mendel’s principle of dominance or recessiveness traits found in humans
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Mendel’s Principle of Dominance or Recessiveness
Traits found in humans
Engage Map of X and Y Chromosomes
Explore 1 Fundamentally Genetics
You and your groups will be looking at each other to determine whether you are dominant or recessive for the following traits.
Tongue Rolling
Earlobes
Earbump Often called Darwin’s Ear Bump Dominant - Having a small bump on the
ear Recessive - Not having the bump
Widow’s Peak
Hitchhiker’s Thumb
Polydactyly
Syndactyly Feet
Syndactyly Hands
Severe Syndactyly
Syndactyly Surgery
Cleft Chin
Clockwise Hair Whorl
Autosomal Dominant and Recessive Huntington Disease – Dominant Disease Cystic Fibrosis – Recessive Disease
Sickle Cell Anemia
Tay-Sach’s
PKU
Explore 2 Bugs, Bugs, Bugs
Genes for traits are encoded and arranged linearly on structures called chromosomes found in the nuclei of most cells. When organisms reproduce, the resulting offspring should receive an equal number of chromosomes from the mother and the father.
In this activity you use the chromosomes and Bug Traits Key to determine the genotype and phenotype of the offspring.
Exploration 3 Wisconsin Fast Plant Genetics Lab
Explore 4 Punnett Squares
You will be able to predict the outcomes of crosses by completing this next activity.
Mendel & The Gene Idea
Explain
Mendel and Genetics Answer the following questions as we
explain the concepts surrounding basic genetic
It All Began with Mendel (FYI) Gregor Mendel was born in 1822. Called the “Father of Genetics” Late 1800 chromosomes and the process of
meiosis were unknown. Mendel’s work was considered obscure and
unimportant until 1900 Walter Sutton proposed the Chromosome
Theory and people began to listen to his ideas. Chromosome Theory – specific genes are
located on specific chromosomes
Three Conclusions to His Research1. Principle of Dominance and
RecessivenessOne allele in a pair may mask the effect of
the other
2. Principle of SegregationThe two alleles for a characteristic separate
during the formation of eggs and sperm
3. Principle of Independent AssortmentThe alleles for different characteristics are
distributed to reproductive cells independently.
Mendelian genetics Character
(heritable feature, i.e., fur color) Trait (variant for
a character, i.e., brown) True-bred
(all offspring of same variety) Hybridization
(crossing of 2 different true-breds) P generation (parents) F1 generation (first filial generation)
Genetic vocabulary……. Punnett square: Gene: point on a chromosome that
controls the trait Allele: an alternate form of a gene
A or a Homozygous: identical alleles for
a character Heterozygous: different alleles for
a gene Phenotype: physical traits Genotype: genetic makeup Testcross: breeding of a recessive
homozygote X dominate phenotype (but unknown genotype)
How can the Chances of an Offspring’s Traits be Determined?
BY USING A PUNNETT SQUARE Get out your Punnett Squares Problems In groups of two come to the board and
complete the given monohybrid problems.
Bb X BbPhenotypic Ratio
3:1Genotypic Ratio
1:2:1 B b
B
b
B B B b
b B b b
Exploration 4 What about two traits? Complete the second half of your Punnett
Square Problems
What about 2 Traits? BbTt x BbTt The Gametes contain one
of each of the alleles. (BT).
Each of the offspring contain four alleles exactly like the parents.(BbTt).
Notice the number of possible offspring has increased.
The phenotypic ratio is 9:3:3:1
BbTt x BbTtBT Bt bT bt
BT BBTT BBTt BbTT BbTt
Bt BBTt BBtt BbTt Bbtt
bT BbTT BbTt bbTT bbTt
bt BbTt Bbtt bbTt bbtt
Exceptions to Mendel’s Rule
Incomplete Dominance The phenotype of the
heterozygote is intermediate between those of the two homozygotes.
Ex) Snap Dragon Color
Red, Pink, White
Co-dominance Phenotype of both
homozygotes are produced in heterozygotes individuals.
Both alleles are expressed equally.
Ex)Roan Cattle White-feathered birds are both homozygotes for both B and W alleles
Multiple Alleles
Ex )Blood type Blood type A and B are co-dominant,
while O is recessive. Forms possible blood types of A, B, AB,
and O.
Blood Also Shows Codominance
Sex-Determination Chromosome pairs 1-22 are autosomes Chromosome pair 23 are sex chromosomes They determine the sex of an individual XX = female XY = male
Sex-Linked Inheritance Traits that are only found on the X
chromosome Colorblindness and Hemophilia are
examples of sex-linked traits. These genes are recessive and found only
on the X chromosome.
Polygenic Inheritance Inheritance pattern of a
trait that is controlled by two or more genes.
Gene may be on the same chromosome or on different chromosomes.
Ex) Skin color and Height
ELABORATION 1Exceptions to the Rule
Punnet Squares: Dihybrid, Sex-Linked, Multiple Alleles, Co-Dominance, Incomplete Dominance
Elaboration 2 Who’s the Parents?
Upon completion of this lab, you will: determine the ABO blood types of two sets of
parents and two newborn children examine the genetic relationships possible
between the parents and children match the “mixed up” children with their proper
parents.
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