Slides cover Meiosis and Mendelian/
Nonmendelian outlines
Interphase
.
MITOSIS
MEIOSIS
Parent cell
(before chromosome replication)
Chiasma (site of
crossing over)
MEIOSIS I
Propase
Prophase I
Chromosome
replication
Duplicated chromosome
(two sister chromatids)
Chromosome
replication
2n = 6
Chromosomes
positioned at the
metaphase plate
Metaphase
Anaphase
Telophase
Sister chromatids
separate during
anaphase
2n
Tetrad formed by
synapsis of homologous
chromosomes
Tetrads
positioned at the
metaphase plate
Homologues
separate
during
anaphase I;
sister
chromatids
remain together
Metaphase I
Anaphase I
Telophase I
Haploid
n=3
Daughter
cells of
meiosis I
2n
MEIOSIS II
Daughter cells
of mitosis
n
n
n
Daughter cells of meiosis II
Sister chromatids separate during anaphase II
n
TWO Divisions (easy version – meiosis)
(First Division)
(Second Division)
Spermatogenesis
Epididymis
Seminiferous tubule
Testis
Cross section
of seminiferous
tubule
Spermatogonium
Sertoli cell
nucleus
Mitotic division, producing
large numbers of spermatogonia
Differentiation and onset of meiosis I
Primary spermatocyte
(in prophase of meiosis I)
Meiosis I completed
Secondary spermatocyte
Meiosis II
Early
spermatids
Lumen of
Seminiferous tubule
Spermatids
(at two stages of
differentiation)
Differentiation
Neck
Sperm cells
Head
Midpiece
Tail
Plasma membrane
Acrosome
Nucleus
Mitochondria
Oogenesis in the ovaries
Ovary
Primary germ cell
in embryo
Differentiation
Oogonium
in ovary
Oogonium
Mitotic
division
Primary
oocyte
within
follicle
Primary
oocyte
Completion of meiosis I
and onset of meiosis II
First polar body
Growing
follicle
Secondary
oocyte
Ovulation
Entry of sperm
triggers
completion
of meiosis II
Second polar body
Mature follicle
Ruptured
follicle
Ovum
Ovulated
secondary oocyte
Corpus luteum
Degenerating corpus luteum
Crossover in Prophase I
Mitosis vs. Meiosis
MITOSIS
MEIOSIS
Parent cell
(before chromosome replication)
Chiasma (site of
crossing over)
MEIOSIS I
Propase
Prophase I
Chromosome
replication
Duplicated chromosome
(two sister chromatids)
Chromosome
replication
2n = 6
Chromosomes
positioned at the
metaphase plate
Metaphase
Anaphase
Telophase
Sister chromatids
separate during
anaphase
2n
Tetrad formed by
synapsis of homologous
chromosomes
Tetrads
positioned at the
metaphase plate
Homologues
separate
during
anaphase I;
sister
chromatids
remain together
Metaphase I
Anaphase I
Telophase I
Haploid
n=3
Daughter
cells of
meiosis I
2n
MEIOSIS II
Daughter cells
of mitosis
n
n
n
Daughter cells of meiosis II
Sister chromatids separate during anaphase II
n
Independent Assortment
Key
Maternal set of
chromosomes
Possibility 2
Possibility 1
Paternal set of
chromosomes
Two equally probable
arrangements of
chromosomes at
metaphase I
Metaphase II
Daughter
cells
Combination 1
Combination 2
Combination 3
Combination 4
Locus
(Gene locations on chromosomes)
Alleles for a gene
True breeds & Hybrids
Phenotype vs. Genotype
Physical Trait vs. Gene allele type
Test Cross
Dominant phenotype,
unknown genotype:
PP or Pp?
Recessive phenotype,
known genotype:
pp
If Pp,
then 2 offspring purple
and 1 2 offspring white:
If PP,
then all offspring
purple:
p
1
p
P
p
p
Pp
Pp
pp
pp
P
Pp
Pp
P
P
Pp
Pp
Monohybrid
Dihybrid
Dihybrid – Normal 9:3:3:1 ratio
Law of Segregation - Anaphase
Independent Assortment
Key
Maternal set of
chromosomes
Possibility 2
Possibility 1
Paternal set of
chromosomes
Two equally probable
arrangements of
chromosomes at
metaphase I
Metaphase II
Daughter
cells
Combination 1
Combination 2
Combination 3
Combination 4
Complete Dominance
Incomplete Dominance
Codominance (AB) &
Multiple Alleles
Pleiotropy (Sickle Cell)
Epistasis
BbCc
BbCc
Sperm
1
1
1
1
1
4
BC
1
4
bC
1
4
1
Bc
4
bc
4
BC
BBCC
BbCC
BBCc
BbCc
4
bC
BbCC
bbCC
BbCc
bbCc
4
Bc
BBCc
BbCc
BBcc
Bbcc
4
bc
BbCc
bbCc
Bbcc
bbcc
9
16
3
16
4
16
Polygenic Inheritance
&
Norm of the Reaction
AaBbCc
aabbcc
20/64
Fraction of progeny
15/64
6/64
1/64
Aabbcc
AaBbCc
AaBbcc AaBbCc AABbCc AABBCc AABBCC
Multifactorial example
(Acid in soil changes the color)
.
Ww
ww
ww
Ww ww ww Ww
WW
or
Ww
Ww
Ww
ww
Dominant trait (widow’s peak)
Second generation
(parents plus aunts
and uncles)
Third
generation
(two sisters)
ww
Widow’s peak
First generation
(grandparents)
No widow’s peak
.
First generation
(grandparents)
Second generation
(parents plus aunts
and uncles)
Ff
FF or Ff ff
Third
generation
(two sisters)
Attached earlobe
Recessive trait (attached earlobe)
Ff
ff
ff
Ff
Ff
ff
FF
or
Ff
Ff
ff
Free earlobe
Genes on Chromosomes
Female (XX) Karyotype
(Remember… “kary” means “nucleus”)
Autosomes and linked genes
Linkage Map based
on Crossover
frequency
Recombination
frequencies
9%
9.5%
17%
b
Chromosome
cn
vg
Locus Gene Maps
Sex –Linked Female – TWO Xs
Sex-Linked Male – ONE X
One from EACH parent
Sperm AND Egg
Pedigree of Color Blindness
Pedigree of Hemophila
Non-Disjunction
Trisomy 21
Chromosome Structure Errors
Extranuclear DNA
(This DNA CAN can affect an organism)