Genes and Health

Question 1

How are the lungs adapted for gas exchange?

Answer 1

Alveoli have a large surface area.

They are surrounded by a number of capillaries which leads to a short diffusion path due to the thinness of walls.

There is a steep concentration gradient between the alveoli and the blood.

Question 2

Describe Fick’s Law.

Answer 2

Increased surface area and a greater concentration gradient increase rate of diffusion.
Thicker surface areas reduce rate of diffusion.

Rate of diffusion is directly proportional to surface area x concentration difference divided by the thickness of the surface.

Question 3

Describe primary structure of a protein.

Answer 3

Two amino acids joined as a dipeptide, via a condensation reaction, with a peptide bond.

Question 4

Describe secondary structure of a protein.

Answer 4

Chain coils into alpha helices caused by hydrogen bonds or folds into beta pleated sheets.

Question 5

Describe tertiary structure of a protein.

Answer 5

Hydrophobic or hydrophilic R groups.

Disulphide, ionic or hydrogen bonds formed.

Question 6

Describe globular and fibrous proteins.

Answer 6

Globular proteins are compact and spherical. They are soluble.

Fibrous proteins are long chains that are strong and cross-linked. They are insoluble.

Question 7

Describe the phospholipid bilayer.

Answer 7

Phosphate heads are polar and hydrophilic. Fatty acid tails are non-polar and hydrophobic.

Question 8

Define diffusion.

Answer 8

Net movement from an area of high concentration to an area of low concentration.

Question 9

Define facilitated diffusion.

Answer 9

Polar molecules and ions cross membranes using proteins or channel proteins.

Channel proteins use a signal. Gated channels use a change in potential difference.

Some proteins are carrier proteins where molecules bind to a site, causing the protein to change shape and carry the molecule across the layer.

Question 10

Define osmosis.

Answer 10

Net movement of water molecules from an area of low concentration to an area of high concentration through a partially permeable membrane. Continues until isotonic.

Question 11

Define active transport.

Answer 11

Movement from an area of low concentration to an area of high concentration using energy supplied by adenosine triphosphate.

Question 12

Define exocytosis.

Answer 12

Release of a substance using vesicles.

Question 13

Define endocytosis.

Answer 13

Taking in a molecule using vesicles.

Question 14

Describe what happens where there is extra water in the mucus.

Answer 14

Sodium is transported across the basal membrane and diffuses through sodium channels. Chlorine diffuses down an electrical gradient. Water is drawn out of cells due to the high salt concentration and then drawn out of the mucus.

Question 15

Describe what happens hen there is too little water in the mucus.

Answer 15

Chlorine is transported across the basal membrane and diffuses through an open CFTR channel. Sodium diffuses down an electrical gradient. Water is drawn out of the cell and into the mucus.

Question 16

Describe what happens in cystic fibrosis sufferers.

Answer 16

CFTR channel is absent or dysfunctional. Sodium channel is permanently open. Water is constantly being removed.

Question 17

Describe the effect of cystic fibrosis on the digestive system.

Answer 17

Difficult to maintain body mass, high basal metabolic rate, requires 120-140% of daily calorie intake.
Pancreatic duct blocked with mucus, prevents release of digestive enzymes, food is not digested properly, resulting in malabsorption syndrome.

Question 18

Describe the effect of cystic fibrosis on the reproductive system.

Answer 18

Females are less likely to become pregnant due to a mucus plug in the cervix.

Males may have a mucus plug in the cast deferens or may lack the vas deferens.

Question 19

Describe the effect of cystic fibrosis on sweat.

Answer 19

It is unusually salty.

Question 20

What is the formula for calculating BMI.

Answer 20

Weight divided by height2.

Question 21

Describe DNA.

Answer 21

Made up of a phosphate, deoxyribose sugar and a nitrogenous base of adenine, thymine, guanine or cytosine. This is a nucleotide, with phosphodiester bonds, formed by a condensation reaction.

Question 22

Describe RNA.

Answer 22

Made up of a phosphate, a ribose sugar and a nitrogenous base of adenine, uracil, guanine and cytosine.

Question 23

Describe transcription.

Answer 23

DNA helicase unzips hydrogen bonds in the double helix. RNA polymerase base pairs free complementary nucleotides, forming the coding strand, which produces a single strand of RNA.

Question 24

Describe translation.

Answer 24

mRNA leaves the nucleus to the ribosomes. Triplets of based form codons which are matched with complementary anticodons on tRNA. Amino acids attached to tRNA forms peptide bonds and primary structure.
Translation is caused by a start and a stop codon.
The code is non overlapping and degenerate.

Question 25

What are the different types of mutations?

Answer 25

Substitution, insertion, deletion, frame shift.

Question 26

Describe replication.

Answer 26

Helicase unzips DNA by breaking the hydrogen bonds. Primase lays primers from 5’ to 3’ on the leading strand. DNA polymerase builds a new strand, ligase glues the fragments together. Single stranded binding fragments stop DNA from recoiling. Primase lays primers from 3’ to 5’ on the lagging strand.

Question 27

Describe Stahl and Meselson’s experiment.

Answer 27

DNA is grown in heavy Nitrogen (15). Moved to 14N. New nucleotides were light, original were heavy. Divided and replicated once.

Question 28

Define molecular phylogeny.

Answer 28

Tests DNA to look for similarities in order to determine sequences.

Question 29

Describe amniocentesis.

Answer 29

15-17 weeks.
Inserts a needle into amniotic fluid.
1% risk of miscarriage.

Question 30

Describe chorionic villus sampling.

Answer 30

8-12 weeks.
Removal of placental tissue through the abdomen or vagina.
1-2% risk of a miscarriage.

Question 31

Describe non-invasive prenatal diagnosis.

Answer 31

7-9 weeks.

Analyses blood plasma.

Question 32

Describe pre-implantation genetic diagnosis.

Answer 32

IVF created embryos of which cells are tested.

Question 33

What are the ethical frameworks?

Answer 33

Human rights and duties
Utilitarianism
Informed consent
Living a virtuous life.

Question 34

What are the treatments for cystic fibrosis?

Answer 34

Bronchodilators, antibiotics, DNAase enzymes, steroids.
Change in diet.
Enzyme supplements.
Physiotherapy.
Transplants
Gene therapy.

Question 35

Describe gene therapy.

Answer 35

Desired gene inserted into a vector. Modified DNA put into a human cell. Produces a functional protein.

Question 36

Define intracellular reactions.

Answer 36

Enzyme reactions that occur inside cells.

Question 37

Define extracellular reactions.

Answer 37

Enzyme reactions that occur outside of the cell.

Question 38

Define catabolic.

Answer 38

Breaking down.

Question 39

Define anabolic.

Answer 39

Building up.

Question 40

Define gene.

Answer 40

A sequence of bases that codes for a characteristic.

Question 41

What happens in sickle cell anaemia?

Answer 41

There is a substitution mutation where adenine replaces thymine, resulting in the non-polar amino acid valine rather than the polar amino acid glutamic acid. This causes haemoglobin to be less soluble. The red blood cells are sickle shaped and carry less oxygen.

Question 42

What happens in cystic fibrosis?

Answer 42

There are a number of different mutations. The most common is the DF508, which is the deletion of three nucleotides, resulting in a misformed protein.

Question 43

Define allele.

Answer 43

Alternative forms of a gene found at the same locus on a chromosome.

Question 44

Define monohybrid inheritance.

Answer 44

A characteristic is only controlled by one gene.