mutations

give 5 processes which result in an increase in genetic variation w/in a species:

• mutations

• independent segregation of homologous chromosomes

• crossing over between homologous chromosomes

• random fertilisation of gametes

  • all produce new allele combinations

what is a gene mutation?

a change in the base sequence of chromosomes

why may not all base substitutions cause a change in the encoded sequence of amino acids?

the genetic code is degenerate - more than one codon may code for the same amino acid

what is a mutagenic agent?

• a factor that increases the rate of mutations

• e.g. UV light, ionising radiation

what is a frameshift mutation?

where an insertion/deletion mutation changes the triplets in a DNA sequence as the sequence shifts right/left (respectively) by one base

what is a point mutation?

a mutation where a single nucleotide is altered

how may gene mutations occur?

spontaneously, if DNA is misread during DNA replication

what are the 5 types of gene mutation?

• substitution

• deletion

• insertion

• duplication

• inversion

what effect may gene mutations have?

• change amino acid sequence coded for by gene

• → different polypeptide

• → potentially different tertiary structure

• → potentially changing organism’s phenotype

• (if enzyme, potentially different active site shape, preventing E-S complex forming)

what is a substitution gene mutation?

one or more nucleotides substituted for another in a DNA base sequence

what is a deletion gene mutation?

one or more nucleotides deleted from a DNA base sequence

what is an insertion gene mutation?

one or more nucleotides inserted into a DNA base sequence

what is a duplication gene mutation?

one or more nucleotides in a DNA base sequence are duplicated

what is an inversion gene mutation?

a group of nucleotides in a DNA base sequence separate and rettach in the same position but in the reverse order

what is a chromosomal mutation?

change in the structure/number of chromosomes in a cell

what causes chromosomal mutations?

errors in cell division

what are the 7 types of chromosomal mutation?

• deletion

• insertion

• duplication

• inversion

• translocation

• non disjunction

what is a translocation mutation?

a portion of one chromosome switches places w/ another non homologous chromosome

what is a non disjunction mutation?

• in meiosis, the chromosomes are not separated properly/all chromosomes stay in one cell

• chromatids go to different poles

what is polyploidy?

a cell having 3 or more sets of chromosome (e.g. triploid/tetraploid cells)