Download Chapter 3 Genetics Study Guide

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Chapter 5 Genetics Study Guide:
Textbook Page 162-181
1. Memorize and be able to communicate the meaning of all key genetics
vocabulary
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Genotype-The genetic makeup (Tt)
Phenotype- The physical appearance (tall)
Homozygous (purebred)- the same alleles (TT or tt)
Heterozygous- (hybrid)-mixed alleles (Tt)
Punnett Square- a chart showing all the possible combination of
alleles
Codominance- neither allele is dominant or recessive: Also results in
a third trait different from the parents ( think black rooster, white
rooster= black and white rooster)
Probability- The chances of an event occurring
Allele- the different forms of a gene
Genes- factors that control a trait
Trait- each different form of a characteristic: (hair color, eye color)
Heredity-The passing on of physical characteristics from parents to
offspring
Genetics- the study of heredity
Dominant- the trait that always shows up when this allele is present:
represented by a capital letter
Recessive- the allele that is masked when a dominant allele is present:
represented by a lower case letter
2. Describe Mendel’s experiment with pea plants. What was the outcome in
both fractions and percentages?
Mendel crossed a purebred Tall with a purebred short. In the first generation,
he got all tall and the short disappeared. In the second generation he got 3 tall
and one short so the short reappeared.
The outcome was 75% had tall stems and 25% had short stems
Or ¾ were tall and ¼ were short
3. What is the difference between a hybrid and a purebred?
 A hybrid is mixed dominant and recessive alleles such as Tt
 A purebred is the same alleles such as TT or tt
4. Draw a Punnett square that shows what the offspring of a purebred tall
pea plant and a hybrid tall pea plant would look like. What % will be
tall? What % will be short?
5. If you have a tall purebred plant and a short purebred plant, what are the
possible outcomes for your pea plant?
6. What are factors that control traits?
genes
7. What do the inside squares of the Punnett Square represent?
All the possible allele combinations
8. How are chromosomes related to heredity?
Chromosomes are made of many genes strung together. Genes are the factors
that control traits.
9. What is the chromosome theory of inheritance?
Genes are carried from parents to offspring on chromosomes
10. How many chromosomes does each sex cell contribute?
half
11. What is the genetic code?
The order of nitrogen bases along a gene
12. What is a mutation?
A mutation is ANY change in a gene or chromosome
13. What makes a mutation harmful to an organism?
If it reduces the chances for the organisms survival and reproduction.
Example- white (albino) kangaroo
14. Where are genes located in the cell?
chromosomes