Mendel’s Principle of Dominance or Recessiveness

1
Mendels Principle of Dominance or
Recessiveness

• Traits found in humans

2
Engage

• Map of X and Y Chromosomes

3
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.

4
Tongue Rolling
5
Earlobes
6
Earbump

• Often called Darwins Ear Bump
• Dominant - Having a small bump on the ear
• Recessive - Not having the bump

7
Widows Peak
8
Hitchhikers Thumb
9
Polydactyly
10
Syndactyly Feet
11
Syndactyly Hands
12
Severe Syndactyly
13
Syndactyly Surgery
14
Cleft Chin
15
Clockwise Hair Whorl
16
Autosomal Dominant and Recessive

• Huntington Disease Dominant Disease
• Cystic Fibrosis Recessive Disease
• Sickle Cell Anemia
• Tay-Sachs
• PKU

17
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.

18
Exploration 3

• Wisconsin Fast Plant Genetics Lab

19
Explore 4

• Punnett Squares
• You will be able to predict the outcomes of
  crosses by completing this next activity.

20
Explain

• Mendel The Gene Idea

21
Mendel and Genetics

• Answer the following questions as we explain the
  concepts surrounding basic genetic

22
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.
• Mendels 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

23
Three Conclusions to His Research

• Principle of Dominance and Recessiveness
• One allele in a pair may mask the effect of the
  other
• Principle of Segregation
• The two alleles for a characteristic separate
  during the formation of eggs and sperm
• Principle of Independent Assortment
• The alleles for different characteristics are
  distributed to reproductive cells independently.

24
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)

25
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)

26
How can the Chances of an Offsprings 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.

27
Bb X BbPhenotypic Ratio31Genotypic
Ratio121
B
b
B
B
B
B
b
b
b
B
b
b
28
Exploration 4

• What about two traits?
• Complete the second half of your Punnett Square
  Problems

29
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 9331

30
BbTt x BbTt
31
Exceptions to Mendels Rule
32
Incomplete Dominance

• The phenotype of the heterozygote is intermediate
  between those of the two homozygotes.
• Ex) Snap Dragon Color
• Red, Pink, White

33
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

34
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.

35
Blood Also Shows Codominance
36
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

37
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.

38
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

39
ELABORATION 1Exceptions to the Rule

• Punnet Squares Dihybrid, Sex-Linked, Multiple
  Alleles, Co-Dominance, Incomplete Dominance

40
Elaboration 2

• Whos 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.