Book One Flashcards
Describe the elongation process of transcription
The large ribosomal subunit has two binding sites (P site and A site): mRNA enters the A site, moves to the P site and is then released.
Translational elongation factors bound to energy releasing GTP molecules bring tRNAs into the A site and the elongation factor hydrolyses GTP to GDP creating a conformational change in the ribosome allowing the tRNA to fully enter the A site.
Movement of RNA codons from A to P is facilitated by another elongation factor (process of translocation) - translocation is also triggered by the hydrolysis of GTP to GDP.
The ribosome catalyses the formation of a peptide bond between the amino acids.
What are the differences between ribosome binding during the initiation of translation in:
a) prokaryotes
b) eukaryotes
a) The two subunits of the ribosome assemble at the ribosome binding site of the mRNA aided by translation initiation factor proteins.
b) There is no ribosome binding site, instead the small ribosomal subunit arrives with a preformed complex of initiation factors. It attaches to the 5’ cap structure which scans the mRNA for the initiation codon then binds to the large subunit.
What are the three main post-transcriptional modifications in eukaryotes and what is the purpose of each?
- Splicing - a complex called the spliceosome cuts out the introns and joins together the exons producing mature mRNA.
- Polyadenylation of 3’ end - addition of multiple adenosine nucleotides generating a Poly (A) tail, a binding site for Poly (A) binding protein which inhibits degredation of mRNA and promotes export from nucleus.
- Capping of 5’ end - modified GTP nucleotide is added to the 5’ end allowing mRNA export through nuclear pores, ribosome binding and prevents degredation.
What are the standard genetic nomenclature for the following scenarios?
a) Allele T and allele t on each homologue
b) Alleles T and M and alleles t and m on each homologue
c) Alleles T and t on one chromosome and alleles M and m on a different chromosome.
a) T / t
b) TM / tm
c) T / t ; M / m
What are the main cell features of:
a) prokaryotes
b) eukaryotes
NOTE a * indicates that it is only present in some species
a) cell wall, cell membrane, capsule, cytosol, free ribosomes, free DNA in an area called the nucleoid, pili, flagellum*
b) cell membrane / plasma membrane, nuclear membrane, cell wall, nucleus, nucleolus, cytosol, free ribosomes, mitochondria, plastids, peroxisomes, lysosomes, rough and smooth endoplasmic reticulum, Golgi apparatus, cytoskeleton
How do you spell the five nucleotide bases of DNA and RNA?
adenine thymine guanine cytosine uracil
The ‘free’ hydroxyl group and the ‘free’ phosphate group are attached to which ends of the DNA strand?
3’ end = hydroxyl group
5’ end = phosphate group
DNA is synthesised in which direction?
DNA synthesis proceeds in a 5’ to 3’ direction. The template strand is read from 3’ onwards.
Looking at a pedigree, what pattern of inheritance would suggest:
a) a dominant disorder
b) a recessive disorder
c) a sex-linked disorder
a) Each affected individual has at least one affected parent. Lineages from unaffected individuals are free of the condition
b) The condition skips generations because some individuals are carriers of the gene for the condition but are not afflicted by it.
c) The condition affects primarily only people of one gender.
a) What are the two surfaces of epithelial cells in the gut and what are they in contact with?
b) What features of gut epithelial cells aid their function?
a)
- The apical surface (in contact with the gut lumen)
- The basolateral surface (in contact with adjacent cells)
b)
- microvilli projections (aid absorption by increasing surface area)
- transporter proteins (on both surface membranes move nutrients into and out of the cell)
- digestive enzymes (secreted from the apical surface of some epithelial cells)
What are the functions of the:
a) smooth endoplasmic reticulum
b) rough endoplasmic reticulum
a) - involved in phospholipid and steroid production
- detoxification of toxins (eg. drugs or ingested chemicals)
b) - synthesis and processing of proteins for export
- lysosomal proteins and protein for secretion and translated into the RER lumen and usually transferred to the Golgi apparatus
- membrane proteins remain partly embedded in the RER membrane and either remain or are delivered to other membranes.
What are linked genes?
Two genes that are located on the same chromosome and are unable to assort independently.
a) Two parents with linked genes PL / pl are crossed. Which gamete genotypes would be entered into a Punett square?
b) What would the expected phenotype ratio of this cross be?
a) PL and pl horizontally and the same vertically.
b) 3:1
Two parents, both R / r ; Y / y are crossed. Which gamete genotypes would be entered into a Punett square?
b) What would the expected phenotype ratio of this cross be?
a) The same four horizontally and vertically:
R ; Y R: y r ; Y r ; y
b) 9:3:3:1
a) 1 m is equal to how many:
- cm
- mm
- µm
- nm
b) how many metres in:
- 1 µm
- 1 nm
a) 1m = 100 cm = 1000 mm = 10^6 µm = 10^9 nm
b) 1 µm = 10^-6 m 1 nm = 10^-9 m
a) What are the two staining methods used to identify cells and some cell components and how do they differ?
b) What is the process of using chemical stains called?
a) 1. Gram stain (a heat-fixed smear of bacteria on a glass microscope slide is stained violet. The smear is treated with solvent to dissolve the purple. Gram-positive bacteria remain purple. A red counter stain is applied: Gram-negative bacteria take it in a turned red/pink.)
2. Haematoxylin and eosin (haematoxylin binds to negatively charged molecules - nucleus - eosin to positively charged molecules - cytosol)
b) histochemistry
Describe the process of immunolabelling?
An antibody is applied to a fixed tissue section or cell sample. The antibody only binds to a specific antigen in the sample.
A secondary antibody specific to the first is applied.
The second antibody is labelled eg. with gold particles or fluorophore which is visible by confocal microscope.
Name some of the principal types of mammalian cell and their function(s)
- epithelial cells (protection, barrier, absorption, secretion)
- endocrine / hormone producing cells (widespread communication)
- muscle cells (movement eg. peristalsis or limbs, contraction eg. heat muscle)
- neurons / nerve cells (rapid and specific communication)
both categorized as connective tissue:
- support cells (support and organisation of tissue structure)
- adipocytes (energy storage)
- blood cells (oxygen transport)
- germ cells (reproduction)
Describe the Oparin-Haldane theory about the origin of organic molecules?
Energy from UV radiation or lightning could have caused molecules of gas in the primordial atmosphere (ammonia, methane and hydrogen) to react with water forming a mixture of simple organic compounds - ‘prebiotic soup’
