Reassessment Flashcards
What is the base pairing rules?
DNA: A and T, G and C
RNA: A and U, G and C
Explain the structure of DNA.
- 2 antiparallel strands, shaped as a double helix
- made up of nucleotides containing a phosphate deoxyribose sugar and a base
- 4 bases ATGC
Where are linear and circular chromosomes found?
Circular - found in prokaryotes
Linear - found in eukaryotes
What joins the fragments of DNA?
DNA ligase
What are the steps of PCR?
Step 1: heating - 94 degrees, breaks bonds between bases, DNA unzips, strands separate
Step 2: annealing - 54 degrees, complementary primers bind to the strands of DNA
Step 3: extension- 72 degrees, taq polymerase binds to primers, extends them in 5’ to 3’ direction
This repeats around 30 times
Describe the leading and lagging strand.
Leading - made continuously
Lagging - made in fragments which are then joined together
What are the differences between the structures of DNA and RNA?
- DNA has deoxyribose sugar, RNA has ribose
- DNA has thymine, RNA replaces thymine with uracil
- DNA is double stranded, RNA is single stranded
What is RNA splicing?
- introns are removed from pre-mRNA, making the mature transcript
What are introns and exons?
Introns - non coding regions
Exons - protein coding regions
During RNA splicing, INTRONS REMOVED, leaving exon to be translated.
What happens at a ribosome during protein synthesis?
The ribosome is the site of protein synthesis
What is the triplet code?
3 bases that code for an amino acid
What does differentiation mean when referring to stem cells and meristems?
- when a cell develops more specialised functions for that type of cell
What is the role of stem cells?
- stem cells have the ability to develop into different types of body cells during embryonic development
- they can either self renew or can differentiate into specialised cells (red blood cell, brain cell etc.)
Give several ethical issues regarding stem cells.
For
- could potentially cure people with diseases like Alzheimer’s
- at 14 days old, the embryo hasn’t developed a nervous system or a brain
- bone marrow transplants
- drug testing
- skin grafts
Against
- embryo has the same rights and protection as the mother
- human life is sacred
- a unique piece of human DNA is created
- could potentially introduce cloning and will pursue natural selection
- in religious views, nobody should be playing God
What does the word ‘genome’ mean?
- is the sum total of all the hereditary material within an organism
What do non-coding sequences of DNA do?
- Protection - some can telomere at the end of the chromosome which prevents ends from fraying
- Non translated forms of RNA - tRNA, rRNA
- Regulating transcription - they can bind to proteins which promote or prevent transcription
What are the different types of single gene mutations? How would you recognise them?
- Substitution - changes only one amino acid (or none at all)
- Deletion - deletes an amino acid, normally effects every triplet (catastrophic)
- Insertion - inserts an extra amino acid into the sequence
What is the difference, in terms of protein produce, between substitution with a deletion or insertion?
Substitution - results in silent or misense mutations which produce the same amino acid or a different amino acid, they both produce the original protein in the end
Deletion and insertion - result in frame shift mutation, changes all the amino acids, results in a different or non functioning protein
What are the 2 types of evolution and how to recognise each one?
Allopatric - occurs when a gene flow is physically prevented, geographical barriers (oceans etc.)
Sympatric - brought around by behavioural or ecological barriers, most common in plants, usually occurs within the same habitat
What is genetic drift and how is it caused?
- the process of random changes in allele frequency in a population
- different to natural selection as it is random
What are the names of the different domains of life?
- Bacteria
- Archaea
- Eukaryotes
What is the process of DNA replication?
Step 1: DNA polymerase breaks hydrogen bonds, unzips DNA
Step 2: the strands open in opposite directions, bases exposed
Step 3: primer is added to DNA, DNA polymerase adds nucleotides to 3’ end, DNA polymerase catalyses the formation of a strong chemical bonds between nucleotides (leading strand)
Step 4: primer added, DNA polymerase adds nucleotides to 3’ end, new primer is added, DNA polymerase extends this to meet the previous fragment of nucleotides, DNASE ligase joins them together, old primer replaced by DNA, process repeats until the strand is complete (lagging strand)
What are prokaryotes and eukaryotes?
Prokaryotes - organisms that lack a membrane bound nucleus, DNA found in cytoplasm, bacteria
Eukaryotes - organisms that have a membrane bound nucleus that stores their DNA, animals plants and fungi
