Genetics Flashcards
Explain the structure of DNA
-Pentose sugar
-Nitrogenous base
-Phosphate group
Explain what Cytosine and thymine are
- Are single carbon nitrogen rings called pyrimidines
Explain what adenine and guanine are
Double carbon rings called purines
Explain the watson and crick theory
- They proped the Double helix model
-DNA is in a twised ladder with chemical bonds
-The side of the ladder is composed of a sugar and phosphate group, held togeehr by strong phosphodiester bonds
Explain the process of DNA coiling
- DNA is wrapped aroud histones to form nucleosomes
-Nuclesomes form helical solenoids
-Solenoids are organised into chromatin loops , each with 100,000 base pairs
Explain the process of DNA replication
- The weak hydrogens break,produicng 2 single strands with their unpaired bases
- Each single strand acts as a template for making a complementary strand
-DNA polymerase adds free nucleotides to the 3 end of the strand - DNA polymerase performs part of a proofreading procedure, checking if the newly added nucloetides are complementary to the templte base
What is the function of replication bubbles
Allow DNA replication to take place at multiple locations on the chromosme, speeding up the replication process
Where does DNA formation and replicaiton occur
Cell nucles
Where does protein synthesis occur
cytoplasm
Explain the structure of RNA
- ribose sugar
- uracil instead of thymine
-single stranded
What is transcription , breif statment
The process where a messenger RNA(mRNA) is synthesized from a DNA template
Explain the process of RNA + modified cap
-RNA polymerase II binds to the promotor site on the DNA, initiating contraction
-DNA polymerase seperatez the DNA strand leaving the bases exposed
-One strand acts as a template
-RNA Polymerases moves along the template in a 3 - 5 direction, creating a complementary strands in the 5- 3 direction
- As transcription progresses, the 5 end of the RNA gets as modified cap , to prevent degredation of the RNA molecule
When does transcriptione end
When the polymerase reaches the termination sequence
What are general transcription factors
Proteins that are required for the transcription of all genes
What are specific transcription factors
Proteins that activate certain genes
What is the function of RNA polymerase
It is a key enzyme in trancription, binding to the promtor region to initiate transcrition, but it cannot
- Locator the promotor region on its ownr
-produces significant amounts of RNA without assistance
What does effectove transcripiton require
It requires the interaction of around 50 proteins including
-Genral transcription factors, which bind to RNA polymerase and specific DNA sequences in the promotor region
Explain enhancers
- Loacted far from the gene, they increase transcriptional activity of a specific gene
-They do not directly interact with genes, but are bound by activators
What do activators bind to
Bind to coactivators, which then bind to general transcription factor compleses
What are silencers
- oppsoite effect to enhancers
- They repress the gene transcription through similar interactoms
What can mutations in enhancers, silencers,promotors or transcriptonal factors lead to
- Genetic diseass
How do transcription factors loacte the specific DNA sequencse
- DNA binding motifs
What is gene expression influenced by
- Several epigenetic modifications including:
- Chromatin structure
-Histone acetylation
-DNA methylation and micor NAs
Where does spliving occur and describe the process
- In eukaryotes-nucleus
- The introns are removed from the primary RNA and then the exons are joined togther to create function mRNA
- The mRNA transcript then leaves the nucleus and moves to the cytoplasm for protein synthesis
What can errors in gene splicing lead to
- Genetic mutations , which may result in diseases
What does alternate splicing allow
It allows a single gene to produce multiple protein products by splicing the primary transcipt in various wyas `
Explain why the gentic code can be seen as degenerate
- As the genetic code consits of 64 possible codons with 3 being stop codons and 61 codons remaining to specifcy 20 amino acids, making the code degenerate as most amino acids are coded by multiple codons
Why is the genetic code NEARLY universal
As the mitochondiral DNA has some codons differing from the nuclear DNA
What happens in translation( brief statment)
- It uses mRNA as a template to synthesis a polypeptide
What is the role of tRNA in translation
Each tRNA binds to a spcecific amino acid and has an anticodon sequcne that is complementary with the mRNA cododn
What is the role of ribosomes in translation
- It binds to mRNA and tRNA faciliating codon by codon reading and peptide bond formation between the amino acids
When does translation end
It ends when the ribosomes encounters a stop codon on the mRNA releasing the completed polypeptide
Name the different types of RNA
-MicroRNAS( miRNA)
-Small interfering rNA( siRNA)
-Long Noncoding RNA
What is noncoding DNA
RNAs that do not translate into proteins
What is the function of microRNAs(miRNA)
They down regulate mRNA expression by binding to specific mRNA targets
What is the function of small interfering RNA (siRNA)
They target single specifc mRNA used in cancer genes
What is the function of Long Noncoding RNA
- They are involved in gene regulation such as X chromosome inactivation in females
