Genetic Change and its Consequences Flashcards
What type of mutations can cause adult onset diseases such as cancer but cannot be transmitted to offspring
somatic mutations
what type of mutations can be detected and heritable in the lineage of germ cells + can be transmitted to offspring
germline mutations
What is a null mutation
completely lacks function
what is a hypomorphic mutation
partial loss of gene function
A DNA sequence variation that is common in the population is called a
polymorphism
the cut off point between a mutation and a polymorphism is __%?
1&
What is a glioblastoma
a highly aggressive brain tumour
what does the karyotype for a glioblastoma show
multiple chromosome rearrangements
intra chromosomal deletion can involve the loss of
many genes
give two examples of syndromes arising from intra-chromosomal deletion
Wolf-Hirschhorn syndrome and cri du chat syndrome
when the chromosomal segment is copied twice and retained as part of the chromosome, this is called
intra-chromosomal duplication
give an example of a disease arising from intra-chromosomal duplication
charcot-marie-tooth disease
when a chromosomal segment is inverted and reinserted into the chromosome, what is this called
chromosomal inversion
what is the most common inversion in humans
in chromosome 9 p12q13
what does Wolf-Hirschhorn syndrome result in
severe mental retardation
cri du chat syndrome is a rare genetic disorder due to the deletion in chromosome 5, give two symptoms of this disease
mental retardation and characteristic mewing sounds
what is chromosomal translocation
rearrangement of parts between non-homologous chromosomes
give three examples of chromosomal translocation diseases
chronic myeloid leukaemia, burkitts lymphoma and acute promyelocytic leukemia
chronic myeloid leukaemia results from a translocation between which chromosomes
chromosome 9 and chromosome 22
a chromosome translocation in chronic myeloid leukaemia results in the formation of a chromosome called the
Philadelphia chromosome
where is the ABL gene found
on chromosome 9
where is the BCR gene found
on chromosome 22
when the ABL gene and BCR gene come together, they fuse - what is activated
the ABL Oncogene
what is an oncogene
a gene that has the ability to cause cancer
where is the abl-bcr fusion gene located
on chromosome 22/ philadelphia chromosome
what is nondisjunction
when chromosomes fail to separate during meiosis
non disjunction can take place in meiosis 1 and
meiosis 2
nondisjunction produces gametes with one missing chromosome or one
extra chromosome
one extra chromosome produced by non disjunction is referred to as
trisomy
one missing chromosome produced by nondisjunction is referred to as
monosomy
trisomy 21 is when an individual has
three copies of chromosome 21
if non disjunction occurs in meiosis 1 there is a ____ chance that there is trisomy or monosomy
50% chance trisomy, 50% monosomy
if nondisjunction occurs in meiosis 2 there is a 50% chance the gametes are
normal
most chromosomal mutations are
lethal
give an example of a disease arising from a single base pair change
sickle cell disease
in sickle cell disease which nucleotide change occurs within the beta hemoglobin gene
adenine to thymine
give an example of a disease arising from the deletion of 3 base pairs
cystic fibrosis , deletion of CTT in the human CFTR gene
a point mutation that changes a purine nucleotide to another purine or a pyramidine to another pyramidine is called a
transition mutation
what are the pyramidines
cytosine and thymine
what are the purines
adenine and guanine
a substitution of a two ring purine for a one ring pyramidine or a pyramidine for a purine is referred to as a
transversion mutation
are transitions or transversions more common
transitions are more common
when a point mutation results in no change to the code it is called a
silent mutation
when a point mutation results in a code that codes for a different amino acid it is called a
missense mutation
when a point mutation changes an amino acid to a stop codon it is called a
nonsense mutation
a frameshift mutation disrupts the
triplet code
an insertion or deletion of a number of nucleotides in splice sites of an intron is called a
splice site mutation
if there is a loss of the splicing site, it can result in the production of
aberrant proteins
what is an indel mutation
insertion or deletion mutation - nucleotides added or removed
a complete loss of function mutation is called an
amorphic mutation / null mutation
with a loss of function mutation the protein structure is altered and no longer
works properly
loss of function mutations are frequently
recessive
a gain of function mutation results in a change to the gene product that means it gains a
new and abnormal function
what is another name for a gain of function mutation
a neomorphic mutation
gain of function mutations are frequently
dominant
what are conditional mutations
mutations only expressed under certain conditions
lethal mutations cause the
death of the organism
supressor mutations
suppress the effect of another mutation
an intragenic suppression mutation occurs in the
same gene as the original mutation
an intergenic (extragenic) suppression mutation occurs
elsewhere in the genome - not on the same gene as the original mutation
an organism with a suppressor mutation is referred to as a
double mutant
supressor mutations have second mutations with alleviate the effects of the already existing mutation restoring the ____ phenotype
original
loss of function mutations usually result in recessive phenotypes but there are two situations in which they can display dominance. they are
haploinsufficiency and the dominant-negative effect
describe haploinsufficiency
single functional copy of gene present, functional copy doesn’t produce enough product, abnormal/diseased state in autosomal dominant disorders
in haploinsufficiency is 50% of the residual gene function causes no effect it is
simple recessive
in haploinsufficiency if loss of 50% of the gene function causes a disease it is
dominant
haploinsufficiency is common in disorders where
gene dosage is crucial
give two examples of phenotypes probably caused by haploinsufficiency
- alagille syndrome, multiple exostoses, tomaculous neuropathy, supravalvular aortic stenosis, trichorhinophalangeal syndrome
what is another name for dominant negative mutations
antimorphic mutations
dominant negative mutations produce an altered gene product
antagonistic to the wild type allele
where are dominant negative mutations found
in cancer - p53, atm, ppargamma
In marfan syndrome the defective glycoprotein product of the fibrillin gene anatgonises the product of the
normal allele
marfan’s also could be as a result of
haploinsufficiency
explain how marfans could be as a result of haploinsufficiency and not domiant negative
absence of one normal allele that causes the disease, not the presence of an abnormal allele
what is marfans
an autosomal dominant disorder that affects connective tissue
what is osteogenesis imperfecta
a group of genetic disorders that mainly affects the bones
in osteogenesis mutations replace glycine with other amino acids, this would show
dominant negative effect
the dominant negative effect in osteogenesis imperfecta would result in a severe/mild phenotype (circle one)
severe
in osteogenesis imperfecta null mutations in either gene result in
haploinsufficiency
null mutations in the genes in osteogenesis would result in a severe/mild phenotype (circle one)
mild
