Genetics

1
Genetics
2
Heredity

• Inheritance of traits

Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall.
3
Genetics

• Gregor Mendel
• Suggested that paired factors, or genes, carry
  inherited traits.
• Predicted how traits were inherited by studying
  pea plants

Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall.
4
Simple Dominant Traits

• Traits that are controlled by one pair of genes
• One dominant allele is all that the organism
  needs to show the dominant trait

Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall.
5
Recessive attached ear lobes
Dominant Free Ear Lobes
Hitch hikers thumb Dominant
Tongue Roll Dominant trait
Regular thumb Recessive
6
Section 10.1 Summary pages 253-262
Seed shape
Flower color
Seed color
Flower position
Pod color
Pod shape
Plant height
Dominant trait
axial (side)
purple
round
yellow
green
tall
inflated
Recessive trait
terminal (tips)
green
white
yellow
short
wrinkled
constricted
Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall.
7
Alleles

• Different forms of a gene type
• Organisms have two genes (alleles) for each
  trait.
• One gene (allele) from female gamete (egg).
• One gene (allele) from male gamete (sperm).

Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall.
8
Dominant gene (allele)

• Stronger of two genes
• Represented with capital letters
• Written first
• Example T for tall plant height

Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall.
9
Recessive gene (allele)

• Weaker of two genes
• Can be hidden by dominant genes.
• Represented with lower case letters
• Example t for short plant height

Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall.
10
Pure (Homozygous)

• Two of the same genes (alleles) for a trait
• Example TT (homozygous dominant) or tt
  (homozygous recessive)

Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall.
11
Hybrid (Heterozygous)

• Two different alleles for a trait
• Example Tt

Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall.
12
Genotype

• Combination of alleles or genes for a certain
  trait
• Example Tt, TT, tt

Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall.
13
Phenotype

• Visible traits (how it looks)
• Determined by looking at organism
• Example tall, short

Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall.
14
Genotype or Phenotype?

• Tt
• Round
• Black
• BB
• Smooth
• rr
• Tall

Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall.
15
In pea plants, green pods are completely dominant
over yellow.

• What are the genotypes?
• Homozygous yellow
• Heterozygous green
• Pure dominant
• Hybrid

gg
Gg
GG
Gg
Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall.
16
In pea plants, green pods are completely dominant
over yellow.
gg

• Pure yellow
• Homozygous recessive
• Pure green
• Heterozygous
• Yellow

gg
GG
Gg
gg
Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall.
17
In guinea pigs, short hair is dominant over long
hair

• What letter should be used for the gene for hair
  length?
• What hair length will be represented by a capital
  S?
• What hair length will be represented by a lower
  case s?

Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall.
18
What phenotypes would result from the following
genotypes?

• SS
• ss
• Ss

Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall.
19
What are the phenotypes of the parent plants?
If both parents are pure, what are their
genotypes?
Short plant
Tall plant
Which gene or allele can each parent pass on to
the offspring?
t
t
T
T
t
T
What is the phenotype of the offspring?
What is the genotype of the offspring?
All tall plants
t
T
20
In pea plants, round pea pod texture is dominant
over wrinkled texture. What is the genotype of
the following?

• homozygous round
• heterozygous
• wrinkled
• pure dominant
• hybrid round

Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall.
21
In pea plants, round pea pod texture is dominant
over wrinkled texture. What is the genotype of
the following?

• pure recessive
• heterozygous round
• pure wrinkled
• hybrid
• pure round

Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall.
22
Punnett Squares

• Punnett squares used to predict and compare the
  genetic differences that will result from a cross.

Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall.
23
Section 10.1 Summary pages 253-262
Monohybrid crosses
Heterozygous tall parent
T
t
T
t
T
TT
Tt
Tt
tt
t
T
t
Heterozygous tall parent
Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall.
24
Generations of Inheritance
Start by crossing homozygous parents
tt
TT
P1
Short pea plant
Tall pea plant
Results in heterozygous offspring
Tt
F1
Crossing heterozygous offspring from F1
generation results in three tall and 1 short
All tall pea plants
TT
Tt
Tt
tt
F2
3 tall 1 short
25
Incomplete dominance

• Alleles BLEND (mix)
• Neither gene is dominant
• A third or new phenotype can be seen
• Think about colors of paint ?

Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall.
26
Red
X
White
PINK

• If a red impatient is crossed with a white
  impatient, the resulting flowers are pink.
• Red and white blend like paint colors to produce
  pink (new phenotype).

Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall.
27
Incomplete Dominance
R
R


RW
RW
W
RW
RW
W
www.nerdscience.com
11-3
28
Codominance

• Both alleles are dominant
• Both alleles are seen (expressed) TOGETHER
• There is NO blending

Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall.
29
Codominance Both alleles or genes are expressed
White
Red
X
Red White
Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall.
30

• Red cow crossed with white cow results in roan
  cattle. Roan cattle have both red and white
  hairs.

Codominance
31
Codominance

• Example
• White chicken x black chicken black and white
  checkered chicken

32
Incomplete or Codominance?

• A white cow and a red cow produce a roan cow, one
  that has both white and red hairs.
• A red flower and a white flower produce pink
  flowers.
• A black cat and a tan cat produce tabby cats,
  cats where black and tan fur is seen together.

33
Incomplete or Codominance?

• A blue blahblah bird and a white blahblah bird
  produce offspring that are silver.
• A certain species of mouse with black fur is
  crossed with a mouse with white fur and all of
  the offspring have grey fur.
• A woman with blood type A and a man with blood
  type B have a child with blood type AB.

34
Blood Types (codominant)
Phenotype (Blood type) Genotype (Alleles or genes for blood type)
A IAIA, IAi
B IBIB, IBi
AB IAIB
O ii

• Blood type is codominant
• 4 different blood types

35
Charles Drew

• Charles Drew impacted blood donation and blood
  banks

Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall.
36

• Three Basic Principles of Genetics

37
The Principle of Dominance

• One gene for a trait may hide the other gene and
  keep it from being seen (expressed) in the
  organism

Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall.
38
Section 1 Check
When Mendel crossed a tall pea plant with a short
pea plant, all the offspring plants were tall.
In such crosses when only one trait was
observed, Mendel called the observed trait
dominant.
Tall plant
t
t
T
T
t
T
F1
All tall plants
t
T
Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall.
39
The Principle of Segregation

• The two genes for a trait separate, or segregate,
  during the formation of gametes (meiosis).
• This happens when pairs of chromosomes separate
  during meiosis

Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall.
40
The Principle of Independent Assortment

• Genes for different traits separate independently
  during the formation of gametes.

Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall.
41
Sex Chromosomes

• X and Y chromosomes
• Determine the sex of the offspring
• Females have two large XX chromosomes
• Males have an X and a smaller Y chromosome (XY).

Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall. Miller, K.
R., Levine, J. S. (2005). Chapter 14 The Human
Genome.Prentice Hall biology (North Carolina ed.,
pp. 340- 365). Upper Saddle River, N.J. Prentice
Hall.
42
Sex Chromosomes

• All other chromosomes are autosomes.
• Human sperm contain 22 autosomes and an X or Y
  chromosome
• Human eggs contain 22 autosomes and an X
  chromosome

Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall. Miller, K.
R., Levine, J. S. (2005). Chapter 14 The Human
Genome.Prentice Hall biology (North Carolina ed.,
pp. 340- 365). Upper Saddle River, N.J. Prentice
Hall.
43
Sex-linked Traits

• Most are carried on the X chromosome
• Also called X-linked traits
• Hemophilia and color blindness are recessive
  sex-linked traits carried on the X-chromosome
• Males show recessive traits more than females

Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall. Miller, K.
R., Levine, J. S. (2005). Chapter 14 The Human
Genome.Prentice Hall biology (North Carolina ed.,
pp. 340- 365). Upper Saddle River, N.J. Prentice
Hall.
44
Sex-linked Traits

• Males get only one allele for a sex-linked trait
  carried on the X chromosome (nothing on Y)
• Females have a second X chromosome that carries
  another allele that can hide recessive traits

Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall. Miller, K.
R., Levine, J. S. (2005). Chapter 14 The Human
Genome.Prentice Hall biology (North Carolina ed.,
pp. 340- 365). Upper Saddle River, N.J. Prentice
Hall.
45
Sex-linked Traits

• Females who have recessive alleles but show the
  dominant trait are called carriers
• A woman can have normal vision but carry the
  recessive allele for colorblindness

Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall. Miller, K.
R., Levine, J. S. (2005). Chapter 14 The Human
Genome.Prentice Hall biology (North Carolina ed.,
pp. 340- 365). Upper Saddle River, N.J. Prentice
Hall.
46
Test Cross

