Chapter 2 - Genes And Genetic Diseases Flashcards
DNA—> double helix model
Two strands held together with hydrogen bonds
Two basic components of DNA
-backbone: deoxyribose-phosphate molecules
-four types of nitrogen bases: thymine, adenine, guanine and cytosine
Purpose of ANTIPARALLEL strands
-one strand serves as template for production of second strand
POSITIVE strand is template for making NEGATIVE strand
Strand is broke starting at
Replication fork
Hydrogen bonds form between
New complementary nucleotides
Overall result of replication
Two identical copies of original DNA
Pyrimidines
Single carbon nitrogen rings
-cytosine
-thymine
Purines
Double carbon-nitrogen
-adenine
-guanine
Nucleotide
Each DNA subunit consists of one deoxyribose molecule, one phosphate group and one base
Codon
Each three sequential nitrogen bases are a code for a specific amino acid
The body contains how many different types of amino acids?
20
A protein is composed of
Specific combination of amino acids
Process of DNA into proteins
-DNA is TRANSCRIBED into mRNA
-mRNA is TRANSLATED into proteins by ribosomes
Nitrogen bases
Forms organisms genetic instructions
-language of the cells instructions for what proteins to make
Proteins are composed of…which is composed off…etc
Proteins = polypeptides = amino acids = codons
DNA coding and template strands divide…
Short RNA strand moves over template strand and appropriate amino acids are constructed on RNA strand
The sequence of amino acids on RNA account for
A recipe for specific proteins
RNA travels
Out of nucleus to the ribosome where it makes the proteins
-now considered mRNA (messenger)
MRNA
Is the messenger for delivering the DNA’s recipe for a new proteins to the ribosome
How is RNA different than DNA
The sugar molecule is ribose rather than deoxyribose
-uracil replaces thymine
-single strand
Transcription
Synthesis of mRNA from a DNA template
TRNA
Transfer RNA
-transport anticodon amino acids to ribosome
-base pairs with mRNA codon
-string of anticodons form polypeptide
Ribosome translates
Sequence into polypeptide protein
Mitosis vs meiosis
Mitosis —> produce two identical 2n daughter cells
Meiosis—>four genetically unique n daughter cells
Autosomes
22 chromosomes homologous in females and males
Gene splicing
RNA sequences removed by nuclear enzymes and remaining sequences are spliced together to form the functional mRNA
-introns spliced
-exons kept for code
Mutation occurs during
DNA replication
Substitution
one nucleotide is replaced by a different nucleotide, only one amino acid is changed
=new amino acid
Eg -sickle cell anemia
Insertion
Insertion of new inappropriate nucleotide, which changes all amino acids afterwards
=multiple new amino acids
Deletion
Appropriate nucleotide removed
=multiple new amino acids
Eg -cystic fibrosis
Mutation =
Evolution
If mutation provides no benefit to environment =
No evolution
If mutation provides negative benefit to environment =
Extinction
If mutation provides a positive benefit to environment =
Becomes dominant in environment
Base pair substations
One pair replaces another base pair
-result in change of one amino acid
-considered silent mutation (may cause change, but most of the time doesn’t change aa sequence)
Missense
Produce a change in a SINGLE amino acid
-base pair substitutions
Nonsense
Produce one of three STOP CODONS
-UAA, UAG, UGA
Produce premature stop codon and terminate translation of the polypeptide
Frameshift mutations
Insertion or deletion of one or more base pairs
-greatly alter amino acid sequence
-causes dramatic change in protein produced at ribosome
Mutagens
Increase the frequency of mutations by altering DNA
-radiation, chemicals, nitrogen mustard
Genotype versus phenotype
Genotype = refers to genetic material passed between generations (genetic code)
Phenotype = observable characteristics or traits of an organism (physical expression)
Autosomal Dominant Inheritance
Autosomal= gene in question is located on one of the numbered or non sex chromosomes
Dominant= single copy of disease associated mutation is enough to cause disease
Autosomal Recessive Inheritance
Autosomal= gene is located on one of the numbered or non sex chromosomes
Recessive= two copies of mutation is required to cause disease
X linked inheritance
-gene carried by mother
Female children (XX) = become carriers (1)
Male children (XY) = become affected (2)
Polygenic traits
Traits affected by more than one gene
-skin colour, hair colour
Predisposing
Inc probability that the disease will occur
Precipitating
Trigger the disease
-condition that causes disease
Epidemiology
The study of Tracking patterns of disease occurrence
Idiopathic
Unknown cause, and spontaneous origin
Latrogenic
Result of treatment
-hair loss from chemo
Remission
Symptoms disappear or diminish
Exacerbation
Sudden inc in severity of symptoms
Complication
Medical problem occurs during disease, or after a procedure/treatment
Morbidity
Condition of being diseased
Co-morbidity = multiple disorders occurring at same time
Prevelance
Indicates all current cases of the disease
-does not differentiate between old and new cases`
Incidence
Indicates number of new cases
Short term diseases —> incidence and prevalence
Incidence and prevalence stay the same year after year
Chronic diseases prevelance and incidence
Prevalence : tends to increase yearly
Incidence: stays the same
Syndrome
Group of signs and symptoms which occur together and characterize a particular abnormality or condition
disorder
Abnormality of function
Ethology
Cause of disease
Ribosome subunits join with
MRNA
Transfer RNA molecules transport
Anticodon amino acids to ribosome
Anticodon base pairs with
MRNA codon (amino acid)
String of anticodons form a
Polypeptide (protein chain)
