Chapter Seven: Molecular Genetics Flashcards
What is bacterial transformation?
The ability of bacteria to alter their genetic make up by absorbing foreign DNA molecules from other bacteria and incorporating it into their own
Which is the molecule of heredity?
DNA
How did Hershey and Chase prove that DNA was indeed the molecule of heredity not proteins?
They tagged bacteriophages (bacteria attacking virus) with different isotopes, one for DNA other for protein coat. When bacteria were infected with the phages, the DNA isotope entered and produced progeny, but the protein isotope did not influence any radioactivity.
Who continued the work of studying DNA structure from Maurice Wilkins, and who got this the Nobel prize?
Rosalind Franklin used X-ray crystallography analysis on DNA to show it to be a helix. Watson and crick used her work to develop their model
What is semi-conservative replication?
A double-stranded molecule of nucleic acid separates into two single strands each of which serves as a template for the formation of a complementary strand that together with the template forms a complete molecule. So each replica consists of 1 new and 1 old strand
What is dna’s twisted ladder like structure said to be?
Double helix
What consists of the 2 opposite running complementary strands of DNA?
They each are polymers of nucleotides.
What does each nucleotide consist of?
A 5-carbon sugar (deoxyribose)
A phosphate group
A nitrogenous base
State the pairing of the bases
A-T
C-G
What is the bond between bases?
Hydrogen bonds
What are the 4 bases?
Adenine
Cytosine
Guanine
Thymine
Which enzyme catalyses the replication of new DNA?
DNA polymerase
When does replication occur in a cells lifetime?
Interphase (S-phase)
What is another function of polymerase apart from catalysing?
Proofreading new DNA
Fixing errors
Minimising mutations
Which enzyme unzips the hydrogen bonds connecting the strands?
DNA helicase
On what basis does the new strand form on the old template?
Base pairing rules
Some nucleotides are lost from ends of chromosomes. What do some eukaryotic cells do to protect these genes?
They have nonsense nucleotide sequences at the ends, repeated thousands of times.
What are the protective ends of chromosomes called?
Telomeres
State 3 ways in which RNA is different from DNA
- It is a single stranded helix
- Instead of Thymine, it’s got Uracil
- ribose sugar not deoxyribose
How is RNA similar to DNA?
- it is a polymer of nucleotides
* the nucleotides have 5-carbon sugar $except it’s ribose), phosphate group, and a base
What is messenger RNA?
mRNA carries messages directly from DNA to cytoplasm during protein synthesis
What are triplet nucleotides (such as AAC,UUU) of RNA called?
Codons
What is transfer RNA?
tRNA carries amino acids to mRNA at the ribosome to form proteins
What are triplet nucleotides of tRNA, complementary to those of mRNA, called?
Anticodons
What is rRNA?
Ribosomal RNA is structural and along with proteins makes up the Ribosomes
What is transcription?
Process by which DNA makes RNA, facilitated by RNA polymerase, which unzips the strand at the specific gene. Triplet code in DNA is transcribed into a RNA codon following base pairing rules; A with U, C with G
How is RNA processed before leaving the nucleus?
Enzymes remove pieces of RNA that do not code for any protein
What are removed regions of RNA called? Describe.
Interons - intervening sequences
What are remaining regions of RNA called? Describe
Exons - expressed sequences
What is translation?
mRNA sequence is converted into an amino acid sequence
How is translation done?
tRNA carry amino acids in the cytoplasm to codons of the mRNA according to base pairing rules
Why can some tRNA bind to 2 or more codons
Because many codons can code for one amino acid
Which amino acid does AUG code for?
Methionine
Which amino acid does UUU code for?
Phenylalanine
Which amino acid does GUU code for?
Valine
Which amino acid does CUU code for?
Leucine
Which amino acid does AGU code for?
Serine
Which amino acid does GGU code for?
Glycine
What is gene regulation?
The turning on and off of genes as per the cells requirement
Eg insulin production
What is an operon?
