Genetics test 2 Flashcards
structure of protein
a sequence of amino acids. They are joined by peptide bonds (the thing elena showed me)
structure of amino acids
N terminus on the left (amino group), hydrogen in middle top, C terminus on right (carboxyl group) and variable group (R group) on bottom.
how amino acids are linked together to form a polypeptide
The peptide bond
different levels of protein structure
Primary, secondary, tertiary, quaternary (see notes for structure)
Explain how the structure of RNA allows it to participate in a variety of cellular functions
Consists of a large number of linked, repeating, nucleotides. They can fold into many shapes. There are also many types of RNA
List the different classes of RNA
mRNA
tRNA
rRNA
miRNA
mRNA
carries coding instructions (in cytoplasm and nucleus)
tRNA
plays crucial roles during protein synthesis(in cytoplasm)
rRNA
plays crucial roles during protein synthesis(in cytoplasm)
miRNA
typically regulate stability of specific mRNAs(in nucleus and cytoplasm)
major components required for transcription
Template (ssDNA), raw materials (ribonucleic triphospates), enzymes and other proteins
Give the substrate for transcription and how it is used to create a polyribonucleotide chain
Ribonucleoside triphosphates are used as the substrates in RNA synthesis. Two phosphate groups are cleaved from a ribonucleoside triphosphate, and the resulting nucleotide is joined to the 3′-OH group of the growing RNA strand
Identify the parts of a typical transcription unit
Stretch of DNA encoding mRNA and sequences necessary for transcription
DNA Transcription general principles:
- Transcription is a selective process; only certain parts of the DNA are transcribed at any one time
- RNA is transcribed from a single strand of DNA. Within a gene, only one of the two DNA strands—the template strand—is usually copied into RNA
- The transcribed RNA molecule is antiparallel and complementary to the DNA template strand.
- always in 5’ to 3’ direction
- Transcription depends on RNA polymerase. RNA polymerase consists of a core enzyme, which is capable of synthesizing RNA, and other subunits that may join transiently to perform additional functions e.g. sigma factor enables the core enzyme of RNA polymerase to bind to a promoter and initiate transcription
- Promoters contain short sequences crucial to the binding of RNA polymerase to DNA; these consensus sequences are interspersed with nucleotides that play no known role in transcription
Transcription is always in the___ direction
Transcription is always in the 5′→3′ direction, meaning that the RNA molecule grows at the 3′ end
three major stages of transcription in bacteria
Initiation, elongation, termination
Initiation bacteria
Promoter recognition
Formation of transcription bubble
Creatorion of first bonds between rNTPs
Escape of transcription apparatus from promotoer
Elongation
DNA is threaded through RNA polymerase; polymerase unwinds + adds new nucleotides to 3’end, rewinds DNA at trailing end
Termination
Recognition of end. The terminator ends it.
Understand the concept of colinearity between genes and proteins and how this gave scientists a clue about the presence of introns and exons in eukaryotic DNA
The thing elena showed me!!
Be able to differentiate exons and introns
Introns go, exons stay. (introns light, exons dark)
Explain the types of processing that occur in pre-mRNA
Moving from primary transcript to mature transcript (pre-mRNA to mRNA). This is done in 3 steps; 5’ capping, 3’ capping and intron splicing
Describe the 5’ cap and its function
A methylguanine is attached to pre-mRNA. This protects it and helps create stability
Describe the poly(A) tail, how it is added, and its function
A bunch of adenine is added to nucleotides at the 3’ end where the cleavage is (where it is likely to break). This creates stability.
Describe how introns are removed from pre-mRNA
By RNA splicing. The spliceosomone cuts the introns in a loop and connects exons
Summarize the different regions of a typical mRNA molecule
5’ untranslated region, protein region (made up of codons), and 3’ untranslated region
Explain what we mean by “the genetic code”
How genetic info is interpreted by protein
Explain how the genetic code is redundant
Multiple codons can code for the same protein
Explain how the reading frame of a gene is determined
By triplets?
Explain what is meant by the universality of the code
All species use the same 4 bases?
Describe the process of elongation, by which amino acids are added to the growing polypeptide chain according to the codons contained in the mRNA
Elongation requires initiation, charged tRNA, elongation factors, peptide bonds, and energy
Describe the process by which amino acids are assembled into a protein through translation of an mRNA
tRNA charging, initiation of teranslation, elongation, and termination
Describe the process of termination that occurs when a ribosome encounters a stop codon
Termination codon stops synthesis
Explain why regulation of gene expression is important and list and explain the different levels at which gene regulation may occur
It prevents protein synthesis from occurring when not necessary. It regulates it. The types
* Operons- on and off switches
* Regulatory elements- DNA sequences that affect expression of DNA to which they are linked
* Operator
* Structural genes
* Regulatory genes
Understand how gene regulation in eukaryotes brings about cell differentiation
Cells are different because they do not all make same proteins
Structural genes
proteins that play a structural or functional role in the cell
Regulatory genes
RNA or protein that interacts with DNA and affect transcription or translocation
Regulatory elements-
DNA sequences that affect expression of DNA to which they are linked
Explain how operons control transcription in bacterial genes
On and off switch
Negative inducible
turned on by repressor.
Positive inducible
activator turns it on
Negative repressible-
repressor turns it off
Positive repressible
activator turns it off
lac operon controls
the metabolism of lactose as an example of a negative inducible operon
glucose affects
transcription through catabolite repression as an example of positive inducible operon
trp operon controls
the biosynthesis of tryptophan as an example of a negative repressible operon
Enhancers/silencers-
enhance or silence transcription. This has a huge impact on cell identity