2.4 Inheritance Flashcards
Explain process of DNA replication
- DNA helicase splits strands
- DNA polymerase binds to both template strands
- free DNA nucleotides bond by complementary base pairings
- DNA polymerase forms phosphodiester bonds between nucleotides
- two new strands of DNA are formed from the original strand
Explain the differences between conservative, semi-conservative and dispersive DNA replication
conservative:
one completely new strand, one old strand
semi-conservative:
both strands half old, half new
dispersive:
both strands complete mix of DNA
Describe the Meselson-Stahl experiment, and how it proved the semi-conservative DNA model
Meselson and grew DNA in a culture containing N15 so all bases contained the isotope
Then they grew the
DNA in a culture of N14 for one generation - the new DNA contained one strand containing 15-N and one strand containing 14-N (tested with centrifuge)
After another generation, half of
the DNA molecules were the same as in generation one =, and the other half contained only 14-N
State and explain different types of mutations
- Substitution (change in one base)
- Insertion (adding another base in)
- Deletion (taking a base out)
- Duplication (adding the same base more than once)
- Inversion (swapping the order of bases around)
Explain the role of the CFTR protein
CTFR - channel protein which transports chloride ions out of
cells of the respiratory tract and into the mucus, causing sodium to follow via electrostatic flow, and water to follow via osmosis (runny mucus)
Explain how a faulty CFTR protein results in thicker, stickier mucus in CF sufferers
No/faulty CFTR causes no movement of chloride ions, no movement of sodium, and therefore no osmosis so sticky mucus
Explain the effects of CF on the respiratory system
Build-up of mucus in the lungs traps bacteria, thus increasing the risk of infection, and decreases the surface area of alveoli involved
exposed to fresh air, therefore reducing the surface area for gas exchange
Explain the effects of CF on the reproductive system, incl. both males and females
Cervical mucus prevents the sperm from reaching the egg (cervix plug)
The sperm duct (vas deferens) is blocked with mucus, sperm cannot leave the testes
Explain the effects of CF on the digestive system
The pancreatic duct connecting the pancreas to small intestine can become
blocked with mucus, so digestive enzymes do not reach the small intestine (food not properly digested and fewer nutrients absorbed)
State and explain types of genetic screening
Amniocentesis – 14-16 weeks - amniotic fluid sample containing foetal cells obtained using a needle
Chorionic villus sampling – 8 to 12 weeks - embryonic tissue sample taken from placenta
Pre-implantation genetic diagnosis - IVF embryos are tested for genetic disorders before they implantation
