________________________
ANAPHASE 2
____________________________________
TELOPHASE 2
____________________________________
6.1 Chromosomes and Meiosis
Sister
Chromatids
Shorten and
Thicken. “Double
File” Find their
“match” or pair up,
(one from mom with
one from dad)
Nuclear
Membrane
Begins to
break down
Centrioles
Move apart
from one
another
Fibers
Form between
centrioles
6.1 Chromosomes and Meiosis
Sister
Chromatids
Become
attached to the
fibers, pulled to
middle of cell
Nuclear
Membrane
Remains
dissolved
Centrioles
move to
opposite ends
of cell
Fibers
Stretch
between two
ends of the cell
6.1 Chromosomes and Meiosis
Sister
Chromatids
Pairs pulled apart
by fibers.
Pairs are
separated…
Sisters/copies are
still connected
Nuclear
Membrane
Remains
dissolved
Centrioles
Still at cell’s
poles
Fibers
Pull matching
pairs apart
6.1 Chromosomes and Meiosis
Sister
Chromatids
Each end of cell
has HALF the
number of
chromosomes.
Chromosomes
DO NOT unwind.
Nuclear
Membrane
Cell Membrane
Fibers
DOES NOT
reform
Begins to pinch
in until the
cytoplasm is
divided in half
forming two new
cells
DO NOT
disappear
6.1 Chromosomes and Meiosis
Sister
Chromatids
Nuclear
Membrane
Still coiled
Has not
reformed
Centrioles
Move apart
from one
another
Fibers
Re-form
between
centrioles
6.1 Chromosomes and Meiosis
Sister
Chromatids
Nuclear
Membrane
Become attached
to the fibers. Are
pulled to middle of
cell
Remains
dissolved
(Single File)
Centrioles
Move to
opposite ends
of cells
Fibers
stretched between
ends of cell. Are
attached to center of
sister chromatids
6.1 Chromosomes and Meiosis
Chromatids
Nuclear
Membrane
Sisters are pulled
apart by fibers.
Remains
dissolved
Each chromatid
is separate from
its “sister”
Centrioles
Still at cell’s
poles
Fibers
Pull each
chromatid
toward
opposite
ends of cell
6.1 Chromosomes and Meiosis
Chromatids
Each end of cell
has HALF and
SINGLE
chromosomes.
Nuclear
Membrane
Begins to reform
Cell Membrane
Begins to pinch
in until the
cytoplasm is
divided in half
forming two new
SEX cells, (4
TOTAL)
Fibers
Begin to
disappear
6.1 Chromosomes and Meiosis
KEY CONCEPT
2
During meiosis, diploid cells undergo _______
cell
HAPLOID
divisions that result in _______________
cells.
6.1 Chromosomes and Meiosis
Cells go through two rounds of division in meiosis.
• Meiosis reduces chromosome number and creates
GENETIC DIVERSITY
_______________________________.
6.1 Chromosomes and Meiosis
• Meiosis differs from mitosis in significant ways.
2
– Meiosis has _____
cell divisions while mitosis has one.
HOMOLOGOUS
– In mitosis, _____________chromosomes
never pair up.
HAPLOID
– Meiosis results in ____________
cells; mitosis results in
DIPLOID
______________
cells.
6.1 Chromosomes and Meiosis
• Meiosis I and meiosis II each have four phases, similar to
those in mitosis.
MEIOSIS 1
– Pairs of homologous chromosomes separate in ___________.
SIMILAR
– Homologous chromosomes are ___________
but not identical.
– One from mom
One from dad
– Brown Eyes
- Blue Eyes
– Attached Earlobes
-Free Earlobes
– Type B blood
-Type A blood
homologous chromosomes
MEIOSIS II
– Sister chromatids divide in _____________.
sister
chromatids
sister
chromatids
6.1 Chromosomes and Meiosis
• Meiosis I occurs after DNA has been replicated.
• Meiosis I divides homologous chromosomes in four phases.
6.1 Chromosomes and Meiosis
• Meiosis II divides sister chromatids in four phases.
• DNA is not replicated between meiosis I and
meiosis II.
6.1 Chromosomes and Meiosis
MEIOSIS
ANIMATION
MORE
MEIOSIS
EXAMPLES
6.1 Chromosomes and Meiosis
Sex cells develop during puberty.
6.1 Chromosomes and Meiosis
•4 CELLS ARE PRODUCED
•EACH CELL HAS ONLY HALF THE NUMBER OF
CHROMOSOMES AS THE ORIGINAL
•MALES: ALL FOUR CELLS ARE “GOOD” SPERM
•FEMALES: 3 CELLS ARE CONSIDERED “POLAR BODIES”
ONLY 1 CELL IS A VIABLE EGG
(THIS IS DUE TO AN UNEVEN DIVISION OF CYTOPLASM DURING
MEIOSIS)
6.1 Chromosomes and Meiosis
Haploid cells develop into mature gametes.
Gametogenesis
• _________________
is the
production of gametes.
• Gametogenesis differs between
MALES
FEMALES
____________
and __________.
– Sperm become STREAMLINED
____________
and _____________.
MOTILE
– Sperm primarily contribute DNA
____
to an embryo.
DNA
– Eggs contribute _______,
_____________,
and
CYTOPLASM
ORGANELLES to an embryo.
____________
DNA
– During meiosis, the ______
gets
most of the contents; the other
POLAR BODIES
cells form _________________.
6.1 Chromosomes and Meiosis
6.1 Chromosomes and Meiosis
Make sure to include the cell
membrane,
nuclear membrane, chromosome,
centrioles, and fibers.
13.1 Ecologists Study Relationships
1.__________
____________
____________
2.__________
____________
____________
3.__________
____________
____________
4.__________
____________
____________
5.__________
____________
____________
Process:
____________
____________
____________
____________
1
2
1
2
1
3
3
4
5
4
6
5
7
1.__________
____________
____________
2.__________
____________
____________
3.__________
____________
____________
4.__________
____________
____________
5.__________
____________
____________
6.__________
____________
7.__________
____________
____________
6.1 Chromosomes and Meiosis
6.1 Chromosomes and Meiosis
The sperm is the smallest cell in the body, whilst the egg is the largest,
it is estimated that it will take 175,000 sperm to weigh as much as a female egg,
which is a lot of sperm!
Average males produce 150 million sperm daily!
Females are born with all the oocytes (eggs) that they will ever
have in a lifetime?
Infertility: sperm counts drop as low as 20 million per ml
6.1 Chromosomes and Meiosis