1. Mendel and the Gene Idea Chapter 14

2. Transmission of characteristics from parents to offspring = ___________________
The science that studies how those characteristics are passed on = _________

3. Two ideas about how genes are passed:
____________- genetic material from parents mix
(like mixing paint: blue + yellow → green)
Problems:
Predicts over time a freely mating population will result
in a uniform population of individuals Doesn’t explain traits skipping a generation
_____________- parents pass on discrete heritable units that
keep their separate identities

4. ______________________________ Father of Genetics
Looked at one trait at a time
Made experimental crosses
Large sample size
Kept careful records

5. MENDEL’S PEA EXPERIMENTS
Peas are “self pollinating” ie., egg and sperm come from same plant
Mendel’s experiments
Allowed him to
experiment and
observe offspring produced from a variety of known genetic crosses

6. MENDEL’S EXPERIMENTS ____ generation (_________) ____ generation
(______= offspring)
___ generation

7. PATTERNS ARE THE KEY
Image modified from:

8. Genetic makeup of organism = _________
Image modified from:
Image from Biology; Campbell and Reece; Pearson Prentice Hall publishing as Benjamin Cummings © 2005
Genetic makeup of organism = _________
Appearance of organism = ____________

9. For each trait, an organism inherits TWO alleles.
MENDEL’S MODEL
Alternative versions of genes account for variations in inherited traits.
For each trait, an organism inherits TWO alleles.
If the two alleles at a locus differ, one determines the organism’s appearance; the other has no effect.
The two alleles for a character separate during gamete formation and end up in different gametes.

10. Image modified from: http://www.newtonswindow.com/problem-solving.htm
Alternative versions of genes account for variations in inherited traits.
____________ =
Observable characteristic
Ex: flower color, height, pod shape
___________ = choices for a trait Ex: blue eyes, green eyes, brown eyes)
From Biology; Miller and Levine; Pearson Prentice Hall publishing as Benjamin Cummings © 2005 Pearson Education Inc

11. 2. For each trait, an organism inherits TWO alleles.
Image from Biology; Campbell and Reece; Pearson Prentice Hall publishing as Benjamin Cummings © 2005
2. For each trait, an organism inherits TWO alleles.
Organisms with two identical alleles for a gene = ____________OR ______________
Organism with two different alleles for a gene = _______________OR ___________

12. 3. If the two alleles at a locus differ, one determines the organism’s
appearance; the other has no effect.
_________________ = allele that masks the presence of another allele
__________________ = An allele that is hidden
Image from Biology; Campbell and Reece; Pearson Prentice Hall publishing as Benjamin Cummings © 2005

13. 4. The two alleles for a trait separate during gamete formation
and end up in different gametes.
= MENDEL’S LAW OF SEGREGATION
Image modified from:

16. Mendel’s Law of Independent Assortment
Two or more pairs of alleles segregate independently of one another during gamete formation.

17. _______________ is the likelihood that a particular event will occur
EX:
If you close your eyes and pick a disk, what is the probability you will pick the white one?
It can be written as a:
Fraction ____
Percent ____
Ratio ____

18. COIN FLIP capital There are 2 possible outcomes: HEADS TAILS
COIN FLIP
There are 2 possible outcomes:
HEADS TAILS
capital
The chance the coin will land on either one is:
____ ____ ____
Alleles segregate randomly just like a coin flip. . . So can use probability to predict outcomes of genetic crosses.

19. PROBABILITIES Past outcomes DON’T affect future ones!
Probability works best in predicting a large number of events.
If last coin flip was heads… there is still a 50/50 chance the next flip will be heads too.
The more flips. . . The closer results will be to
the expected 50:50 average.