A cluster of functional genes plus the switches that turn them on/off in a bacterium
What is the inducible operon?
An operon that’s normally turned off unless actively triggered/induced by something in the environment
What is a repressible operon?
Is always turned on unless actively turned off because it is temporarily not needed
What is the promoter? And state it in terms of operon
The binding site of RNA polymerase. It is like an on switch
What is the operater? And state it in terms of operon
Binding site for the repressor. Turns off the inducible operon
What is the TATA (Thymine Adenine alternating sequence) box?
Helps RNA polymerase bind to the promoter
What are mutations?
Changes in genetic material
When do mutations occur?
They are random
What causes mutations?
Mutagenic agents ie toxic chemicals and radiation
What is a point mutation?
It is a base-pair substitution, where one nucleotide converts to another
Is sickle cell anaemia inherited or caught and developed?
It’s genetic
How does sickle cell anaemia result (in terms of genes)
A point mutation in the gene that codes for haemoglobin
What is the effect of sickle cell anaemia and why?
Tissues are deprived of oxygen
Because the abnormal haemoglobin cause red blood cells to sickle when available oxygen is low
When a point mutation could serve as beneficial for an organism what is it called?
Natural selection
Do mutations in DNA always change amino acid sequence?
No
What is single nucleotide deletion?
Loss of a base
What is single nucleotide insertion?
Addition of a base
What do insertions and deletions result in?
Frameshift
What is frameshift and why can it be disastrous?
When the entire reading frame is altered and unreadable, causing altered or no polypeptide formation
What are chromosome mutations?
Alterations in chromosome number or structure
What is it called when there are abnormal number of chromosomes?
Aneuploidy
Official term for downs syndrome?
Trisomy-21
What is the mutation in Trisomy-21?
Extra #21 chromosome
What is polyploidy and how is helpful in flowers?
Having entire sets os chromosomes (3n, 4n)
Large bright coloured flowers
What do aneuploidy and polyploidy result from?
Nondisjunction
What is genome?
Organisms genetic material
How many genes do humans have?
20,000
What are pseudogenes?
Former genes that have accumulated mutations over a long time
In the 97% of DNA not used for protein coding, state 3 thing other than pseudogenes
- regulatory sequence (control gene expression)
- introns (interrupt genes)
- repetive sequences that may never get transcribed (Telomeres)
What is recombinant DNA?
Taking DNA from 2 sources and combining them in one cell
What is genetic engineering?
Branch of science using recombinant DNA
2 concerns behind genetically modified organisms?
- they may spread the engineered genes to wild species
- they may adversely affect people who eat them
How can gene therapy be used to treat genetic diseases?
Insert functioning genes into cells to replace non-functioning ones eg CF and SCA
How is environmental cleanup done with genes?
Mircobes are being engineered to degrade oil at oil spills or decontaminate harmful chemicals toxic mines
What are restriction enzymes?
They cut DNA at specific recognition sequences of sites
What are pieces of DNA resulting from restriction enzymes called?
Restriction fragments
What is gel electrophoresis?
It separates large molecules of dna on the basis of their rate of movement through an agarose gel in an electric field
Relate molecule size and rate of movement through the gel
The smaller it is, the faster it runs
What can be changed to provide a better separation of tiny DNA fragments ?
Concentration of the gel
How is DNA prepare before it’s put in gel?
It’s cut up by restriction enzymes, pieces small enough to migrate though the gel
What is polymerase chain reaction?
It is an automated technique where by many copies of a specific dna can be copied or amplified in vitro using heat-stable enzymes and then be studied/compared with other dna samples
What is Frameshift?
mutationinwhichanumberofnucleotidesnotdivisiblebythreeisinsertedordeletedso as tochangethereadingframeofsometripletcodons
What proportion of genes are in the mitochondria?
8/15
16000/30000
Where are restriction enzymes extracted from?
Bacteria
NOT there in humans
