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
-How a PEDIGREE shows a particular trait in families

2. MAIN IDEA
The inheritance of a trait is shown over several generations in a pedigree.

3. REVIEW VOCAB: enzyme -PROTEIN that speeds up biological reactions
READING Q’s
REVIEW VOCAB:
enzyme
-PROTEIN that speeds up biological reactions

4. READING Q’s
IDENTIFY
-CIRCLE 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
-DETERMINE the genotypes:
recessive genetic disorder
dominant genetic disorder
DD Dd dd X X
DD Dd dd X

5. READING Q’s
EXPLAIN
-Why do ganglioslides build up in the brain of people with Tay-Sachs disease?
-ENZYME missing that breaks down ganglioslides—fatty acids

6. READING Q’s
EXPLAIN
-How scientist determine if achondroplasia developed from a new mutation
-achondroplasia is a dominant disorder: dwarfism
-if BOTH parents are average height it dev from MUTATION
Parents would be homozygous recessive so could only pass on a recessive allele—dominant allele would have to be a mutation

7. READING Q’s EXPLAIN the purpose of a genetic pedigree
-track a trait or disorder throughout several generations
DRAW the symbols used in a pedigree for:
MALE=
FEMALE=

8. EVALUATE -Circle the carriers in the second generation
READING Q’s
EVALUATE
-Circle the carriers in the second generation

9. READING Q’s
CALCULATE
-What percentage of the children in this family inherited Tay-Sachs disease?
-1/4=25%

10. IDENTIFY -Do any grandchildren in this family have polydactyly? -NO
READING Q’s
IDENTIFY
-Do any grandchildren in this family have polydactyly?
-NO

11. READING Q’s EXPLAIN -Why are recessive traits difficult to study?
-Not all people who carry the recessive allele have the trait
-Don’t know if you are a carrier unless___
-1 parent shows the trait = homozygous recessive
-offspring shows trait = both parents carriers

12. GROUP WORK: APPLICATION NOTES
-As a group complete the guided note sheet using your knowledge from the reading.

13. REVIEW VOCAB DEFINE: gene -segment of DNA on chromosome carrier
-heterozygous for a recessive disorder--Aa

14. RECESSIVE/DOMINANT GENETIC DISORDERS
CONSTRUCT:
A concept map that includes three facts about recessive heredity
-homozygous rec
-Dr. Garrod identified a recessive genetic disorder- alkaptonuria
-disorder caused by REC genes:
*cystic fibrosis
*Tay Sachs
*albinism
-for offspring to inherit REC trait, BOTH parents must have REC allele

15. RECESSIVE/DOMINANT GENETIC DISORDERS
COMPARE:
RECESSIVE GENETIC DISORDERS
-only present if homozygous recessive
-parents are carriers if don’t have disorder
DOMINANT GENETIC DISORDERS
-present if have at least 1 dominant allele
-must have a parent with the disorder
[mutations are exceptions]
-don’t always appear until later in life

16. RECESSIVE/DOMINANT GENETIC DISORDERS
IDENTIFY:
1-four examples of recessive genetic disorders in humans
1-CYSTIC FIBROSIS
2-TAY-SACHS
3-ALBINISM
4-GALACTOSEMIA
5-ALKOPTONURIA
2-two examples of dominant genetic disorders in humans
1-HUNTINGTON’S
2-ACHONDROPLASIA

17. RECESSIVE/DOMINANT GENETIC DISORDERS
EXPLAIN why recessive disorders are more common than dominant disorders.
-don’t always know there are carriers of disorder
-parents may not know the disorder is in the family
parents with a dominant disorder may choose to not have children or may not survive to age of procreation
===========================================
a recessive trait may be more functional than the dominant, therefore a dominant trait could be eliminated over many generations

18. 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 body’s inability to tolerate galactose
-GALATOSEMIA
-gene found on chromosome 15;characterized by lack of enzyme that breaks down fatty acids
-TAY SACHS

