What is a homologous chromosome?

ObjectivesWhat 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.