20. MULTIPLICATION & ADDITION RULES
To determine the probability of two or more independent events:
MULTIPLICATION RULE: Multiply the probability of one event by the probability of the other
What is the probability two coins tossed simultaneously will both end up on heads?
½ X ½ = ¼

21. MULTIPLICATION RULE WORKS FOR PREDICTING GENETIC CROSSES, TOO
Tt X Tt
What is the probability offspring will be tt ?
Each egg has a ½ chance of passing on t.
Each sperm has ½ chance of passing on t.
½ X ½ = ¼
Punnett by Riedell

22. ½ X ½ = ¼ ¼ + ¼ = ½ ADDITION RULE
To figure out the probability of an offspring being heterozygous (Tt)
T can come from mom and t from dad OR
t can come from the mom and T from the dad
but not both (events are mutually exclusive)
1st probability
T from mom
t from dad
½ X ½ = ¼
2nd probability
t from mom
T from dad
½ X ½ = ¼
¼ + ¼ = ½
Punnett by Riedell

23. T t t t Tt tt Tt Tt HOW CAN YOU TELL THE GENOTYPE?
Tall plant has two possible genotypes
___ OR ___
Make a ___________
with a _____________________
T t t
T T t
Tt tt
Tt Tt
Images from: BIOLOGY by Miller & Levine; Prentice Hall Publishing ©2006

24. GENES are more complicated than Mendel thought
Environment influences gene expression
Spectrum of dominance
Multiple allele traits
Polygenic traits
Gene Linkage
Pleiotropy
Epistasis

25. Environment influences Phenotype “Nature vs Nurture”
Siamese cats and Himalayan rabbits have dark colored fur on their extremities
Allele that controls pigment production is only able to function at the lower temperatures of those extremities.
Images from slide show by Tracy Nelson

26. Environment influences Phenotype “Nature vs Nurture”
Color of hydrangea flowers varies
depending on pH of soil
Images from:

27. GENES are more complicated than MENDEL thought
Spectrum of DOMINANCE
____________________

28. COMPLETE DOMINANCE If two alleles are present DOMINANT allele masks
the RECESSIVE allele
Recessive trait shows again in F2 generation in 3:1 ratio

29. INCOMPLETE DOMINANCE Heterozygous snapdragons show a blended
intermediate
trait
Image modified from:

30. CO-DOMINANCE
BOTH traits are expressed at the same time side by side in heterozygote
A ROAN HORSE has both RED and WHITE hair side by side

31. CO-DOMINANCE
Both traits are expressed together (NO BLENDING) in heterozygote
Persons with an A allele AND a B allele have AB blood type

32. REMEMBER
Membrane proteins with sugars attached that help cells “recognize self”
= ______________
Type of sugars attached gives cell its “Blood type”
I is used for blood type alleles

33. BLOOD TYPES Person with IA IA OR IA i genotype
has cells with a certain
glycoprotein “A”
on its surface
TYPE “A” BLOOD

34. BLOOD TYPES Person with IB IB OR IB i genotype
has cells with a different
glycoprotein “B”
on its surface
TYPE “B” BLOOD

35. BLOOD TYPES Person with i i genotype have neither “A” nor “B”
glycoproteins on their surface
TYPE “O” blood
Note: Cells have
other glycoproteins…
just not A or B

36. A and B are CO-DOMINANT Person with IA IB genotype has BOTH
glycoproteins on its surface
TYPE “AB” Blood

37. BLOOD TYPE FREQUENCY IN USA
40% B
10% AB 4% O
46%

38. BLOOD TYPES YOU DON’T HAVE ANYTHING I DON’T HAVE!
DONOR BLOOD
YOU DON’T HAVE ANYTHING I DON’T HAVE!
See A blood cells as DIFFERENT!
IMMUNE SYSTEM ATTACKS!
Body images modified from:

39. BLOOD TYPES YOU DON’T HAVE ANYTHING I DON’T HAVE! DONOR BLOOD
A and O see B cells as DIFFERENT! IMMUNE SYSTEM ATTACKS!
YOU DON’T HAVE ANYTHING I DON’T HAVE!
Body images modified from:

40. BLOOD TYPES YOU’RE LIKE ME! DONOR BLOOD
A, B, and O see AB cells as DIFFERENT! IMMUNE SYSTEM ATTACKS!
Body images modified from:

