PEDIGREE CHARTS A family history of a genetic

What is a pedigree chart? ¢ ¢ ¢ A record of the family of

Studying human genetics ¢ ¢ You cannot make humans of different types breed together

Symbols used in pedigree charts ¢ ¢ ¢ Normal male Affected male Normal female

Organising the pedigree chart ¢ A pedigree chart of a family showing 20 individuals.

Organising the pedigree chart l Generations are identified by Roman numerals. I II IV

Organising the pedigree chart ¢ ¢ Individuals in each generation are identified by Arabic

Hints for analyzing pedigrees: 1) If the individual is homozygous recessive, then both parents

¢ ¢ If two affected individuals give rise to an unaffected child the affected

Tongue rolling rr rr rr © 2016 Paul Billiet ODWS

Tongue rolling ¢ All non-rollers must be genotype rr © 2016 Paul Billiet ODWS

Tongue rolling rr Rr rr rr © 2016 Paul Billiet ODWS Rr Rr rr

Tongue rolling ¢ ¢ If one of the parents is a roller and the

Albinism aa Aa Aa Aa aa aa Aa aa © 2016 Paul Billiet ODWS

Albinism - a recessive condition ¢ ¢ If two unaffected individuals give rise to

B) Determining inheritance 1. Autosomal dominant – A=affected, a=normal a) USUALLY every generation b)

2 Autosomal recessive a) MAY skip generations b) If affected offspring with 2 healthy

3. Sex-linked recessive a) Males affected MUCH more than females! b) MUST SHOW sex

Draw your own pedigree. 1. 2. 3. Draw a pedigree showing all individuals described

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What is a pedigree chart? ¢ ¢ ¢ A record of the family of an individual Used to study the transmission of a hereditary condition Useful when there are large families and a there is a good family record over several generations. © 2016 Paul Billiet ODWS

Studying human genetics ¢ ¢ You cannot make humans of different types breed together Pedigree charts offer an ethical way of studying human genetics Today genetic engineering has new tools to offer doctors studying genetic diseases A genetic counselor will still use pedigree charts to help determine the distribution of a disease in an affected family. © 2016 Paul Billiet ODWS

Symbols used in pedigree charts ¢ ¢ ¢ Normal male Affected male Normal female Affected female Marriage. A marriage with five children, two daughters and three sons. The middle son is affected by the condition Eldest child Youngest child © 2016 Paul Billiet ODWS

Organising the pedigree chart ¢ ¢ Individuals in each generation are identified by Arabic numerals numbered from the left Therefore the affected individuals are II 3, IV 2 and IV 3. I II IV © 2016 Paul Billiet ODWS

Hints for analyzing pedigrees: 1) If the individual is homozygous recessive, then both parents MUST have at least one recessive allele (parents are heterozygous or homozygous recessive). 2) If an individual shows the dominant trait, then at least one of the parents MUST have the dominant phenotype. 3) If both parents are homozygous recessive, then ALL offspring will be homozygous recessive.

Tongue rolling ¢ ¢ If one of the parents is a roller and the other is a non-roller all the roller children must be heterozygous rollers (Rr) If a roller parent has a non-roller child the parent must be heterozygous. © 2016 Paul Billiet ODWS

Albinism - a recessive condition ¢ ¢ If two unaffected individuals give rise to an affected child, the allele for the affected condition is recessive The unaffected parents are carriers (heterozygous) Thus recessive conditions can skip several generations Inbreeding increases the chance of carriers producing an affected child. © 2016 Paul Billiet ODWS

B) Determining inheritance 1. Autosomal dominant – A=affected, a=normal a) USUALLY every generation b) EVERY affected offspring has at least 1 affected parent

2 Autosomal recessive a) MAY skip generations b) If affected offspring with 2 healthy parents MUST BE RECESSIVE

3. Sex-linked recessive a) Males affected MUCH more than females! b) MUST SHOW sex chromosomes when labeling

Type of Inheritance?

Draw your own pedigree. 1. 2. 3. Draw a pedigree showing all individuals described in problem Label the genotypes of as many individuals in the pedigree as possible. Shade in half of the symbol if you know the individual is heterozygous or a carrier. Condition of Interest: Albinism is a condition in which there is a mutation of several possible genes, each of which helps code for the protein melanin. This gene is normally active in cells called melanocytes which are found in the skin and eyes. Albinism is lack of normal coloration to their skins/eyes. Inheritance Pattern: normal melanin protein is produced by an autosomal domain allele; albinism results from a lack of melanin and is caused by an autosomal recessive alleles. Use the letter A or a to represent dominant/ recessive forms of albinism. Two normally pigmented parents have 3 children. The first child (a girl) and their second (boy) have normal pigmentation. Their third child (girl) has albinism. That girl marries a normally pigmented male and they have four children. The first three (two girls and a boy) have normal pigmentation. Their fourth child (girl) has albinism like her mother.

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