Genetics Flashcards
____ are the foundation for all cellular structure and function
Proteins
How many genes in the human genome
50,000
What percent of DNA is used to make proteins?
10%
8% is regulatory and 2% is the actual code for the protein
Exons
Portion of gene that is transported out of the nucleus and translated into a protein
Different types of introns
Portion of gene removed from RNA transcript before translation.
- Non coding part
- No translation to protein (RNA splicing)
- Regulation of gene expression
What factors may effect transcription?
External factors such as toxins and medicine
Internal factors such as cytokines
Both can elicit or inhibit RNA transcription.
Epigenetics and examples
Extra-DNA modifications to the genome. Influences phenotype. Does not change the DNA sequence and is not encoded in the DNA sequence.
Examples of epigenetics that can affect genome
Chemical compounds. Methylation silences.
Can be inherited
Can be acquired by external factors such as diet, pollutants.
How does methylation affect the genome
It silences the gene. No transcription.
Autosome vs allosome
Autosome: Homologous pairs (1-22)
Allosome: Sex chromosomes (23)
How is DNA wound?
Double helix organized by histones into nucleosomes. Condensed into chromatin that make up chromatids.
Locus
Location of a gene/marker on a chromosome.
Diploid cells have ___ loci per gene
- One per chromosome
Allele:
Gene variant at a particular locus.
Homozygous vs heterozygous
Homo: Both alleles are the same on each gene locus.
Hetero: different alleles. Some genes have few alleles, other have thousands.
Non-mendelian genetics
Penetrance (complete and incomplete) and expressivity.
Both can be affected by lifestyle/environmental factors.
Penetrance
Likelihood of manifesting a particular phenotype given the same genotype.
Complete- everyone with the same genotype manifests the same phenotype.
Incomplete (variable)- Everyone has the same genotype, but some do not manifest the same phenotypes.
Expressivity
Degree to which the phenotype is expressed.
Variable expressivity: Degree of phenotype expression varies between individuals with the same genotype.
Mendelian Inheritance (6 patterns of inheritance are observed)
Co-dominant Autosomal dominant Autosomal recessive X-linked dominant X- linked recessive Mitochondrial
Autosomal dominant disorder passing down rate
Each child has a 50% chance of inheriting the disorder.
Affects male and females in each generation
Ocular examples of autosomal dominant disorders
Retinitis Pigmentosa. Progressive vision loss.
Dominant Optic Atrophy. Progressive vision loss.
Retinoblastoma
Rb1 gene mutation.
90% of patients who have the gene will develop the condition.
Considered autosomal dominant with reduced penetrance.
Usually unilateral.
Autosomal recessive disorder passing down rate.
Each child has a 25% chance of being affected.
Both parents must be at least heterozygous (carriers) to transmit the disorder.
Appears equally in male and female children of unaffected parents.
Autosomal recessive disorder almost always associated with the _____ of the affected gene.
Loss of function.
