23 Patterns of Inheritance Flashcards
what is a monogenetic trait?
a characteristic controlled by a single trait
how does a mutation in the CFTR gene on chromosome 7 cause cystic fibrosis?
gene codes for transporter protein that allows Cl- ions to pass out of alveolar cells
the mutation cause non-functionality of the protein
Cl- ions cannot move out of the cell ∴ no water is drawn out by osmosis ∴ surfactant mucus remains thick
ciliated epithelium cannot move it ∴ it accumulates ∴ bacteria are trapped –> infection
what are the three types of substitution mutations to the genetic code?
silent = same nucleotide/amino acid exchanged
missense = disruption of tertiary structure of protein
nonsense = early stop codon ∴ shortens polypeptide chain
what is PKU?
{phenylketonuria}
mutation prevents formation of enzyme required to breakdown phenylalanine
∴ phenylalanine accumulates in blood/tissue fluid –> brain damage
what is Huntington’s disease?
accumulation of protein fragments in brain neurones, reducing ability to talk, walk and think
due to an insertion mutation on chromosome 4 - CAG repeated 40+ times
what is sickle anaemia?
a substitution in the gene which codes for the β polypeptide chain in haemoglobin
valine replaces glutamate
what is codominance?
two or more alleles that do not show complete dominance, resulting in an intermediate condition of the phenotype
what is the function of HLAs?
to help the immune system distinguish the body’s own proteins from proteins made by pathogens
what do HLA-A, -B and -C do?
produce proteins present on cell surfaces
if from ingesting a foreign body, causes an immune response and the cell to self-destruct
what is a chromosome mutation?
a random change in the number of chromosomes or chromosome structure, usually following an error in mitosis
what is sex-linkage?
inheritance of genes on the X and Y chromosomes
what is haemophilia A?
a sex-linked genetic disorder where clotting factor VIII is not produced, causing an increase in clotting time
what is translocation?
a piece of chromosome breaks off and is transferred to another chromosome
what is non-disjunction?
a change in the diploid number of chromosomes
when homologous chromosomes don’t separate in meiosis I/sister chromatids don’t separate in meiosis II
what is Turner’s syndrome?
non-disjunction during oogenesis causes one oocyte to be XX, the other is OO
resulting zygote is XO and has 45 chromosome (2n-1)
