Transcript Subtle Accents

The Laws of Inheritance
Biology 1
Mrs. Wilkemeyer
Image taken from kentsimmons.uwinnipeg.ca/cm1504/mendel.htm
Q - Space
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How do scientists predict what traits offspring
will receive when genetic counseling is
needed?
How might researchers use the laws of
inheritance in agriculture?
Agenda
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SOL Knowledge
Objectives
Genetics
Gregor Mendel's work
Law of segregation
Law of probability
The use of punnett squares
Law of independent assortment
Summary of laws of inheritance
Beyond dominant and recessive
SOL Knowledge
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Bio.6 d
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Students will investigate and understand
common mechanisms of inheritance and protein
synthesis
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Including the prediction of inheritance of traits based
on Mendelian laws of heredity
Objectives
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We will...
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Understand the difference between genotypes
and phenotypes
Understand how to identify homozygous and
heterozygous individuals
Apply the law of probability to determine patterns
of inheritance with a punnett square
Understand the difference between complete
and incomplete dominance
What is Heredity?
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The study of genetic traits and how they are
passed from one generation to the next.
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Where did you get your green eyes, red hair or
tall height?
Gregor Mendel pioneered genetics
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Studied pea plant traits
A trait = a specific characteristic that varies
among individuals
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Color or height
By crossing peas of different traits Gregor Mendel
formed the laws of heredity
Image taken from www.biologycorner.com/bio4/notes/mendel.html
Genes & Dominance
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Hybrids – the offspring of crosses between
parents with different traits
Genes – a sequence of DNA that determines
a particular trait
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Alleles – one of a number of different forms of a
gene
Link to baby:
http://www.abpischools.org.uk/res/coResourceI
mport/modules/genome/fullscreenflash19f9.cfm?
flash=enflash/eyecolour.swf&title=Eye+colour&version=
6
Image taken from dj003.k12.sd.us/SCHOOL%20NOTES/chapter_03.htm
Early Ideas on Inheritance
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Gregor Mendel
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Concluded from his research that certain traits
pass from one generation to the next
Some alleles are dominant and others are
recessive
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Aka the principle of dominance
During reproduction alleles segregate into
separate gametes
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Aka the law of segregation
Image taken from www.softchalk.com/.../lesson/genetics/index.html
Image taken from www.biologycorner.com/bio4/notes/mendel.html
Gambling Heredity
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Probability – the likelihood that a particular
event will occur
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Toss a coin – the chance of a heads is 50%
Principles of probability can be used to predict
the outcomes of genetic crosses
Punnett Squares
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Punnett squares – used to predict and
compare the genetic variations that will result
from a cross
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Homozygous – TT or tt
Heterozygous – Tt
Phenotype – physical characteristics
Genotype – genetic makeup
Punnett Squares
Image taken from: http://www.scienceclarified.com/Ma-Mu/Mendelian-Laws-of-Inheritance.html
Do all traits segregate together?
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Gregor Mendel
performed a dihybrid
cross to test this
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Proved genes for
different traits can
segregate indep.
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Later known as the
law of independent
assortment
Accounts for much of
the genetic variation
observed in plants
and animals.
Image taken from www.biologycorner.com/bio4/notes/mendel.html
Summary of Mendel's Principles
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Characteristics are inherited from parent to
offspring through genes
When two or more forms of a trait exist (alleles)
some forms may be dominant and some recessive
In sexually reproducing organisms adults have 2
copies of each gene that are segregated when
gametes are formed
 Offspring receive one allele from each parent's
gamete
Alleles for different genes segregate independently
of one another
Beyond Dominant vs Recessive
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Some alleles are neither and many traits are
controlled by multiple alleles or genes
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Incomplete Dominance
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Codominance
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Both alleles contribute to the phenotype
Multiple Alleles
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No allele is dominant
Heterozygous phenotypes are “in between” as in pink
snapdragons when red is crossed with white
More than two alleles exist
Human genes for blood type
Polygenic Traits
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Gene interactions result in a wide range of
phenotypes as in skin tone
Blood Types
A case of multiple alleles
Blood Types
in Humans
A
B
O
A
AA (AA)
AB (AB)
AO (A)
B
AB (AB)
BB (B)
BO (B)
O
AO (A)
BO (B)
OO (O)
Human blood type is determined by 3 alleles.
Both A and B are co-dominant, while type O is recessive.