Vocabulary Wordle
Life Science
Chapter 4-1 Mendel's Work Key Concepts: > What were the results of Mendel's Experiments, or crosses? > What controls the inheritance of traits in organisms?
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Vocabulary Defined Word genetics
Definition
Example
The scientific study of heredity
Observable Traits David has dark hair, just like his parents. Leticia’s hair is dark, too, just like her father. Her mother’s hair, however, is blond. It is easy to understand why David’s hair is dark. Both of his parents have dark hair. How about Leticia? Why is her hair dark? Why not blonde?
A characteristic that an organism can pass on to its offspring through its genes The passing of traits from parents to offspring. The set of information that controls a trait; a segment of DNA on a chromosome that codes for a specific trait.
Gregor Mendel, who is known as the father of genetics, first answered these questions back in the mid 1800’s. He discovered the Law of Dominance while he worked with pea plants. The Law of Dominance states:
alleles
The different forms of a gene.
The stronger gene shows up. The gene that shows
recessive allele
An allele that is masked when a dominant allele is present.
up is called the dominant gene. The “hidden”
dominant allele
An allele whose trait always shows up in the organism when the allele is present.
fertilization
The joining of a sperm and egg.
hybrid
An organism that has two different alleles for a trait. The offspring of many generations that have the same traits.
trait heredity gene
purebred
1. An organism receives two genes for each trait, one from each parent. 2. One of the genes may be stronger than the other.
gene is called the recessive gene for that trait.
If an offspring (child in humans – kitten in cats and puppy in dogs) receives two of the same genes (either two recessive or two dominant), the offspring will inherit that trait. However, if an organism has one dominant gene and one recessive gene for a certain trait, the organism will have the trait of the dominant gene. The recessive trait will be “hidden.” Let’s look at Leticia again. Leticia has genes for dark hair and for light hair. The gene for dark hair is dominant over the gene for light hair. That is why Leticia’s hair is dark.
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Observable Traits
Observable Traits
Copy the chart in your Science Lab Notebook Circle whether you have the dominant or recessive trait
Look at the pictures below to determine what each characteristic looks like.
1. Left thumb over right thumb
Right thumb over left thumb
Traits
Dominant
Recessive
1. Thumb position
Left over right
Right over left
2. Cheeks
Dimpled
Nondimpled
3. Tongue
Roller
NonRoller
4. Widows Peak
Present
Absent
5. Earlobes
Free
Attached
# withdominant
# with recessive
2. Dimples
No Dimples
3. Tongue Roller
Non Roller
4. Unattachedearlobes
Attached earlobes
5. Straight hair line
Widow’s peak
6. Hair Color Dark
Light
7. Eyesight Normal
Glasses
Questions:
1. Which trait had the highest number of dominant genes showing up? ____________ 2. Which trait had the highest number of recessive genes showing up? ____________ 5. Are recessive traits always hidden? __________ Why not? __________________________________
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Discovery Activity
Observable Traits Create a graph with the results for the dominant traits in your Science Lab Notebook
Label the y axis
Give it a title
# # # # #
What does the Father Look Like?
Observe the colors of the kitten in the photo. Record the kitten’s coat colors and pattern. Include as many details as you can.
# #
Observe the mother cat in the photo.
xxxxxxxxx
xxxxxxxxx
xxxxxxxxx
xxxxxxxxx
xxxxxxxxx
xxxxxxxxx
xxxxxxxxx
Record her coat color and pattern.
Label the x axis
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Mendel's Work What are some physical similarities and differences among your family members?
Think It Over Inferring Based on your observations, describe what you think the kitten’s father might look like. Identify the evidence on which you based your inference.
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Mendel's Experiment Every living thing has traits inherited from its parents. Until the work of Mendel, people did not understand how traits were passed from parents to offspring.
Have you ever wondered why some family members look very similar while others look very different?
Read page 110 Jan 207:24 AM
Mendel's Experiment
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Mendel's Experiment
Read page 111-112 Jan 207:24 AM
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Mendel's Experiment What is a purebred organism? The offspring of many generations that have the same trait.
Dominant and Recessive Alleles Remember, the trait of shortness did not disappear in the F1 generation of pea plants.
What did Mendel find when he crossed purebred tall plants with purebred short plants? The offspring were all tall.
When Mendel crossed the offspring, or F1 generation, with one another, was the trait for the shortness lost? Explain. No, some of the offspring were tall and some were short.
No, they were not all identical to the parent plants
Read page 113-114 Genes and Alleles
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Dominant and Recessive Alleles
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Dominant and Recessive Alleles PREDICTING
Figure 3 Pea Plant Crosses
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In fruit flies, long wings are dominant over short wings. A scientist crossed a purebred long-winged male fruit fly with a purebred short-winged female. Predict the wing length of the F1 offspring. If the scientist crossed a hybring male F1 fruit fly with a hybrid F1 female, what would their offspring look like? F1 Hyprid Purebred Long Winged Purebred Short Winged Female fruit fly
Look at the seed shape. What does it mean for this trait to be dominant?
Male fruit fly
Male fruit fly
W w w
W
F1 Hyprid Female fruit fly
Are the plants in the F1 generation purebred plants?
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Dominant and Recessive Alleles
Dominant and Recessive Alleles What are the factors that control the inheritance of trait? Genes
What are alleles? The different forms of a gene.
What is a dominant allele? An allele whose trait always shows up in the organism when it is present.
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What kind of allele can be hidden when a dominant allele is present? A recessive allele. What kind of alleles does a hybrid organism have? Both a dominant and a recessive allele. Why were purebred pea plants important for Mendel's experiments? They have two identical alleles for a gene, so in a cross, each parent contributes one allele, making the inheritance pattern easier to detect
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Dominant and Recessive Alleles In your science notebook choose a pea trait and use the symbols for alleles to diagram the crosses that Mendel made.
Phenotype
physical appearance, visible traits
Genotypegenetic make up; allele combinations
ex Bb Tt tt
Then write a JS Paragraph comparing and contrasting dominant and recessive traits. dominant traits
recessive traits.
homozygous an organism with 2 identicle alleles for a trait
example: BB, bb tt
heterozygous. an organism that has 2 different alleles for a trait.
example: Bb, Bb Tt
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