concept 14 - BIO10008

define and provide an example of a spontaneous mutation

spotaneous mutations occur with no outside influence

eg deamination the removal of an NH3 group cytosine → uracil

most spontaneous DNA mutations are repaired explain how mutations can be retained in a cell

it can be retained in DNA replications through transposons, which have the gene sequence to move and copy themselves (transposition) inserting transposons in the new replicated DNA. If a transposon lands within a gene, it may lead to functional problem in the encoded protein sequences through interuptions

name two ways mutations can be induced

radioactively through ultraviolet light (radiation) - covalent bonds in adjacent thymine bases, x rays and gamma rays - breaks the sugar phosphate back bone

nitrous acid - causes deamination

benzopyrene - adds chemical group to guanine

induced mutation

occurs with outside influences that come from outside of the cell and causes mutagens

what is a germline mutation

germline mutations occurs in the gametes (sexual reproduction) this is passed through prior fertilisation, this mutation is in every cell of the body

what is somatic mutation

occuring in the NON reproductive cells and can be passed into the daughter cells via mitosis after fertilisation but is not passed on through sexual reproduction. Thus, only specific cell on the body will carry the mutation.

what are the potential outcomes of a germline mutation

mutations in all cells in the organism and can be passed onto offsprings

what is the potential outcomes of a germline mutation

cannot be passed through offsprings, only in specific cells in the body

what are the conditions that induce DNA damage

heat water radiation and oxidation

spontaneous DNA damage caused by water are hydrolytic reactions. what is deamination and depurination

deamination - the removal of a NH2 group in pyrimidine bases (cytosine → uracil)

depurination - loss of purine bases due to the cleavage of the bond between base and deoxyribose at apurinic sites

describe how the structure of DNA supports the accuracy of DNA repair mechanism

the structure of DNA is antiparallel and double stranded thus, if there was any damages to the DNA it can be repaired easily due to the template strand and complementary strand for DNA replication

what is the outcome of a synonymous (or silent) mutation in a gene

nucleotide is mutated but the amino acid is not altered - mutation with no phenotypic effect

large mutations

gene duplication, genome duplication and inversion

small mutation

single point mutation, deletion, insertion

synoynmous mutation

a mutation that alters one nucleotide in the triplet code of amino acids, but does not alter the amino acids shown.

non-synonymous mutation

the change in nucleotide results in an alteration in the amino acid thus change in function (either loss or gain)

nonsense mutation

the RNA sequence is stopped prematurely due to a single point mutation that changed the amino acid into a stop codon

missense mutation

the original amino acid is altered into a different one (insertion)

what is the outcome of a non-synonymous (missense/nonsense) mutation

affects the function of the protein, nonsense mutations: causes protein to not function at ALL

explain how a frameshift mutation affect a gene and mRNA that it encodes

framshift mutation throught insertion/deletion of a letter (cannot be pass 3// only +1 -2) between bases, this shifts the reading frame thus the amino acid is changed beyond the point of insertion/deletion.

copy number variation (CNV)

dependent on the number of copies in functional genes, only in large DNA sequences structural variations/genomic (insertion, duplication, deletion). thus, population can have more than one copy of a gene (duplication), no copies at all (deletion) or just one (insertion)

larger structural variations that cover more than 1kb of DNA sequence.

single nucleotide polymorphism (SNP)

random, single base substitution across genome/ single nucleotide or single point

allele

the variation of a gene at a particular region on a chromosome

diploids carry two copies of each gene

hemizygous: possess only one copy of the allele

homozygous: same copy of the allele (two)

heterozygous: different copies contained in the alleles (two)

incomplete dominance

a blend of the recessive and the dominant phenotypes, red and white flowers’ offspring would produce pink flowers

co-dominance

both recessive and dominant phenotype coexist, instead of pink flowers the offspring will contain red spots and white petals