1. Topics 4 and 10 GENETICS
Genetics is the study of how inherited information is passed on from one generation to the next using genetic material….genes made of DNA.

2. Topic 4.1 Eukaryotic Chromosomes
Made of DNA wrapped around histone proteins
In eukaryotes that reproduce sexually chromosomes always come in pairs (except in sex cells or gametes)
Humans have 46 chromosomes (or 23 pairs)
Prokaryotes (bacteria) have only one chromosome and it is not associated with proteins

3. Chromosomes in different species
# of chromosomes
Fruit fly 8
Human 46
Rye 14
Ape 48
Guinea Pig 16
Sheep 54
Dove
Horse 64
edible snail 24
Chicken 78
Earthworm 32
Carp
104
Pig 40
Butterflies
~380
Wheat 42
Fern
~1200

4. Topic 4.1.2 Define gene, allele and genome
Gene = a heritable factor that controls a specific characteristic
Heritable means passed on from parents to offspring
Characteristic refers to genetic traits such as hair color
Our approx genes are organized into chromosomes
Allele = different variations of a gene
ex. Some alleles give you brown eyes and
others give you blue eyes
Alleles of the same gene occupy the same place (locus) on each chromosome of a pair

5. Genome = the complete set of an organisms base sequences
Complete genomes have been fully written out for a few organisms (ex. fruit fly and E. coli bacterium)
If each DNA nucleotide base pair (A-T, C-G) were typed out, a human cell would contain more letters than 10 sets of encyclopedias!!!!!

6. Topic 4.1.3 Define Gene Mutation
A mutation is a random, rare change in genetic material
A gene mutation involves a change of the sequence of bases in DNA
e.x. the base thymine (T) might be put in place of adenine (A) along the DNA sequence
This results in the corresponding bases along mRNA being altered during transcription
This could lead to errors in translation and protein synthesis

7. Topic 4.1.4 Explain base substitution mutation using the example of sickle cell anemia
Consequence of changing one base could mean that a different amino acid is placed in the polypeptide chain
This may have little or no effect on the organism or it may have a major influence on the organism’s characteristics
In humans, a mutation is sometimes found in the gene which creates hemoglobin for red blood cells.
The resulting condition is called sickle cell anemia

8. Sickle Cell Anemia Caused by a base substitution mutation
Codon GAG becomes GTG so during translation instead of adding glutamic acid, valine is added instead
This causes a change in the shape of the hemoglobin molecule which leads to a very different shape to the red blood cell
Sickle is a curved knife used to cut tall plants
O2 cannot be carried efficiently leading to weakness, fatigue and shortness of breath
The hemoglobin tends to crystallize within the red blood cells leading to slow blood flow or blockages

9. Sickle cell disease and malaria
Demographics of sickle cell = the mutated gene is found mostly in populations originating from West Africa or the Mediterranean
Sickle cell disease and malaria
Malaria is one of the most deadly diseases in the world
The parasite which causes malaria has difficulty infecting a person with sickle cell
People with sickle cell have a natural resistance to malaria
Therefore the mutated gene has been successfully passed on through natural selection

10. Exercises:
Draw and label a chromosome. Include the following labels: chromatid, centromere, Indicate an example of a locus.
What is the difference between an allele an a gene?
Compare and contrast prokaryotic DNA and eukaryotic DNA.
Explain why eukaryotic chromosomes always come in pairs.