Neurogenetics Flashcards
How many pairs of chromosomes in the human body?
23
The double helix is composed of 2 chains of what?
Phosphate and deoxyribose
Watson, Crick, Wilkins and Franklin discovered the double helix in what year?
1953
What holds the structure of DNA together?
Deoxyribose chains
Name the nucleotide bases
- Adrenaline and thymine
- Cytosine and guanine
What are the natural variations in DNA called?
Single nucleotide polymorphisms
What are single nucleotide polymorphisms responsible for?
What makes us unique and different from one another
Where does mitosis occur?
In somatic cells
Which type of cell division makes identical daughter cells?
Mitosis
Where does meiosis occur?
In the gametes
What is the term for the swapping and mixing up of DNA in the chromosomes during meiosis?
Homologous recombination
How many daughter cells are produced in meiosis?
4
In the second division of meiosis what are the resulting cells called?
Haploid cells
Homologous recombination allows for what in the population?
Genetic diversity
What is a binding sequence and where in the gene is it found?
- It is a sequence of DNA specific to attract a transcription factor
- Found at the top end of a gene
In the first stage of transcription, the transcription factor reads down the gene and produces what?
mRNA
After the mRNA is produced it leaves the nucleus and something attaches to it, what is this?
Ribosome
What is a triple codon?
Three nucleotide base pairs
Describe the process of translation
- Ribosome reads the triple codon
- Using transfer RNAs, the ribosome puts together a chain of amino acids
- This chain becomes a protein
Who discovered the inheritance of pea plants in 1865?
Gregor Mendel
If genes are identical (TT) what are they called?
Homozygous
If the genes are not identical (Ts) what are they called?
Heterozygous
What is the difference between the genotype and the phenotype?
Genotype = genetic information
Phenotype = how it displays
What is an allele?
The variants of the gene
What is a single gene disorder?
Where the disorder is caused by a single gene, and can be inherited following either dominant or recessive inheritance
Huntington’s Chorea is inherited through what type of inheritance?
Autosomal dominant inheritance
What happens to the striatum in patients with Huntington’s chorea?
It degenerates
What are the three main factors affected in Huntington’s chorea?
Movement, temperament, and cognition
What does autosomal dominant inheritance mean?
A single copy will be dominant and lead to the disease
How does the single gene disorder on chromosome 4 causes Huntington’s disease?
It causes excessive repeats of CAG bases
What does it mean that CAG is an insatiable triplet?
The repeats can increase in subsequent generations
Name a disorder caused by autosomal single inheritance?
PKU (phenylketonuria)
PKU is caused by a mutation in what gene?
PAH gene
What does the mutation of the PAH gene do?
Affects the the enzyme that breaks down phenylalanine
A build up of phenylalanine can lead to what?
Learning disabilities, behavioural difficulties, and epilepsy
Name the two types of chromosomal abnormalities
Monosomy and Trisomy
What causes downs syndrome?
Trisomy in chromosome 21 due to an error in the first meiotic division
Symptoms of DS include smaller brain size, mid to moderate intellectual ability, and a high risk of early onset alzheimers. Why does the link between DS and alzheimers exist?
The amyloid precursor protein gene is found o chromosome 21, and it is known that mutations in the gene can cause alzheimers
Why does the error on chromosome 21 seem to be the most common?
Because the phenotype for the extra chromosome in 21 is the only one mild enough for people to survive it
What does X inactivation do in females?
It switches off one copy of the X chromosome during embryogenesis
During X-inactivation in females, what % of cells have the maternal X switched off, and what % has the paternal X switched off?
It will be 50/50
Name 2 X-linked disorders
Rett syndrome and Fragile X
Name 2 X-linked conditions
Rett syndrome and Fragile X
The deficits in Rett syndrome are similar to what?
Autism
Rett syndrome is caused by a mutation in what gene?
MePC2
What is the MePC2 gene responsible for?
Turning off the expression of unwanted genes
Why is there variable penetrance of Rett syndrome?
Due to X-inactivation, not all cells will express the mutated MePC2 gene
What X-linked disorder is the most common inherited form of learning disability?
Fragile X
What gene is affected in Fragile X?
FMR1
Briefly, how does maternal licking reduce stress in rat pups?
- Maternal licking switches on the release of seretonin
- Seretonin actions lead to the switching on of the gene that expresses glucocorticoid receptor protein, which is important for regulating stress in the hippocampus
What gene becomes permanently methylated in an absence of maternal licking?
Nr3C1
What is the role of the Nr3C1 gene?
Expresses glucocorticoid receptor protein
What is transgenerational epigenetics?
Environmental influence on parents can affect offspring
What can modify histones?
Chemicals such as drinking and smoking
What are the 2 definitive reasons for alzheimers?
Tau microfibrillary tangles and amyloid plaques
What is the name for the amyloid precursor protein gene called?
PSEN
What does it mean if there are mutations in the PSEN1 or 2 gene?
Beta amyloid does not get broken down
APOE4 is linked with what disease?
Alzheimers
Why do we use mice in studies? (4)
- Similarly organised brain
- Behavioural traits similar to mammals
- Wealth of background on the biological processes
- Well defined behavioural tests
How can inbred strains be used to study behaviour?
Have different genetics and neurobiology and therefore comparison of these strains can show how genes influence behaviour
What is the goal of BXD recombinant breeding?
To create a population of mice with a mix of traits from each inbred parent strain in order to study how different combinations of genes affect behaviours and traits
Name the three types of genetically engineered mice
- Knock-out mice
- Knock in mice
- Transgenic mice
What happens in transgenic mice?
Researchers insert genes from another species in order to study the function of specific genes
What did studies of knock-out mice reveal about retts syndrome?
Showed that the MePC2 gene is implicated because rats who had the gene removed show similar symptoms