genetics Flashcards
What does a square represent on a family pedigree?
Male member of the family
What does a circle represent on a family pedigree?
Female member of the family
How are decreased females represented on a family pedigree?
A circle with a line through it
How is an affected male represented on a family pedigree?
A square that is fully coloured in
How is a female carrier represented on a family pedigree?
A circle that is partially shaded in
How is an unaffected male represented on a family pedigree?
A square that is unfilled
How are twins represented on a family pedigree?
A “triangle line appearance”
What is genetic information in eukaryotic cells carried on?
On the chromosomes
How many pairs of chromosomes do humans have?
23 Pairs
What are 2 chromosomes in metaphase attached by?
A centromere
Define haploid
One set of chromosomes
Define diploid
Two sets of chromosomes
What is DNA wound around?
DNA is wound around histones giving a bead and string like structure
What are nucleosomes?
Condensed DNA packed into chromatin fibres
Condensed DNA packed into chromatin fibres are called what?
nucleosomes
What are nucleosomes attached to?
A scarfords made of proteins
Where is genetic information found in the cell?
In the nucleus
What are complimentary DNA strands held together by?
Hydrogen bonds on specific nucleotide base pairs
What are the 2 types of nucleobases in DNA called?
- Purine bases
2. Pyrimidine bases
Name bases are purine?
Adeneine
Guanine
Name bases are Pyrimidine?
Cytosine
Thymine
Uracil
What are DNA bases attached to?
Deoxyribose which has at least 1 phosphate molecule
Define codon
3 nucleobases that code for a specific amino acid
Define mutations
They are inheritable permanent changes in the base sequence of DNA
What are the different types of mutations?
- Point mutations
2. Deletion/Insertions
What are point mutations?
Mutations that happen in 1 base pair leading to change
What are the 2 types of point mutations?
- Transition
2. Transverse
What do transition pain mutations do ?
They convert G-C bond into A-T
What do Transverse pain mutations do ?
They convert G-C bond into T-A
What are Deletion/Insertions mutations?
They are the loss or gain of nucleotides that may result in a frame shift in reading genetic code
What can the consequence of mutations be?
- Silent
- Missense
- Nonsense
What are silent mutations?
They are when nucleotides change but the amino acid doesn’t
When do silent mutations usually occur?
In point mutations
What are Missense mutations?
When the nucleotide changes and so does the amino acid
Leads to a new primary structure
What are nonsense mutations?
A mutation results in a stop codon resulting in truncated proteins
What are truncated proteins?
Shortened proteins
How do mutations arise?
- Due to DNA replication fidelity
2. Mutagens
What are the 2 types of mutagens?
- Physical
2. Chemical
Give examples of physical mutations
Ionising radiation E.G. X-rays
Non-ionising radiation E.G UV lights
What does ionising radiation do?
Causes strands to break
Sugar or base destruction
What does non-ionising radiation do?
Causes new chemical bonds to form
Give examples of chemical mutagens
Base analogues:
Nitrous acid
Alkylating agents
What are base analogue mutagens?
They are derivatives of normal bases but they can cause altered base pairings
What are nitrous acid mutagens?
Cytosine turns to uracil causing the C-G bond to become the A-T
What are Alkylating agents mutagens?
EG Methylmethane sulfate
These cause lesions that result in error prone repair
Define allele
Different forms of the same genes
Define dominent
A gene that is preens expressed a certain characteristic
Define recessive
Only expressed if the dominant allele is absent
Define genotype
The genetic components
Define phenotype
The visible appearance
Give examples of some monogenic disorders
Cystic fibrosis
Sickle cell anaemia
Huntingtons
Amelogenisis imperfecta
What causes cystic fibrosis
Muttion of the transmembrane condlictane regulator (CFTR)
This gene control export of chlorine ions in the epithelial cells of the airway
Failure of the CFTR leads to a build up of sticky mucus which the bacteria then invade
What causes sickle cell anaemia?
It is caused by a single base mutation which affects how the beta globin molecules form the structural tetramers that carry oxygen around the body
What causes amelogenis imperfecta?
Caused by a C->T substitution in the Dentin sialophosphoprotein (DSPP)
It can result in poorly formed dentine resulting in early tooth loss
What causes Huntington’s disease?
Caused by an increase in the number of repeats of the CAG codon
Normal people have 15 sufferers have 36+
Disease can lead to dementia, depression and involuntary spasms
What is the gene dosage effect?
When the number of copies of the mutated triplet you have increases the severity of the disease
E.G Huntingtons
How can an X links disease easily be spotted?
By using a pedigree
If only the males are affected but the father doesn’t have the disease then it is x links
Give some examples of X linked diseases?
- Haemophilia
2. Amelogenesis imperfecta
What is Haemophilia?
A disorder where blood doesn’t clot properly due to a mutation in the blood clotting gene
What is amelogenesis imperfecta
Poorly formed tooth enamel which results in stripes teeth due to the alternating pattern of creamy coloured poorly formed enamel and whiter enamel
Define multifactorial genetic disorders
When many genes are involved in the disease process
Give examples of some Muti factorial diseases
Congenital spinal bifida Cleft lip and palette Congenital heart disease Late onset arthritis Multiple sclerosis Epilepsy Psychiatric depression Alcoholism Alzheimers Schizophrenia Oral cancer ect PERIODONTAL DISEASE
Name the 8 ethos we can use to determine gene components
- Family studies
- Twin studies
- Linkage analysis
- DNA hybridisation
- PCR
- Nucleotide sequencing
- Microarrays and gene chips
- Next generation sequencing
Why are molecular biology technique important?
- Gene mutations can have serious consequences
- Dental diseases are caused by gene mutations
- Molecular bio techniques can hep differentiate between normal and mutated genes
What does periodontal disease result in?
Results in erosion in tissues supporting teeth
It is now thought ti be caused by an autoimmune disease
What is the human genome project and why is it important?
Analysing the whole nucleotide sequence for the human genome
Important in comparing ‘normal DNA’ to ‘genetically disordered’ DNA
Why is restriction endonucleases important?
Useful in adding specific genes to plasmids can recognise a specific sequence and break the Phosphodiester bonds between the nucleotides
Describe the process of gel electrophoresis and why it is important
- Fragments can be separated on the gel according to their weight
- Fragments can therefore be compared (by weight)
- Polyacrylamide gel separates low molecular weight fragments
- Agarose gel separates high molecular weight fragments
What are plasmids?
Plasmids are small circular DNA found in prokaryotes
What can plasmids be used for?
Extra chromosomal DNA can be added to the plasmid
Plasmids therefor act as a vector in carrying new genes
What must a vector be?
- Must be able to self replicate in host
- Must be able to be digested (by restriction endonuclease)
- Must posses a selector marker (new gene in the plasmid)
Describe the process of gene cloning
- Same restriction exonuclease used to cut the 2. DNA ligase is used to join 3. Recombinant DNA can now be placed into prokaryotes (that have been made permeable
What are the 3 methods we can use to determine the genes responsible for genetic disorders?
- PCR (modern molecular analysis)
- Southern blotting
- Sanger method
