What are chromosomes made of?
DNA.
Cambridge IGCSE (9–1) Biology 0970 (Extended) (2026–2028) · 17.1
Revise Cambridge IGCSE (9–1) Biology 0970 (Extended) (2026–2028) specification point 17.1, Chromosomes, genes and proteins, with free active-recall flashcards. Flip through the set or review every question and answer below.
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What are chromosomes made of?
DNA.
What do chromosomes carry?
Genetic information.
What is a gene?
A length of DNA that codes for a protein.
Where are genes located in chromosomes?
They are parts of the DNA in chromosomes.
What is an allele?
An alternative form of a gene.
What are the typical sex chromosome combinations in human females and males?
Females: XX; males: XY.
How do the egg and sperm determine the offspring’s sex chromosome combination?
The egg contributes X; the fertilising sperm contributes X or Y, producing XX or XY, respectively.
What does the base sequence of a gene determine in the protein it encodes?
The order of amino acids used to make the protein.
How can differences in amino acid sequence affect protein molecules?
They can cause the proteins to have different shapes.
How is information from a protein-coding gene conveyed from the nucleus to the cytoplasm?
The gene remains in the nucleus. An mRNA copy is made there and moves to the cytoplasm.
What does a ribosome do as mRNA passes through it?
It assembles amino acids into a protein.
What determines the order in which amino acids are assembled into a protein?
The sequence of bases in the mRNA.
How does DNA influence what a cell does?
By controlling which proteins the cell produces.
What role do enzymes play in cells?
They catalyse reactions.
What do membrane carrier proteins do?
They move substances across membranes.
What role do receptors for neurotransmitters play in cells?
They allow cells to respond to chemical signals.
What does it mean for a gene to be expressed?
The gene is used to make its protein.
How can body cells with largely the same genes produce different sets of proteins?
They express different subsets of genes. Many genes remain unexpressed, while each cell makes the specific proteins it needs.
What is a haploid nucleus?
A nucleus with one set of chromosomes, containing one chromosome of each type.
What is a diploid nucleus?
A nucleus with two sets of chromosomes, containing a pair of each type.
How many chromosome pairs and total chromosomes are in a human diploid cell?
23 pairs, or 46 chromosomes in total.
Does the haploid–diploid distinction depend on whether chromosomes contain genes?
No. It concerns the number of chromosome sets in a nucleus.