41. BLOOD TYPES YOU DON’T HAVE ANYTHING I DON’T HAVE!
____ can donate to EVERY BLOOD TYPE
= _____________________
NO A’s or B’s on surface to
recognize as “NOT SELF”
YOU DON’T HAVE ANYTHING I DON’T HAVE!
Body images modified from:

42. BLOOD TYPES ______ can RECEIVE FROM EVERY BLOOD TYPE
= ________________________
Body image modified from:

43. ABO SYSTEM is NOT THE ONLY ONE
Rh Rh-

44. OTHER BLOOD TYPES NO PROBLEMS IF: MOM is _____ & BABY is ____ Rh+ Rh+
Image modified from:

45. Can be a ___________ IF: Mom is _____ Baby is _____
PROBLEM
Can be a ___________ IF: Mom is _____ Baby is _____
Rh-
Rh+
Image modified from:
1st baby OK but few baby cells
entering mom’s bloodstream
put mom’s immune system on
alert for + cells.
Next + baby, mom’s immune
system can attack baby as it is
growing
= ERYTHROBLASTOSIS FETALIS
Mom given shot (RhoGAM) after birth to prevent this

46. CLOSER LOOK AT RELATIONSHIP
BETWEEN DOMINANCE AND PHENOTYPE REVEALS AN INTRIGUIGING FACT:
DOMINANCE ? CODOMINANCE? INCOMPLETE DOMINANCE ? Depends on how you look at it!

47. TAY-SACHS DISEASE Human genetic disorder in which brain cells are
Image from:
TAY-SACHS DISEASE
Human genetic disorder in which brain cells are
unable to metabolize certain lipids because
a crucial enzyme does not work properly.
As these lipids build up in brain infant suffers seizures, blindness, loss of motor & mental function > > > leads to early death.
At ORGANISMAL LEVEL acts as a recessive trait. Child with two copies of Tay-Sachs allele (tt-homozygous) has the disorder. Child with Tt or TT does not (COMPLETE DOMINANCE)
At BIOCHEMICAL LEVEL- Tt individual has enzyme activity level
in between the TT and tt person (INCOMPLETE DOMINANCE ?)
At the MOLECULAR LEVEL – Tt individual makes equal number of normal and dysfunctional enzyme molecules (CODOMINANT ?)

48. GENES are more complicated than Mendel thought
MULTIPLE ALLELE TRAITS have MORE THAN 2 allele choices
EX: blood type
Allele choices ___ ___ ___

49. GENES are more complicated than MENDEL thought
POLYGENIC TRAITS are governed by the cumulative effect of MORE THAN ONE GENE
Polygenic traits show a
whole range of
in-between phenotypes
EX: human height. intelligence, skin & eye color

50. The results form a bell shaped curve.
POLYGENIC traits are recognizable by their expression as a gradation of small differences (a continuous variation).
The results form a bell shaped curve.
Image from Biology; Campbell and Reece; Pearson Prentice Hall publishing as Benjamin Cummings © 2005

51. Linked Genes
Genes close together on same chromosome are called linked genes
Linked genes do not exhibit independent assortment and they move together during crossing over if they are very close together on the chromosome.

52. Sex Linked Genes
Genes carried on the X chromosome are called X-linked traits.
Red-green colorblindness, hemophilia, an Duchenne muscular dystropy are examples of X-linked traits.

53. Hairy pinnae Y-LINKED GENES: Genes carried on the Y chromosome
Y-linked genes only show up in MALES
SRY gene initiates male sex
determination
Hairy pinnae

54. X and y chromosomes
NON-HOMOLOGOUS partners

55. PLEIOTROPY Most genes have multiple phenotypic effects
Image from Biology; Campbell and Reece; Pearson Prentice Hall publishing as Benjamin Cummings © 2005

56. EPISTASIS
Gene at one locus alters the phenotypic expression of a gene at another locus
EX: Coat color in mice
B = Black b = brown
C = color deposited in coat
c = color NOT deposited
cc-mouse looks white even though it has color genes
Image from Biology; Campbell and Reece; Pearson Prentice Hall publishing as Benjamin Cummings © 2005

