Genes to Behavior Flashcards
Phenotype
- determines specific characteristic
- cannot be transmitted to following generations
- influenced by genotype
- determined by the properties of the proteins in its cells and the properties of the proteins are determined by its amino acids
Genotype
- genetic constitution of an individual organism
- it gives rise to phenotype (one way street) and next generation genotype
Role of proteins
- responsible for shape and structure of cells
- form connecting tissues
- control the many chemical reactions that a body needs to function : hormones, enzymes, antibodies
Proteins are made up of amino acids. What are their properties?
- 20 different types of amino acids
- properties of amino acids are determined by which amino acids are incorporated and in what order
Role of genes
they encode amino acids recipes for a particular protein
-> sequence of DNA bases that determines trait
Logic of Life
genes ( sequences of DNA bases) make up proteins ( sequence of amino acids) -> formation of bodies
Classical Genetics
1 particles of inheritance (genes) passed on from parents to offspring determine phenotypic characteristics
2 genes often come in alternate forms (=alleles) -> gene codes for general characteristic colour and two allele for white and red
3 individuals have two copies of the same gene (one from each parent) -> diploid organisms
How many chromosomes do human have?
23 pairs of chromosomes ; 22 pairs of autosomes and one pair of sex chromosome ( xx and xy)
Nirtrogenous bases
adenine - thymine ( 2 hydrogen bonds)
cytosine - guanine ( 3 hydrogen bonds)
Nucleoside
base + sugar
Nucleotide
base + backbone
Polynucleotide strand
- meaning that each strand is made up of many small individual units called nuceotides
antiparallel -> subunits run in opposite directions
5’ = phosphate group
to
3’= OH group of sugar
Codons
triplets of bases (64) which code for the 20 amino acids that make up enzymes and proteins
central dogma
characteristics of phenotypes themselves are not transmitted to next generation
- genes affect properties of proteins but proteins do not affect properties of genes
-> flow of information is one way
example : huge muscles that developed throughout training are not transmitted to next generation ( training causes changes in phenotype and not in genotype)
Silent carriers
genotypic characteristics of parents that are not observable in their own phenotypes but show up in their offsprings
somatic cells ( most cells) -> making more phenotypes
- carry full copy of genome
- make more genotypes through mitosis ( 2 cells are created that are identical to the first cell)
- diploid
example : cells in skin and heart produce other cells in skin and heart but are not capable for producing neurons ornew human being
Germ cells / Gameters
-> making more genotypes
- carry only half of genome
- make more genotypes through meiosis ( reduction from diploid to haploid cells)
- haploid cells
example : sperm in males and egg cells in females
( Mutations ) - Substitution
Replacement of one nucleotide pair with another
genetic code
mapping from particular codons in the mRNA to particular amino acids
code means for example whenever sequence of bases CGU is encountered on mRNA an arginine molecule A is added to protein chain
characteristics of genetic code
(1) universal and not random
(2) degenerates and regenerates
(3) not ambigious
codon AUG
codes for methionine
-> initates process of translation
codon UAG, UGA, UAA
indicate end of protein has been reached -> terminate translation
significant properties of a codon
1 Error reading third base -> Transition
often makes no differnece to amino acid produced
= no difference ; synonymous substitution
-> interchange of two-ring-purines or one ring pyrimidine
2 Transversion - codons differing by just the first base tend to produce amino acids that are chemically similiar to each other
-> interchange of purine for pyrimidine
= robustness to errors
chemical bonds -> within each strand
covalent bonds
extremely strong
-> if two strand are caused to split apart each strand will maintain its integrity
chemical bonds -> between two strands
hydrogen bonds
weaker than covalent bonds
-> principle of base pairing
Differential Gene Expression
- difference between cells is not due to presence but due to expression ( all cells have same genome)
Epigenetics
study of heritable phenotype changes that do not involve alterations in the DNA sequence.