19. RECESSIVE/DOMINANT GENETIC DISORDERS
IDENTIFY:
the disease for each dominant/recessive disorders
-affects the nervous system; no treatment; breaks down part of brain
-HUNTINGTON’S
-dominant
-affects mucus-producing glands, digestive enzymes, sweat glands
-CYCTIC FIBROSIS
-recessive
-affects height and body size
-ACHONDROPLASIA

20. RECESSIVE/DOMINANT GENETIC DISORDERS
-SHOW a cross between 2 carriers
-what is the probability 2 carriers of cystic fibrosis will have a child w/CF?
-25% F f F FF Ff f Ff ff

21. RECESSIVE/DOMINANT GENETIC DISORDERS
PREDICT:
-can 2 normal height parents have a child w/achondroplasia? a a a aa aa a aa aa

22. RECESSIVE/DOMINANT GENETIC DISORDERS
PREDICT:
-can 2 individuals w/achondroplasia have a child that is normal height? A a A AA Aa a Aa aa

23. RECESSIVE/DOMINANT GENETIC DISORDERS
COMPLETE:
-A _______________ shows the inheritance of a particular trait over
several generation.
-An organisms with two of the same _______________ for a
particular trait is said to be _______________ for that trait.
-An organism with two different ________________ for a particular
trait is heterozygous for that trait.
-When alleles are present in the _______________ state, the
_______________ trait will be observable.
-An individual who is heterozygous for a _______________ disorder
is called a carrier.
-Examples of genetic disorders in humans are _______________ and
_______________.
pedigree
alleles
homozygous
alleles
heterozygous
dominant
recessive
albinism
cystic fibrosis

24. SUMMARIZE: pedigree symbols
MALE
-square -
FEMALE
-circle
AFFECTED MALE
-shaded square
AFFECTED FEMALE
-shaded circle
CARRIER
-half shaded symbol /
PARENTS
--circle joined to square
PARENTS/OFFSPRING
-line down from parent/ circles/squares on second row -

25. PEDIGREE CHART

26. PEDIGREE CHART
GRANDPA X GRANDMA
MOM X DAD
GRAMPS X GRANNY

27. 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

28. ANALYZING PEDIGREES X X X X ANALYZE and RESPOND:
-RECALL if the trait is rec or dom
based on the following information:
-In the pedigree, individuals I-1 and I-2
are unaffected -- 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

29. ANALYZING PEDIGREES X X X X 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
-In a pedigree, one who does not express the trait is represented by a darkened circle/square
-In a pedigree, a horizontal line between 2 symbols shows that these individuals are the parents of the offspring X
MANY X X X

30. ANALYZING PEDIGREES DIAGRAM: -both parents carry recessive gene
Suppose both parents can roll their tongues but their son cannot.
IDENTIFY this trait as: dominant recessive
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%

31. Connecting Pedigree Symbols
parents
offspring
These symbols also represent relationships between people. some may have to each other.

32. EX- PEDIGREE CHART
This is just an example of a pedigree and there can be many more different types.

33. Interpreting a Pedigree Chart
1- Determine whether the trait/disorder is
dominant or recessive
-If the trait/disorder is dominant, one of the parents must have the disorder
-If the trait/disorder is recessive, neither parent has to have the disorder because they can be heterozygous
The second step is to determine if the disorder is dominant or recessive. It is important to find out if a disorder is dominant or recessive. For example, Huntington’s disease is a dominant disorder. If you have only one dominant gene you will have Huntington’s disease, which is a lethal disorder. The disorder does not show up until a person is in their middle ages such as 45. It will quickly decrease their motor skills and the brain will begin to deteriorate.
If a disorder is dominant, one parent must have the disorder (either homozygous dominant (TT) or heterozygous recessive (Tt). Both parents do not have to have the disorder. One parent might not have the disorder or be a carrier. If a disease is dominant, it does not skip a generation unless one parent is heterozygous dominant (Tt) and the other parent is homozygous recessive (tt). In this case the child has a chance of not receiving the dominant gene.
If the disorder is recessive, a parent does not have to have the disorder, but could still pass it to their offspring. This would happen when a parent is heterozygous recessive (Tt) and passes on the recessive (t) gene. This means this disorder can skip generations. An example of a recessive disorder would be sickle cell anemia.

