1.2 Gene Expression, Cellular Differentiation Flashcards
state the of meanings genotype, allele, phenotype
allele - different forms of a gene
genotype - the alleles present in an organism
phenotype - appearance of an organism
explain the term gene expression
gene expression involves transcription and translocation of DNA sequences in the process of protein synthesis
link between phenotype and gene expression
phenotype is influenced by genes and environmental factors
structure of RNA nucleotide
RNA is single stranded, composed of nucleotides containing a ribose sugar, phosphate and 4 bases A, U, C, G
describe the forms and structure of the 3 types of rna
mRNA - carries copy of DNA code from the nucleus to the ribosome ( nucleus, ribsome/cytoplasm)
tRNA - folds due to complementary base pairing. Each tRNA molecule carries its specific amino acid to the ribosome ( cytoplasm/ribosome)
rRNA - together rna and proteins form the ribosome (ribosome)
codons and anticodons
codon - triplet of bases on the mRNA which codes for a specific amino acid
anticodon - exposed triplet of bases at the end of tRNA molecule which is complementary to a codon on the mRNA.
describe the process of transcription and where it occurs
1 - RNA polymerase enzyme moves along section of dna (gene) unwinding double helix.
2 - hydrogen bonds between base pairs break which allows the unwinding of the double helix.
3 - as RNA polymerase breaks the bonds, it synthesises a primary transcript of mrna using rna nucleotides which form hydrogen bonds with the exposed dna strand by complementary base pairing to the dna nucleotides.
4 - primary transcript of mrna is then ready to be spliced to produce a mature mrna transcript.
5 - mature mrna transcript is now ready to leave the nucleus and travel to ribosome.
process of RNA splicing
- primary mrna transcipt formed in (transcription)
- non coding introns removed from primary transcript by
rna splicing - mature RNA transcript formed by slicing coding exons
together - order of the coding exons is unchanged during RNA
splicing
process of translation
1 - translocation begins at start codon and ends at stop codon.
2 - anticodons on tRNA join to codons on mRNA by complementary base pairings.
3 - as more tRNA molecules arrive at the ribosome carrying specific amino acids this translates the genetic code into a series of amino acids.
4 - peptide bonds form between amino acids in the sequence and join them together.
5 - each tRNA molecule then leaves the ribosome and a polypeptide ( chain of many amino acids) is formed.
how different proteins can be produced by alternative RNA splicing
different mature transcripts are made from the primary transcript. This depends on which exons are spliced together in the mature mRNA transcript.
different types of bonding and folding patterns that contributes to the 3D shape of the protein
- proteins are composed of amino acid sequences linked together by strong peptide bonds which form polypeptides
- these polypeptides chains which are folded to get their 3D shape are held together by hydrogen bonds and other interactions between individual amino acids.
describe the process of cellular differentiation
process by which a cell expresses certain genes to produce the proteins characteristic for that type of cell. This allows a cell to carry out specialised functions.
differentiation in plants
meristems are regions of unspecialised cells that can divide(self renew) or differentiate.
differentiation in animal cells
tissue (adult) stem cells can divide (self renew) or differentiate
Embryonic stem cells are cells found in very early embryonic tissue, which as all the genes can be switched on, are able to differentiate into all cell types that make up an organism are pluripotent.
Tissue (adult) stem cells are involved in the growth, repair and renewal of cells in a specific tissue. Can develop into all cells of a specific type of tissue are said to be multipotent.
e.g blood cells in bone marrow can develop into all types of blood cells.
describe the therapeutic use of stem cells using examples.
therepuetic use of stem cells involve the repair of damaged/diseased organs or tissues. e.g corneal repair in the eye and regeneration of damaged skin.
