Sheet 9.5 Revision Chromosome number
Sheet 9.5 Revision
Chromosome number
Diploid and haploid
Human body cells are diploid, meaning they have a full set of chromosomes. In humans the
diploid number is 46 chromosomes. Human sex cells (eggs and sperm) are haploid, as they
contain half a set of chromosomes. In humans the haploid number is 23 chromosomes. We
get half a set of chromosomes from each parent (when a sperm fertilises an egg).
Chromosome numbers in diferent species
The number of chromosomes in each species varies greatly, but is the same for all the
individuals within a species. The number of chromosomes is not related to whether an
organism is bigger or more complicated. The symbol N is used to represent the number of
chromosomes. Haploid is abbreviated to 1N. Diploid is abbreviated to 2N. Most species are
diploid with haploid sex cells. However, a few species only have haploid cells, while others
have three, four or more sets of chromosomes.
diploid A cell with a full set of chromosomes
haploid A cell with half a set of chromosomes; in humans these are sex cells (eggs and sperm)
species Organisms that can breed and produce fertile offspring
Chromosome numbers in diferent species
The number of chromosomes in each species varies greatly, but is the same for all the
individuals within a species. The number of chromosomes is not related to whether an
organism is bigger or more complicated. The symbol N is used to represent the number of
chromosomes. Haploid is abbreviated to 1N. Diploid is abbreviated to 2N. Most species are
diploid with haploid sex cells. However, a few species only have haploid cells, while others
have three, four or more sets of chromosomes.
Science for the New Zealand Curriculum Years 9 and 10
© Donald Reid, Catherine J. Bradley, Des Duthie, Catherine Low, Matthew McLeod, Colin Price 2010
Published by Cambridge University Press www.nzscience.co.nz www.cambridge.edu.au
1
Sheet 9.5 Revision Chromosome number
Science for the New Zealand Curriculum Years 9 and 10
© Donald Reid, Catherine J. Bradley, Des Duthie, Catherine Low, Matthew McLeod, Colin Price 2010
Published by Cambridge University Press www.nzscience.co.nz www.cambridge.edu.au
2