Genetics Flashcards
How many chromosomes does a person have?
46
What is mitosis?
A diploid parent produces 2 dipped daughter cells
What is meiosis?
A diploid parent produces 4 haploid daughter cells
What is crossing over?
Genes segregate independently even if on the same chromosome
What is the process of DNA to protein?
DNA
Pre-mRNA (spliced)
mRNA (transcription and translation)
Protein
What is a variant?
Any change to DNA sequence
What is a mutation?
Any heritable change to DNA
What is a polymorphism?
A variation in human genome with population frequency >1% or any variant that doesn’t cause disease in its own right
What is a somatic mutation?
One that occurs during mitosis
What is a germ line mutation?
One in the gamete before fertilisation
What is a post-zygotic mutation?
One that occurs in the child
What is robertsonian translocation?
Two acrocentric (missing the short arm - p) stuck end to end
What is a balanced translocation?
Sections of two chromosomes have switched places
What is aneuploidy?
A whole extra or missing chromosome
What is the mutation: 47XY +18?
Edward’s syndrome
What is the mutation: 45X?
Turner’s syndrome
What is x-inactivation?
In females in each cell one X-chromosome is randomly switched off
What is a good first-line test for things like Downs?
aCGH (array comparative genomic hybridisation)
What is FISH good for?
Looking for translocations, deletions
What is the reference sequence?
Commonest sequence in white north American Caucasian male
What is penetrance?
The likelihood of having the disease if you have the mutation
What is expression?
The variation in phenotype if you have the disease
What is a Mendelian disorder?
A high penetrance monogenic disorders which segregate in families by Mende’s laws
What are examples of Mendelian disorders?
Autosomal dominant/recessive
X linked
Mitochrondrial
What are examples of non-mendelian monogenic disorders?
Methylation
Imprinting
What are histones?
DNA strands associate with proteins called histones to be wound into chromosomes
What are the differences of RNA compared to DNA?
Single stranded not double
Nucleic acid bases held on ribose (not deoxyribose) sugar backbone
Uracil instead of thymine
What is the process of a cell cycle?
G1 - cells increase in size and cell contents duplicated
S - replication occurs
G2 - second growth phase in preparation for division
M - mitosis
