Biology SL Chapter 4.1 (Chromosomes, Genes, Alleles and mutations)

Structure of eukaryotic chromosomes
Formed of DNA wrapped around histone proteins. This structure is called a nucleosome, which when packed together forms a chromatim which condense during prophase, forming chromosomes.
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Define a gene
A heritable factor that controls a specific charateristic, consisting of a length of DNA occupying a particular position on a chromosomes
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Define an allele
One specific form of gene, differing from other alleles by one or a few bases and occupying the same locus as other allels of a gene.
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Define a genome
The whole genetic information of an organism
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Dfine a gene mutation
A change in the nucleotide sequence of a section of DNA coding for a particular feature
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Base substitution mutation
Is the change of a single base in a sequence of DNA, resulting in a change to a single mRNA codon during transcription.
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Cause of sickle cell anemia
Caused by 6th codon on bate chain of haemoglboin changed from GAG to GTG. This causes change in mRNA codon (GAG to GUG) resulting in amino acid change from glutamic acid to valine. This alters strucutre of haemoglobin, changes shape of red blood cell
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Consequences of sickle cell anemia
The haemoglobin can not effectively carry oxygen,individual feels instantly tired. Sickle cells can accumulate in capillaries and form clots, blocking blood supply.causes anaemia(low RBC count).Occurs in people who have 2 copies of sickle cell allele
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Card 2

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Define a gene

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A heritable factor that controls a specific charateristic, consisting of a length of DNA occupying a particular position on a chromosomes

Card 3

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Define an allele

Back

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Card 4

Front

Define a genome

Back

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Card 5

Front

Dfine a gene mutation

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