Exam 1 Flashcards
Major Events in Genetics
9-10,000 BC: Domestication of Plants and Animals’
1859: Charles Darwin published Origin of the Species
1866: Mendel published paper on Genetics of Pea Plants
1871: Miescher: Isolated DNA
1883: Galton: Eugenics
1909: Garrod: Inborn errors of Metabolism
1941: Beadle and Tatum: One gene=one enzyme
1944: Avery, Macleod, & McCarty: DNA is genetic material
1953: Watson and Crick: Structure of DNA
1956: Tijo & Levan: 46 chromosomes
1960: Elucidation of Genetic Code
2003: “Completion” of the Human Genome Project
Portrait of a chromosome
P arm: short arm
Q arm: long arm
Telomeres: The ends
Heterochromatin: Where the Chromosome is dark
Euchromatin: Where the Chromosome is light
Centromere: Constriction where the two chromosomes are attached
Genomics
Field that analyzes and compares genomes of different species
Genes
Parts of DNA that contain the instructions within the cells for RNA production
Gene Terminology (Promoter, Coding Region, Non-coding Region, UTR, Polyadenylation Signal
Promoter: sequence that signals start of a gene
Coding region: series of codons that represent the amino acid sequence
Non-coding region: outside of the region coding for the amino acid sequence
Untranslated Region: 3’ and 5’ - noncoding sequence at the ends of a gene
Polyadenylation signal - codes for addition of the poly-A-tail (a string of adenine based nucleotides to an RNA molecule to make it more stable and prevent degradation)
Nucleotide
Made up of a sugar, phosphate, and a nitrogenous base
The nitrogenous bases are adenine, guanine, cytosine, thymine, and uracil
Purine vs. Pyrimidine
Purine: the nitrogenous bases that have a two ring structure, adenine and guanine
Pyrimidine: the nitrogenous bases that have a one ring structure, thymine cytosine and uracil
Properties that Stabilize DNA (Bonds, Hydro-, & Charges)
Hydrogen Bonds - weak bond between the bases, billions between strands of DNA
Hydrophobic Bonds - Weak bonds between stacked bases
Phosphodiester Bonds - Strong covalent bonds between sugars
DNA is hydrophobic on the inside and hydrophilic on the outside
DNA is negatively charged on outside which allows for association w/ the positively charged histones
Human DNA
3 billion bp
25,000 genes
1.5% encodes for protein
5% codes for regulatory elements
50% unique sequence
DNA is in every cell except for RBCs
Chromosome 21 is the smallest w/ 50 million bp and 250 genes
Chromosome 1 is the largest w/ 250 million bp and 2,000 genes
Noonan Syndrome
Symptoms/Example:
Woman with short stature, pulmonary stenosis (narrowing of pulmonary valve), developmental delay, facial dysmorphology, webbed neck, sparse and very coarse hair, and sparse eyebrows and eyelashes
Cause: A cytosine was incorporated in place of a thymine, causing a single nucleotide substitution in the PTPN11 gene
Alleles
Variation of a gene that is not necessarily a mutation
Ex. Allele T - ACGTC Allele t - AGGTC
Every somatic cells contain two alleles (one from each chromosome)
If an allele leads to a disease it is called a mutant allele
Expressivity
The genotype is the alleles itself, but the phenotype is how the people actually turn out. Expressivity is how the change appears.
Complete/Fully Penetrant: When you have the genotype, you have the disease
Incomplete/Reduced Penetrance: When you have the genotype, you may or may not have the disease
Modes of Inheritance
For this test we only need to know the autosomal inheritance
This can be autosomal dominant or recessive
Huntington Disease is autosomal dominant because it affects both sexes and typically appears every generation
Cystic Fibrosis is autosomal recessive because it affects both sexes but can skip generations through carriers
Autosomal Dominant
Criteria:
1. Males and females can be affected, as well as male-to-male transmission can occur
2. Males and females transmit the trait with equal frequency
3. Successive generations are affected
4. Transmission Stops after a generation in which no one is affected
Phenotype (Genotype): Sick (DD or Dd) or Well (dd)
Autosomal Recessive
Criteria:
1. Males and females can be affected
2. Affected males and females can transmit the gene, unless it causes death before reproductive age
3. The trait can skip generations
4. Parents of an affected individual must be heterozygous or have the trait.
5. More likely to occur in families with consanguinity (incest)
Phenotype (Genotype): Sick (rr) or Well (Rr and RR)
Inheritance of Common Traits
Dominant: Dimples, Widow’s Peak, Freckles, and Cleft (Butt Chin)
Recessive: Round Cheeks, Straight hairline, no freckles, round chin
Inborn Errors of Metabolism and Phenylketonuria
Inborn Errors of Metabolism: disorder due to absent or altered enzymes, this causes too much substrate, too little product, or too much product, and affects the major biomolecules
Phenylketonuria (PKU): this is an example of an inborn error of metabolism
Cause: deficiency or abnormal Phenylalanine Hydroxylase enzyme (PAH). PAH converts the amino acid phenylalanine to tyrosine. W/o PAH the phenylalanine builds up in tissues and the brain, and patients become deficient in tyrosine. This build up of phenylalanine leads to mental retardation and behavior problems. The lack of tyrosine results in eczema, fair skin, and blue eyes because melanin cannot be produced from phenylalanine.
Compartmentalization
Definition: Areas of the cell that are isolated by at least one selectively permeable membrane
Compartments: cytosine, ER, Golgi apparatus, nucleus, peroxisome, lysosome, and mitochondria
Organelles vs. Structures
Organelles: nucleus, ER, Golgi apparatus, mitochondria, lysosomes, peroxisomes, and vesicles
Structures: cytoskeleton, cilia, flagella, microvilli, ribosomes, centrioles, centrosomes, and proteasomes
Lysosomes
Membrane-bound save containing more than 40 types of digestive enzymes which require an acidic environment. They remove or recycle bacterial remnant, worn-out organelles, and other materials like excess cholesterol. The enzymes also break down some digested nutrients into forms that the cell can use.
