Embed Size (px)
Citation preview
Mendel’s Principle of Dominance or Recessiveness
Traits found in humans
Modified by Mrs. Snyder
January 2015
What is the relationship between DNA and your physical appearance?
Take a moment to think about what you know about DNA, chromosomes, and ribosomes. Write down several ideas.
Now, look at the image to the right.
What are genes? See page 111
What are genes?
If genes control traits, then we need to find out how they do this. Two alleles exist for each gene (because
chromosomes are paired.) (page 111) For now we will keep things simple. The presence or absence of an allele impacts
an organism’s appearance. The terms dominant, recessive,
homozygous, and heterozygous are important for you to understand.
Terms defined Dominant – page 109 Recessive – page 109 Homozygous vs
heterozygous How are alleles
represented? Probability: pages
111- 113
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.
More terms Genotype phenotype
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
Cleft Chin
Clockwise Hair Whorl
Here is the link to the lab we are going to do Obtain a lap top when directed. Create an excel chart It should have 8 columns Label as directed
Period 3 Lab: Partners – randomly generated John, Rebecca Laura, Ilana Tae, Jessie Alex, Gino Kylie, Maria
Grace, Justin Andrew, Robert Nia, Gianna DJ, Cooper
You are a team of scientists. You are studying the random distribution of traits (this occurs during meiosis) and will use your traits as an example. One person is the “mother” and one is the father.
Period 7 Partners – randomly generated
You are a team of scientists. You are studying the random distribution of traits (this occurs during meiosis) and will use your traits as an example. One person is the “mother” and one is the father.
Period 8 Partners – randomly generated
You are a team of scientists. You are studying the random distribution of traits (this occurs during meiosis) and will use your traits as an example. One person is the “mother” and one is the father.
Explore 2 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.
