Chromosomes, Genes and ProteinsCambridge IGCSE Biology: Flashcards

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Define a gene.

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Define a gene.: A length of DNA that codes for a protein.
Define an allele.: An alternative form of a gene.
What are chromosomes made of?: DNA, which contains genetic information in the form of genes.
Which chromosomes determine sex in humans?: X and Y chromosomes — XX is female, XY is male.
What determines the sequence of amino acids in a protein?: The sequence of bases in the gene (and mRNA) coding for that protein.
Why do different genes produce proteins with different shapes?: Different genes have different base sequences, giving different amino acid sequences, which fold into different shapes.
What is mRNA?: Messenger RNA — a copy of a gene made in the nucleus that carries the genetic code to the ribosome.
Where in the cell is a protein assembled?: At a ribosome in the cytoplasm.
List the first three steps of making a protein from a gene.: The gene stays in the nucleus; mRNA is made as a copy of the gene; the mRNA moves from the nucleus to the cytoplasm.
Name three types of protein controlled by DNA.: Enzymes, membrane carriers, and receptors for neurotransmitters.
Why do a muscle cell and a nerve cell look different if they have the same DNA?: Because only some of their genes are expressed — each cell type only makes the specific proteins it needs.