genetic diversity Flashcards
gene mutations
what is a gene/point mutation?
a change in the base sequence of DNA (which can cause a frameshift)
when does a gene mutation occur?
- can occur during the formation of gametes
- or during DNA replication
what are the 3 types of point mutation?
- Addition
- Deletion
- Substitution
are all mutations harmful?
no, there are some neutral mutations, which do not change the amino acid that it codes for. mutations can be harmful, helpful (unlikely) and neutral
which part of DNA/ nucleic acid experiences the mutation?
- the bases in the nucleotide
what are the 3 types of point mutation?
- Addition
- Deletion
- Substitution
what point mutation is sickle cell anaemia caused by?
substitution
what is a substitution mutation?
- a random base in the base sequence of DNA is substituted to a different base so changes the way the base sequence is read/ codes for a different amino acid
- Affects only one codon the way the triplet is read
what is an insertion mutation?
- where a new base is inserted ino the base sequence of DNA. this causes a frame-shift to occur.
what is a deletion mutation?
- where a random base is deleted from the base sequence of DNA
- a nucleotide is lost from the normal base DNA sequence
what is a frameshift?
since bases are read in codons/triplets. this changes the way the base sequence is read and changes the amino acid it codes for.
how can the rate of mutation be increased?
by mutagenic agents
examples of mutagenic agents?
- High energy radiation e.g. UV light
- Ionising radiation e.g. X rays and
gamma rays. - Alpha particles, beta particles
- Chemicals e.g. Mustard gas,
benzene, pesticides
what are aquired mutations?
occur in cells after conception, so cannot be transmitted to children e.g. some cancers
what are hereditary mutations?
A gene change in a gamete that becomes incorporated into the DNA of every cell in the body of the offspring. Passed from parents to offspring e.g. Cystic fibrosis
what two genes is the rate of cell division controlled by?
- proto-oncogene - stimulates cell division
- Tumour suppressor gene - slows or inhibits cell division.
what happens if a point mutation occurs in a proto-oncogene?
If a point mutation occurs in a proto-oncogene it can form an oncogene. This can stimulate excessive cell division, leading to the formation of a tumour.
what happens if a point mutation occurs in a tumour suppressor gene?
If a point mutation occurs in a tumour suppressor gene it can become inactivated. This allows the rate of cell division to increase unregulated.
what is a chromosome mutation?
a change in the number or structure of the
chromosomes. It is caused by errors that occur during cell division.
what are the 4 types of chromosome mutations?
- deletion
- inversion
- duplication
- translocation
chromosome mutations an arise spontaneously and take which three forms?
- polyploidy
- non-disjunction
- changes in chromosome structure
explain what is non-disjunction mutation?
changes in the number of individual chromosomes. homologous pairs of chromosomes fail to separate during meiosis or chromatids fil to separate in anaphase II
what is the result of a non-disjunction chromosome?
Results in gametes with extra chromosomes
draw a diagram showing non-disjunction mutation
what is important about non-disjunction mutations?
they are lethal
give a condition which is caused by non-disjunction mutations?
down syndrome - extra chromosome 47
what is polyploidy mutation?
changes in whole sets of chromosomes occur when organisms have 3 or more sets of chromosomes rather than the usual two
mostly in what organisms does polyploidy mutations occur in?
plants and Many of these polyploid organisms
are fit and well-adapted to their environments.
draw a diagram showing polyploidy mutations?