• Done to determine the genotypes of organisms that
  show dominant traits
• Unknown genotype organism is crossed with a
  homozygous recessive (Example tt)

Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall. Miller, K.
R., Levine, J. S. (2005). Chapter 14 The Human
Genome.Prentice Hall biology (North Carolina ed.,
pp. 340- 365). Upper Saddle River, N.J. Prentice
Hall.
47
Test Cross

• If all offspring have the dominant trait then the
  genotype is probably pure (TT x tt)
• If some of the offspring show the recessive
  trait, then the genotype is heterozygous.(Tt x
  tt)

Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall. Miller, K.
R., Levine, J. S. (2005). Chapter 14 The Human
Genome.Prentice Hall biology (North Carolina ed.,
pp. 340- 365). Upper Saddle River, N.J. Prentice
Hall.
48
Pedigree Study

• Method of determining the genotype of individuals
  by looking at inheritance patterns

Miller, K. R., Levine, J. S. (2005). Chapter
14 The Human Genome.Prentice Hall biology (North
Carolina ed., pp. 340- 365). Upper Saddle River,
N.J. Prentice Hall.
49
Human Genetics

• 23 pairs of chromosomes (46 total)
• Pedigrees are used to trace genetic traits

Miller, K. R., Levine, J. S. (2005). Chapter
11 Introduction to Genetics. Prentice Hall
biology (North Carolina ed., pp. 262- 285). Upper
Saddle River, N.J. Prentice Hall.
50
Male
Parents
Siblings
Female
Pedigrees illustrate inheritance
Affected male
Known heterozygotes for recessive allele
Affected female
Mating
Death
Miller, K. R., Levine, J. S. (2005). Chapter
14 The Human Genome.Prentice Hall biology (North
Carolina ed., pp. 340- 365). Upper Saddle River,
N.J. Prentice Hall.
51
Pedigrees illustrate inheritance
Female
Male
I
1
2
II
2
1
3
4
5

• In a pedigree, a circle represents a female a
  square represents a male.

III
1
4
2
3
?
IV
5
3
4
2
1
Miller, K. R., Levine, J. S. (2005). Chapter
14 The Human Genome.Prentice Hall biology (North
Carolina ed., pp. 340- 365). Upper Saddle River,
N.J. Prentice Hall.
52
Pedigrees illustrate inheritance
I
1
2
II
3
2
1
4
5

• Highlighted circles and squares represent
  individuals showing the trait being studied.

III
1
4
2
3
?
IV
2
3
5
1
4
Miller, K. R., Levine, J. S. (2005). Chapter
14 The Human Genome.Prentice Hall biology (North
Carolina ed., pp. 340- 365). Upper Saddle River,
N.J. Prentice Hall.
53
Pedigrees illustrate inheritance
I
1
2
II

• Circles and squares that are not highlighted
  represent individuals that do not show trait.

2
3
1
4
5
III
1
4
2
3
?
IV
3
5
2
4
1
Miller, K. R., Levine, J. S. (2005). Chapter
14 The Human Genome.Prentice Hall biology (North
Carolina ed., pp. 340- 365). Upper Saddle River,
N.J. Prentice Hall.
54
Pedigrees illustrate inheritance

• A half-shaded circle or square represents a
  carrier, a heterozygous individual.

Miller, K. R., Levine, J. S. (2005). Chapter
14 The Human Genome.Prentice Hall biology (North
Carolina ed., pp. 340- 365). Upper Saddle River,
N.J. Prentice Hall.
55
Pedigrees illustrate inheritance

• A horizontal line connecting a circle and a
  square indicates that the individuals are
  parents, and a vertical line connects parents
  with their offspring.

I
1
2
II
4
3
2
1
5
III
1
4
2
3
?
IV
2
3
5
1
4
Miller, K. R., Levine, J. S. (2005). Chapter
14 The Human Genome.Prentice Hall biology (North
Carolina ed., pp. 340- 365). Upper Saddle River,
N.J. Prentice Hall.
56
Pedigrees illustrate inheritance

• Each horizontal row of circles and squares in a
  pedigree designates a generation, with the most
  recent generation shown at the bottom.

I
1
2
II
1
3
2
4
5
III
1
2
4
3
?
IV
3
5
1
2
4
Miller, K. R., Levine, J. S. (2005). Chapter
14 The Human Genome.Prentice Hall biology (North
Carolina ed., pp. 340- 365). Upper Saddle River,
N.J. Prentice Hall.
57
Pedigrees illustrate inheritance

• The generations are identified in sequence by
  Roman numerals, and each individual is given an
  Arabic number.

