PedigreesPedigree : a chart that shows how a trait and the

genes that control it are inherited in a family.

Parts : male female Affected Affected

male female

DeathCarriers : Heterozygousfor the recessive allele

*Roman Numerals = generations

Pedigree

Parents

Offspring

I

II

III

Karyotypes

Karyotype : a photograph that shows an individual’s chromosomes in

homologous pairs. (23 pairs)

*Can be used to show any chromosome abnormality that is visible.

http://www.gla.ac.uk/medicalgenetics/nhs/karyotypemovie.htm

http://www.biology.iupui.edu/biocourses/N100/2k2humancsomaldisorders.html

I. Autosomal Genetic DisordersDisorders found on the chromosome pairs 1-22, not sex

chromosomes1. Sickle Cell Disease – codominance disorder

where red blood cells have abnormal sickle shape. *Makes blood cells stick in capillaries causing low blood flow, anemia, and tissue damage.

*occurs in about 1 and every 500

African American births, and 1 out of 12 African Americans are carriers.

Sickle cell is a result of a point mutation

http://www.hhmi.org/biointeractive/media/malaria_mosquito-lg.mov

http://www.hhmi.org/biointeractive/media/malaria_human-lg.mov

Autosomal Genetic Disorder (continued)

2. Tay-Sachs Disease - incurable disorder where lipids build up in the brain cells and destroy them.

3. Cystic Fibrosis - the most common fatal inherited disorder among whites in the United States. Caused by recessive allele on chromosome 7 which causes excessive secretion of thick mucus from the pancreas, lungs, and other organs.

http://www.pbs.org/wgbh/nova/genome/program.html#03

4. PKU- (Phenylketonuria) an autosomal recessive disorder in which the body is unable to use the essential amino acid phenylalanine because the enzyme phenylalanine hydroxylase is deficient.

Phenylalanine occurs in significant amounts in milk, eggs, and other common foods. The artificial sweetener NutraSweet (aspartame) also contains phenylalanine. If treatment is delayed or the condition remains untreated, brain damage will occur

Autosomal Genetic Disorder (continued)

Autosomal Genetic Disorder (continued)

5. Huntington’s Disease - inherited disorder caused by a dominant allele. The disease causes a progressive breakdown of muscle coordination and mental deterioration, leading to death.

Chromosomal DisordersAdditions or deletions on chromosomes1. Down Syndrome - disorder that results from an

extra copy of chromosome #21. This causes mental retardation and physical abnormalities.

XXXhttp://www.livingwithtrisomy13.org/trisomy-13-

videos.htm2. Turner’s Syndrome - caused by the presence of

only one X chromosome - Resulting female has underdeveloped sexual characteristics. Genotype is : XO and individual is sterile.

Chromosomal Disorders (con’t)

3. Klinefelters syndrome - A person with two X’s and a Y in each cell, resulting male has underdeveloped sex organs. Genotype is: XXY and individual is sterile.

http://www.biology.iupui.edu/biocourses/N100/2k2humancsomaldisorders.html

Sex Linked DisordersFound on sex chromosomes1. Hemophilia - blood is unable to clot.

Recessive gene is carried on X chromosome.

Hemophilia is sometimes referred to as “the royal disease” because several members of noble families in Europe were affected by it. Queen Victoria had no ancestors with the condition but soon after the birth of her eighth child, Leopold, in 1853, it became evident that he had hemophilia. Queen Victoria was thus an example of how the condition can arise as a spontaneous mutation. Leopold died at the age of 31 from an intracerebral haemorrhage after a fall. Two of Queen Victoria"s own daughters, Alice and Beatrice, were also carriers of hemophilia. The condition was transmitted through them to several royal families in Europe, including Spain and Russia. Perhaps the most famous affected individual was the son of Tsar Nicholas II of Russia, Tsarevich Alexis, who was born in 1904. There has been speculation that the illness led to severe strain within the royal family, and enabled Rasputin to gain influence over the family, ultimately leading to the downfall of this once powerful dynasty.

British Royal Family

*The allele has been traced back to Queen Victoria, and since royal families tend to marry into royal families this allele has spread into Russia and Spain

Take a look at Queen Victoria’s son Leopold’s family. His daughter, Alice of Athlone, had one hemophilic son (Rupert) and two other children—a boy and a girl—whose status is unknown. a)What is the probability that her other son was hemophilic? b)What is the probability that her daughter was a carrier? Hemophilic? c)What is the probability that both children were normal?

2. Duchenne Muscular Dystrophy - muscle tissue breaks down during childhood and the recessive gene is carried on the X chromosome. Individuals usually do not live beyond their teens.

Sex Linked Disorders

Dystrophin is crucial to the muscle building and muscle maintaining processes. As muscles are used they quickly deteriorate due to the lack of dystrophin to repair and maintain muscle growth. Eventually the chest muscles deteriorate causing breathing difficulties. These difficulties lead to respiratory infections which continue until the process takes the life of the child.

Sex linked Disorders (con’t)

3. Color Blindness - recessive disorder carried on the X chromosome where an individual cannot perceive certain colors (usually red and green).

* Very few females have these conditions but they can be carriers of the defective allele

*Males with the condition can pass it on to a daughter, but NOT a son. .

Linkage maps estimate distances between genes. The closer together two genes are, the more likely they will be

inherited together.Cross-over frequencies are related to distances between genes.

The further the dist the higher the percentage of crossover.Linkage maps show the relative locations of genes.

Cross-over frequencies can be converted into map units.

– gene A and gene B cross over 6.0 percent of the time

– gene B and gene C cross over 12.5 percent of the time

– gene A and gene C cross over 18.5 percent of the time

Incomplete Dominance - when two contrasting alleles contribute to an individual with a trait not exactly like either parent.

Example : flower color (snapdragons)R = red genotype RRW = white genotype WW

*Individuals with red & white flowers are always homozygousR R

WW

R R

R R

W

W

W

W

*Offspring are heterozygousfor both dominant traits.

RW = pink flowers

*Neither red or white are completely dominant so when they are crossed we get an intermediate type….pink flowers!

Codominance - 2 dominant alleles are expressed at the same time.

Example: Roan Coat in some cattle

Homozygous red x Homozygous white shorthorn cattle shorthorn cattle

CRCR CWCW

Offspring Roan Coat CRCW

*Individual shows both red and white = roan coat

Multiple Alleles - three or more different alleles for a specific trait.

Human Blood Types

3 Alleles

1. A2. B3. O

* O is recessive * A & B are both dominant over O but neither are dominant over each other!* A & B are codominant and both alleles are expressed

*Can use the capital I to show a dominant allele and the lowercase i to show a recessive allele.

A is dominant so ……………IA

B is dominant so ……………IB

O is recessive so …………… i

Genotypes Phenotypes1. IAIA A blood2. IBIB B blood3. IAIB (codominant) AB blood 4. IAi A blood 5. IBi B blood 6. ii O blood

Polygenic traits are

produced by two or more genes.

Order of dominance: brown > green > blue.

exps: eye color, skin pigment, hair color