1.3 gene expression Flashcards
Name the 2 main processes involved in gene expression
Transcription (making mRNA)
Translation (making protien)
State three structural differences between DNA and RNA molecules
-RNA nucleotides have ribose sugar and DNA has deoxyribose sugar.
- RNA bases are similar, however RNA has the base uracil instead of thymine
- RNA and DNA structure resemble one another in they both are composed of nucleotides
State the complementary base pairs that form between DNA and RNA
DNA- AT, GC
RNA- A and uracil, GC
Identify the four different types of nucleic acid molecules found in cells
DNA : deoxyribose nucleic acid
mRNA : messenger ribose nucleic acid
tRNA : transfer ribose nucleic acid
rRNA : ribosomal ribose nucleic acid
State the role of mRNA during the process of gene expression
mRNA (messenger RNA)- Transports a copy of the genetic code from DNA in the nucleus to the ribosome.
State the role of tRNA during the process of gene expression
tRNA (transfer RNA)- Carries specific amino acids to the ribosome where they are assembled to make polypeptides
State the role of rRNA during the process of gene expression
rRNA (ribosomal RNA)- Combines with protein to make up structure of a ribosome
State the differences in structure between mRNA and tRNA molecules
mRNA has a linear structure and carries genetic information copied from DNA. tRNA has an L shaped 3D structure
State the location of transcription in a cell
Nucleus
Stage one of transcription
DNA strands become unwound
Stage two of transcription
Weak hydrogen bonds between two bases are breaking causing the two DNA strands to separate
Stage three of transcription
Free RNA nucleotides find their complimentary nucleotide on DNA
Stage four of transcription
Weak hydrogen bonds are forming between two complimentary bases
Stage five of transcription
Strong chemical bond is forming between the sugar of one RNA nucleotide and the phosphate of the next. The linking of nucleotides is brought about by RNA polymerase
Stage six of transcription
Weak hydrogen bonds between DNA and RNA bases are breaking allowing the mRNA to become separated from DNA
Stage seven of transcription
mRNA leaves the nucleus
Stage eight of transcription
Weak hydrogen bonds form between 2 DNA strands again
Identify the key enzyme required for transcription
RNA polymerase unwinds and unzips the double helix
Identify the coding and non-coding riegons found in a primary mRNA transcript
Introns- Non-coding regions
Exons- Coding regions
describe RNA splicing
Introns are cut out and removed from the primary transcript of mRNA and the exons are spliced together to form mRNA with a continuous sequence of nucleotides. This modified mRNA is called the mature transcript of mRNA and passes out of the nucleus to the cytoplasm and heads to the ribosome for translation to occur
State the location of translation in a cell
Ribosome
Define the process of translation
Translation is the process that turns nucleic acid language into amino acid language. This happens at a ribosome where tRNA’s are used to convert the genetic code carried by the mature mRNA strand into a polypeptide chain to form a specific protein molecule.
State the term used to describe a triplet of bases on an mRNA molecule
Codon
State the term used to describe a triplet of bases on a tRNA molecule
Anticodon
Describe the complementary nature of codons and anticodons and explain the role that this plays in translating the genetic code
The nucleotide bases in the codons (mRNA) and anticodons (tRNA) form complementary base pairs held together by weak hydrogen bonds.
The complementary base pairs are : Adenine – Uracil (A-U)
Cytosine – Guanine (C-G)
State the terms used to describe the mRNA codons that initiate and terminate the translation of a protein code
Start stop codons
Describe the role of tRNA molecules in the process of translation
tRNAs carry amino acids to the ribosome and join with their complementary codons
Describe the sequence of events involved in converting the genetic code into a sequence of amino acids
DNA to mRNA is transcription and mRNA into protein is translation
Explain how the process of alternative RNA splicing can result in different proteins being expressed formed one gene code
After the primary mRNA transcript has undergone RNA splicing, the mature primary mRNA transcript is formed.
State the type of chemical bonds formed between adjacent amino acids during translation
peptide bonds
Identify the molecule that is formed from these linked amino acids
poly peptide chains
Describe how the specific 3-dimensional shape of a protein molecule is achieved
The shape is achieved by chemical bonding to fold up and hold the protein in a specific 3-D structure using hydrogen bonds and other interactions between individual amino acids such as sulphur bridges.
Give examples of proteins with specific shapes which determine their function
Enzymes, active site
Antibodies
Hormones
Explain the role of gene expression in determining the phenotype of an organism
Gene codes for protein and a protein determines a phenotype
