17.1-17.5 Flashcards
Gene Expression
The process by which DNA directs the synthesis of proteins (or in some cases the RNAs)
Stages of Gene expression
Transcription and Translation
Examples of proteins that are not enzymes
Keratin and Insulin
What is a primary transcript?
Initial RNA transcript from any gene, including those specifying RNA that is not translated into protein
What is the central dogma
DNA–> RNA–> protein
How many possible combinations can there be of amino acid code
4^3 = 64 possible combinations
Which way do strands get read?
5’ –> 3’
What does RNA polymerase do?
It pries two strands of DNA apart and joins together RNA nucleotides complementary to the DNA template strand.
Initiation
RNA polymerase binds to promoter, DNA strands unwind, and polymerase initiates RNA synthesis at START POINT on template strand.
Elongation
Polymerase moves downstream (after gene), unwinding DNA and elongating the RNA transcript 5’–> 3’. Also DNA strands re form a double helix
Termination
Eventually, the RNA transcript is released and polymerase detaches from DNA.
What is the promoter?
The DNA sequence where RNA polymerase attaches and initiates transcription
Initiation promoter binding
RNA polymerase II must bind to the promoter AFTER transcription factors (bunch of protiens) bind to the promoter.
What is a transcription initiation complex?
Complex of transcription factors, and RNA polymerase II bound to the promoter.
Initiation in Eukaryotes `
In the PROMOTER, there is a TATA box (25 nucleotides upstream from the starting point-before)
The transcription factors RECOGNIZE the TATA box and bind before RNA polymerase II binds.
Functions of the Poly-A tail and 5’ cap
- To facilitate export of mature mRNA from nucleus
- To help PROTECT mRNA form degredation by hydrolytic enzymes
- Help ribosomes attach to the 5’ end of mRNA once it reaches the cytoplasm
snRNPs
‘snurps’ they recognize the splicing sites
made up of RNA and protein molecules
‘ small nuclear ribonucleoproteins’
They join with protiens to form a spliceosome
What are ribozymes?
RNA molecules functioning as enzymes, Intron RNA functions as ribozyme and catlyises its own excision. Pre-rRNA removes its own introns.
e.g. protist Tetrahymena
Alternative RNA splicing
Lots of genes giving rise to two or three different polypeptides dpeending on which segments are treated as exons during the RNA processing.
Exon shuffling
introns increase probabilty of crossing over beween exonss of alleles in gene. (by providing more terrain for it ) Could lead to new combinations of protiens with new functions.
Which enzyme matches the tRNA and amino acid?
Aminoacyl-tRNA synthetases
P site
Holds the tRNA carrying the growing polypeptide chain
A site
holds the tRNA carrying the next amino acid to be added to the chain
E site
Exit site.
SRP
signal- recognition particle- brings the ribosome to a receptor protein built into the ER membrane.
A series of enzymes catalyse the reaction X -> Y -> Z -> A. Product ‘A’ binds to the enzyme that converts X to Y at a position remote from its active site. This binding decreases the activity of the enzyme. In this example, substance ‘X’ functions as:
a. a competitive inhibitor.
b. an intermediate.
c. an allosteric inhibitor.
d. a substrate.
e. a coenzyme
d. Substrate
The capsid of influenza virus is cloaked by a:
a. sheath
b. cell wall
c. repeating units of the capsomer
d. lipid envelop with embedded glycoprotein
e. viral envelopes of protomers and glycoprotien
d. lipid envelop with embedded glycoprotein
During the secretory phase of the menstrual cycle:
a. endometrial arteries and glands enlarge.
b. the corpus luteum secretes glycogen.
c. the corpus luteum secretes estradiol and progesterone.
d. the oocyte is most susceptible to fertilisation.
a. endometrial arteries and glands enlarge.
How does tropomyosin control the muscle contraction?
a. It binds with sodium ions
b. It acts as a bridge between actin and myosin
c. Changing its shape opens membrane calcium channels
d. It provides a site where ATP can be utilised
e. Its position changes, exposing myosin binding sites on the actin
e. Its position changes, exposing myosin binding sites on the actin
Bone tissue consists of __________ cells in a matrix of __________.
a. chondrocyte; calcium phosphate
b. osteoblast; myosin and actin
c. colagen; calcium phosphate
d. osteoblast; polysaccharide
e. osteoblast; collagen and calcium phosphate
e. osteoblast; collagen and calcium phosphate
When the concentration of glucose in the medium falls during catabolite activation:
a. the concentration of CAP rises.
b. the concentration of repressor rises.
c. the concentration of cAMP rises.
d. the concentration of RNA polymerase increases.
c. the concentration of cAMP rises.
In the fish circulatory system:
a. blood leaving the gills in under high pressure.
b. blood leaving the heart moves directly to body tissues.
c. blood moves from the muscular ventricle to the gills.
d. blood entering the heart is under high pressure.
c. blood moves from the muscular ventricle to the gills.
External _____are highly branched folds of the body surface that maximise gas exchange.
Gills