Transmission In Genetics Flashcards
What does monogenic mean?
A Neuro genetic disease with a single gene cause
What percentage of Alzheimer’s disease is monogenic
1%
What percentage of Parkinson’s disease is monogenic
10%
What percentage of motor neurones disease is monogenic
5%
What was mendels work and when did he publish it
Published in 1865
- bred peas that gave rise to similar characteristics in every generation
- identified 7 characteristics that were consistent in generation after generation of self-fertilisation
- the parental lines of peas could be considered pure-breeders
What characteristics of the peas did Mendel study
Colour and texture of peas
Colour of pea pods and flower
Height of the plant
Outline Mendels principle of independent assortment
-genes get sorted into gametes independently
-second generation all dominant
Third generation is in a 9:3:3:1 ratio
What was mendels 1st law
Law of dominance and uniformity- some alleles are dominant while others are recessive; an organism with at least one dominant allele will display the effects of the dominant allele
What was mendels 2nd law
Law of segregation- during gamete formation, the alleles for each gene segregated from each other so that each gamete carries only one allele for each gene
What was mendels 3rd law
Law of independent assortment- genes of different traits can segregate independently during the formation of gametes
What was mendels chromosomal theory of inheritance in the 1900
Meiosis cell division that occurs in germ cells- in the process of making sperm and eggs (pollen and ovules in plants)
-as egg cells matured, there comes a point where chromosomes numbers are reduced in half
What is the concept of the germ line
Cells that can pass genetic material to the next generation
-includes haploid sperm and egg cells (gametes) and all the diploid precursor cells from which they arise by cell division, going all the way back to the zygote
What are non-germ line cells known as
Somatic cells
How many cells does meiosis result in?
4 haploid cells
Outline random assortment of homologous chromosomes in meiosis
-for each chromosome in metaphase 1, homologous chromosomes line up at the equator
-orientation of pairs of chromosomes is random
-random assortment of chromosomes into gametes
What does independent assortment in meiosis provide?
Independent assortment of maternal and paternal homologous chromosomes during meiosis provides variation in the genetic composition of sperm or eggs
How can the risk of being affected by disease for family members of an affected individual be predicted
-screening
-treatment
How can the risk of being a carrier of disease for family members of an affected individual be predicted
-risk to the unborn child
-reproduction choices
Is the sickle cell allele recessive or dominant
Recessive allele
How many genes does the X chromosome have
800
How many genes does the Y chromosome have
70
Definition of complete penetrance
All individuals have the phenotype
Definition of incomplete penetrance
Individuals a genotype may or may not. Develop a phenotype
Outline epistasis
Interaction between genes, whereby the protein product of one gene interferes with the expression of another gene
Definition of epistatic gene
A gene that masks the phenotypic effect of another
What are missense mutations
Codes for a different amino acid
-the synthesis of an altered protein
Outline missense non-conservative substitutions
Amino acid is chemically dissimilar- has a different charge the structure oft he protein will be altered
Outline missense conservative substitutions
Some single base-pair substitutions resulting the replacement of an amino acid that is chemically similar.
Outline nonsense mutations
-Formation of a stop codon will result in premature termination of translation of a peptide chain
-premature stop codon may lead to expression of a truncated protein. However usually the mRNA is degraded by nonsense mediated decay, so NO protein is made
What is nonsense mediated decay
Nonsense mediated decay is a form of RNA surveillance that is believed to protect the body from the possible consequences of truncated proteins interfering with normal function
What does InDel usually result in?
Premature stop codon downstream of the mutations; this manny result in a truncated protein
How to identify disease genes in humans
coding region can be sequenced from cDNA, or the whole genome can be sequenced
How was the mutations for Charcot-Marie tooth identified?
Exome sequencing (sequencing cDNA) using 2nd generation sequencing (illumina sequencing)
