Lecture 4: Polyploidy and Replication

What is a genome

A genome is the complete set of genetic information in an organism and can be referred to as 1C, or one haploid complement.

What does diploid mean

Diploid (2n) means a cell contains 2 sets of chromosomes, one inherited from each parent

How many chromosome sets and chromosomes do humans have?

Humans are diploid with 2 sets of 23 chromosomes, giving 46 chromosomes total.

How does ploidy differ between bacteria and mammals

Bacteria are generally haploid (one chromosome set), while mammals are diploid (2 chromosome sets)

What is the advantage of having multiple copies of genetic info

Multiple copies can mask harmful or recessive mutations because another normal copy may still provide the functional gene product

Why are mutations more likely to be expressed when fewer gene copies are present?

With fewer copies, less chance for a normal copy to mask mutation, so its effect is more likely to appear phenotypically

Autopolyploid

An organism with multiple chromosome sets from same species, so sets are identical

How can autopolyploids arise

Arise fron unreduced gametes that accidentally retain a full chromosome set. Autotetraploid has four sets (4x)

Allopolyploid

An organism with chromsomes sets from different species, so sets are similar but not identical

How can allopolyploids arise?

Through hybridization between different species followed by chromosome doubling. An allotetraploid has four sets (4x).

Can ploidy vary among cells within the same organism?

Yes, some tissues contain cells with different ploidy levels. Human liver cells can become polyploid through endopolyploidy, and polyploid cells are also common in tumors