Topic 2 - Genes & Health🫁🩻

What are the differences between RNA & DNA?

• RNA is single-stranded, whereas DNA is double stranded

• RNA contains a Ribose sugar, whereas DNA contains a Deoxyribose sugar

• DNA has a Thymine base, whereas in RNA a Uracil base replaces Thymine.

What is Transcription?

What is Translation?

Put in the right blanks:

the template strand of DNA & the DNA coding strand

During transcription, the mRNA strand’s base sequence is complimentary to__A__.

And is therefore the same as the__B__.

A =The template strand

B = The DNA coding strand

The order of ……… determines the order of bases on the mRNA

The order of bases on the DNA

What molecules can pass through a cell surface membrane via simple diffusion?

• small molecules like O2, CO2 & H2O

• lipid-soluble substances like certain hormones

What substance maintains the fluidity of the membrane?

Cholesterol

What allows the movement of substances in & out of the membrane?

Channel and Carrier proteins

What is in charge of cellular recognition?

Glycolipds

What acts as the cell’s receptor for chemical signals?

Glycoproteins

What 4 components make up the phospholipids?

2 fatty acid tails, a phosphate head and glycerol

What provides the energy required to move vesicles in Exocytosis and Endocytosis?

ATP

What is Cystic fibrosis caused by?

Caused by a mutation in the CFTR gene that causes the CFTR protein to have the incorrect shape.

Why do people with cystic fibrosis have thick sticky mucus?

Cl- ions are normally removed from the CFTR channel protein, into mucus and water will follow those Cl- ions into mucus making it more fluid.

In CF the CFTR channel protein cannot remove Cl- from the cell membrane resulting in thick sticky mucus.

Why do men with CF have fertility issues?

Men with CF find it difficult to release sperm cells due to thick sticky mucus that blocks their sperm ducts.

Why should people with CF eat high-energy diets?

Those with CF need high-energy diets that are high in carbohydrates because they are much more easily digested. This is because thick sticky mucus blocks the release of enzymes from the pancreatic duct into the small intestine, so by eating quickly broken-down carbs, the individual won’t suffer from malnutrition or malabsorption.

What issues are faced in the lungs of individuals with CF?

• The cilia in the lungs find it difficult to move the mucus which builds up and makes them prone to lung infections

• A slower rate of diffusion because mucus blocks the bronchioles which disrupts gas exchange in the alveoli and causes a decreased surface area for diffusion

How are the lungs adapted for gas exchange?

1. Large surface area

   • Many alveoli that all have folded shapes

2. Short diffusion distance

   • The walls of the capillaries and alveoli are both 1 cell thick

3. Large concentration gradient

   • Due to the continuous blood supply provided by the capillaries

What is the primary structure of a protein?

The sequence of amino acids

What is the secondary structure of a protein?

Alpha-helices or Beta-pleated sheets are formed by the hydrogen bonding of slightly negative Oxygen and slightly positive Hydrogen.

The structure that forms depends on the positioning of these hydrogen bonds.

What is the tertiary structure of a protein?

Further folding of secondary structure.

Because the R-groups are now closer in proximity, different bonds start to form, and the order of the amino acids decides where these bonds form giving the 3D shape.

What is the quaternary structure of a protein and do all proteins have this structure?

When multiple polypeptide chains join together giving rise to globular or fibrous proteins. Only some proteins have this structure, most stop at tertiary.

What bonds/interactions can be formed in the tertiary structure?

• Ionic bonds

• Disulphide bridges

• Hydrogen bonds

• Hydrophilic/Hydrophobic interactions

Name a Fibrous protein and its properties.

Collagen

• 3 polypeptide chains bonded together

• Does not have a tertiary structure

• Incredibly strong due to the extensive H-bonds in the structure

• Has a-helices as a secondary structure

Name a globular protein and its properties.

Haemoglobin

• 4 polypeptide chains bonded together

• Contain an additional heme group that helps it carry oxygen

• Its a conjugated protein

What special about conjugated proteins?

They have additional chemical groups that are necessary to their function

What are 5 key differences between Fibrous and globular proteins.

1. Fibrous are linear whereas Globular have a 3D shape

2. Fibrous proteins are usually insoluble and have their hydrophobic groups on the outside whereas Globular are usually soluble with their hydrophilic groups on the outside.

3. Fibrous proteins are usually structural (e.g skin, hair & bones), and Globular proteins are usually metabolic (e.g enzymes & hormones)

4. Fibrous usually have a repetitive sequence of amino acids whereas Globular proteins don’t.

Define Genotype

The combination of alleles an organism has

Define Phenotype

The displayed characteristics an individual has due their genotype

Define incomplete dominance

When the characteristics of a heterozygous genotype are both partially expressed in either a mixed or completely different phenotype.

What is amniocentesis, when is it carried out and what is the risk of miscarriage?

The collection of amniotic fluid containing foetal cells to detect defective genes.

Carried out 15-17 weeks of pregnancy

risk of miscarriage = 1%

What is Chorionic villus sampling (CVS), when is it carried out and what is the risk of miscarriage?

The removal of placenta tissue for analysis.

Carried out at 8-12 weeks

risk of miscarriage = 1-2%

How is non-invasive prenatal diagnosis done, when is it carried out and what is the risk of miscarriage?

It analyses the foetus’ DNA fragments in the mother’s blood plasma.

Carried out at 7-9 weeks

No risk of miscarriage.

What are the pros and cons of CVS and amniocentesis?

Pros

• provides info on abnormalities

• gives couples the option to proceed or discontinue the pregnancy

Cons

• The small risk of miscarriage & losing a perfectly healthy baby

• Possible false positives which could lead to the wrong decision

• Could damage the foetus and risk other issues