Mutations caq

🧟 Mutations Created Tags Difference between gene mutation and chromosomal aberrations June 16 , 2025 128 AM Mut ations 1

Notes what recessive mutations mean Both copies of the gene must be mutated Mutations will result in non-functional protein/ no protein produced Normal allele will mask the effect of mutated allele if only one copy is mutated Explaining how a point mutation can result in a non-functional protein/ disease/ any condition or effect Explain what the type of mutation given in the question means Insertion mutation: adding of nucleotide into the nucleotide sequence A single base substitution from original base to new base This will result in the change of sequence of mRNA and a change in codon Mut ations 2

Causing a different anticodon binding to the mutated codon, carrying a different amino acid with different R group chemical properties Changes in primary structure Change in specific 3D conformation If an enzyme, can cause enzyme to no longer be complementary to substrate Can cause enzyme to be non functional May introduce stop codon causing a shortened polypeptide and hence the protein wonʼt be produced Effect of mutations on haemoglobin sickle cell anaemia) A single base substitution from thymine to adenine Results in a change of sequence of mRNA and change in codon Change from GAG coding for amino acid glutamate to GUG which codes for valine Hydrophillic charged glutamic acid is replaced by hydrophobic non-polar valine This changes the primary, secondary and tertiary structure because polypeptide chain folds is affected by change in R group and bonds formed At low oxygen, loss of oxygen from HbS results in an unusual conformational change that causes a hydrophobic patch to stick out This hydrophobic patch attaches to a hydrophobic patch on an other HbS causing them to polymerise into insoluble fibres es Long insoluble HbS fibres within red blood cell causes its shale to be distorted from a normal biconcave to a sickle shape, resulting in them being more fragile, having a shorter lifespan This causes shortage of RBC and poor oxygen transport causing anaemia The RBC can also get lodged in small blood vessels, interfering in blood circulation causing organ damage Mut ations 3

Explain why somatic mutations have a milder consequence than Germaine mutations Notes mtDNA mutation Notes Describing effect of mutation Ref to nucleotide substitution/ insertion/ mutation (mechanism) Ref to missense/nonsense/frameshift mutation/extensive missense and may result in nonsense mutation (effect) Mut ations 4

Ref to different amino acid added, changing 3D structure of protein/ premature termination of translation/ synthesis of truncated protein effect of mutations in inter-ionic region Creates a new alternative splice site within interionic region As a result, alternative splicing, both normal splice and incorrectly spliced mRNA are produced Effect of mutation in upstream region Mutation occurs in the promoter region/enhancer/silencer Reduces binding efficiency of general transcription factors/ RNA polymerase/activator OR increases binding efficiency of repressors Less mRNA synthesised/ less gene expression/ transcription and hence less protein produced Describe how gene mutations may affect the protein coded for by a gene A gene mutation is a change in the nucleotide/ base sequence in DNA Substitution mutation is where a nucleotide is replaced by a different nucleotide, resulting in a change in sequence of mRNA and a change in codon, causing a different Sequence of amino acid which leads to different folding of polypeptide to 3D conformation of same folding of polypeptide to 3D conformation as new amino acid coded is chemically similar Insertion or addition occurs when one or several nucleotides are inserted in a sequence and deletion occurs when one or several nucleotides are removed from a sequence of bases, resulting in a frameshift mutation and different sequences of amino acid, leading to different folding of polypeptide to 3D conformation or a truncated polypeptide and hence non functional Inversion is a segment of nucleotide sequence separated from the allele and rejoins at the original position but it is inverted causing in different codons on Mut ations 5

mRNA and a different amino acid leading to different folding of polypeptide to 3D conformation or truncated polypeptide hence non Functional polypeptide For a named genetic disease, describe the mutation and effect of phenotype Sickle cell anaemia a result of a point substitution mutation where thymine is replaced with adenine in a gene coding for the beta globin chain A change in a single base in the 6th triple codon results valine to replace glutamine amino acid Valine being non-polar compared with charged glutamine results in a change in properties of polypeptide chain causing change in primary, secondary and tertiary structure leading to different folding of polypeptide to 3D conformation and normal haemoglobin becomes sickle cell haemoglobin When oxygen levels are low in the blood, the Hb Scmolecule undergoes an unusual conformation change that allows Hb S to polymerise/ crystallise to form rigid fibres This causes rbc to change from a circular biconcave shape to sickle shape Sickled RBC May obstruct blood vessels and interfere with blood circulation causing organ failure It is also more fragile and susceptible to lysis and active destruction of spleen results in reduction in rbc numbers causing anaemia It is a recessive condition requiring both alleles to the Beta globin chain to be mutated in order for the symptoms to appear How to know phenotypic features of an individual from its karyotype 3 copies of chromosome 21 Person has Down syndrome and should have characteristics facial features such as short stature, hear defects, susceptibility to respiratory infection and mental retardation Mut ations 6

Having 2 homologous chromosome 23  same height, size) Female with female reproductive structure such as ovaries Mut ations 7