57. Pedigrees are diagrams that show how genes are passed on in families over several generations
Image from Biology; Campbell and Reece; Pearson Prentice Hall publishing as Benjamin Cummings © 2005
Pedigrees can be used to predict future offspring in families with genetic disorders

58. Drawing a pedigree chart

59. http://www. ikm. jmu. edu/Buttsjl/ISAT493/Hemophilia/hemophiliaeurope

60. Human Genetic Disorders

61. have to do with human genetics?
THINK ABOUT IT
What does a can of
Diet Coke and
this song
have to do with human genetics?
(Answers to come in this slide show!)

62. Many genetic ___________ result from
MANY HUMAN GENES HAVE BECOME KNOWN THROUGH THE STUDY OF GENETIC DISORDERS
Many genetic ___________ result from
changes in the DNA code so _________________ proteins are produced.
DISORDERS
NON-FUNCTIONING

63. A mutation in an allele that causes a protein to be NON-FUNCTIONAL would appear
_______________ to the normal working allele.
Examples of __________________________ GENETIC DISORDERS:
____________________
AUTOSOMAL RECESSIVE

64. Phenylketonuria (PKU)
CAUSE: Mutation in gene for an enzyme the breaks down an amino acid called phenylalanine
Build up causes ________________________
MENTAL RETARDATION

65. Phenylketonuria (PKU)
ALL babies are tested for PKU before they leave the hospital.
Treatment: Need a diet low in phenylalanine to extend life and prevent mental retardation
If phenylalanine is an _____________,
what type of foods should PKU patients avoid? __________________
Amino acid

66. THINK ABOUT IT What does a can of Diet Coke have to do
with human genetics?
LOOK AT THE WARNING LABEL !
NUTRASWEET
______________ is made with phenylalanine

67. CYSTIC FIBROSIS thick mucous CAUSE:
Loss of 3 DNA bases in a gene for the ion channel protein that transports Cl- ions
Salt balance is upset
Causes a build up of thick mucous in lungs and digestive organs
thick mucous
Image from: BIOLOGY by Miller and Levine; Prentice Hall Publishing ©2006

68. CYSTIC FIBROSIS
Leads to:
Respiratory and digestive complications, increased susceptibility to infections;
“Salty skin” is a symptom
More common in Caucasians but can affect all races.
30,000 people in U.S. have cystic fibrosis
1 in 31 people are carriers

69. Heteroygous individual That carries one recessive allele for a
CARRIER
Heteroygous individual
That carries one recessive allele for a
genetic disorder
Doesn’t show the
disorder themselves,
but can pass it on to
offspring

70. TAY-SACHS DISEASE Human genetic disorder in which brain cells are
Image from:
TAY-SACHS DISEASE
Human genetic disorder in which brain cells are
unable to metabolize certain lipids because
a crucial enzyme does not work properly.
As these lipids build up in brain infant suffers seizures, blindness, loss of motor & mental function > > > leads to early death.
At ORGANISMAL LEVEL acts as a recessive trait. Child with two copies of Tay-Sachs allele (tt-homozygous) has the disorder. Child with Tt or TT does not (COMPLETE DOMINANCE)
At BIOCHEMICAL LEVEL- Tt individual has enzyme activity level
in between the TT and tt person (INCOMPLETE DOMINANCE ?)
At the MOLECULAR LEVEL – Tt individual makes equal number of normal and dysfunctional enzyme molecules (CODOMINANT ?)

