L11-14: Eukaryotic genes and transcripts & Inheritance Flashcards
What does polycistronic mean?
It is when clustered genes are often transcribed as a single molecule or mRNA
What parts of the transcription unit are not encoded in the genome?
The cap and the poly A tail
How do differences in gene organisation impact geneticsin eukaryotes and prokaryotes?
In prokaryotes if there is a mutation it effects the recognition of all genes but in eukaryotes its only impacts one
What are transcription promotors?
Region of DNA upstream that contains specific nucleotide sequences that transcription factors associate with which allows the recruitment of RNA polymerase
What are the key features of prokaryotic promotors?
Conserved sequences upstream
Conserved sequences recognised by sigma factor which positions the polymerase:
RNA pol + sigma factor = holoenzyme
What are the RNA polymerases in eukaryotes?
RNA pol I - rRNA
RNA pol II - all protein coding genes
RNA pol III - tRNA, 5S rRNA and other small ‘non-coding RNAs’
What are features of RNA polymerase II in eukaryotes?
TATA-box that is bound by the transcription factor IID complex
TFIID recruits other TFs and RNA polymerase II
5’ cap is added while mRNA is transcribed
When is the poly A tail added?
At a specific signal AAUAA when RNA is cut releasing it from the DNA then the poly A tail is added
What is a microarray?
DNA corresponding to each gene in the organisms genome spotted onto a slide
How does splicing take place?
Spliceosome removes introns from RNA
What are the functions of the small and large subunits of the ribosome?
Small: reading mRNA, finding ORF and interpreting the codon
Large: synthetic peptidyl transferase centre
How does bacterial translation take place?
Using the Shine-Dalgarno sequence which is recognised by the small subunit by base pairing
Large and small subunit bind which initiates translation
How is translation initiated in eukaryotes?
Small subunit binds to cap and moves along to the first AUG
How are genes polygenic?
When multiple genes interact
What is the difference between linked and unlinked genes?
Linked genes cannot assort independently whereas unlinked can
What phenotypic and genotypic ratios are typically used to work out allele frequency?
1:2:1 and 3:1
What is the Hardy-Weinburg equation?
p^2+2pq+q^2=(p+q)^2=1
How do populations retain genetic variability?
Due to the genotypic ratios in a randomly-breeding population remaining constant from generation to generation
When does Hardy-Weinburg not apply?
Gene flow
Genetic drift
Nonrandom mating
Natural selection
What does Hardy-Weinburg assume?
Large population, random mating and no evolutionary forces acting
What are examples of human autosomal recessive conditions?
Albinism
Phenylketoneuria
Tay-Sachs
CF
Sickle-cell anemia
Haemochromatosis
What are examples of autosomal dominant conditions?
Huntington’s
Polycystic kidney disease
Achondroplastic dwarfism
Polydactyly
Hypercholesterolemia
FASPS
What are characteristics of sex linkage?
X and Y share little homology
X has more genes than Y
Many genes on Y are for male sex determination
Many genes on X that are not involved in determination
The presence of a gene on X or Y leads to distinct patterns of inheritance
What are examples of X-linked recessive disorders in humans?
Haemophilia
Duchenne & Becker muscular dystrophies
Fragile-X syndrome
Deuteranopia (colourblindness)
