Genetics: Flashcards
Genetics & Genomics Definition:
Genetics: study of biologic hereditary
Genomics: field of genetics concerned w/ structural and functional studies of the genome
Human Genome Project
Sequence and map the genome of our species 1990-2003
Notable for ethical, legal, social implications/Transparencies/legal designation of human genes as naturally occurring not subject to patent
Only found about 24,000 genes
Much of genome made up of DNA that doesn’t code for protein (noncoding sections act as switches to regulate when and where coding genes are activated)
Pharmacogenomics:
uses individual’s genome to determine whether or not a therapy would work
Precision Medicine:
Using someones genome as a roadmap for patients clinical care
Oncology especially
Newborn Screening:
Every baby tested at birth for 29-50 severe, inherited, treatable genetic diseases
Whole genome would give enable clinicians to look for mutations
First job of DNA in genome is?
Fetal Development
Once formed, DNA in genome is interpreted to make protein which direct somatic growth and homeostasis processess
Where does protein synthesis occur?
Occurs in RNA Transcription phase which occurs in the nucleus
Where does Translation occur?
occurs in cytoplasm and proteins are generated using mRNA as a template
tRNA brings corresponding amino acids to the protein chain
Binds 5’ end of mRNA chain
Moves along until encounters stop codon AUG
What are chromosomes?
Units of DNA/histones called nucleosomes which winds together to form chromatin fiber
Somatic Cells- 46 chromosomes (23 pairs)
Gamete Cells- 23 chromosomes
Chromosome markings:
Short arm= P
Long arm= Q
Centromere= attach chromatids
Telomere=region containing multiple base pairs
What mutation is transmitted to offspring?
gametes
Silent/Missense/Nonsense/Frameshift mutations:
-Silent: Doesn’t change amino acid sequence of a gene
-Missense: results in single amino acid change in translated gene product
-Nonsense: mRNA stop codon produces premature stop
or removes stop
-Frameshift: alteration of DNA addition or deletion of base pair occurs
Gain of function:
Assoc. with dominant disorders
production of new proteins
over-expression of protein product
Loss of function:
Assoc. with Recessive disorders
Loss of 50% of protein product
(may not be adequate for normal function)
Single Gene Disorders (inherited):
Autosomal Dominant/Recessive and sex-linked
Incomplete Dominance:
Trait inherited in a dominant manner but is less severe than expressed in parent
Co-dominance:
Ability to detect expression of 2 alleles (mixed)
Autosomal disorders:
Occurs as a result of mutation in genes with loci on chromosomes 1-22
Males/females equally affected
Equal transmission
Autosomal Dominant Disorder:
Most common
Between unaffected homozygous parent and affected heterozygous parent (Aa)
Expressed equally
Gain of function
Ex: achondroplasia (over express chondrocytes-inhibit growth)
Age Dependent: Huntington’s disease/Familial cancers
Autosomal Recessive Disorders:
Most common situation is union between two unaffected heterozygous parents
expressed equally in M/F
Loss of function
Ex: cystic fibrosis, sickle cell disease, tay-sach’s
Sex Linked Disorders:
On X or Y chromosome
usually effects son
usually only given by mom
X-linked Recessive Disorders:
Most common situation is union between an unaffected carrier female and affected male
examples: hemophilia, duschenne muscle dys, SCID, color blindness
Penetrance
Probability that an individual will express a given phenotype given that individual possesses a predisposing genotype
all or none concept
may be influenced by environmental factors
Reduced penetrance:
condition not manifested in all individuals with predisposing genotype