1 on DNA Level example : methylation ; the addition of a methyl group, or a “chemical cap,” to part of the DNA molecule, which prevents certain genes from being expressed
2 On Histone Level
Methylation
Acetylation
Deacytelation
polygenic gene (characteristic)
difference in phenotype is determined by multiple genes example is height
single gene (characteristic)
differneces in phenotype determined by which allele the individual has at just ONE genetic locus (=spot on chromosome) -> mendelian disease
backbone
sugar and phosphate
- run down on each side of the helix; chemically in opposite directions
What is 5’ AGGTCCG 3’ ?
3’ TCCAGGC 5’
-> you can use one base sequence predict the counterpart
Three major differences between DNA and RNA
1 RNA is a single-stranded molecule so no double helix
2 sugar in RNA is ribose and not deoxyribose -> has one more oxygen atom
3 RNA does not contain Thymine and instead Uracil
Helicase
unnwinds the parental double helix
Helicase
unwinds the parental double helix
Primase
serves as starting point
- > leading strand leads primase once at very beginning
- > lagging strand : primase gives polymerase a starting point ( remember polymerase can only go 5’->3’ ) starting point enables polymerase to work backwards
DNA Polymerase III
adds DNA nucleotides to the 3’ end of RNA primer
Okazaki fragment
short section that arises at lagging strand during replication for supporting and enabling polymerase to add nucleotides
DNA polymerase I
replaces primers with DNA nucleotides
DNA ligase
combines Okazaki fragments
RNA Splicing and Splicesomes
(Pre) RNA contains intron and exons
-> Spliceosomes remove introns to create mRNA -> breakting the junk (introns) segments down so that their bases can be reused so they stick together the ends of the good stuff (exons)
Replication
DNA -> DNA
Transcription
DNA -> RNA -> mRNA
Translation
mRNA -> Protein
What is the role of ribosomes in translation?
mRNA binds to ribosomes to initiate the process of translation
( ribosomes are a mix of proteins and rRNA )
rRNA
doesnt contribute any genetic information to the process BUT it has binding sites that allow the incoming mRNA with tRNA
tRNA
transfer or translation RNA -> translates from language of nucleotides into language of amino acids and proteins
-> binds to codon at ribosmose to form amino-acid-chain
(eg AUG -> protein Methionine) -> when triplet codon is detected the fitting anticodon is added by tRNA
Redundancy
multiple codons code fr the same amino acid
Silent mutation
codes for same amino acids due to redundancy -> nothing changes -> synonymous
Missense mutation
changes amino acid (litte to huge effect) -> nonsynonymous
-> new base is added so that codon encodes for another (possibly) amino acid
non-sense mutation
codon becomes stop codon -> causses translation to be terminated -> usually non functional protein
Frameshift mutation
- happens whenever the number of nucleotides inserted / deleted is not a multiple of 3
result : extensive missense ending with nonsense & premature termination
Histone
- regulation of gene expression
Histone acetylation
leads to uncoiling of chromatin structure which allows it to be accessed by transcriptional machinery for the expression of genes = euchromatin -> increases gene expression
Histone deacetylation
leads to condensed or closed structure of the chromatin -> less transcription of genes =heterochromatin -> decreases gene expression
Histone methylation
gene silencing
-> more permanent method of down-regulating transcription of genes
-> abnormal DNA methylation has been associated with cancer
Histone phosphorylation
addition of phospahte group promotes loosening
-> increases gene expresiion
DNA methylation
turns off genes -> methylation patterns are passed on during cell division
permanent gene silencing : eg cell differentiates in final form and needs to shut off genes coding for other cell types)
What is simultanous Activation of Genes
- result often in response to chemical signals from outside the cell ( genes with same control element are activated by same chemical signal)
hormone receptor complex : serves as a transcription activator
-> can be associated with cancer
Linkage Studies
study within a family ( some have the phenotypic characteristic of interest and others dont)
Association Studies
two samples of population
expansion of triplet repeats such as CAG
associated with 14 disorders , including Huntingtons disease
disjunction
a lack of correspondence and consistency
non-disjunction
the failure of one or more pairs of homologous chromosomes or sister chromatids to separate normally during nuclear division, usually resulting in an abnormal distribution of chromosomes in the daughter nuclei.
