4.1 Chromosomes, Genes, Alleles and Mutations Flashcards Preview

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Flashcards in 4.1 Chromosomes, Genes, Alleles and Mutations Deck (8)
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1

Describe the structure of eukaryotic chromosomes

Eukaryotic chromosomes consist of DNA wrapped around histone proteins

2

Define gene

A heritable factor that controls a specific characteristic

3

Define allele

A specific form of a gene, occupying the same locus as other alleles of the gene

4

Define genome

The whole of the genetic information of an organism

5

Define gene mutation

A change in the nucleotide sequence of a gene

6

Define base substitution mutation

The change of a single base in a sequence of DNA, resulting in a change to a single mRNA codon during transcription

7

Describe and explain the effects of sickle-cell anaemia as an example of a base substitution mutation

• Sickle cell anaemia is inherited and cannot be passed on through infection
• Affected gene found on chromosome 11
• A base substitution mutation changes GAG to GTG causing glutamic acid to be replaced by valine
• The resulting amino acid change alters the shape of the haemoglobin, causing it to form fibrous, insoluble strands
• As a result, the haemoglobin are a lot less efficient at transporting oxygen, causing anaemia

8

State and explain the relationship between malaria rampancy and sickle-cell anaemia rates

• In areas where malaria is rampant, sickle cell anaemia is more common because the malaria parasite cannot infect the mutated haemoglobin
• Thus sickle cell anaemia gives carriers an advantage