Mendel and His Gene- ius Idea… - Willis' Science · Big Idea 3: Living systems store, retrieve,...
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Big Idea 3: Living systems store, retrieve, transmit, and respond to info essential to life processes. Mendel and His Gene- ius Idea…
Transcript of Mendel and His Gene- ius Idea… - Willis' Science · Big Idea 3: Living systems store, retrieve,...
Big Idea 3: Living systems store,
retrieve, transmit, and respond to
info essential to life processes.
Mendel and His Gene-ius Idea…
Essential Knowledge
• 3A3: The chromosomal basis of
inheritance provides an understanding
of the pattern of passage of genes
from parent to offspring.
•… “particulate”
hypothesis is the idea
that parents pass on
discrete heritable units
(genes)…
Gregor Mendel
1822-1884
Mendel’s
Peas…
Planned
experiments
using characters
(flower color) and
traits
(purple/white)
Purple =
dominant
White =
recessive
3:1 Ratio
Mendel’s heritable factor = gene
Alternate versions =alleles
Law of Segregation and I.A. apply to genes
on diff. chromosomes.
• Genes near
each other
on same
chromosome
tend to move
as a unit
• Probability of
segregation
is a fxn of
the distance
b/t them.
Dominant vs Recessive
• Use Punnett Squares
to predict heredity
outcomes.
• Dominant alleles:
Use upper case. Ex: R
• Recessive alleles:
Use lower case. Ex: r
• Homozygous:
alleles for trait are
same. Ex: TT
(purebred)
• Heterozygous:
alleles for trait are
different. Ex: Tt
Use probability to analyze passage of
single gene traits from parent to offspring
Punnett
Squares
!!
One Factor Punnett
Square
• Monohybrid cross.
• Ex: Cross a tall
dominant
homozygous pea
plant (TT) w/ short
recessive
homozygous pea
plant (tt).
TT is a parent
who is Tall
tt is a parent
who is Short
Both are
homozygous
that make
heterozygous
offspring.
Monohybrid Cross
Ratios to Know
TT x tt = 100% Dominant, but heterozygous
Tt x Tt = 75% Dominant, 25% Recessive, 3:1
Two factor Punnett
Square
• Cross 2 traits =
dihybrid cross.
• Example: Cross a
dominant green,
smooth pea plant
(GGSS) with a
recessive yellow,
wrinkled pea plant
(ggss)
Ratios to Know
SsTt x SsTt = 9:3:3:1
9 dominant in both traits
3 dominant in one trait or the other trait
1 recessive for both traits
Human Genetic Disorders
• Can be received by inheriting a single gene trait or
specific chromosomal change
• Ex: Tay-Sachs Disease: Mutation on Chrom. 15
causing deterioration of nerve cells.
What’s This??
Punnett Square Sample Probs
