1.3 - Control of gene expression Flashcards
A cell’s genotype is determined by what?
The sequence of DNA bases in its gene
A cell’s phenotype is determined by what?
The proteins that are synthesized when the genes are expressed
The structure and function of a protein (coded for by a gene) is determined by what?
The sequence of amino acids
Amino acids are linked by ____ bonds to form ____
- Peptide
2. Polypeptides
Polypeptide chains fold to the three dimensional shape of a protein, what type of bond holds it together?
Hydrogen
Sub-units that join together to form a polypeptide
amino acid
Transcription and translation use 3 types of RNA, what are the types of RNA?
- Messenger
- Transfer
- Ribosomal
What are the three differences between DNA and RNA?
- DNA - deoxyribose sugar, RNA - Ribose sugar
- DNA - has thymine , RNA - has uracil
- DNA - double stranded , RNA - single stranded
What is transcription?
Transcription is the process in which a copy of DNA is made, This copy is known as mRNA and it occurs in the nucleus.
What is stage one of transcription?
RNA polymerase moves along the DNA, unwinding the helix
What is stage two of transcription?
Weak hydrogen bonds between the bases break
What is stage three of transcription?
Free nucleotides pair up with complementary DNA bases
What is stage four of transcription?
RNA polymerase enzyme controls the formation of the backbone between adjacent RNA nucleotides forming an RNA chain
What is stage five of transcription?
The weak hydrogen bonds between DNA nad RNA break. This leaves a single strand of mRNA (primary transcript)
What is stage six of transcription?
The two strands of DNA come together again and wind up
What is RNA splicing?
Non-coding regions (introns) are removed from the primary transcript which forms the mature transcript.
What is alternate splicing?
Different proteins exposed from one gene.
What is translation?
Tranlation is when mRNA is translated into proteins by ribosomes in the cytoplasm.
Which codons begin and end translation?
START and STOP codons.
What happens during translation at the ribosome?
tRNA with complementary anticodons bond with codons on the mRNA by complimentary base pairing, translating the code into a sequence of amino acids. Peptide bonds form between amino acids.
What is the ribosome composed of?
rRNA and protein
Which process produces a primary mRNA transcript?
Transcription
Which process is when the mature mRNA is used to direct the synthesis of a protein?
Translation
What is the function of RNA polymerase?
Unwinds the double helix and breaks the hydrogen bonds between the bases. It synthesises a primary transcript of mRNA from RNA nucleotides by complementary base pairing.
What is the function of tRNA?
Carries a specific amino acid to the ribosome and has an anticodon which is complementary to a codon.
What is the function of mRNA?
It carries a complementary copy of the DNA code from the nucleus to a ribosome in the cytoplasm.
Describe the structure of a tRNA
It folds due to complementary base pairing and has an amino acid attachment site at one end and an anti-codon at the other end.
What is a codon?
A sequence of three bases on mRNA which codes for one specific amino acid.
