Chapter 3.1 Genes

Question 1

Gene

Answer 1

a heritable factor that consists of a length of DNA and influences a specific characteristic.

Question 2

Locus

Answer 2

the location on a chromosome which a gene for a specific trait occupies.

Question 3

Complete achromatopsia

Answer 3

When a mutation of this gene stops a person from being able to make the protein transducin properly, which is necessary to transmit information about colour from the eye to the brain, as a result, the person will not see in colour.

Question 4

Alleles

Answer 4

variations or versions of a gene. one specific form of a gene, differing from other alleles by one or a few bases.

Question 5

cystic fibrosis

Answer 5

the gene CFTR found on chromosome 7 plays a key role in the production of mucus, an essential substance for the body. The standard version of this gene allows a person’s mucus-producing cells to function properly, whereas an allele generated by a mutation of the CFTR gene causes cystic fibrosis –> people then produce abnormally excessive quantities of mucus in various organs and have difficulties with their respiratory and digestive system, among others.

Question 6

Comparison of the number of genes in humans and other species

Answer 6

Virus (bacteriophage) --> 11
Bacterium --> 4 377
Nematode (roundworm) --> 20 000
Human --> 21 000
Asian Rice --> up to 56 000
Baker's yeast --> 5 770 
Mouse-ear cress ---> 25 000
Fruit fly --> 27 407

Question 7

Mutation

Answer 7

random, rare change in genetic material. One type involves a change of the sequence of bases in DNA.

Question 8

Genome

Answer 8

whole of the genetic information of an organism

Question 9

Positive mutations

Answer 9

LRP5 is a gene that helps immune system cells make a certain type of protein that acts as receptor on their surfaces. This receptor is used by HIV to infect the cells. People with a mutation of LRP5 are naturally immune to HIV.

Question 10

Gene to help digestion

Answer 10

After breast-milk, our ancestors couldn’t digest milk at adulthood, couldn’t break down the disaccharide in milk called lactose. More than 1/2 of the population has lactose intolerance. However for the past 10 000 years, many human populations have adopted an agricultural based lifestyle.

Question 11

Base substitution mutation

Answer 11

the type of mutation that results in a single letter being changed.

Question 12

Sickle cell disease

Answer 12

A mutation sometimes found in the gene that codes for haemoglobin in red blood cells. This mutation gives a different shape to the haemoglobin molecule. The difference leads to red blood cells that look very different from the usual disc with a hollow in the middle –> curved shape. Base substitution mutation is the cause of sickle cells.

Question 13

Human Genome Project

Answer 13

In 1990, an international cooperative venture set out to sequence the complete human genome. It hoped to determine the order of all the bases A, T, C and G in human DNA. In 2003, the Project announced that it had succeeded in achieving its goal. Now, scientists are working on deciphering which sequences represent genes and which genes do what.

Question 14

How do we use DNA to make medecines

Answer 14

• find beneficial molecules that are produced naturally in healthy people
• find out which gene controls the synthesis of a desirable molecule
• copy that gene and use it as instructions to synthesize the molecule in a laboratory
• distribute the beneficial therapeutic protein as a new medical treatment