Neurogenetics Flashcards
describe the DNA structure function.
- double helix structure made from two chains of phosphate and deoxyribose.
- four nucleotide bases - adenine, thymine, cytosine, guanine
what is natural variations in human genetics known as?
single nucleotide polymorphisms.
what is the difference between mitosis and meiosis?
mitosis involves somatic cells where daughter cells are identical to parent, whereas meiosis involves gametes where daughter cells contain half the number of chromosomes.
defne genes.
long sequences of base pairs in the DNA that encode proteins.
what are genes turned on by?
transcription factors, which are activated during development or intra signalling cascades.
define transcription.
in the nucleus, the genes DNA sequence is copied into messenger RNA (mRNA).
mRNA is translated to form proteins, define translation.
a ribosome attaches to the mRNA and moves along the mRNA, reading each triplet codon and using transfer RNAs to put together the amino acid chain to make a protein.
describe mendel’s law.
peas:
- inherited properties in pea plants - tall V short
- height - dichotomous trait (tall or short)
- trait is controlled by a single gene
in mendel’s law, when cross fertilised, F1 offspring are (tall/short).
tall
in mendel’s law the short character reappears in the in F2, what is the ratio to tall and short.
3 tall : 1 short (one quarter are short in offspring)
which out of tall and short is dominant?
tall is dominant, short is recessive.
homozygous means…
identical genes
heterozygous means…
non-idneitical genes
what is the difference between genotype and phenotype?
genotype refers to genetic information, whereas phenotype refers to how it is displayed.
define alleles.
variants of a gene.
what do single gene disorders involve?
- dominant
- recessive
what do gene variations and mutations affect?
function (coding sequence) and expression (regulatory sequences).
describe Huntington’s disease.
- dominant inheritance.
- onset age: 35-55 years.
- degeneration of movement, temperament and cognition.
- if one parent has Huntington’s, 50% the offspring will.
what chromosome does Huntington’s effect?
chromosome 4, due to excessive repeat of CAG bases.
how is phenylketonuria caused?
- recessive inheritance
- mutation is PAH gene (phenylalanine hydroxlase)
if both parents are carriers of PKU, what is the effect on their offspring?
25% will have the disease, 50% will be carriers.
what are the effects of PKU?
- learning disabilities
- behavioural difficulties
- epilepsy
give evidence of interplay between genes and environment in PKU.
genotype will show mutation, but dietary intervention can mean pheotypes appears normal.
describe the difference between monosomy and trisomy.
monosomy has a single copy of chromosomes and spontaneous abortion in early pregnancy, whereas trisomy has three copies of a chromosome and a high rate of spontaneous abortion.