34. PRACTICE: Interpreting
Dominant or Recessive?
Is this pedigree dominant or recessive?

35. Answer
Recessive
It is recessive because a parent in every generation does not have the disorder. Remember the disorder can skipped a generation if the disorder is recessive. The parents can be heterozygous and be carriers of the disorder but not have the symptoms of the disorder.

36. PRACTICE: Interpreting
Dominant or Recessive?
Is this pedigree dominant or recessive?

37. Answer
Dominant
It is dominant because a parent in every generation have the disorder. Remember if a parent in every generation has the disorder, the disorder has not skipped a generation. If the disorder has not skipped a generation the disorder is dominant.

38. Interpreting a Pedigree Chart
2- Determine if the pedigree chart shows an autosomal or X-linked trait/disorder
-If most of the males in the pedigree are affected the trait/disorder is X-linked
-If it is a 50/50 ratio between men and women the trait/disorder is autosomal.
When interpreting a pedigree chart of a family with a disease like muscular dystrophy, it is important to consider two steps. The first is to determine if the disorder is autosomal or X-linked.
If the disorder is X-linked most of the males will have the disorder because the Y-chromosome cannot mask the affects of an affected X-chromosome. A female can have the disorder, but it would be a very low percentage. For a female to be affected, she would have had to receive an affected gene from the mother and the father. This means that the father would have the disorder and the mother was a carrier.
In an autosomal disorder, the disorder is not found on the X or Y chromosome. It is found on the other 22 chromosomes in the human body. This means that men and women have an equal chance of having the disorder. The mother and father can be homozygous dominant, heterozygous, and homozygous recessive. If a person is homozygous dominant, the person has two of the same dominant genes. For example if someone is homozygous dominant for being tall it may be represented as TT. Capital letter always represent a dominant gene. If a person is heterozygous, this person would have a dominant trait and a recessive trait. It may be represent as Tt. The dominant gene will mask the recessive gene, so the person is still tall. If a person is homozygous recessive, the person has two of the same recessive genes. For example if someone is homozygous recessive for height, it may be represented as tt. The tt would mean the person is short.

39. PRACTICE: Interpreting
Is it Autosomal or X-linked?
Take a minute and try to decide if this slide is autosomal or X-linked.

40. Answer
Autosomal
It is autosomal because it is 50/50 men to women with the disorder, if it was X-linked most of the men in the diagram would have the disorder.
Make sure you count the number of men with the disorder and the number of women with the disorder. In this pedigree, 3 men and 3 women have the disorder.

41. Summary -Pedigrees are family trees that explain your genetic history.
-Pedigrees are used to find out the probability of a child having a trait/disorder in a particular family.
-To begin to interpret a pedigree
-determine if the trait/disorder is:
1-dominant or recessive
2-condition is autosomal or X-linked
This summary will help reiterate the important parts of this lesson.
[Created by Lauren Almaguer, CDC Science Ambassador, 2004.]

42. PEDIGREE PRACTICE 1-A

43. PEDIGREE PRACTICE 1-B

44. PEDIGREE PRACTICE 1-C

45. PEDIGREE PRACTICE 1-D

46. PEDIGREE PRACTICE 2-A

47. PEDIGREE PRACTICE 2-B

48. PEDIGREE PRACTICE 2-C

49. PEDIGREE PRACTICE 2-D

50. 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 symbols—include names
-CONTINUE with other members in the family
-DETERMINE genotypes as you gather enough information