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

genome

Answer 2

the whole of the genetic information of an organism.
Size of a genome is the total amount of DNA (or total length of DNA) in one set of chromosomes in that species
humans have 46 chromosomes, 32 from each parent

Question 3

alleles

Answer 3

alternative forms of a gene; each gene has a minimum of two alleles that differ from each other by one or only a few bases.

Question 4

gene locus

Answer 4

the specific location of a gene on a chromosome

Question 5

Sickle cell anaemia

Answer 5

a common genetic disease in areas where malaria while endemic. it is caused by a mutation of the gene that codes for the alpha-globin polypeptide in hemoglobin

Question 6

The Human Genome Project

Answer 6

began in 1990 and aims to find out the base sequence of the entire human genome

Question 7

Name the number of genes for the following:
Prokaryotes - Escherichia coli (E.coli);
Protoctista - Trichomonas vaginalis;
Fungi - Yeast;
Plants - Rice;
Animals - Homo sapiens (Humans)

Answer 7

3,200
60,000
6,000
41,000
23,000

Question 8

How is Sickle Cell Anaemia caused?

Answer 8

1. Base substitution mutation converts the sixth codon of the gene from GAG to GTG, changing HbA into a new allele HbS
2. mRNA has GUG as its sixth codon instead of GAG when the allele is transcribed
3. As one codon in the mRNA is different, one amino acid in the polypeptide is altered, from glutamic acid to valine
4. Haemoglobin molecules stick together in tissues with low oxygen concentrations, distorting red blood cells to sickle shape
5. The sickle cells cause damage to tissues by becoming trapped in blood capillaries, blocking them and reducing blood flow; when they return to high blood concentration, the haemoglobin bundles break up and the cells return to their normal shape
6. Haemoglobin and plasma membrane are damaged and the life of a red blood cell can be shortened to as little as 4 days; the body cannot replace red blood cells at a rapid enough rate and anaemia develops

Question 9

What is mutation? How does it occur?

Answer 9

Mutation: random change to the base sequence of a gene

Question 10

What has the completion of the Human Genome Project led to?

Answer 10

mapping
medicine
ancestry
screening