Mendel and Heredity
SC.7.L.16.1 Understand and explain that every organism requires a set of instructions that specifies its traits, that this hereditary information.
Objective: I can describe what heredity is because I can identify traits and characteristics
What is heredity? .
Heredity is the passing of traits from parents to offspring.
Traits, such as eye color, result from the information stored in the genetic material
What did Gregor Mendel discover about heredity?
Gregor Mendel was an Austrian monk in the 1800s.
He did the first controlled experiments in heredity.
His research gave scientists a
basic understanding of Genetics the study of how traits are passed from parents to offspring
Mendel studied seven characteristics of pea plants
A characteristic is a feature that has different forms in a population.
The different forms of a characteristic are called traits.
The seven different characteristics Mendel studied were:
flower and pod position
Is flower color a trait or a characteristic?
How did Mendel perform his experiments?
1. He started with plants that were true-breeding plants that
always produce the same trait in their offspring
Ex/ Purple flowers that always has offspring with purple flowers
And white flowers that always have offspring with white flowers
He crossed a purple flowered plant with a white flowered plant
How did Mendel perform his experiments?
2. He took the pollen from one plant and put it on the other cross pollinated
Results: 3. The first generation plants all had purple flowers.
Conclusions: 4. Purple = dominant trait the one that masks
(covers up) the other White Recessive trait the one that seems to disappear
5. He crossed 2 of the first generation purple plants.
The second generation plants had about purple and white.
What did Gregor Mendel conclude about heredity?
After analysing his results, Mendel concluded that 2 factors control each inherited trait.
Some traits could only be observed if a plant had two of the same factors.
(like white flowers) A plant with two different factors would show the dominant factor but still
pass on both factors to its offspring.
Today scientists call the factors that control traits genes They call the different forms of the gene alleles. Ex: Gene for flower color has 2 alleles purple and white
We will go through the most common traits that people have
On your sheet, record if you have the mentioned trait or not
You may have to ask your neighbor for help
What is heredity?
What is dominant?
What is recessive?
What is an allele
A farmer crosses a true breeding tall pea plant with a true breeding short pea plant. All of the offspring are tall. Explain these results.
If the farmer crosses 2 of the new (1st gneration) tall pea plants what can he expect his new pea plants to look like
IFC : Write the question and the sentence of your answer choice for the IFC questions
Mendel was studying the trait of seed color in Pea plants. He crossed yellow seeds and green seeds and found all of the offspring were yellow. 1. What are the 2 alleles of this trait? 2. Which allele was dominant? Why? 3. Which was recessive? Why?
How are traits inherited?
Mendels ideas can be even further explained by our modern understanding of DNA
Genes are segments of DNA found in
chromosomes They give instructions for producing a
certain characteristic Alleles the different forms of a gene Each offspring gets one allele from
Dominant alleles - shown with CAPTITAL letter
recessive alleles shown with same lowercase letter.
How do we use symbols in Genetics?
Heterozygous - An organism with one dominant and one recessive allele for a gene is for that gene (sometimes called hybrid)
homozygous - An organism with two of the same alleles is for that gene. (can be either 2 recessive alleles or 2 dominant alleles Example: _________ is heterozygous ________ and ________ are homozygous
Purple flowers are dominant and white flowers are recessive
For flower color, if P is for purple, what would we use for white flowers?
What color is this flower?
How do genes determine traits?
The combination of alleles
that you inherited from your
Heterozygous or Homozygous
Ex: Pp or PP or pp
Ex: Purple or white
1 allele for Purple flowers and 1 allele for white
What does it mean when we say genotype determines phenotype?
Summary: The genes you inherit from your parents determine your traits
Your Genotype determines your phenotype
HW: Phenotype genotype ws