learning targets “i can…” -describe homologous chromosomes and identify the chart used to...

Learning Targets“I Can…”

-Describe homologous chromosomes and identify the chart used to organize homologous chromosomes.

-Create a karyotype from a given set of chromosomes.

-Identify the sex chromosomes on a karyotype to determine the gender of an individual.

-Diagnose any nondisjunction errors in a given karyotype.

Karyotype

Sex Determination

Assignment for today:

• Create a karyotype from the given set of chromosomes

• Determine:1. The gender of your child2. If there are any missing or extra chromosomes and where3. The name of the disorder (if there is one)4. The symptoms of the disorder

Defects in the number of chromosomes can come

from chromosome NONDISJUNCTION

during meiosis

Down Syndrome(aka Trisomy 21)

Normal Meiosis

• Chromosomes separate from each other during . . . – Anaphase I– Anaphase II

Nondisjunction during meiosis

NONDISJUNCTION increases with the mother’s age

• No one is sure why this happens!

• After age 35, amniocentesis is suggested to diagnose extra or missing chromosomes

• Nondisjunction errors are RANDOM!

Nondisjunction of 21st Chromosome (Most Common)

Nondisjunction of Sex Chromosomes

Assignment for today:

• Create a karyotype from the given set of chromosomes

• Determine:1. The gender of your child2. If there are any missing or extra chromosomes and where3. The name of the disorder (if there is one)4. The symptoms of the disorder

References• http://www.stjohnsmercy.org/images/chromosome.gif• http://ghr.nlm.nih.gov/handbook/illustrations/chromosomes.jpg• http://www.biotechnologyonline.gov.au/images/contentpages/chrom

osomes.jpg• http://openlearn.open.ac.uk/file.php/1638/SK220_1_011i.jpg• http://www.genetics.com.au/images/factsheets/fs29-2.gif• http://www.miscarriage.com.au/images/pages/t21karyo.jpg• http://www.biology.arizona.edu/human_Bio/problem_sets/

human_genetics/graphics/klinefelters.gif• http://www.genetics.com.au/images/factsheets/fs28-1.gif

• http://www.mydr.com.au/files/images/categories/babies/amniocentesis.gif