1. Genomes Genes and Alleles
Nature of Biology 1
Chapter 13 pg

2. Three quick questions
1. Name one positive and one negative about sexual and asexual reproduction 2. Although independent assortment leads to a huge number of possible human variation in our sex cells crossing over brings that number up to nearly infinity. Explain this statement. 3. Name the five stages of the cell cycle denoted by the letters S, G2, G1, C, and M and place them in a logical order.

3. Study Design Unit 2, Area of Study 2 – Genomes, genes and alleles
The distinction between a genome, gene and allele
The genome as the sum total of an organism’s DNA measured in the number of base pairs contained in a haploid set of chromosomes

4. What makes you, you?

5. DNA revisited
Deoxyribonucleic acid is a biomacromolecule which carries the genetic code for protein expression, dictating essentially all aspects of life.
The nitrogenous base sequence of DNA is what results in the variety of living things in the world

6. What is a Gene? A gene is the basic functional unit of heredity.
Made up of a specific strand of DNA and act as instructions to make a specific protein molecule.
In humans, genes vary in size from a few hundred DNA base pairs to more than 2 million base pairs.
Within a species such as humans 99.9% of our DNA is the same as the person next to us.

7. So where is the variation?
It makes sense that we are so genetically alike…
We are more similar to each other as a species than we are to other species
Variation in genes come from changes in the nitrogenous base sequence of the DNA that makes up the gene
Different variations of the same gene is termed an Allele.

8. