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Semester 1, Day 7. Meiosis. Agenda. Study for Virus Quiz Turn in Virus Homework (18.1 and 18.2) Virus Quiz Lecture and Activity for Meiosis Practice Meiosis Reading/Work Time for Meiosis Review Meiosis Questions. Study. Reasons why viruses are non-living Parts of a virus - PowerPoint PPT Presentation
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Semester 1, Day 7
Meiosis
Agenda Study for Virus Quiz Turn in Virus Homework (18.1 and 18.2) Virus Quiz Lecture and Activity for Meiosis Practice Meiosis Reading/Work Time for Meiosis Review Meiosis Questions
Study Reasons why viruses are non-living Parts of a virus Diagram of virus cycles Steps of virus cycles
Homework to Turn In Cornell Notes: Section 18.1, 18.2 Questions:
Section Assessment 18.1: #1-6 Section Assessment 18.2: #1-6 Chapter 18 Assessment: #1-17, 19-26
Quiz Viruses
Reproduction & Genetic Material Production of Offspring
Asexual: 1 parent, genetically identical offspring Prokaryotic organisms, some plants
Sexual: 2 parents (1/2 DNA from each), genetically different offspring
“Not”
Fertilization
Sperm (Male) Ovum (Female)Zygote (Fertilized Ovum)
First cell of
an organis
mGametes: sex cells
Reproduction & Genetic Material Recall: DNA = genetic information
Image Source: www.riversideonline.com
DNA doesn’t
naturally occur like
this!
Chromosome: coiled
DNA
Reproduction & Genetic Material Unduplicated vs. Duplicated Chromosomes
Image Source: histology.kasralainy.edu.eg
Chromosomes Genes: Portion of DNA
that codes for a protein
Homologous Chromosomes: a pair of
chromosomes of the same length,
same centromere position, and carry
genes that control the same traits.
One chromosome from each parent
makes a pair.
Chromosome Number: Humans have
23 homologous pairs
Different
Genes
From Mom
From Dad
Same centromere
position
Genes that control a trait (ex.
eye color)
Same Length
23pair
sx
2 chromosome
s=
46chromosom
es1 pair
Chromosomes Karyotype: number & visual appearance of chromosomes in
an organism
Sex Chromosomes:-23rd “pair”-Female: X X-Male: X Y
Image Source: www.biotechnologyonline.gov.au
Chromosomes What would happen if human gametes each had 46
chromosomes?
Therefore… Gametes must have half (23) of the chromosomes!
Fertilization
Zygote
Can’t be
human!
46 46 92
MaleFemale
Fertilization
Zygote
Human!
23 23 46
MaleFemale
Chromosomes Let’s represent the # of chromosomes in a
gamete for ANY organism as “n”.
Fertilization
Zygote
n n 2nMale
Female
All Sexual Reproductio
n
“Haploid” = nGk. Haplos = Single “Diploid” = n
Gk. Diplos = Double
Chromosomes You receive one chromosome for every homologous pair from each
parent.
Child (2n)
Mom (2n) Dad (2n)
Pass on “n” Pass on “n”
Make your own chromosomes You have 4 small, 4 medium, and 4 large
chromosomes Decorate 2 small, 2 medium, and 2 large for MOM
All should be identical Example: polka dots
Decorate 2 small, 2 medium, and 2 large for DAD All should be identical Example: stripes
Meiosis Mom and Dad are both “2n”. How do they
make gametes of “n”?
2n 2nMom Dad
nn
Ovum Sperm
2n
Child
Fertilization
Process? Process?Process? = MEIOSIS• Cell division that
halves the chromosome number. Creates gametes for sexual reproduction.
Meiosis
MeiosisInterpha
se
Gap
1
Synt
hesis
Gap
2
Meiosis IPr
opha
se I
Met
apha
se
IAn
apha
se
ITe
loph
ase
I
Meiosis II
Prop
hase
II
Met
apha
se
IIAn
apha
se
IITe
loph
ase
II
PMAT I PMAT II
Meiosis Meiosis I: 1st Cell Division Meiosis II: 2nd Cell Division
Meiosis I Meiosis II
Body Cell2n
(Diploid)n
(Haploid)
n(Haploid)
Gametes
(become sperm
or ovum)
Meiosis Interphase (before division):
preparing for cell division G1 Phase (Gap 1)
Cell is growing Normal functions Prepping for DNA duplication
S Phase (Synthesis) DNA is copied Single chromatids Sister
chromatids G2 Phase (Gap 2)
Cell continues growing Prepping for cell division
Ignore other organelles for
nowDNA is
uncondensed (not in
chromosomes) and is called
chromatin
Gap 1
Synthesis
Gap 2
Your Body Cell (2n)Single Chromatids
Your Body Cell (2n)Sister Chromatids
Act this out with our chromosomes
Meiosis Meiosis I: 1 cell 2 cells
Prophase I Chromatin condenses into
chromosomes Homologous chromosomes pair
up; crossing over occurs Nuclear envelope breaks down Spindle fibers form from the
centrioles
Image Source: legacy.owensboro.kctcs.edu
HomologousChromosomes
Crossing Over
Genetic information exchanges = increased variation
From your mom
From
your dad
NuclearEnvelope
**Recall: In humans, 23 pairs of homologous chromosomes in a
human (2n = 46). Here, we are using 2 pairs (2n
= 4).
Centrioles: organize cell
during division
Your Body Cell (2n)Sister Chromatids
Act this out with our chromosomes
Meiosis Meiosis I (cont.)
Metaphase I Spindle fibers attach to
centromeres of chromosomes
Homologous pairs line up at equator of cell
Anaphase I Homologous
chromosomes separate and move along spindle fibers to opposite poles
Equator
Your Body Cell (2n)Sister Chromatids
Your Body Cell (2n)Sister Chromatids
(n) at each pole
(n) at each pole
Act this out with our chromosomes
Meiosis Meiosis I (cont.)
Telophase I
Spindles break
down
Chromosomes
uncoil, nuclei
reform
Cell divides into
two
Cytokinesis
(n) ChromosomesSister Chromatids
(n) ChromosomesSister Chromatids
Act this out with our chromosomes
Meiosis Meiosis II: 2 cells 4 cells
Prophase II Chromatin condenses into
chromosomes (again!) Nuclear envelopes break
down (again!) Spindle fibers form from
centrioles (again!) and attach to chromosomes
Metaphase II Centromeres of chromosomes
line up at equator of each cell (not in pairs!)
(n) ChromosomesSister Chromatids
(n) ChromosomesSister Chromatids
(n) ChromosomesSister Chromatids
(n) ChromosomesSister Chromatids
Equators
Act this out with our chromosomes
Meiosis Meiosis II (cont.)
Anaphase II Centromeres split Sister chromatids
separate & move to opposite poles
Telophase II 4 nuclei reform Spindles break down Chromosomes uncoil Cells divide
(n) ChromosomesSingle Chromatids
(n) at each pole
(n) at each pole
(n) at each pole
(n) ChromosomesSingle Chromatids
(n) at each pole
Cytokinesis
Act this out with our chromosomes
Meiosis Final Products
Spermatogenesis Oogenesis
Meiosis
Act this out with our chromosomes
Meiosis Spermatogensis
In males, only a special diploid (2n) cell called spermatocyte in a testis can undergo meiosis to create a sperm. 4 sperm cells are formed.
Image Source: www.mun.ca
Meiosis Oogensis
In females, only a special diploid (2n) cell called an oocyte in an ovary can undergo meiosis to create an ovum. 1 ovum is formed, 3 polar bodies that die are also formed.
Image Source: www.mun.ca
Practice Show me:
Interphase, G1 Interphase, G2 (Assume
Interphase S occurred) Prophase I Metaphase I Anaphase I Telophase I Prophase II Metaphase II Anaphase II Telophase II
Show me: Metaphase II Prophase I Interphase G1 Anaphase II Prophase II Telophase I Interphase G2 (Assume
Interphase S occurred) Anaphase I Telophase II Metaphase I
Reading/Work Time Cornell Notes on Section 10.2 (Meiosis) 10.2 Section Assessment:
#1-5 Chapter 10 Assessment:
#1, 4-6, 9, 10, 13, 15, 18, 25, 26-28, 30