Unit 1 Flashcards
Chromatin
DNA + Protein
Allele
Variant of a gene that differs at the DNA sequence level
Wild type
Most common allele of a gene in a population
Dominant allele
An allele that produces the associated phenotype when present in one copy.
Recessive Allele
An allele that required in two copies to produce the associated phenotype.
Genotype
Composition of a gene or set of genes
Phenotype
Physical manifestations of a specific genotype
Homozygous
Two of the same
Heterozygous
Mixed (carrier)
Phenotype - wildtype
Wild types are the most common PHENOTYPE
CFTR gene
Monogenic - on chromosome 7 - homozygous recessive (cystic fibrosis)
Haploid
One copy of every chromosome - 23 chromosomes (n)
Diploid
2 copies of every chromosome - 46 chromosomes (2n)
Dna v rna
Dna: Double stranded (more stable, less reactive) - OH at corner instead of at two corners - uses thymine not uracil.
Template strand
Will be used for transcription
Nontemplate strand (coding strand)
not used - will be ALMOST SAME to the coded RNA strand (except for T-U)
RNA
Will look JUST like the non template (T-U)
Transcription
Process by which RNA is produced using the base sequence in the DNA template strand
Promoter
DNA sequence (TATA) near beginning of gene that signals where transcription begins
Transcription factors
They recognize the promoter and bind to the DNA + recruit transcriptional machinery
RNA polymerase
Synthesizes rna from a dna template
3 phases of transcription
Transcription initiation:
Txn factors recognize The promoter DNA sequence near start of gene + RNA polymerase
Transcription elongation:
Polymerase melts double strand BONDS of DNA + read the template strand to make 5-3 complementary and parallel ssrna molecule. Template strand is 3-5 so rna will be 5-3.
Termination:
Rna polymerase falls off + rna strand falls off
Amplification of genetic information
Multiple copies of the same RNA are made by multiple simultaneous transcription
RNA processing
During txn rna is modified AS it is transcribed.
- Modification (cap and tail)
- Splicing (intron removal)
- Export
mRNA
Two forms: premature which is processed to form mature mRNA.
mRNA cap and tail
5’ cap: modified base added to the 5’ end of mRNA - protects strand - signal for transportation from Nucleus-cytoplasm
3’ poly A tail: prevents enzymatic degradation of the rna in the cytoplasm. Aids in export.
Splicing
Introns and Exons are read and transcribed into pre-mRNA. Introns are cut and removed. Exons are spliced together.
Introns
Non coding segments of DNA - removed from mRNA
Exons
Coding regions of dna sequence
Gene expression (central dogma)
Why is the process of transcription the sequence of bases in a gene instructs production of RNA with a specific sequence of nucleotides
Alternative splicing
Different permutations for a sequence of exons. Different combinations of exons mean alternative RNA strands. When translated, you get different protein isoforms.
Protein
Macromolecule composed of amino acids - 4 different kinds of amino acids
What determines the structure and function of a protein
Sequence of amino acids
Amino acid chain
Held together by peptide bonds
Protein structure
Determines function
Anti Codon
Complementary and antiparallel to the codon
tRNA
Transfer RNA
Type of RNA produced in txn of a gene molecule that that connects mRNA to amino acids
Codon
3 base pairs that make an amino acid
Ribosome
Large complex of proteins and RNA molecules
rRNA (ribosomal) + tRNA
3 phases of translation
Initiation:
Ribosome attach to the RNA in the cytoplasm. Searches for the start codon AUG (methonine).
Elongation:
Ribosome travels from 5’ to 3’ of the RNA. Builds proteins as tRNA match with the mRNA codons attaching aa to each other.
Termination:
Ribosome encounter the stop codon. Ribosome is thus released, so is the polypeptide chain. THEN the protein may properly fold.
Translation elongation
Second tRNA arrives and base pairs w the mRNA codon
Ribosome moves along 5-3 and peptide bonds form to create a polypeptide chain
Translation termination
ribosome reaches a stop codon to which a release factor protein binds to (instead of a tRNA). Once bound, synthesis is stopped and everything detaches.
Ribosomes are reused.
Multiple ribosomes
Multiple ribosomes can move down a single mRNA to amplify expression!
Genetic code is degenerate
Many different codons can make a single amino acid.
But there are some amino acids that ONLY HAVE ONE CODE (methionine).
Aug
Is the first codon and sets the pattern for how the codons are meant to be read for the ribosome.
Missense mutation
A change in one aa to another
Nonsense mutation
A point mutation that results in a premature stop codon.
Cuts the chain short.
Frameshift
Deletion or insertion of a nucleotide. changes the WHOLE THING. Self evident by name.
Point mutation
Change JUST 1 nucleotide
Diamond blackfan anemia
Bone marrow does not produce enough blood cells
Disease caused by error in translation.
Failure or inability to produce ribosome proteins
RBC are prone to apoptosis
Dominant allele
RNA Polymerase
Moves along template strand 3-5
Assembles RNA 5-3
Gene expression
Transcription + translation of a gene to produce protein
Different patterns of gene expression on different cell types
Results in difference in amount and type of mRNA made in a given cell (cell differentiation, cell identity, cell function)
Transcriptional control
Control at initiation
Control at chromatin (epigenetics)
Assembly of txn initiation complex at promoter
Post translational control
Transcriptional control relies on
- the state of the chromatin
Nucleosome
Dna is wrapped around 4 pairs histones (like cubes). This set is a nucleosome. When open the DNA may be expressed, if closed it will not be expressed
Transcription factors
Proteins that control txn by binding to specific dna sequences
(Specific proteins that bind to specific sequences of the dna)
2 txn factors
General transcription factors (gtf)
Specific/specialized transcription factors
General txn factors
Class of TF that bind at the promoter to recruit RNA polymerase
Specific txn factors
Class of TF that bind to dna at:
- Activators: enhances the expression
- Repressors: silence the expression
Stem cell
Cell with the ability to replicate into 2 daughter cells. One cell will remain a stem cell, the other has the ability to differentiate.
(Most potent (totipotent) stem cell is the Embryo)
Potent cells
Totipotent embryo
Pluripotent embryonic stem cell:
Mesoderm, ectoderm, endoderm
Multipotent stem cells
Master TFs
Oct4
SOX2
NANOG
Promote genes that preserve the stem cell state.
