11.1 BASIC PATTERNS OF HUMAN INHERITANCE

1
11.1 BASIC PATTERNS OF HUMAN INHERITANCE

• ?WHAT YOU WILL LEARN
• -How to determine if an inherited trait is
  dom/rec
• -Examples of DOMINANT/RECESSIVE disorders
• -Construct / Interpret PEDIGREES

2
READING Qs

• 1-IDENTIFY
• -Check the term that describes the genotype of a
  person who expresses a recessive trait
• -HOMOZYGOUS
• organism with 2 of the same alleles for a
  particlular trait
• -aa

3
READING Qs

• 2-CATEGORIZE
• The following genetic disorders as RECESSIVE or
  DOMINANT
• a-albinism ?recessive ?dominant
• b-Huntington's ?recessive ?dominant
• c-cystic fibrosis ?recessive ?dominant
•  

4
READING Qs

• 3-EXPLAIN
• -For what purpose is a genetic pedigree used?
• -study genetic relationships
• -trace inheritance of a trait generation to
  generation

5
READING Qs

• 4-DRAW
• The symbols that are used to represent a male AND
  female in a pedigree
• MALE- FEMALE-

6
READING Qs

• 5-EVALUATE
• -Circle the carriers in the second generation

7
READING Qs

• 6-CALCULATE
• -What percentage of the children in this family
  inherited Tay-Sachs disease?
• -1/425

8
READING Qs

• 7-IDENTIFY
• -Do any grandchildren in this family have
  polydactyly?
• -NO

9
READING Qs

• 8-EXPLAIN
• -Why are recessive traits difficult to study?
• -Not all people who carry the recessive allele
  have the trait

10
GROUP WORK APPLICATION NOTES

• -As a group complete the areas below using your
  knowledge from the reading/discussion.
• ?MAIN IDEA
• ?REVIEW VOCAB
• ?RECESSIVE / DOMINANT GENETIC DISORDERS
• ?VOCAB
• -carrier
• -pedigree

11
?MAIN IDEA

• -PEDIGREES?inheritance of traits over several
  generations

12
?REVIEW VOCAB

• DEFINE gene
• -segment of DNA on chromosome
• DEFINE homozygous
• -2 identical alleles TT / tt
• DEFINE heterozygous
• -2 different alleles Tt

13
?RECESSIVE/DOMINANT GENETIC DISORDERS

• COMPARE/CONTRAST
• recessive and dominant genetic disorders
• RECESSIVE
• -expressed when indv HOMO recessive tt
• DOMINANT
• -expressed when indv HOMO dominant TT or HETERO
  Tt

14
?RECESSIVE/DOMINANT GENETIC DISORDERS

• EXPLAIN why recessive disorders are more common
  than dominant disorders.
• -DOMINANT only one allele must be inherited to
  be affected
• -if DOM trait interferes w/ survival- no pass on
• -RECESSIVE carriers do NOT display the disorder
• -many carriers are unaware they carry an
  affected gene

15
?RECESSIVE/DOMINANT GENETIC DISORDERS

• IDENTIFY
• the disease for each dominant/recessive disorders
• -caused by altered genes results in lack of skin
  pigmentation
• -ALBINISM
• -RECESSIVE
• -characterized by bodys inability to tolerate
  galactose
• -GALATOSEMIA
• -RECESSIVE
• -gene found on chromosome 15characterized by
  lack of enzyme that breaks down fatty acids
• -TAY SACHS
• -RECESSIVE

16
?RECESSIVE/DOMINANT GENETIC DISORDERS

• IDENTIFY
• the disease for each dominant/recessive disorders
• -affects the nervous system no treatment breaks
  down part of brain
• -HUNINGTONS
• -DOMINANT
• -affects mucus-producing glands, digestive
  enzymes, sweat glands
• -CYCTIC FIBROSIS
• -RECESSIVE
• -affects height and body size
• -ACHONDROPLASIA
• -DOMINANT

17
?RECESSIVE/DOMINANT GENETIC DISORDERS

• PREDICT what are the chances of 2 carriers of
  cystic fibrosis having a child with cystic
  fibrosis?
• ¼ 25

F f
F f
FF
Ff
Ff
ff
18
?RECESSIVE/DOMINANT GENETIC DISORDERS

• Positive Exposure
• Positive exposure video clip Rick Guidotti - PART
  2
• Positive Exposure Inside Edition Part I - YouTube

