Transcript Genetics Review

Genetics
Review
Biology Class
Vocabulary Review
• trait
-A physical characteristic.
• heredity
-The passing of traits from
parents to offspring.
• genetics
- The scientific study of
heredity.
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Question
Which of the following is an example
of a trait?
A. Bb
B. Talking loud
C. Brown eyes
D. Bleach blonde hair
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Alleles
• Genes are the factors that control
Traits.
• Alleles are the different forms of
Genes.
• Individual Alleles control the
inheritance of Traits.
• An offspring receives one allele
from each parent.
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Question
What is the term for factors that
control traits?
A. Genes
B. Purebreds
C. Recessives
D. Parents
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Question
Which term refers to physical
characteristics that are studied in
genetics?
A. Traits
B. Offspring
C. Generations
D. Hybrids
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DOMINANT and recessive
Alleles
• A dominant allele is one whose
trait always shows up in an
organism when the allele is
present.
- capital letter (AA, Aa)
• A recessive allele is covered up
when the dominant allele is
present.
- lower case letter (aa)
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Practice
• R is the dominant allele for a one
eyed monster.
• r is the recessive allele for a
monster with two eyes.
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Monster Genetics
• Rr
• How many eyes will our monster
have?????
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Monster Genetics
• RR
• How many eyes will our monster
have??
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Monster Genetics
• rr
• How many eyes will our monster
have??
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Question
What does the notation TT mean to
geneticists?
A. Two dominant alleles
B. Two recessive alleles
C. No dominant alleles
D. One dominant and on recessive
allele
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Codominance
• Some alleles are neither dominant
or recessive.
• Codominance is when alleles are
neither dominant or recessive,
both alleles are expressed in the
offspring.
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What will Happen?
• You have two flowers, a white and
a red, that are crossed.
• The flowers are codominant.
• What color will their offspring be.
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Phenotype
• Phenotype is an organisms
physical appearance or its visible
traits.
• Example: a pea plant stem height
can be short or tall.
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Genotype
• Genotype is an organisms genetic
makeup, or allele combination.
• Example: TT, Tt, tt
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Describing genotypes
• Homozygous (or Purebred) is
used to describe an organism that
has two identical alleles for a trait.
• Example: TT and tt
• Heterozygous (or Hybrid) is
used to describe an organism with
two different alleles.
-Example: Tt
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Question
Pick the answer that best describes
“Aa”.
A. Homozygous
B. heterozygous
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Punnett Squares
• A punnett square is a chart that
shows all possible combinations of
alleles that can result from a
genetic cross.
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Punnett Example
• Yellow is dominant over Green.
• What is the probability that the
offspring will be yellow?
100%
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Punnett Problems
• In purple people eaters, one-horn
is dominant and no horns is
recessive.
• Draw a Punnet Square showing
the cross of a purple people eater
that is hybrid for horns, with a
purple people eater that does not
have horns.
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Answer
• Hybrids have two different alleles
for one trait.
• Hh is the hybrid in the example.
• No horns would have to be hh
because it is a recessive allele.
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Punnett Problems
• In Bears the dominant allele for
brown fur is R, black fur is
recessive.
• The female bear is Rr and the
male bear is rr.
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Question
• What are the four possible
phenotypes for the cubs?
A. RR, Rr
B. Rr, rr
C. 2 brown, 2 black
D. 3 brown, 1 black
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Question
• What is the probability that the cub
will have black fur?
A. 50%
B. 25%
C. 75%
D. 100%
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Question
What do you call one set of
instructions for an inherited trait?
a. alleles
b. phenotype
c. albinism
d. genes
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Question
Two forms of a gene, one from each
parent, are called
a. alleles.
b. phenotypes.
c. albinism.
d. genes.
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Question
What is a plant that has two
dominant genes or two recessive
genes called?
a. organism
b. genotype
c. homozygous
d. heterozygous
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Question
The allele for freckles, F, is dominant
among humans. If a woman with
freckles (FF) and a man without
freckles (ff) have children, what are the
possible genotypes of the children?
A. Ff
B. FF, Ff, ff
C. Ff, ff
D. ff
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Question
Part of a mouse’s tail is cut off as the mouse
escapes from a cat. The mouse later
reproduces. Which explanation best
describes why the mouse’s offspring have
long tails?
A. Long tails are a dominant trait.
B. Short tails do not appear in the first
generation or the second generation.
C. Cutting the tail of the mouse changed
its genes.
D. Cutting the tail of the mouse did not
change its genes.
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Question
What is the genotype of the offspring
represented in the upper left-hand box of
the Punnett square?
A
RR
B
Rr
C
rr
D
rrr
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Question
What is the genotype of the offspring
represented in the upper left-hand box of
the Punnett square?
A
RR
B
Rr
C
rr
D
rrr
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Question
What is the ratio of Rr (purple-flowered
plants) to rr (white-flowered plants) in the
offspring?
A
1:3
B
2:2
C
3:1
D
4:0
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Question
Green seed color (G) is dominant to
yellow seed color (g). If two
heterozygous parents are crossed,
what will be the resulting genotypes
of the offspring?
A. GG, Gg, gg
B. Gg, gg
C. GG, Gg
D. gg, GG
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