Lecture 2-Genetics Flashcards
Chromosome
Highly ordered structure composed of DNA and proteins that carries genetic information
Gene
A sequence of nucleotides that represents a functional unit of inheritance; a region of DNA that codes for a product, either RNA or protein
Aspects of sickle cell mutations
Single mutation can give resistance to malaria
Double mutation gives the sickle cell disease
Inherited gene complement
Mutations may be transmitted from one or both parents
Typically called the constitutional genome
Acquired gene complement
A subset of cells in an individual that arose by clonal propagation from a single mutation in one cell (ex: cancer)
Syndrome
Set of characteristics which occur together and are assumed to have a common basis
Not all characteristics occur in all affected individuals
Range of variability within a population
Biochemical genetics
Subspecialty of genetics that deals with the diagnosis, treatment, and research of inborn errors of metabolism
Inborn errors of metabolism
Genetically determined biochemical disorder in which a specific enzyme defect produces a metabolic block (can cause an accumulation of substrate or a deficiency of products)
Single enzyme defect
Recessive
First four inborn errors of metabolism
Alcaptonuria, cysonuria, pentosuria, albinism
Simple biochemical pathway
Precursor–A–B–product (with enzymes in between)
Effects of blocks in the tyrosine to melanin pathway
If all functions correctly–tyrosine gets converted to melanin and a black/dark brown cat is produced
If pathway is blocked at last step–conversion is incomplete and a brown/grey cat is produced
If pathway is blocked at first enzyme (tyrosine oxidase) then an albino cat is produced
Salvage pathways
Can be seen in more complex pathways. If there’s a mutation and a substrate cannot bee converted to the normal product, secondary pathways may show an increase in activity.
Avoid the over accumulation of a potentially toxic substance in cells.
General clinical features of inborn errors of metabolism
Poor growth, mental retardation, problems with metabolism, neurological problems
Hyperphenylalaninemias
Group of biochemical disorders related to the function of phenylalanine hydroxylase which converts phenylalanine to tyrosine
Phenylketonuria
PKU
Mutation of phenylalanine hydroxylase prevents conversion of phenylalanine to tyrosine
PHE accumulates in cells–toxic
First genetic disease linked to mental retardation
Put patients on a low PHE diet
Non-PKU hyperphenylalaninemias
About a ten fold increase in PHE levels
Less damaging
Variant PKU
Between full PKU and non-PKU
Special diet but not as restrictive as full PKU
Tetrahydrobiopterin
BH4
BH4 is a cofactor that can also cause PKU
This type of mutation requires supplements of neurotransmitters since BH4 is involved in the production of neurotransmitters
Basics of human chromosomes
46 chromosomes in a somatic cell (23 pairs)
Members of a pair are homologous chromosomes (homologs)
One homolog from each parent (normally)
Mitosis
Somatic division
2N–4C–2N
Interphase–DNA replicates, 2N becomes 4C
Prophase
Metaphase–most important phase for cytogenetics
Anaphase–centromeres divide
Telophase
Meiosis
Germ cell division (reduction division)
2N–N
-at metaphase 1 homologous chromosomes pair
-in anaphase 1 centromeres remain together and homologs separate (REDUCTION DIVISION)
-Then the two chromatids separate in the second round of division
Isodisomy
2 chromosomes from the same source (duplication of 1 chromosome)
Heterodisomy
2 chromosomes from different sources
Nullosomic
Missing a chromosome
