03: Anatomy of the Gene Flashcards
Which base is this?
Adenine
Which base is this?
Guanine
Which base is this?
Thymine
Which base is this?
Cytosine
What is the sense strand?
The coding strand; the strand of DNA that has the same sequence as the mRNA.
What is a gene and what are its components?
A sequence of chromosomal DNA that is required for the production of a functional product.
Has a promotor, enhancers, splice sites, exons and introns.
What are microRNAs?
Untranslated genes which are ~22bp and control gene expression by translational repression or by loading the RNA Induced Silencing Complex (RISC), which destroys mRNA.
What is a locus control region?
Segments of a gene which determine in part the chromatin structure and access to transcription factors.
What components of a gene are important for transcription?
The TATA box and CAT box are immediately 5’ of the start of transcription.
The GC rich region often helps bind transcription factors.
What are the splicing consensus sequences?
These consensus sequences include nearly invariant dinucleotides at each end of the intron, GT at the 5’ end of the intron, and AG at the 3’ end of the intron.
A is the branch site.
How is DNA packaged?
- DNA is wrapped around histones to make chromatin.
- Each histone octamer has DNA wound around it twice (a nucleosome) for a total of 140bp.
- Long strings of nucleosomes are further compacted into solenoids, which attch to the scaffold/matrix within the nucleus to form loops.
- Less tightly packaged areas are better able to bind transcription factors (euchromatin).
Note: There is also a mitochondrial genome which is 16kb in length and maternally inherited.
What is ChIP-sequencing?
Analysis of protein interactions with DNA. Combines chromatin immunoprecipitation (ChIP) with massively parallel DNA sequencing to identify binding sites of DNA-associated proteins.
What is DNase-Sequencing?
Analysis of the location of regulatory region, based on genome-wide sequencing of regions super sensitive to cleavage by DNase I.
Whatis the significance of 5p13.1?
Gene desert, but contains SNPs associated with inflammatory diseases (Crohn’s disease, Ulcerative colitis, Multiple sclerosis).
Genetic variants modulate the expression of flanking genes; affect occupancy of a GATA factor in an allele-specific manner.
What is the signal sequence for the Poly A tail?
AAUAAA
What is uniqe about the first exon of a gene?
Very CG rich to allow for binding of transcription factors.
What DNA sequence establishes the reading frame?
ATG; template for AUG (methionine).
Describe the globin gene family.
Grew as a result of multiple gene duplications; now located on chromosomes 11 & 16 (alpha).
Multiple alpha/betagene family members expressed differentially during development to allow for transportof oxygen under various oxygen tensions.
Many globin genes are pseudogenes: nonfunctional, vestigial remnants of previously functional genes.
What are transposable elements?
DNA segments which can change their position within the genome (may even be inserted in middle of previously functional gene).
This is the cause of hemophilia (factor VIII).
What is the genetic basis of Hemophilia B Leyden and Hemophilia B Brandenburg?
Both result from promoter mutations which decrease the production of Factor IX.
Leyden improves at pubery when levels of androgen increase.
Brandenburg Factor IX levels remain low even after puberty.
What is Huntington’s Disease?
A triple repeat disease (CAG) in which pathological changes in repeat sequences disturb the function of a gene.
(CAG)10-26 normal
(CAG)27-35 at risk for expansion
(CAG)35-41 variable penetrance
(CAG)42-121 affected
Trinucleotide repeats (TNRs), if in coding region, cause long runs of amino acids that affect protein function. If in non-coding regions, can affect gene expression.
Large deletions are commonly seen in what two conditions?
Alpha thalassemia
Duchenne muscular dystrophy
