Download IT`S IN THE GENES

Student Resource Sheet COT - 5
IT’S IN THE GENES!
To gather more information regarding the variation among dogs, you decide to
interview a local veterinarian. During your interview, you took the following notes:
YOU: How’s it possible to have so much variation within a litter of
puppies?
VET: What do you mean by “variation”?
YOU: Well, sometimes the puppies look just like the mom, sometimes they look like the
dad, sometimes they look like a combination, and sometimes they look like
neither.
VET: Oh, I see what you mean. Well, it all has to do with genes.
YOU: You mean like the designer jeans I wear?
VET: No, no, genes are factors that are passed from parents to offspring. Genes control
the physical appearance of all living things.
YOU: Interesting. What else can you tell me about these “genes”?
VET: Do you have six months?
YOU: Huh? Six months? For what?
VET: Genetics is a large and sometimes complicated topic. I’ll email you an
investigation I did when I was your age that helped me figure out the basics of
genetics. Now get outta here kid, you’ve already asked too many questions.
YOU: HUH?!?!?! What do you mean I ask too many questions? By the way, do you
know what time it is?
You leave the office and head home to read the email the veterinarian promised you.
Objective
When you have completed this investigation, you should be able to
1. describe how specialized cells within male and female parents combine in order to explain
how sexual reproduction allows for genetic variation.
Activity A: Modeling the Patterns of Inheritance
When you arrive home, you immediately check your email and see the following message in
your inbox.
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Student Resource Sheet COT - 5
1. Reread the procedures and highlight the action words.
2. Explain what the beans in the different bags represent.
____________________________________________________________________________
____________________________________________________________________________
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3. Complete the investigation.
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Student Resource Sheet COT - 5
CHART 1
POSSIBLE GENE PAIRS IN OFFSPRING
FEMALE PARENT (XX)
RED
WHITE
TRIAL
BEANS (R) BEANS (r)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
MALE PARENT (XY)
RED
WHITE
BEANS (R) BEANS (r)
GENE
PAIRS
COLOR OF
OFFSPRING
4. Complete Chart 2, “Gene Pair Totals,” by determining the total number of each gene
combination.
CHART 2
GENE PAIR TOTALS
GENE PAIR
RR
TOTAL
Rr
rr
5.
Determine if all of the offspring will look the same. Support your response using
information from the investigation.
_________________________________________________________________________
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Student Resource Sheet COT - 5
Activity B: Dominant vs. Recessive Traits
6.
Read the paragraph about dominant and recessive traits in organisms.
Individual genes control the inheritance of traits. Some traits are dominant while other traits
are recessive. A dominant trait is one that always shows up in the organism when it is
present. Dominant traits are represented by a capital letter. A recessive trait, on the other
hand, is masked or covered up whenever the dominant trait is present. The only way for a
recessive trait to be expressed is if a dominant trait is not present. A recessive trait is
represented by a lower-case letter.
7.
Reread the paragraph and identify the dominant and the recessive traits for the investigation.
Dominant trait: ____________________________
Recessive trait: ____________________________
8.
Review the gene combinations in Chart 1. Use what you know about dominant and
recessive traits to determine the color of each offspring from the investigation. Record the
color for each gene pair in Chart 1.
Activity C: The Cell and Inheritance
You found that the investigation the veterinarian sent to you was helpful in
understanding why there are different traits in the puppies. However, you are still
unclear about how the puppies actually receive these traits from the parents. As a result,
you decide to do further research.
9.
Read pages 96 – 97 in Prentice Hall: Science Explorer, Cells and Heredity.
10. Identify the relationship between chromosomes and genes.
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
11. Complete the graphic organizer, “Chromosome Theory,” as you read.
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Student Resource Sheet COT - 5
CHROMOSOME THEORY
Number of
chromosomes
in female
grasshopper’s
body cells =
__________
Number of
chromosomes
in female
grasshopper’s
sex cells =
__________
FERTILIZATION
Number of
chromosomes
in male
grasshopper’s
body cells =
__________
Number of
chromosomes
in offspring’s
body cells =
__________
Number of
chromosomes
in male
grasshopper’s
sex cells =
__________
12. State the reason why the number of body cells in the offspring is the same as the number of
body cells in each parent. Use evidence from the text to support your response.
_________________________________________________________________________
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13. Explain how the traits of an offspring from sexual reproduction are a combination of both
parents. Your response must include the following terms:
 chromosomes
 genes
 traits
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________________________________________________________________________
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________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
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Student Resource Sheet COT - 5
Analysis
1.
Brown eyes in dogs are dominant to any other eye color. Suppose a male boxer with hazel
eyes was bred with a female boxer with brown eyes. Determine which trait for eye color
would be the most frequent among the offspring. Use evidence from the investigation to
support your response.
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
2.
Explain how sexual reproduction allows for variation within organisms. Provide an
example to support your response.
________________________________________________________________________
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TAIL TALLY: The wolf and domestic dog reproduce through sexual
reproduction. Would you expect the offspring of gray wolves to look
exactly like their parents or would the offspring have slight variations?
Justify your response with evidence from the investigation.
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