1. Patterns of inheritance
A quick refresher for the teacher on important terms:
Autosomal gene- a gene found on any chromosome except for the sex chromosome. These are chromosomes numbered 1-22.
Sex-linked gene- a gene found on a chromosome designated as a sex chromosome (X or Y).
Dominant- Refers to an allele that is expressed phenotypically and masks any recessive counterpart.
Recessive- An allele that is not phenotypically expressed when its counterpart is dominant.
Chapter 11.1

2. Genetic disorders
Problem caused by one or more abnormalities in the genome.
Usually present at birth (congenital)
Occur rarely

3. Recessive genetic disorders
Recessive traits can only be expressed when the individual is homozygous recessive.
Individuals that are heterozygous for are called carriers

4. Examples of Recessive disorders
Cystic fibrosis – excessive mucus production causes digestive and respiratory failure.
Albinism – absences of pigment in skin, eyes, and hair.

5. Dominant genetic disorders
disorders are caused by dominant alleles.
People without the disorder are homozygous recessive
People with the disorder are homozygous dominant or heterozygous.

6. Examples of Dominant Disorders
Huntington’s disease – gene affecting mental function.
Achondroplasia – gene that affects bone growth

7. What is a Pedigree?
A pedigree is a chart of the genetic history of family over several generations.
Scientists or a genetic counselor find out about your family history and make a chart to analyze.
A pedigree is a chart of the genetic history of family over several generations. Scientists or a genetic counselor would find out about your family history and make this chart to analyze it. For example, a couple might like to know their chances of having a child that has muscular dystrophy. So the scientists or a genetic counselor would find out who had muscular dystrophy in the mother’s and/or father’s families. This information would be used to and then calculate the probability of the couple having a child with MD.

8. Constructing a Pedigree
Female
You must learn the symbols of the pedigree charts before you can start to learn how to interpret it. These are the symbols that represent a male and a female.
Male

9. Constructing a pedigree
Affected
Unaffected
Carrier

10. Connecting Pedigree Symbols
Marriage
Generation
Siblings
These symbols also represent relationships between people. some may have to each other.

11. Example I 1 – I 2 – Unaffected Male II 1 – II 2 – Female Carrier
This is just an example of a pedigree and there can be many more different types.
Female Carrier
Unaffected female
Male Carrier
Unaffected Male
Female Carrier

12. Interpreting a Pedigree Chart
Dominant – one of the parents must have the disorder.
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.

13. Dominant or Recessive?
Recessive

14. Dominant or Recessive?
Dominant

15. Dominant Female Affected by disorder Homozygous recessive
1) Dominant or Recessive? 2)What is the Gender of III 3? 3) What is the phenotype of I 3? 4) What is the genotype of II 6? I II
III
Dominant
Female
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.
Affected by disorder
Homozygous recessive

16. 1) Dominant Or Recessive. 2) What is the Genotype of II 2
1) Dominant Or Recessive? 2) What is the Genotype of II 2? 3)What is the genotype of I 3? 4) Who can you determine are Carriers? I II
III
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.
Homozygous recessive
heterozygous
I 1, I 2, I 3, I 4, II 3, III 1, III 3

17. I II
III
1) Dominant or Recessive? 2) What is the Genotype of I 1? 3) What is the phenotype of III 3? 4) What’s the genotype of III 3?
Recessive
Heterozygous
Affected by disorder
Homozygous recessive

18. Autosomal vs. Sex linked
autosomal disorders appear on the chromosomes 1-22.
Dominant or Recessive
Sex linked disorders are on the Sex chromosomes.
X or Y

19. Sex linked traits Usually linked to the X chromosome.
Inherited differently for males and females
Examples:
color-blindness,
hemophilia

20. How are sex linked traits passed on?
Colorblindness is
On the X
chromosome
Female receive two
Alleles
Males only receive
One allele.

21. Hemophilia and the Royals
Hemophilia is an X-linked recessive disorder characterized by the inability to properly form blood clots.
Until recently, hemophilia was untreatable, and only a few hemophiliacs survived to reproductive age because any small cut or internal hemorrhaging, after even a minor bruise, was fatal.

22. Hemophilia and the Royals

23. Hemophilia and the Royals
What is the symbol for a carrier female?
White circle
What is the symbol for a hemophilic man?
Orange square

24. Hemophilia and the Royals
How many children did Queen Victoria have? 9
What ratio of her daughters were carriers?
2/5

25. Hemophilia and the Royals
Look at the last generation. What is the ratio of hemophilic to normal men?
6/10 = 3/5

26. Hemophilia and the Royals
Nicholas II of Russia
Married Princess Alexandra of Hesse, who was the granddaughter of Queen Victoria.

27. Hemophilia and the Royals
Nicholas and Alexandra’s son, Tsarevich Alexy Nikolaevich
Youngest of five children and the only son
Hemophilic

28. Hemophilia and the Royals
Gregory Rasputin ( )
Known as the “Mad Monk,” but was not really religious.
“Faith healer”
Alexandra thought he could control her son’s hemophilia. For this reason, he was important to the royal family, but he used his position for money and power. He played a small but important role in the downfall of the Romanov dynasty and the royal family.

29. Hemophilia and the Royals
In 1917, Russia had a revolution led by the communists. Nicholas was forced to abdicate (give up being Tsar) and he and his family were arrested. On July 17, Nicholas, his wife, and their five children were all killed by a Soviet firing squad.