Download Chapter 10 Test (Lessons 1,2,3) Study Guide

Study Guide-7th Grade-Lessons 10.1, 10.2, 10.3
A gene is a “factor” that controls a trait.
An allele is a different form of a gene.
A purebred organism is an offspring that is the result of many generations that have the same form of a trait. An
organism that has the same alleles passed through many generations.
A hybridorganism has two different alleles for a trait.
Adominant allele is one whose trait always shows up in the organism; “stronger”
A recessive allele is one that is hidden or masked; “weaker”
Genetics is the study of heredity.
Heredity is the passing of genetic traits from parent to offspring.
A chart that describes all the ways alleles can combine in a genetic cross is called a Punnett Square.
An organism’s phenotype refers to its physical appearance or visible traits.
An organism’s genotype refers to its genetic make-up or the alleles it has.
What is an organism called for having two identical alleles for a trait? Homozygous (HH or hh)
What is an organism called for having two different alleles for a trait?Heterozygous (Hh)
What is fertilization? The union of a sperm cell and an egg cell.
What is probability? The likelihood that an event will happen.
Inheritance Patterns
Multiple alleles is when three or more alleles determine the trait.
Incomplete dominance is where one allele is only partially dominant; the heterozygote (hybrid) will have a blended
appearance
Polygenic inheritance is when more than one gene affects the trait.
Codominance is when both alleles of a gene are expressed equally; both alleles will be present in the heterozygote.
*Environmental factors can influence the way genes are expressed.
*Most traits are the result of complex inheritance patterns.
Examples of inherited traits include: the ability to cough, natural skin color, the ability to run
Environmental factors influence things such as: dyed hair color
Both genetics and environment affect: the ability to sing well, being able to play a sport well
SHORT ANSWER-Practice!!!
1.In all of Mendel’s genetic crosses with pea plants, what proportion did he find the “lost” form of the trait
reappear in the F2 generation? Choices: (1/4, 1/2, 3/4, all) ________________________________
2.What is the probability of producing a tall pea plant from a genetic cross between two hybrid tall pea
plants? (perform the Punnett Square to solve)_______________________________
3.A purebred chicken with white feathers is crossed with a purebred chicken that has black feathers. Each of
their offspring has both black and white feathers. What inheritance pattern can explain the offspring’s
traits?_________________________________
4.If a homozygous dominant black guinea pig is crossed with a homozygous recessive white guinea pig, what
is the probability that an offspring will have black fur? (perform the Punnett Square to solve)
_________________________________
5a.A blue frog is crossed with a yellow frog. All the offspring are green. What inheritance pattern can
explain the blended appearance of the hybrid offspring?_______________________________________
5b. If two green frogs are crossed, what is the probability their offspring will be blue? green? yellow?
(perform a Punnett Square to solve) blue:_________green:_________yellow:___________
Use the Punnett Squares above to answer the questions below.
6.Which trait—white flowers or purple flowers—is controlled by a dominant allele? ________________
7.In which generation (F1 or F2) are the parents hybrids? ______________________________
8.In the F1 generation, what is the genotype of the offspring?_________________________
9.In the F2 generation, what percent of the offspring have purple flowers? ______________________
SHORT ANSWER (Answers)
1.one-fourth
2.75%
T
T
T
t
TT
Tt
Tt
(TT and Tt will be tall; tt will be short)
tt
3codominance
2)100%
B
B
b
Bb
Bb
b
Bb
Bb
5aincomplete dominance_________
5b blue:__25%___green:___50%____yellow:____25%___
6. white
Y
B
Y
YY
YB
B
YB
BB
7. F2
(YY=yellow, YB=green, BB=blue)
8.heterozygous (hybrid) Ww
9.25%