Unit 1 Key area 3 Flashcards
What are the two stages in the process of gene expression?
- Transcription
- Translation
Is it true that all of the genes in a cell are expressed?
No, only a fraction of the genes in a cell can be expressed
What are the types of RNA that are involved in gene expression?
- mRNA
- tRNA
- rRNA
Explain the structure of an RNA molecule?
RNA molecules are single stranded, they contain a phosphate group and a ribose sugar, and one of 4 bases, Adenine, guanine, cytosine, and uracil (replacing thymine)
What is mRNA?
Single stranded molecule of RNA transcribed from the DNA, and translated into a protein, each triplet of nucleotides is called a codon and codes for a specific amino acid
What is the role of transfer RNA in gene expression?
tRNA folds due to complementary base pairing. Each tRNA molecule carries a specific amino acid to the ribosomes. As every tRNA molecule has an attachment site for a specific amino acid and an anti-codon that is complementary to the mRNA codon. Allowing specific amino acids to be transported to the ribosomes.
Give an account of the transcription stage of gene expression?
During transcription RNA polymerase moves along the DNA molecule unwinding it and breaking apart the hydrogen bonds between base pairs. The RNA polymerase then produces a primary transcript of mRNA by adding RNA nucleotides to the DNA until a terminator sequence is reached causing the primary transcript and RNA polymerase to detach from the DNA.
RNA splicing then occurs to form the mature mRNA transcript which is then translated in the nucleus
Explain the process of RNA splicing?
During RNA splicing introns are removed from the primary mRNA transcript, while exons are retained and joined together. The order of exons remains unchanged.
Give an account of the process of Translation?
tRNA is involved in converting mRNA into a polypeptide. This process occurs at the ribosome.
- Translation begins at a start codon, and ends at a stop codon
- anti-codons of the tRNA molecule bind to the codons of the mRNA molecule by complementary base pairing.
- the specific amino acids coded for by the mRNA are joined together by peptide bonds
- the tRNA molecules then leave the molecule and a new peptide is formed.
State what the ribosomes are made up of?
rRNA, and proteins
Describe the process of alternative mRNA splicing?
The process by which different genes can be expressed from the same primary transcript as a result of different exons being retained.
Name the bonds which hold together the three dimensional structure of a DNA molecule?
Hydrogen bonding
What does the shape of a protein determine?
The shape of a protein determines its function
What is phenotype determined by?
Phenotype is determined by the proteins produced by genes that are expressed.
What factors can have an impact on phenotype?
Environmental factors can have an impact on phenotype
