Genetics Flashcards
When does DNA replication occur?
During S - Synthesis phase
Mutation?
May or may not cause a disease
What is an acrocentric chromosome?
A chromosome in which the centromere is located quite near one end. They are number 13, 14, 15, 21 and 22
Aneuploidy vs Translocation
Aneuploidy is an extra or missing chromosome
Translocation is rearrangement of chromosome
What causes Down Syndrome
Extra chromosome 21, acrocentric chromosome
What is Robertsonian translocation?
Two acrocentric chromosomes stuck end to end
Edwards Syndrome
Trisomy 18
Small head, clenched fist, cleft lip or palate, toes may be clubbed or fused
Causes of the following -
Turners Syndrome
Triple X
Klinefelter Syndrome
Turners Syndrome - 45 X
Triple X - 47 XXX
Klinefelter Syndrome - 47 XXY
Which translocations have no effect on phenotype
Balanced translocations
What can large unbalanced dislocations result in?
Miscarriage
What is FISH used for
FISH - Florescent in Situ Hybridisation is used to detect and localize the presence or absence of specific DNA sequences on chromosomes
Microarray CGH
Array Comparative Genomic Hybridisation (aCGH)
Detects missing or duplicated chromosomes
However, many changes seen might be polymorphisms
What is mosaicism
Different individual cells have different genetic constitution
Polymerase Chain Reaction
Allows us to select one small piece of human genome and amplify it
Example of an enzyme used in PCR
Heat - resistant Taq Polymerase
What is missense mutation?
Type of point mutation in which a single nucleotide change results in a codon that codes for a different amino acid
What is post zygotic mutation
Mutation that occurs in the embryo
What is penetrance
The likelihood of having a disease if you have a genetic mutation
What is Achondroplasia caused by?
Achondroplasia is caused by a mutation in Fibroblast Growth Factor Receptor 3 (FGFR3)
Salient feature of autosomal dominant
Every generation is affected, 50% risk for children
Salient feature of autosomal recessive
Only one generation affected, 25% chance
X linked recessive inheritance
Carrier father, female offspring always carrier
Passes from female carrier to affected male to female
No male to male transmission