Control of Gene Expression (Cambridge (CIE) IGCSE Co-ordinated Sciences (Double Award)): Revision Note
Control of Gene Expression: Extended
Extended Tier Only
Haploid and Diploid Cells
All humans have 23 different chromosomes in each cell
In most body cells, not including the gametes (sex cells), we have 2 copies of each chromosome, leading to a total of 46 chromosomes
Nuclei with two sets of chromosomes are known as diploid nuclei
The gametes (egg and sperm cells) only have one copy of each chromosome, meaning they have a total of 23 chromosomes in each cell
Nuclei with one set of unpaired chromosomes are known as haploid nuclei
Human gametes (sperm and egg cells) are haploid
Examiner Tips and Tricks
An easy way to remember the difference between haploid and diploid is to remember:
Haploid = Half the normal number of chromosomes
It’s worth noting that the human diploid chromosome number is 46. In an exam, you may be given information about a different species, with a different number of chromosomes. Make sure you read exam questions carefully.
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