Transcript this PowerPoint show of Mendelian Genetics

Review…
1. My somatic cells have ____ (#) chromosomes or
__n and they are _______
2. My sperm/egg (pick one) cells have ____
chromosomes or __n and they are _______
3. I got these chromosomes from:
4. Each sex cell is genetically unique because:
5. Two purposes of Meiosis:
1.
______________________
2. _______________
Heredity
Gregor Mendel: Augustinian Monk,
1822-1884 (Watch this 2:35 Video)
Genetic studies on pea plants
Discovered dominant and
recessive traits in all
organisms that are randomly
given to offspring.
Important things Mendel learned
– SEGREGATION - genes occur in pairs (one
from each homologous chromosome), which
separate during meiosis to form gametes with
1 copy of each gene
– INDEPENDENT ASSORTMENT – the 23
chromosomes you inherit from each parent are
randomly selected [For instance: 10 of them
might be from your grandpa and 13 from
grandma]
– DOMINANCE - some genes can block others
from being seen
Alleles
Dominant vs. Recessive
+
=
+
=
+
=
Ex: Tall is dominant to short
• Genotype
TT
Phenotype
_________
Tt
_________
tt
_________
Xh Y
dd
tt
Ee
CC
bb
Mm
Genotype
Receding Hair Line
Dimples
Short
Detached earlobe
Curly Hair
Blonde hair
Melanin Produced
Phenotype
Heterozygous
•
•
•
•
•
•
Tt
Bb
Gg
Nn
Aa
Dd
Homozygous
•
•
•
•
•
•
TT
bb
gg
NN
aa
dd
Hybrid
•
•
•
•
•
•
Tt
Bb
Gg
Nn
Aa
Dd
Purebred/ True breeding
•
•
•
•
•
•
TT
bb
gg
NN
aa
dd
Examples
TT
_________
Tt
_________
tt
_________
…So what can we do with all this
vocab???
• Is there an easier way to understand
this??
Reginald Punnett sure thinks so!
A Punnett Square is a device used
to predict the results of a cross.
T
T
EGGS
(from
who?)
x
t
t
Sperm
(from
who?)
We are going to figure out the
offspring if we were to cross a
true Tall Pea Plant with a true
short pea plant!
TTx tt
TTx tt
t
t
Sperm
(from
who?)
T
TT
EGGS
(from
who?)
You just did exactly what Mendel
DID!! How Many…
T
t
T
Genotype
TT=
Tt=
tt=
Ratio=
t
Phenotype
Tall=
Short=
Ratio=
Your Turn!
• Show a Punnett Square and Analysis of
two tall heterozygous plants being crossed
• Remember
– (show the egg & sperm)
– Fill in the punnett square
– ANALYZE
A Heterozygous Cross
How Many…
Genotype
TT=
Tt=
tt=
Ratio=
Phenotype
Tall=
Short=
Ratio=
Punnett Square
• Black fur is dominant to white fur in
rabbits. If a heterozygous black rabbit
mates with a white rabbit, what is the
chance they will have a white bunny?
Punnett Square Practice
• The color red in roses is dominant to
yellow. If a homozygous red rose is
crossed with a heterozygous red rose,
what is the chance a yellow rose will be
produced.
Big Punnett Squares Example
•If having brown eyes
(B) is dominant to blue
eyes (b), then what is
the phenotypic ratio
of the offspring when
crossing a
heterozygous brown
eye father with a blue
eyed mother?
• If two plants were crossed and they had 52
offspring that were white and 58 that were
red, what is the ratio of red to white
• Perform a Punnett Square between a man
and woman to determine the chances of
having a baby girl