What is a homologous
chromosome?
Objectives
What is a karyotype?
What are homologous chromosomes?
Differentiate between autosomes and sex
chromosomes.
Karyotype
• A karyotype is
a picture of
ALL a person’s
chromosomes
Autosomes vs. Sex Chromosomes
• There are two types of chromosomes
– Sex chromosomes are chromosomes that
determine gender
• XX = female
• XY = male
• These are the 23rd pair on a human karyotype
– Autosomes are any chromosomes that are not sex
chromosomes
• These are pairs 1-22 on a human karyotype
Check for Understanding
• How many chromosome pairs do you have?
• Are your sex chromosomes XX or XY?
• Where do the pairs come from?
Chromosome Pairs
•
In each pair, one chromosome comes from mom
and one comes from dad
•
Each pair of chromosomes is referred to as a
homologous pair
What are homologous chromosomes?
• Homologous chromosomes are a pair of
chromosomes
– They have the same size and shape with the same
organization.
– Most importantly, they have the same genes but the
version of the gene may be different.
• Example:
–Gene=eye color
–Version= brown eyes or blue eyes
Check for understanding:
• Are homologous chromosomes identical to each
other? Explain.
Check for Understanding- Answer
• No, they are very similar in size and shape and
carry the same type of genes, but the version
of the genes may differ.