Genetics
Genetic or congenital disorder Genetic or
familial tendencies
Genetic and environmental aspects Characteristics as well
as disease
Genetic Familial
tendency
Albinism Coronary heart disease
Huntington`s chorea Malignant
disease
Cystic fibrosis Diabetes mellitus
Tay-Sachs disease Rheumatoid arthritis
Sickle cell anaemia Schizophrenia
Phenylketonuria Obesity
Chromosomes
Composed of protein and genes Found in the nucleus
of all cells
Visible during cell division 46
chromosomes, 23 pairs
22 autosomes, (non-sex chromosomes). 2
gametosomes (sex chromosomes).
Male X and Y Female
X and X
44 autosomes and 2 gametosomes. One
member of each pair from Mum one from Dad
A pair -
homologous chromosomes or homologs.
Genes
A unit of genetic information Carry the genetic code for a product
Each gene is represented twice in each
cell Two alleles eg. blue
eyes and brown eyes
DNA
Deoxyribonucleic acid A
molecule - self replicating eg. healing and growth
Fertilized egg - zygote
Dominant and recessive
Two forms - alleles One gene is
expressed and the other is not
Dominant gene - will express itself in preference to a recessive gene
Recessive gene - only be expressed in the phenotype if both
of the alleles for the specific characteristic are recessive.
Genotype Phenotype
Expression of dominant and recessive
genes
Homozygous and heterozygous
Homozygous - same Heterozygous
- different
Mitosis and meiosis
Two forms of cell division Mitosis -
conservation division Meiosis
- reduction division.
Mendelian
inheritance 1865
Inheritance of a single characteristic Monohybrid
inheritance
Patterns of inheritance depend whether
the gene is dominant or recessive.
Autosomal dominant or autosomal recessive
Dominant - will be expressed if present
Recessive - only expressed in the absence of a
dominant gene
Inheritance of a dominant characteristic
Brown eye colour Huntington`s chorea Achondroplasia Neurofibromatosis
Recessive characteristic inheritance
Cystic fibrosis Albinism Phenylketonuria Deafness B Thalassaemia Friedreich's ataxia Sickle cell disease Tay-Sachs disease
TERMS
Genotype
The genes present in the cells of an
individual.
Phenotype
The
expression of the genes as seen in the presentation of an individual.
Recessive gene
a gene which will only be expressed in
the homozygous state.
Dominant gene
a gene which will be expressed
irrespective of the presence of a recessive gene.
Alleles
Two forms of the same gene.
Homozygous
when the two alleles are represented by identical genes.
Heterozygous
when the two alleles represent different
genes.
Mitosis
body cell division, chromosomal number maintained
Meiosis
gamete cell production, chromosomal number
halved
Sex Linked Inheritance
Sex-linked inheritance
Characteristics coded for by genes
carried by the X or the Y chromosome.
44 non-sex chromosomes autosomes 2 sex chromosomes - gametosomes.
female - male
-
Meiosis
Diploid cells - Haploid
cells -
Gender determination
Sex Linked Inheritance
X Linked Dominant Traits
Vitamin D resistant rickets
X Linked Recessive Traits
Haemophilia Christmas disease Glucose
- 6 - phosphate dehydrogenase deficiency Muscular dystrophy, (Duchenne`s and Becker`s) Retinitis pigmentosa
Hunter`s syndrome, (mucopolysaccharidoses) Nephrogenic
diabetes insipidus
Blue green colour blindness
Over 100 gene defects on the X
chromosome
Characteristics transmitted by the Y chromosome
Very uncommon Hairy ears Lambert type "porcupine" Aspermatogenesis
Abnormalities of sex chromosome number
Additional X chromosome in males - XXY
- Klinefelter`s syndrome
XYY in men
Turner`s Syndrome - females - one X chromosome
(XO)
Females 3 or 4 X chromosomes have been
described
Prospects for future treatments
Somatic cells Germ line
Nurse in counselling families with genetic disorders
Health educator Information
How transmitted Possibilities
of future children being effected
Information empowers the individual Informed
choices about their lives
We do not make these choices an behalf of an individual.
Empathise regarding feelings Right to know,
or not
Key terms
Autosome
a non-sex chromosome, ie. one of the 44
Factor VIII
an essential blood clotting factor
deficient in haemophilia
Gamete
a sperm or egg cell, always haploid
Gametosome
sex chromosome, ie. X or Y
Gene
the coded genetic message for production
of a protein
Germ line cell
a cell which gives rise to gametes for
the production of the next generation
Haploid
a cell containing 23 chromosomes, half
the number of a somatic cell
Homologous chromosomes
members of a pair
Homologous
the same
Locus
the position on a chromosome where a
particular gene is located
Somatic cell
a normal body cell containing 46
chromosomes
Allele
Chromosome
Diploid
Dominant
Gamete
Genotype
Haploid
Heterozygous
Homologous chromosome
Homozygous
Linkage
Sex linkage
Meiosis
Mitosis
Ovum
Phenotype
Recessive
Zygote
Many new developments in genetics have
ethical implications
Prenatal testing
Detection of carriers
Somatic gene therapy
Germ line gene therapy
Stem cells – unipotnet, pluripotent,
multipotent
Auto stem cells, e.g. myskin, teeth
Donor stem cells
Cloning
Therapeutic cloning
Human genome project
Positive eugenics
Negative eugenics
Genetic engineering
Transgenic organisms
DNA fingerprinting
Gene for criminality, intelligence,
aggression
Life insurance
Right to know / not to know
Dilemmas over treatments after
diagnosis – patient’s best interests v scientific progress
Animal transplantation
Diagnosis of sex
Transsexualism