2. Genes and Health (2)

Question 1

What does semi-conservative replication ensure?

Answer 1

Genetic continuity between generations of cells. Genetic information is passed on from one generation from the next

Question 2

What is the process of DNA Replication

Answer 2

1.The double helix unwinds and the hydrogen bonds between the complementary bases break, catalysed by DNA helicase, thus separating the two strands of DNA.

2. One of the strands is used as the template and complementary base pairing occurs between the template strand and free nucleotides.
3. Adjacent nucleotides are joined by phosphodiester bonds formed in condensation reactions, catalysed by DNA polymerase.

Question 3

What did Meselson and Stahl’s experiment involve

Answer 3

E. coli grown in broths containing lighter N14 isotopes and heavier N15 isotopes

Question 4

What did Meselson and Stahl’s experiment show?

Answer 4

Generation 0 - one band containing only N15
Generation 1 - intermediate strand between lighter N14 and N15. First round shows that the dna was a mix of heavy and light dna (which worked for dispersive, semiconservative theories but not conservative.)
Generation 2 - 2 bands, one intermediate band, one higher band for N14

The experiment done by Meselson and Stahl demonstrated that DNA replicated semi-conservatively, meaning that each strand in a DNA molecule serves as a template for synthesis of a new, complementary strand.

Question 5

How do errors in DNA give rise to mutations

Answer 5

Even a change in one base can change the amino acids present in the primary structure

Question 6

Deletion

Answer 6

Removing one base

Question 7

Substitution

Answer 7

Change in one base

Question 8

Insertion

Answer 8

Adding one base

Question 9

Duplication

Answer 9

adding more than one base

Question 10

Inversion

Answer 10

Swapping bases around

Question 11

Gene

Answer 11

DNA with a specific set of bases that codes for certain proteins

Question 12

Allele

Answer 12

Alternative versions of Genes

Question 13

Genotype

Answer 13

All the alleles of an organism

Question 14

Phenotype

Answer 14

Observable characteristics of an individual resulting from the interaction of its genotype with the environment

Question 15

Recessive dominance

Answer 15

an allele that produces a feature only if two copies are present

Question 16

Incomplete dominance

Answer 16

a form of intermediate inheritance in which one allele for a specific trait is not completely expressed over its paired allele

Question 17

Homozygote

Answer 17

an individual having two identical alleles of a particular gene

Question 18

heterozygote

Answer 18

an individual having two different alleles of a particular gene

Question 19

What is cystic fibrosis

Answer 19

homozygous recessive condition. CFTR gene not functioning = build up of mucus/ formation of mucus plugs.

Question 20

How does cystic fibrosis impair the functioning of the reproductive system.

Answer 20

CFTR transports chloride ions out of the cells of the respiratory tract into the mucus. No CFTR = very sticky mucus
Excess mucus in lungs increases diffusion distance which slows down rate of gas exchange
Mucus plugs preventing reproduction - cervical Mucus plug blocks sperm from reaching cell
Mucus in sperm duct prevents the release of sperm

Question 21

How does cystic fibrosis impair the digestive system

Answer 21

Thick mucus covers duodenum preventing the absorption of nutrients.
Pancreatic duct blocked with mucus so digestive enzymes are unable to reach small intestine, food not properly digested leading to less nutrients absorbed

Question 22

The role of chloride ions in mucus thickness.

Answer 22

The channel transports negatively charged particles called chloride ions into and out of cells. The transport of chloride ions helps control the movement of water in tissues, which is necessary for the production of thin, freely flowing mucus That can be bat away by cillia

Question 23

Amniocentesis

Answer 23

14-16 weeks, sample of amniotic fluid taken containing foetal cells.

Question 24

Chronius Villus Sampling (CVS)

Answer 24

8 - 12 weeks, embryonic tissue is taken and a tissue sample is taken from the placenta and sent to a lab for analysis.

Question 25

Preimplantation Genetic Diagnosis

Answer 25

embryos created via ivf are screened before they are implanted into the uterus

Question 26

Implications and ethics of Prenatal genetic screening

Answer 26

if the child has a genetic disorder the couple may have to abort or at least feel the need to.
Having to terminate pregnancy/ abortion - controversial due to religious viewpoints on embryos being life.
False positives - end up in people wrongly terminating pregnancies
Emotional stress, and physical stress from some of the more invasive procedures
Possible risk of harm to foetus / miscarriage