Eukaryotic genes

Created by

Pierre Gasly

Cards (45)

what are the classes of non-coding DNA
Regulatory sequences [e.g. promoters].
Introns.
Repetitive DNA sequences.
Why are eukaryotic genomes large
They have more genes but also more non-coding DNA.
How much human DNA is coding and non-coding in %.
1.5% is coding and 97% is non-coding.
How much of the non-coding seuqences are introns in e.g. a%
20%
What binds to the promoter
Transcription factors and RNA polymerase
What are the main classficiations of repetive seuqneces
Interspersed and tandemly also known as satellite.
Briefly describe the features of intersperesed repetitive DNA
They are repeated units scattered throughout the genome.
A single unit consits of 100 - 10,000 base pairs.
They copies are not identical but closely related.
These make up 25 - 40% of the mammalian genome.
What are Alu elements an example of
Interspersed repetitive DNA
Describe the features of Alu elements
They are made of 300 base pair repeats.
It makes up 5% of the genome.
They are positioned near coding genes.
Describe the properties of satellite DNA
It is made of 5 base pair repeats.
They are located at the telomeres and centromeres meaning they have a structural role.
Types of tandemly repetitive (satellite) DNA
Regular satellite DNA: 100,000-10 million bp per site
Minisatellite DNA: 100-100,000 bp per site
Microsatellite DNA: 10-100 bp per site
Describe the features of telomeres
They are repetitive DNA at the end of chromosomes.
During DNA replication it does not extend to the end of the chromosomes and so the telomeres shorten. This prevents the loss of DNA during replication.
How long is the DNA double helix
6cm
Describe the packing of DNA
The DNA double helix is wrapped around a histone octamer to form a nucleosome bead. Histone H1 sits on the outside of the nucleosome.
The nucleosome winds up to form a chromatin fibre.
The chromatin fibre loops and is attached to a protein scaffold to form the euchromatin form.
The looped structure folds up to form the heterochromatin form.
Heterochromatin
Highly condensed during interphase, not actively transcribed
Euchromatin
Less condensed during interphase, able to be transcribed
How do histones attract DNA to form a nucleosome
Histones are positively charged and DNA is negatively charged
What are the ways that a gene can be regulated between DNA and protein
DNA unpacking.
Transcription regulation.
RNA processing.
RNA transport and localization.
mRNA degradation or translation regulation.
Protein activation.
What is coarse adjustment of gene expression
These affect multiple genes
What are the two types of coarse chemical modifications for gene expression
DNA methylation and histone acetylation or deactylation.
Describe DNA methylation
It is associated with gene silencing and accounts for genomic imprinting.
How does DNA methylation work
A methyl group is attached to DNA bases this forms the heterochromatin form.
What is histone aceytlation
The attachment of an acetyl group to histones. This results in the euchromatin form.
What enzyme is responsible for DNA methylation
DNA methylase
What DNA is responsible for histone acetylation
Histone acetylase
What enzyme is responsible for histone deacetylation
histone deacetylase
What are the forms of RNA polymerase [Use numbers]
1, 2 and 3
What does RNA polymerase 1 produce

Ribosomal RNA
What does RNA polymerase 2 produce
Messenger RNA
What does RNA polymerase 3 produce
Small RNA such as tRNA
What is a promoter
A DNA sequence upstream of the gene.
What does a promoter regulate
The rate of transcription and where transcription is initiated
Where is the TATA box located
It is part of the promoter and is 10 - 35 base pairs upstream of the gene
What binds to the TATA box
The preinitiation complex
Describe the steps inolved in the intiation of transcription [Use I instead of 1]

TFIID binds to the TATA box
General transcription factors bind [These are TFIIA and TFIIB]
TFIIF binds to RNA polymerase II which binds to The TATA box
TFIIE and TFIIH bind
This forms the preinitiation complex
What are TFIIA and TFIIB
general transcription factors
What is TFIID made of
TATA binding protein [TBP] and TATA associated proteins [TAF].
TAFs locate the TATA box.
What is the basal promoter region
The preinitiation complex
How is the rate of transcription regulated
Using specific transcription factors which can be activators or repressors.
They bind to the distal [Known as enhancers] and proximal control elements, which are upstream of the promoter.
When an activator binds to the distal control element this folds the DNA so the distal control element is closer to the promoter. This intitates transcription.
What is the name for the structure of Transcription factors
Modular