TASK 1 Flashcards
Variation
Phenotype
- Expression of the genotype
- observable characteristics that change
Genotype
- Underlying genes/sequence of genes which determine specific characteristics
Haploid cell
- Cells with only 1 set of chromosomes
- germ cells: egg/sperm cells
Pyrimidine
Cytosine, Thymine
- only single organic ring
Purine
Adenine, Guanine
- have two organic rings (stronger bond)
Nucleotide
= base + backbone
- -> nitrogenous base, five carbon sugar and (at least) one phosphate group
- building blocks of nucleic acids
- nucleoside = base + sugar
Gaussian curve of human nature
- Bell curve
- “normal” and most common behaviour around the mean / peak and extreme behaviours to the left and right ends
Recombination
Production of offspring with combinations of traits that differ from those found in either parent
- Eukaryotes: genetic recombination during meiosis can lead to a novel set of genetic information that can be passed on from the parents to the offspring.
Genetic linkage
- tendency of DNA sequences that are close together on a chromosome to be inherited together
- during the meiosis phase of sexual reproduction
Epigenetics
- study of changes in organisms caused by modification of gene expression (= how many copies of certain RNA molecule are made)
- rather than alteration of genetic code itself
- -> methylation (DNA level)
- -> acetylation (Histone level)
Methylation
= methyl groups are added to DNA molecule
- can change activity of a DNA segment without changing the sequence
- -> methylated: repress/stop gene transcription/expression
- -> not methylated: enhanced gene expression
Acetylation
= acetyl groups (-COCH3) are attached to lysins (AA) in histone tails (N-terminus)
- Histone code hypothesis: specific combinations of modifications & the order in which they occur helps determine the chromatin configuration –> in turn influences transcription
- -> acetylated: chromatin structure more loose = easier access for transcription proteins
- -> not acetylated: removal of acetyl groups; chromatin more compactly folded = no access for transcription proteins
Gene mutation
- Permanent alteration in the DNA sequence such –> differs from what is found in most people
Frameshift mutation
- addition or deletion of one or more base pairs in the DNA –> whenever number of nucleotides added/deleted not multiple of 3
- alters reading frame of genetic messages
Types of mutations
- point mutation/single-base substitutions
- slippage
- transposition/segmental duplication
- chromosomal mutations
- mutagens
- frameshift mutation
Point mutation/Single base substitutions
- only affecting 1 or very few nucleotides in a gene sequence
- -> transitions
- -> transversion
Slippage/Simple sequence repeat expansion/contraction
- leads to trinucleotide or dinucleotide expansion/ contraction during DNA replication
- normally occurs when a sequence of repetitive nucleotides is found at the site of replication
Transposition/Segmental duplication
- chromosomal segment is transferred to a new position on the same or another chromosome
Synonymous mutation
- no amino acid change
- Due to the redundancy of the genetic code
- silent mutation: no change in phenotype
Non-synonymous mutation
- amino acid change
- changes in phenotype
Central dogma in genetics
- Flow of genetic information within a biological system
- only in one direction and not the other
= DNA –> (via transcription) RNA –> (via Splicing) mRNA –> (via translation) Proteins
Genome
- haploid set of chromosomes in a gamete
- consists of all genetic information instruction of cell
- all the chromosomes together
Somatic cells
Any cell of a living organism other than the reproductive cells
Germ cells
- Cell containing half the number of chromosomes (only 23)
- able to unite with one form of the opposite sex to form a new individual (gamete)
Gametes
- Reproductive cells
- haploid = only carry one copy of each chromosome
Chromosomes
Thread like structure of nucleic acids and proteins carrying the genetic information (DNA) in the form of genes
Autosomes
Any chromosome that is not a sex chromosome
Eukaryotic cell
Cells with a nucleus enclosed with membranes
- humans
Prokaryotic cell
Cells that have no nucleus, DNA can be everywhere
- bacteria
Mitosis
- Cell division
- results in 2 daughter cells each having the same number and kind of chromosomes as the parent nucleus (occurs in tissue growth)
Meiosis
- Cell division
- results in 4 daughter cells each with half the number of chromosomes of the parent cell (occurs in the production of gametes)
Nucleotides / base pairs / nucleobases
- Building blocks of nucleic acids
- Adenine + Thymine