I
1
2
II
1
3
2
4
5
III
1
2
4
3
?
IV
3
5
1
2
4
Miller, K. R., Levine, J. S. (2005). Chapter
14 The Human Genome.Prentice Hall biology (North
Carolina ed., pp. 340- 365). Upper Saddle River,
N.J. Prentice Hall.
58
Pedigree Chart
59
Simple Pedigree
60
Nondisjunction

• Chromosome pairs do not separate correctly
• One gamete has too many the other too few

Miller, K. R., Levine, J. S. (2005). Chapter
14 The Human Genome.Prentice Hall biology (North
Carolina ed., pp. 340- 365). Upper Saddle River,
N.J. Prentice Hall.
61
Nondisjunction

• Examples
• Trisomy 21 - Down Syndrome (extra chromosome 21)

Miller, K. R., Levine, J. S. (2005). Chapter
14 The Human Genome.Prentice Hall biology (North
Carolina ed., pp. 340- 365). Upper Saddle River,
N.J. Prentice Hall.
62
Down Syndrome
63

• XXY syndrome (Klinefelter Syndrome)

Miller, K. R., Levine, J. S. (2005). Chapter
14 The Human Genome.Prentice Hall biology (North
Carolina ed., pp. 340- 365). Upper Saddle River,
N.J. Prentice Hall.
64
Genetic Disorders

• Most caused by recessive alleles
• Cystic fibrosis
• Sickle-cell anemia
• Phenylketonuria (PKU)
• Tay-Sachs disease

Miller, K. R., Levine, J. S. (2005). Chapter
14 The Human Genome.Prentice Hall biology (North
Carolina ed., pp. 340- 365). Upper Saddle River,
N.J. Prentice Hall.
65
Karyotype

• Chart of chromosome pairs
• Shows unusual number of chromosomes
• Can detect trisomy 21 (Down syndrome)
• Identifies male or female

Miller, K. R., Levine, J. S. (2005). Chapter
14 The Human Genome.Prentice Hall biology (North
Carolina ed., pp. 340- 365). Upper Saddle River,
N.J. Prentice Hall.
66
Karyotype
Normal Female
67
(No Transcript)
68
Karyotype
Female with Down Syndrome
69
Autosomal Disorders in Humans
14-1
www.nerdscience.com
70
Dihybrid Cross
RrYy x RrYy
RY Ry rY ry
RY RRYY RRYy RrYY RrYy
Ry RRYy RRyy RrYy Rryy
rY RrYY RrYy rrYY rrYy
ry RrYy Rryy rrYy rryy
www.nerdscience.com
11-3
71
Extra Studying

• While all of these chapters where not used in
  this Power Point, you may find it useful to go
  and read, or re-read, the following chapters in
  your text book.
• Chapter 11 Introduction to Genetics
• Chapter 12 DNA and RNA
• Chapter 13 Genetic Engineering
• Chapter 14 The Human Genome
• Chapter 16 Evolution of Populations

Underlined Chapters are covered in Power Point.
72
Bibliography

• Miller, K. R., Levine, J. S. (2005). Chapter
  11 Introduction to Genetics. Prentice Hall
  biology (North Carolina ed., pp. 262- 285). Upper
  Saddle River, N.J. Prentice Hall.
• Miller, K. R., Levine, J. S. (2005). Chapter
  12 DNA and RNA. Prentice Hall biology (North
  Carolina ed., pp. 286- 317). Upper Saddle River,
  N.J. Prentice Hall.
• Miller, K. R., Levine, J. S. (2005). Chapter
  13 Genetic Engineering. Prentice Hall biology
  (North Carolina ed., pp. 318- 339). Upper Saddle
  River, N.J. Prentice Hall.
• Miller, K. R., Levine, J. S. (2005). Chapter
  14 The Human Genome.Prentice Hall biology (North
  Carolina ed., pp. 340- 365). Upper Saddle River,
  N.J. Prentice Hall.
• Miller, K. R., Levine, J. S. (2005). Chapter
  16 Evolution of Populations. Prentice Hall
  biology (North Carolina ed., pp. 392- 415). Upper
  Saddle River, N.J. Prentice Hall.