DNA Structure & Protein Synthesis Flashcards
Similarities and differences between the structures of chloroplasts and mitochondria
Differences
- Chloroplasts contain chlorophyll, mitochondria do not
- thylakoids Vs cristae
- stroma Vs matrix
- pigments Vs no pigments
- starch grains Vs no starch grains
Similarities
- double membrane
- both contain circular DNA
- both contain ribosomes
Describe the function of DNA helicase and DNA polymerase
DNA Helicase - breaks the hydrogen bonds between bases so they can be free floating to pair up
DNA Polymerase - Builds the DNA strand by catalyzing reactions to form phosphodiester bonds between adjacent nucleotides
Give two differences between the structures of ATP and a nucleotide found in DNA
- ATP has 3 phosphate groups, DNA only has 1
- ATP has ribose sugar, DNA has deoxyribose sugar
Other than being smaller, give 2 ways in which prokaryotic DNA is different from eukaryotic DNA
- prokaryotic cells have circular/non-linear DNA
- Prokaryotic DNA is not associated with histones
- prokaryotic DNA contains no introns
Explain how humans and grasshoppers have very similar % of each base in their DNA but are very different organisms
- have different genes
- triplets are in a different order
- different amino acid sequence is therefore coded for
Explain how the DNA of a virus is different to that of other organisms
- Virus contains one single strand of DNA, not 2 paired in a double helix
- this would mean the percentages of the bases would be uneven
- use eg from table if there is one
How does cytarabine prevent DNA replication (+ given diagram)
- cytarabine has a similar structure to cytosine
- means it can bond to guanine in place of cytosine and prevent further replication
Name 2 biological molecules that can be coded for by a gene
- rRNA
- Pre mRNA
- tRNA
Name 2 types of molecule from which a ribosome is made
- RNA
- Polypeptide
Give 4 structural differences between a DNA molecule and a mRNA molecule
- DNA double stranded in a double helix, mRNA single stranded
- DNA deoxyribose, mRNA ribose
- DNA has hydrogen bonds, mRNA doesn’t
- DNA is long, mRNA is short
- DNA contains thymine as a base, mRNA contains uracil as a base
Explain the meaning of degenerate
more than one triplet for each amino acid
Explain the meaning of non-overlapping
Each base is part of only one triplet
What is a gene
A sequence of DNA bases that code for a polypeptide
Describe how the production of mRNA in a eukaryotic cell is different to that of a prokaryotic cell.
- Pre mRNA only produced in eukaryote
- splicing only occurs in eukaryote
- introns removed in eukaryote
Describe the role of ATP in the process of translation in protein synthesis
- releases energy
- so peptide bonds form between amino acids
Describe how mRNA is produced from an exposed template strand of DNA, not including DNA helicase or splicing
- free RNA nucleotides form complimentary base pairs
- phosphodiester bonds form
- by action of RNA polymerase
Define the term exon
A base/nucleotide/triplet sequence coding for polypeptide/sequence of amino acids
Crossing over greatly increases genetic diversity.
Describe the process of crossing over and explain how it increases genetic diversity.
- homologous pairs of chromosomes form a bivalent
- chiasma form
- alleles are exchanged
- producing new combinations of alleles
Give 3 wayas in which the DNA in a chloroplast is different from DNA in the nucleus
- DNA shorter in chloroplasts
- Fewer genes in chloroplasts
- DNA circular not linear in chloroplasts
- Chloroplast DNA not associated with histones/proteins
- Introns absent in chloroplast DNA
Define proteome
The range of different proteins a cell is able to produce
Starting with mRNA in the cytoplasm, descrive how translation leads to the production of polypeptide [Do not include descriptions of transcription or splicing] [5]
- mRNA associated with a ribosome
- Ribosomes finds start codon
- tRNA brings specific amino acid
- Anticodon on tRNA complementary to codon on mRNA
- Ribosome moves along to next codon
- Process repeated and amino acids join by peptide bonds via a condensation reaction
