Pedigrees Part 1

Pedigrees Today, we will be discussing Pedigrees. What do you think of when you hear the word Pedigree?  

Create your own family tree Mom MS. GLEASON! Dad Sister- Stephanie Nephew- Robert Brother- Liam Brother- Patrick Sister- Kate Sister- Anne

The family tree of genetics Pedigree Charts The family tree of genetics 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. X-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.

What is a pedigree? - a genetic family tree 1. A chart of an individual's ancestors used in genetics to analyze inheritance of certain traits, especially of family diseases.  

Pedigrees are useful for… 2. Pedigrees are useful for tracking the transmission (passing on) of a trait across generations. 3. There are many diseases that are genetic. This means that people can not “catch” the disease, the disease must be inherited from their relatives.  

Examples of Genetic Diseases 4. These are some of the genetic diseases that you will see used in pedigree questions: Cystic fibrosis, Sickle Cell Disease, Colorblindness, Hemophilia, Down Syndrome, and Tay-Sachs Disease.

KEY Explains what the symbols on the pedigree mean

How to read a pedigree -A circle represents a 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. -A circle represents a female -A square represents a male

Connecting Pedigree Symbols Married Couple Siblings (children of married couple) These symbols also represent relationships between people. some may have to each other. -A horizontal line connecting a male and female represents a marriage -A vertical line and a bracket connect the parents to their children

Symbols in a Pedigree Chart Affected Carrier Unaffected Half shaded means the person isn’t affected but they still carry the trait These are examples of different types of symbols. These symbols would be the same for males or for females, except for X-linked carrier which is only used for females. So an affected male would be a square that is filled in completely. A deceased female would be a circle with a diagonal slash. -A circle/square that is shaded means the person HAS the trait/ is AFFECTED. -A circle/square that is not shaded means the person does not have the trait/ is unaffected.

Marriage Male-DAD Female-MOM Has the trait Female-daughter Male- Son Male-Son

Organizing the pedigree chart Generations are identified by Roman numerals (I, II, III) I II III IV © 2007 Paul Billiet ODWS

Organizing the pedigree chart Individuals in each generation are identified by numbering from the left to the right Therefore the affected individuals are II3, IV2 and IV3 I II III IV © 2007 Paul Billiet ODWS

Practice How many males in the family are affected with colorblindness? Which individuals are carriers in generation II? How many children do the parents of generation I have? In generation IV, how many females are affected? How many males are there in generation III? What is the relationship between individual II-4 and II-5?

Practice Problem Answers How many males in the family are affected with colorblindness? Six Which individuals are carriers in generation II? II-2, II-4, II-7 How many children do the parents of generation I have? Five In generation IV, how many females are affected? One How many males are there in generation III? Five What is the relationship between individual II-4 and II-5? They are married.

Assignment Work on the Pedigree Chart Worksheet independently on CODE RED. Unfinished classwork will become homework