Samenspel van Genen en Omgeving, jaar 2 periode 4
Hoorcollege aantekeningen aangevuld met paar punten uit het boek
Schematisch, visuele aantekeningen
Overzicht erfelijkheid bijgevoegd
1: History & Mendel
HISTORICAL PERSPECTIVE MENDEL (1822 – 1884)
ANCIENT
§ Hereditary schemes
§ Pythagoras: father supplies essential ® Mendel’s two elements:
characteristics, mother material building blocks S (dominant) or s (recessive)
§ Aristotle: children made from purified blood § The Law of Segregation (1st law)
from the tests (semen) and menstrual blood ® Two elements for each trait
® Menstrual blood because if not bleeding, it ® Elements separate during
means pregnant reproduction
® Offspring receive one of two
1600 - 1700 elements from each parent
§ The Law of Independent Assortment (2nd law)
§ Antonie van Leeuwenhoek & Nicolaas ® Inheritance pattern of one trait will not affect
Hartsoeker: invented the microscope the inheritance pattern of another
§ Sperm contains complete preformed individuals; ® Exceptions:
homunculus 1. X-linked inheritance: sex-dependent
§ Problems with the theory of performationism; transmission (like color blindness)
® Homunculus must have other homunculus 2. Quantitative traits: complex traits
® Genocide: killing a lot of semen consisting of multiple genes
® Siblings should be twins § Punnet Square: diagram used to
® What about resemblance to the mom? predict probability of offspring
® Wasteful having a particular genotype
1800 - 1900 MENDELIAN DISORDER
§ Francis Galton: founded psychometrics Follow a Punnet Square: so mostly when a disease
Studied twins and family trees to understand is dependent on only one gene
hereditary/genetic influences
§ Charles Darwin: evolution theory § Huntington’s Disease: brain disorder causing
§ Voyage of the Beagle: most important trip in all progressive deterioration of physical, cognitive
of science and emotional self
® His father objected; it was a waste of time ® Uncontrollable movements, abnormal
® South America > Aussie > Africa balance, slurred speech, thinking difficulties
® Saw one element in a bird slightly adjusted for and personality changes
a different purpose in another bird ® Dominant: H
® Natural selection: best adapted organisms § Phenylketonuria (PKU): metabolic disorder
survive and reproduce caused by a liver enzyme PAH deficiency
§ Blending inheritance: traits of parents blend to ® Prevents normal metabolization of PHE which
create traits of offspring is present in rich protein foods
§ Darwin’s theory of pangenesis/inheritance: ® Damage in SN leads to mental retardation
contributions to egg or sperm from every body ® Recessive: p
part
® Problem: if this was the case, there would be Scurvy (scheurbuik): Vitamin C deficiency
no variation Disorder caused by a single gene
Everyone has that defect: no variation in
humans
Therefore, not a genetic disorder
, INTERPLAY GENES & ENVIRONMENT
2: RNA, DNA & Genetics
GENERAL DNA/RNA STRUCTURE
NUCLEOTIDES
Driving force: survival of genes
Mechanism: evolution § 1953: discovery of double helix by Watson & Crick
§ Selection of properties that favor survival and § Simple molecule (nucleotide) carries a lot of
reproduction information and can duplicate itself
§ Hereditary material: DNA ® Point X-ray beam at crystallized DNA
molecule
THE CELL ® Photo 51
§ Linked together by phosphodiester bonds from
5’ to 3’
What does DNA/RNA stand for?
§ RNA: Ribo, Nucleic, Acid
® Ribo (a sugar)
§ DNA: Deoxyribo, Nucleic, Acid
® Deoxyribo (sugar without oxygen)
THE FOUR BASES IN DNA
Base pairing between two strand involves hydrogen
bonding between A-T or C-G
§ Adenine - Thymine
1. Eukaryotes: animals, plants, fungi § Cytosine - Guanine
§ Contain membrane bound compartments
including nucleus and organelles
§ DNA located in:
® Nucleus
® Mitochondria (powerhouse)
To remember…
> used to be an independent organism, base ATCG(U), nitrogen base
hence have their own DNA nucleotide phosphor + sugar + base
® Chloroplasts (plants only) ® DNA: deoxyribose & double
stranded
2. Prokaryotes: bacteria ® RNA: ribose & single stranded
§ Lack extensive internal compartments amino acid consists of 3 nucleotides
§ DNA located in ® also, codon
® Plasmids ® anticodon match of codon
® Genome in nucleoid start codon AUG / Methionine
§ Horizontal gene transfer: transferring genes stop codon UAA /
without family relationships, exchanges genes polypeptide amino acid chain,
® also, protein
with other cells
ribosome anticodon + tRNA + single amino acid
exon coding DNA
intron non-coding DNA
, INTERPLAY GENES & ENVIRONMENT
DNA REPLICATION
Takes place before mitosis
1. TRANSCRIPTION
1. Enzyme helicase tears DNA strings (sense
and antisense strand) by tearing apart the
hydrogen bonds
® Happens at many places in the DNA
molecule at the same time
2. Enzyme primase binds RNA primer to
leading strand
® Leading strand = antisense (3’ to 5’)
3. Enzyme DNA-polymerase binds to primer
and matches new bases to leading strand
(3’ to 5’), which creates a new strand (5’ to 3’)
to complete helix
® Wrong match: mutation
4. Replicating lagging strand (3’ to 5’) not fully
possible, so starts in middle of molecule and
happens in different parts (Okazaki-fragments)
5. Ligase secures both strands and connects
Okazaki-fragments
6. Splicing: introns removed so exons can be
duplicated
7. In the end: mRNA
® Uracil (U) instead of Thymine (T) in leading/lagging strand
® Messenger RNA: encodes protein
® Transfer RNA: transports to ribosomes
® Ribosomal RNA: forms the ribosomes
1. TRANSLATION
Translating mRNA into polypeptides
§ 5’ to 3’
1. Ribosome reads mRNA, connects tRNA, amino
acid and anticodon
2. Anticodon on tRNA binds tRNA and amino acid to mRNA
® Amino acid linked to codon on mRNA
NOT anticodon on tRNA!!
3. tRNA + anticodon travel to cytoplasm to find
new amino acid, while previous amino acid is connected
to next amino acid in line
4. If stop codon is reached, polypeptide and ribosome will
release
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