Genetic diseases Flashcards
Genetics
- Study of heredity in general and of genes in particular
Heredity
- The passing of the traits from the parent to offspring (inheritance)
Phenotype
- The indavidulas observable traits
Genotype
- The set of genes in our DNA which are responsible for a particular trait
True breeding
When the plants self-pollinate, all their offspring are of the same variety
Hybridisation
Mating, or crossing, of two varieties
Monohybrid cross
A cross between two parents that breed true for different versions of a single trait
Homozygous
An organism possessing two identical alleles for that trait (gene)
Heterozygous
An organism possessing two different alleles for that trait (gene)
Somatic mutations
Changes to the DNA of somatic cells after the birth, its non-heritable
From DNA to protiens
- DNA sequence transcribed into RNA
- Mature mRNA is translated into proteins. RNA sequence is read consecutively in groups of three consecutive nucleotides (codons), from the start codons
- Codons are nonoverlapping and the message has no gaps
- There are stop codons that block the translation
Single gene disorder
- Mutations can lead to a gain-of-function but also to a loss-of-function
- The resulting protein alteration/deficiency is responsible for the disease symptoms
- A condition that is present from birth
Autosomal dominant
If a single mutated allele is sufficient to cause the disease (heterozygosis)
Autosomal recessive
If both mutated allele must be inherited to be affected (homozygosis)
X-linked recessive or dominant
Mutated gene is present on the X chromosome
Missense mutations
- These are base changes that alter the codon for an amino acid resulting in its replacement with a different amino acid
Nonsense mutations
- Base changes that convert an amino acid codon to a stop codon, resulting in a premature termination of translation and the production of a shortened protein
Silent mutations
Do not cause any change in an amino acid
Frameshift mutation
- These mutations result from the insertion or deletion of one or more bases causing the alteration of the reading frame of the gene and a different set of codons, leading to an altered protein
Promoter mutations
- Affect the way gene transcription is regulated, often abnormally reducing or enhancing the expression of certain genes
Sickle Cell Anaemia
- Autosomal recessive
- Caused by homozygous gene mutation beta globlin gene
- Red blood cells form an abnormal crescent shape
- Haemoglobin (protein) is abnormally shaped
- Don’t move easily through your blood vessels
- Form clumps and get stuck in the blood vessels
Numerical Abnormalities
- When an individual is missing either a chromosome from a pair or has more than two chromosomes of a pair
Structural Abnormalities
When the chromosome’s structure is altered
Euploid
- 46 chromosomes in somatic cells which is 22 chromasomes and 2 sex chromasomes
Aneuploid
- Results from nondisjunction in meiosis of the germ line cells leading to genetically unbalanced eggs or sperm
Monosomy - only one of a particular type of chromosome
Trisomy - three of a particular type of chromosome
Nondisjunction
- Abnormal mumber of chromasomes chromasomes in each cell
- Can cause some some forms
Stomatic mosaicism
- Two or more cell lines with different chromosome compositions in an individual
Trisomy
- Occurs when an individual has three of a particular type of chromosome
Downs syndrome
- Short stature
- Eyelid fold
- Flat face
- Stubby fingers
- Wide gap between first and second toes
Edward Syndrome
- A small, abnormally shaped head
a small jaw and mouth
delayed growth - Trisomy extra chromasome
Patau syndrome
- Mental deficiency
- Severe central nervous malformations
- Sloping forehead, malformed head
- Scalp defect
- Trisomy extra chromasome 13
Turner syndrome
- Female born with single X chromasome
- Short, with broad chest and widely spaced nipples
- Can be of normal intelligence and function with hormone therapy
- Life expectancy is normal in most cases
Klinefelter syndrome
- Male with underdeveloped testes and prostate; some breast overdevelopment
- Long arms and legs; large hands
- Near normal intelligence
- No matter how many X chromosomes, presence of Y renders individual male
- XXY chromasome Trisomy
Deleation mutation
- One or both ends of chromasome breaks off
- 2 breaks at the same time causes loss of internal segment
Duplication mutation
- Chromasomal segment more than once in the same chromasome
Inversion mutation
- Chromasome is broken down and inverted and reattached
- Gene occours in reversed order
Translocation mutation
- Portion of chromasome is transfered to another chromasome
- Insertion which causes a frame shift
- Robertsonian follows breakage of two nonhomologous chromosomes and improper re-assembly
Multifactor disorder
- Familiar clustering but doesn’t conform to single gene inheretance
- Non communicable no change in DNA but there is a change in expression with the effects of environment
- Additive effects impacts on gene
- Type 2 diabetes caused by genes and environment
Cancer
- Genetic (breast cancer) but not necessarily inherited dependant on environment and gene
- Only germ line inherited other cancers are somatic
- Unregulated cell proliferation - undetect mistakes in the DNA caould cause DNA replication faster
Malignant tumor
- Uncontrolled cell division that has a metastatic spread
- Spread of the cells by breaking away
- Via lyphatic or blood
- loose cellular funtion and apoptosis
Mutation of Oncogenes
- Activation stimulates cell growth and division in response to specific signals
- In cancers its predominently switched on
Mutations of tumor supressor gene
- Unable to block or regulate division
- Cell is unable to undergo apoptosis
- Permenently switched off (P53)
Genetic polymorphism
- 2 or more diffrent forms of Dna sequence on the same locus present in 1% of a population
- Due to susbstitution of single nucleotide (SNPs)
- Determine the diversity of indaviduals and sometimes have a role in drig response present risk factors for disease