- Cytosine + Guanine
Sugar-phosphate backbones
Makes up the strands of the DNA
Replication
- 2 strands of the parental molecule separate (replication fork) –> each functions as a template for synthesis of a new complementary strand
- only works continuously for leading strand
- result: 2 x new (identical to previous) DNA
1. Helicase
2. Primase
3. DNA polymerase III
4. DNA polymerase I
5. DNA ligase
Helicase (1)
- “unpackages” an organisms genes (open up the DNA so it can duplicate)
- recognise sequence of nucleotides –> attach to DNA –> start separating the 2 strands
- replication bubble with Y-shaped replication fork at both ends
DNA polymerase III (3)
- adds DNA nucleotides (= monomers) to the 3’ end of the RNA-primer
- -> Come from nucleoside triphosphates
Replication fork
Place where the helicase splitted up the 2 strands of DNA
Introns
- Non-coding part of the DNA
- stay in nucleus
- Pseudogenes = genes that have ceased to be translated (e.g. olfactory)
- Transposable elements = multiple near-identical copies of particular sequences of bases; around 43% of ncDNA; can be thought of as parasites; ability to copy themselves into different parts of genome
- Simple sequence repeats = short internally repetitive sequences
- -> shorter = microsatellites
- -> longer = minisatellites
Exons
- Coding part of the DNA that exit the cell nucleus
- gets translated into mRNA –> encodes amino acids at ribosomes
Transcription
- First step of gene expression
- synthesis of RNA –> using information in DNA by RNA polymerase II
- use template/lagging strand –> make copy of non-template strand/coding strand of DNA
Splicing
- Editing pre-mRNA/RNA into mRNA
- removing of introns + ligation (putting together) of exons
- Spliceosomes remove introns
Translation
- Process in which ribosomes synthesise proteins
- tRNA adds up the amino acids coded for by the mRNA
- synthesis of a protein (polypeptide) using the information in the mRNA
- initiation codons (AUG) + termination codons: start + stop signals for translation
- site of translation: Ribosomes
- change in language –> monomers are amino acids (rather than nucleotides)
- tRNA: binds to codon at ribosome to form amino-acid-chain
- -> Redundancy
Ribosomes
- Molecular machine that serves protein synthesis
- link amino acids together in the order specified by the mRNA
RNA
= Ribonucleic acid
- formed through transcription
- uracil instead of thymine
- one strand not two
- contains exons + introns
mRNA
= Messenger RNA
- only contains the exons and leaves the cell nucleus in order to travel to the ribosomes
tRNA
Transfer RNA that transports the amino acids and delivers them to the ribosomes when needed
Amino acids
- Organic compounds containing amine and carboxyl functioning groups
- building blocks of proteins
Protein
Made up of amino acid (chains)
Triplet / Codon
- set of 3 nucleotides
- as a group (triplet) code for one specific amino acid
Genetic code
Relation between triplet and amino acid
Redundancy
- multiple coding code for same amino acid
- protection against variation
Diploid cell
- cell with 2 sets of chromosomes
- all somatic cells
DNA
= deoxyribonucleic acid
- functions: replication + synthesis of proteins
Primase (2)
synthesises primer = short stretch of RNA –> serves as starting point (5-10 nucleotides long)
Leading strand/Forward strand
- 5’ > 3’ direction (toward replication fork)
- -> polymerase can only add nucleoside triphosphates to the 3’ end –> only one primer required
- replication only works continuously for leading strand
Lagging strand/Reverse complement strand
- 3’ > 5’ direction
- replication works discontinuously –> series of segments away from the fork –> requires more primer
- -> Okazaki fragments (each fragment must be primed separately)
DNA polymerase I (4)
replaces primers with DNA nucleotides
DNA ligase (5)
joins/puts together backbones of Okazaki fragments
Transition
- interchange of purines (A G) or of pyrimides (C T)
Transversion
- interchange of purine (A/G) with pyramid (C/T)
Mutagens
- physical/chemical agents that interact with DNA in ways that cause mutations
Whole genome duplication
- creates an organism with additional copies of the entire genome of a species
Transcription factors (TF)
- locate right gene at the right time & regulate transcription
- General TF = essential for transcription of ALL protein coding genes
- Specific TF = essential for transcription of PARTICULAR genes (in addition to general TF)
Alternative splicing
- different mRNA molecules are produced from the same primary transcript
- depending on which RNA segments are treated as exons and which as introns
- -> important for variation
