DNA and genes Flashcards
Features of RNA
-Single stranded
-Short in length
-Ribonucleic acid (has the oxygen on the second carbon unlike DNA)
- Bases are; Guanine, adenine, cytosine and uracil
-Acts as a messenger molecule, it transfers information that DNA contains into proteins
Features of DNA
-Double stranded
-Very long
-Deoxyribose (doesn’t have that extra oxygen like RNA )
-Bases; Adenine, cytosine, thymine and guanine
Function of DNA
-Contain genetic information for the development and function of the organism
-Each cell divides for growth and repair of damaged cells
-Each cell needs a full set of the DNA, 46 chromosomes
Give 3 structural differences between DNA and RNA
-DNA has 2 strands whereas RNA has only 1 strand
-DNA has the bases; cytosine, adenine, guanine and thymine. RNA has cytosine, adenine, uracil and guanine
-DNA is longer than RNA
-DNA has deoxyribose meaning it doesn’t have that extra oxygen on the second carbon like RNA
Describe the structure of a mononucleotide found in RNA
Has ribose sugar, phosphate and a base. The bases are uracil, adenine, cytosine and guanine
Describe how DNA replicates (6 marks)
-DNA helicase breaks through hydrogen bonds between complementary bases
-DNA strands separate
-Each new strand is used as a template
-Free nucleotides bind to complementary pairs (A+T and C+G) using DNA polymerase
-Hydrogen bonds are reformed between these base pairs
-DNA ligase forms the phosphodiester bonds of the backbone
-This is known as ‘semi-conservative replication’
What is a gene?
A hereditary unit consisting of a sequence of DNA that occupies a specific location on a chromosome and determines a particular characteristic in an organism
Explain what an intron and and exon is
Exon - Coding section
Intron - Non coding section
Explain the process of translation
-mRNA binds to a ribosome tRNA. tRNA binds to a specific amino acid
-Complementary tRNA anticodons bind to mRNA codons and are held in place by hydrogen bonds.
-The ribosome joins the amino acids attached to the two tRNA molecules by a peptide bond
-tRNA molecules detach from amino acid
-Ribosome then moves along to next codon and forms a long polypeptide chain
Explain the process of transcription
- Complementary hydrogen bases break and DNA uncoils. DNA helicase does this
- This exposes the gene to be transcribed and a complementary copy of the gene is made by building mRNA
- Free nucleotides pair up with complementary bases of unzipped strand (via hydrogen bonds)
- The sugar phosphate groups of these RNA nucleotides are then bonded together using the enzyme RNA polymerase
- mRNA then moves through nuclear pore and attaches to ribosome for translation.
What is meant by degenerate code?
More than one triplet codes for the same amino acid
What is meant by non-overlapping code?
-Each triplet is only read once
-Triplets dont share any bases
What is meant by triplet code?
Each 3 bases codes for one amino acid.
Contains start and stop codons which either start or stop protein synthesis.
Give features of fibrous proteins
-Long parallel polypeptides
-Insoluble
-Very little tertiary structure
-Occasional cross-linkages which form microfibre for tensile strength
Give features of globular proteins.
-Complex tertiary or quaternary structures
-Many uses e.g. hormones, antibodies, carrier proteins
Outline features of collagen and its role in the body
-Fibrous protein
-High tensile strength due to both hydrogen and covalent bonds.
-Collagen molecules are made from 3 polypeptides which form alpha triple helix which forms strong collagen fibres
-Collagen forms the structures of bones, cartilage and connective tissue, a main component of tendons which connects muscle to bones. Found in artery walls.
What is an enzyme?
A biological catalyst which increases the rate of reaction by lowering activation energy of the reactions they catalyse, including both anabolic, catabolic, extracellular and intracellular reactions.
4 factors affecting enzyme controlled reactions.
Enzyme concentration
Temperature
Substrate concentration
PH
How does Ph effect the rate of enzyme controlled reactions?
Enzymes work in a specific range of Ph values. Values above or below this alter the bonds within the structure, hence the shape of its active site
How does enzyme concentration affect rate of enzyme controlled reactions?
Rate of reaction increases as enzyme concentration increases as there are more active sites to bind to. However, after a certain point, increasing enzyme conc has no effect on rate of reaction as there are more active sites than substrates so substrate concentration becomes the limiting factor.
How does substrate concentration affect rate of enzyme controlled reactions?
As substrate conc increases, rate of reaction increases. However, beyond a certain point rate of reaction no longer increases because enzyme concentration becomes the limiting factor.
How does temperature affect rate of enzyme controlled reactions?
As temperature increases, so does rate of reaction. however after a certain point, enzymes become denatured due to high temperatures.
What are the 5 different mutations?
Substitution (change in one base)
Insertion (adding in one base)
Deletion (taking out one base)
Duplication (adding the same base more than once)
Inversion (swapping the order of bases around )
Features of mRNA
-Copy of genetic code
-Moves out of the nucleus to ribosomes
-Acts as a template for translation
Features of tRNA
-Binds to an amino acid, takes amino acid to ribosome
-tRNA is specific for amino acid
-Holds the amino acid in place
-single stranded
-has ribonucleic acid
Compare and contrast the process of transcription with the process of DNA replication. (4 marks)
Similarities:
-Involves formation of phosphodiester bonds.
-Involve DNA helicase
Differences:
-Transcription uses RNA nucleotides and replication uses DNA nucleotides
-Transcription uses RNA polymerase whereas replication uses DNA polymerase`
Muscle cells contain globular and fibrous proteins.
Compare and contrast the molecular structures of globular and fibrous proteins.
(4)
Differences:
-Fibrous proteins are long parallel polypeptides whereas globular proteins are more compact and rounded
-Fibrous proteins have very little tertiary or quaternary structure whereas globular proteins have tertiary and quaternary structures.
Similarities:
-Both are chains of amino acids joined by peptide bonds
-Both have hydrogen/disulphide/ionic bonds