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Chapter 5 Vocabulary
1. Fraternal Twins 10.Gregor Mendel
Dominance
2. Identical Twins 11.Dominant
22.Blood type
3. Conjoined 23.Co‐dominance
12.Recessive
Twins
13.Homozygous 24.Polygenic 4. Genetics
Inheritance
14.Heterozygous
5. Traits
25.X‐Linked traits
15.Phenotype
6. Genes
26.Sickle cell 16.Genotype
anemia
7. Down 17.Punnett Square
27.Cystic fibrosis
Syndrome (Trisomy 21) 18.Monohybrid 28.Sex Cross
chromosomes
8. Turner’s 19.Dihybrid
Cross
Syndrome
29.Pedigrees
20.Allele
9. Klinefelter’s
30.Carriers
21.Incomplete Syndrome
Chapter 5 Heredity
Some Interesting Questions:
What do you know about twins?
Fraternal twins happen when two eggs develop
in the womb. Identical twins happen when one egg splits during early fetal development. The cells are genetically similar.
If the egg does not split all the way, it is possible
to have conjoined twins that are identical. Sometimes two independent eggs will fuse within the womb and the result will be conjoined twins that are not identical. 5.1 What is Genetics?
A. What have you inherited? Eye color, nose shape, skin color, hair color, and size are just a few characteristics that you have inherited
from your parents.
B. Traits are inherited through genes. Genes are portions of DNA that code for a trait, found in chromosomes.
Everyone has one
set of chromosomes
from Mom and one
set from Dad.
Trisomy 21
Down Syndrome
Xo = Turners
XXY = Klinefelter’s syndrome
C. The first scientist to study how traits are inherited was Gregor Mendel. He is considered to be the “father” of genetics.
In 1856, he was able to predict flower color in pea plants. Definitions
• Phenotype: physical
expression of a trait
• Genotype: set of alleles
(genes)
Definitions
• Dominant: trait that is always
expressed when present
• Recessive: trait that can be
hidden when present (unless
there are no dominant traits)
Definitions
• Heterozygous: two different
alleles (Rr)
• Homozygous: two of the same
alleles (RR or rr)
What kinds of traits do I have? Fill in this chart:
Trait
Tongue Rolling
Ear Lobes
Hairline
Freckles
Chin
Little Finger
Thumb
Dominant
Recessive
What kinds of traits do I have? Fill in this chart:
Trait
Dominant
Recessive
Thumb
Hand‐
Clasping
# of Fingers
2nd
Knuckles
Hair
Eyelashes
Eye Color
Tongue Rolling
(R)
Tongue Clover
The ability to roll your
tongue is a dominant trait.
Ear Lobes (E)
Free ear
lobes are
dominant
Attached ear
lobes are
recessive
Widow’s Peak (W)
A Widow’s
Peak is a
dominant
trait.
Freckles (F)
Freckles (even a few)
are dominant.
Chin Cleft (C)
A cleft chin is
dominant.
Shape of little
finger (F)
A bent little finger is
dominant.
Hitchhiker’s Thumb (t)
A hitchhiker's thumb
is recessive.
Hand-Clasping (H)
Left Thumb over Right
is dominant.
6
Polydactyl – More than
5 fingers is dominant
5
nd
2
Hair on
Knuckles (H)
…is a dominant trait.
Hair (H)
Curly hair is dominant;
straight is recessive
Eyelashes (E)
Long eyelashes are
dominant; short are
recessive
Eyes (B)
Blue eyes
are
recessive.
Light blue
0 dominant alleles
Blue
1 dominant allele
Blue-green
2 dominant alleles
hazel
3 dominant alleles
Light brown
4 dominant alleles
Brown
5 dominant alleles
Dark brown / black
6 dominant alleles
Lesson 2
Punnett Squares
Chapter 5
Mendel’s Conclusions:
1. An individual
has two
copies of each
gene (one from
each parent)
2. There are alternative
versions of genes called
alleles
3. When two alleles occur
together, one might be
expressed (DOMINANT)
and the other “hidden”
(RECESSIVE)
4. Alleles separate from one
another when gametes (sex
cells) are formed
Mendel’s findings in Modern
Terms:
Dominant Allele = Capital
Letter (Purple flower = P)
Recessive Allele = lowercase
letter (white flower = p)
Homozygous: individual has two
of the same alleles for a gene (PP,
pp)
Heterozygous: individual has two
different alleles for a gene (Pp)
Question: What flower color will a
heterozygous pea plant have?
Genotype: set of alleles that an
individual has (AA, Aa, or aa)
Phenotype: physical appearance
of a trait (blue or black)
Punnett Squares
X
X
X
XX
XX
Y
XY
XY
2/4 = ½ = 50% = .50 = 1:1
male or female
F
f
f
Ff
ff
f
Ff
ff
heterozygous
Genotypes: 50% Heterozygous (Ff),
No freckles 50% Homozygous recessive (ff) or
1:1 Ff:ff
Phenotypes: 50% freckles, 50% no
freckles or 1:1 freckles:no freckles
Red is controlled by the gene called: H
White is controlled by the gene called: h
H is dominant
h is recessive H H
H h
They look the same. They have the same Physical
Appearance. The genes, however, are different.
H H
H h
Homozygous
dominant
Heterozygous
genotype: HH
phenotype: red
genotype: Hh
phenotype: red
h h
homozygous recessive
(hh)
genotype: hh
phenotype: white
This flower has no gene for
the red color. Parents, are they purebred?
First Generation
Second Generation
Yes
Parents, are they purebred?
H H
H H
First Generation
H H
H H
H H
H H
H H
H H
Second Generation
H H
H H
H H
H H
Punnett square
H
H
H
HH
HH
h
Hh
Hh
Punnett square
H
h
H
HH
Hh
h
Hh
hh
Punnett square
H
h
h
Hh
hh
h
Hh
hh
CC Cc
cc Cc?
CC?
Cleft Chin: C (dominant)
No Cleft Chin: c (recessive)
What are the possible genotypes?
CC
Cc
What if we know that her mom did not have a cleft chin?
Then we could rule out which
genotype?
Why? Her mom has to be cc
Her dad could be either Cc or CC
cc X CC = Cc cc X Cc = Cc or cc Cc
cc
So what if these babies grow up
and have kids together? How many of their offspring will have cleft chins?
Punnett square
c
c
C
Cc
Cc
c
cc
cc
50%