71. TAY-SACHS DISEASE ___________________
AUTOSOMAL RECESSIVE
CAUSE: Mutation in gene for an enzyme the breaks down a kind of lipid in the developing brain
As these lipids build up in brain infant suffers seizures, blindness, loss of motor & mental function > > > leads to early death.
Found more frequently in people with Jewish, Mediterranean, or Middle Eastern ancestry
Image from:

72. BY ____________________
DISORDERS CAUSED
BY ____________________
____________________
AUTOSOMAL CODOMINANT ALLELES
CAUSE: A changed to T in gene for
__________________
(protein in red blood cells
that carries oxygen in blood)

73. SICKLE CELL DISEASE SYMPTOMS:
Red blood cells become sickle shaped under low oxygen condition in persons with two sickle cell alleles (ss)
Ss=Sickle cell trait Normally healthy, but can suffer some sickle cell episodes

74. SICKLE CELL DISEASE Circulatory problems Cells stick in capillaries
Loss of blood cells (anemia)
Organ damage (brain, heart, spleen)
Can lead to DEATH

75. SICKLE CELL DISEASE
More common in _________________
1 in 400 = have sickle cell disease
1 in 10 = carriers for allele
Also affects persons of _______________ and _________________ descent
Why do so many African Americans carry the sickle cell allele?
MEDITERRANEAN
MIDDLE EASTERN

76. SICKLE CELL DISEASE Many can trace their ancestry to west
central Africa where ___________,
a serious parasitic disease that
infects red blood cells is common.
Watch a video about
sickle cell and malaria
Images from:

77. AT MOLECULAR LEVEL Sickle cell allele is CODOMINANT
ss- has abnormal hemoglobin; unhealthy
SS-has normal hemoglobin and can be infected with malaria
Ss-makes both normal and abnormal hemoglobin; resistant to malaria infection
Sickle cell disease is a trade off for malaria resistance

78. GENETIC LINK TO DISEASE
Many human genetic disorders may be the small “price we pay” for mutations that provide protection from otherwise lethal diseases
Persons heterozygous for cystic fibrosis are resistant to typhoid
Changes in Vitamin D receptors confer resistance to tuberculosis, but result in greater susceptibility to osteoporosis

79. A mutation that codes for a new protein
whose action masks the normal allele
appears as a ______________ mutation.
Examples of _________________________ GENETIC DISORDERS:
____________________

80. HUNTINGTON’S DISEASE ______________________
AUTOSOMAL DOMINANT
CAUSE: Extra ______________ at end of gene on chromosome 4
The _____________ the more __________ the symptoms.
more repeats
severe

81. HUNTINGTON’S DISEASE Begins in middle age
Huntington’s brain
Begins in middle age
Causes progressive loss of muscle control and mental function
1 in 10,000 people in U.S.
have Huntington’s disease
Normal brain

82. A person with
Huntington’s disease
has a _____ chance of
passing the disorder on to
their offspring.
50%
Problem: Symptoms of disorder usually don’t show until ____________ . . .
so you don’t know you have it until ________ you have had children.
MIDDLE AGE
AFTER

83. THINK ABOUT IT What does the song have to do with human genetics?
“This Land is My Land” was written by a musician named Woody Guthrie before he began to show the symptoms of Huntington’s disease.
Click to hear
Woody’s song

84. Before 1993 there was no test for Huntington’s.
Woody Guthrie had a son named Arlo that was a popular musician during the 70’s
Click to hear one
of Arlo’s songs
Before 1993 there was no test for Huntington’s.
If one of your parents showed symptoms, you had to wait to see if it had been passed on to you.

85. Arlo Guthrie is still performing today.
Arlo Guthrie is still performing today.
He never developed symptoms for Huntington’s disease.
If there is no cure, would you want to be tested and find out if you have the gene?

86. ACHONDROPLASIA (One kind of Dwarfism)
AUTOSOMAL DOMINANT
CAUSE: ___________________________ gene
1 in 25,000 births
DD = lethal
Dd = dwarf phenotype
dd= = normal height
200,000 “little people” worldwide
One of oldest known disorders – seen in Egyptian art

87. ACHONDROPLASIA (One kind of Dwarfism)
Normal size head and torso; short arms and legs
Problem with way cartilage changes to bone as bones grow

88. Image from Biology; Campbell and Reece; Pearson Prentice Hall publishing as Benjamin Cummings © 2006

89. A __________ is a picture of an organism’s chromosomes

90. SEX DETERMINATION
XX =
female
Xy =
male

91. Karyotype can show: Sex of baby Missing or extra chromosomes
Major deletions or translocations
Can’t see individual gene changes