Download Crossing Over

Crossing Over Manipulative & Lab
Crossing Over SHOULD ONLY occur between
Homologous Chomosomes during Meiosis
Oogenesis - the creation of an egg/ovum
Spermatogenesis - the creation of sperm
In Mitosis, homologous
chromsoomes are present,
but do NOT pair up
Chromosomes
Homologous chromosomes
Chromosome #1
Preparing to
divide
Crossing over
A mixing of
genetic traits
mom
dad
Karyotype of chromosomes
With fluorescent markers at
gene sites
2 pairs of sister chromatids
= a tetrad
Meiosis - production of gametes
Chiasma - point where crossing over occurs
Interphase
What 3 things happen here?
Synapsis - pairing of homologous chromosomes
Prophase I
Haploid (n) or Diploid (2N)?
Haploid (n) or Diploid (2N)?
Metaphase I
Anaphase I
Haploid (n) or Diploid (2N)?
Prophase II
Telophase I
No Interphase between Meiosis I
and Meiosis II, means that
G1, S, and G2 do not occur.
Metaphase II
What is the end result in terms
Of the chromosome number?
Anaphase II
Telophase II
4 genetically unique cells
1 egg
3 smaller polar bodies
4 genetically unique sperm
Haploid (n) or Diploid (2N)?
Genes Gene loci
centromere
genetic instruction determining traits/characteristics
turned on (expressed) or turned off
Artist
Amateur
Doodlist
Hair color
Eye color
ethnicity
Musician
Amateur
Listener
height
Artistic
Shy, outgoing, friendly, introverted,
extroverted, quiet, bubbly, funny,
intellectual, secretive, stoic, silly,
Hair color
charming, energetic, kind, loyal,
reliable, moody, sociable, thoughtful,
Eye color
witty, stubborn, vain, gullible,
ethnicity
impulsive, domineering
height
Artistic
hand hand
Brilliant
Smart
Average
Music
IQ
personality
Olympian
Jock
Spectator
Athletic ability
Hair type
Music
IQ
personality
Athletic ability
Hair type
Describing
YOUR
traits!
Homologous Chromosomes
Hair color
Hair color
Eye color
ethnicity
height
Eye color
ethnicity
height
Artistic Artistic
hand
music
IQ
personality
IQ
Athletic ability
Hair type
Eye color
ethnicity
height
hand
music
IQ
personality
Athletic ability
Hair type
Eye color
ethnicity
height
Artistic Artistic
hand
music
Hair color
Hair color
personality
hand
music
IQ
personality
Athletic ability
Hair type
Each tetrad provides information about the same trait
Athletic ability
Hair type
Homologous Chromosomes Crossing Over
Hair color
Hair color
Eye color
ethnicity
height
Eye color
ethnicity
height
Artistic Artistic
hand
music
IQ
personality
IQ
Athletic ability
Hair type
Eye color
ethnicity
height
hand
music
IQ
personality
Athletic ability
Hair type
Eye color
ethnicity
height
Artistic Artistic
hand
music
Hair color
Hair color
personality
Athletic ability
Hair type
hand
music
IQ
personality
Athletic ability
Hair type
Each tetrad provides information about the same trait
Are the gametes genetically the same as each other or unique?
Mom Dad
Crossing Over
Hair color
Hair color
Eye color
ethnicity
Eye color
Separate the gamete’s tetrad,
height
Hair color
Artistic
hand
Eye color
ethnicity
height
music
IQ
personality
Athletic ability
Hair type
ethnicity
draw them down & id person
Artistic
height
Hair color
Eye color
ethnicity
height
Artistic
hand
music
IQ
IQ
personality
Athletic ability
Hair type
hand
music
hand
music
Artistic
personality
Athletic ability
Hair type
IQ
personality
Athletic ability
Hair type
Crossing Over
“Mixing the Gene Pool!”
Separating & Exchanging Genes
Chromosome
Genes
Loci
Traits
Alleles
Dominant
Recessive
Homozygous
Heterozygous
Hybrid
Chromosome 1
A
A
a
a
A
a
A
a
b
b
b
b
b
b
b
b
c
c
c
c
c
c
c
c
d
d
D
D
d
D
d
D
E
E
E
E
E
E
E
E
F
F
f
f
F
F
f
f
G
G
g
g
G
G
g
g
h
h
h
h
h
h
h
h
i
i
i
i
i
i
i
i
J
J
j
j
J
j
J
j
k
k
K
K
k
K
k
K
Identical sister chromatids
Identical sister chromatids
Chromosomal Errors
Philadelphia Chromosomes
During Meioisis, Crossing Over between
Homologous Chromosomes
but not at the same place = missing info and extra info
Shows up in EVERY Cell of the person
Non-Disjunction
Down Syndrome (21)
During Mitosis, Translocation between
Non-Homologous Chromosomes
shows up only in the cells that have undergone the error
during mitosis
Junction - come together
Disjunction - don’t come together
Non-Disjunction - come together even when you’re not supposed to?
And more variation…

Crossing over



Typically 1 - 3 cross overs per
chromosome
creates completely new
combinations of traits
in next generation
223 = 8.4 million possible
chromosomal combinations due
to independent assortment
Random fertilization
Any 2 parents will produce a zygote with
(223 x 223) = over 70 trillion diploid combinations
Sexual reproduction creates variability
Sexual reproduction allows us to maintain
both genetic similarity & differences.
Kirk & Michael
Douglas
Baldwin brothers
Martin & Charlie Sheen, Emilio Estevez
Meryl Streep & Mamie Gummer
The Judds
Kate Hudson & Goldie Hawn
Jamie Lee Curtis & Janet Leigh
Melanie Griffith & Tippi Hedren
Venus & Serena Williams