LECTURE 1 CHAPTER 2 GENETICS AND EVOLUTION
Darwin’s Theory of Evolution: all organisms are related and share a common ancestor
Natural selection=modifications process of modern organisms; beneficial
characteristics=survival *survival of the fittest* (variation, heritability, struggle for existence,
survival and reproductive rates)
Selective breeding=specific and intentional act that produces offspring with particular
characteristics
Genetic modification=genes are added/deleted for the benefit of the organism
Y-chromosomal Adam-most recent common ancestor
Mitochondrial Eve-the most recent woman from whom all living humans are descended
matrilineally through transmission of mitochondrial DNA
All humans are 99.9% genetically identical (0.1%-genetic differences)
Evidence in support of the Theory of Evolution
· Biogeography
· Fossil records
· Structural similarity
· Embryology; Ontogeny Recapitulates Phylogeny (ORP, Haeckel) =during development,
every organism goes through every stage of its evolutionary past
· Molecular biology
Hominies australophitecus
Homo (erectus, sapiens)
Out of Africa hypothesis-homo sapiens appeared 200,000 years ago in Africa
Metopic sutures=joints in the top of the skull; Selective pressures favoring delayed fusion
might have developed from the difficulty of giving birth to large-headed neonates, high early
postnatal brain growth rates, reorganization and expansion of the frontal cortex. (Falk et al.,
2012)
What makes us different from chimpanzees?
ü Changes in the protein sequences in the genome
, ü Regional brain differences
ü Cerebrum and cortex (size and functions)
Qualitative traits=influenced by a single gene and follow a simple patter of inheritance,
unaffected by environment
Penetrance=an allele which does not always lead to the disorder (low penetrance)
Mosaicism=not all of the cells in the body are genetically agents (Turner’s syndrome)
Phenocopies=copies of the phenotype (rubella virus)
Quantitative traits=more variable, less predictive, the phenotype is expressed along a continuum
(e.g., ADHD)
Quantitative trait loci (QTL)=how multiple genes at different locations on the chromosome
contribute to the quantitative trait
,Mendelian Genetics (Gregor Mendel 1822-1884)-differences in conspecifics, dominant vs
recessive traits
Huntington’s disease: dominant H
Phenylketonuria (PKU): recessive p, no P; a person can be a carrier of PKU, but not express it
Chromosomes and Inheritance
Genes are located on chromosomes=constructed from the strands of the DNA molecules,
come in matched pairs (haploid=one set of chromosomes => 23 pairs=diploid, 46 individual
chromatids)
Autosomes=the first 22 chromosomes, do not differ between the sexes
The 23rd is the sex chromosomes: XX (females) and XY (males)
Karyotype=complete organized set of chromosomes
, Centromere=anchor point, NO genetic information; short arm-p arm, long arm-q arm
Telomeres=repeated genetic sequences at the end of the arms, protects the DNA during cell
division
Genome=
Cytogenetic bands=stripes on chromosomes
The process of meiosis=chromosomes duplicate and divide in order to produce gametes in
male and female
Metosis= a) cellular division occurs after fertilization in order to complete the organism b)
chromosomes cross over, break, rejoin and produce new variations in the genetic code
(exchange of alleles=>recombined genes)
DNA (deoxyribonucleic acid) the building block of life: replicates itself to make new cells and
makes proteins and determines the function of the cell
The DNA molecule is along the length if each chromosome and is mate out of carbon, sugar,
nitrogenous base (Adenine, Cytosine, Guanine, Thymine), phosphate group. The two DNA
strands are held together by a mutual attraction of the nucleotides-double helix.
Histone=proteins used to fold the DNA
Replication=the two strands of nucleotide bases unravel, exposure attracts their complement
(mutations=errors in replication)
Protein synthesis (<2% of the DNA are functional gens coding for proteins)
STEP 1 TRANSCRIPTION (in nucleus)
Nucleotide base=basic elements of code that permits the construction of amino acids
(=>enzymes, proteins and polypetides)
Codon=sequence of three nucleotides
During transcription, a strand of DNA code acts as a template for the creation of messenger
ribonucleic acid (mRNA) which carries the code from the nucleus to the cytoplasm. mRNA
splices the exons together (and exit the nucleus) and removes the introns (stay in and are
recycled).
Exons=base sequences that code for proteins; introns=non-coding sequences
STEP 2 TRANSLATION
mRNA connects with Ribosomes (=translators of the sequence of nucleotide bases contained
in mRNA; they read the sequence and add amino acids as the condons instruct), each mRNA
codon merges with tRNA.