19
?PEDIGREE BASICS

• the FAMILY TREE of genetics
• ?WHAT is it
• -diagram explaining genetic history
• ?WHO uses it
• -scientist
• -genetic counselors
• ?WHY use it
• -probability of child having disorder/condition
• -determine disorder/condition as autosomal/sex
  linked

20
?PEDIGREES

• SUMMARIZE pedigree symbols

MALE -sqaure - FEMALE -circle - AFFECTED
MALE -shaded square - AFFECTED FEMALE -shaded
circle -
CARRIER -half shaded symbol - /
PARENTS/OFFSPRING -line down from parent,
circles/squares on second row PARENTS -circle
joined to square - GENERATIONS -I, II , III, IV, V
21
?STEPS for INTERPRETING PEDIGREES

• 1- DETERMINE if the pedigree chart is showing
• AUTOSOMAL or X-LINKED disorder
• -autosomal
• -If it is a 50/50 ratio between men and women
• -x-linked
• -If most of the males in the pedigree are
  affected
• 2- DETERMINE if disorder is DOMINANT or RECESSIVE
• -dominant
• -one of the parents must have the disorder.
• -recessive
• -neither parent has to have the disorder because
  they can be heterozygous.

22
?Connecting Pedigree Symbols

• Married Couple
• Siblings

23
?EX- PEDIGREE CHART
24
?PRACTICE INTERPRETING

• Determine if the pedigree chart shows an
  autosomal or X-linked disease.
• -If most of the males in the pedigree are
  affected the disorder is X-linked
• -If it is a 50/50 ratio between men and women the
  disorder is autosomal.

25
PRACTICE Interpreting

• Is it Autosomal or X-linked?

26
Answer

• Autosomal

27
Interpreting a Pedigree Chart

• Determine whether the disorder is
• dominant or recessive
• -If the disorder is dominant, one of the parents
  must have the disorder.
• -If the disorder is recessive, neither parent has
  to have the disorder because they can be
  heterozygous.

28
PRACTICE Interpreting

• Dominant or Recessive?

29
Answer

• Dominant

30
PRACTICE Interpreting

• Dominant or Recessive?

31
Answer

• Recessive

32
?ANALYZING PEDIGREES

• EVALUATE
• the inheritance of achondroplasia shown in the
  pedigree
• -parent w/ disorder
• -father
• -children with disorder
• -1 / 1st born son
• -genotype of younger son
• -homozygous recessive / aa

33
?ANALYZING PEDIGREES

• ANALYZE and RESPOND
•  
• -RECALL if the trait is rec or dom
• based on the following information
• -individuals I-1 and I-2 are unaffected
• but have affected child
• ?RECESSIVE ?DOMINANT
• -SPECIFIY if parents II-1 and II-2, who have an
  affected child, are carriers of that trait
• ?CARRIER ?NOT A CARRIER
• -TELL whether there is a dominant gene in the
  genotype of II-4
• ?NONE ?A LEAST ONE
• -Individual II-1is in generation 2
• ?TRUE ?FALSE

X
X
X
X
34
?ANALYZING PEDIGREES

• THINK BACK and RESPOND
• -A scientist uses a pedigree to study family
  history
• ?TRUE ?FALSE
• -A pedigree traces the inheritance of a
  particular trait through only two generations
• ?TRUE ?FALSE
• -In a pedigree, one who does not express the
  trait is represented by a darkened circle/square
• ?TRUE ?FALSE
• -In a pedigree, a horizontal like between 2
  symbols shows that these individuals are the
  parents of the offspring
• ?TRUE ?FALSE

X
MANY
X
X
X
35
?ANALYZING PEDIGREES

• DIAGRAM
• Suppose both parents can roll their tongues but
  their son cannot.
• TONGUE ROLLING DOMINANT / T
• ?DRAW a pedigree showing this trait ?LABEL each
  symbol with the appropriate genotype
• ?What was the probability that they would have a
  non-tongue roller offspring?
• (hint punnet square)
• -both parents carry recessive gene
• -parent genotype Tt
• -son genotype tt
• -probability of child tt 25

36
PEDIGREE CHART PRACTICE

37
?PEDIGREE PRACTICE A
38
?PEDIGREE PRACTICE B
39
?PEDIGREE PRACTICE C
40
?PEDIGREE PRACTICE D
41
?INVESTIGATING HUMAN PEDIGREES

• -USE the information provided in the transcript
  to construct a pedigree showing hairy earlobes
  in a family HE
• -DETERMINE the oldest couple in the family
• -DRAW their pedigree symbolsinclude names
• -CONTINUE with other members in the family
• -DETERMINE genotypes as you gather enough
  information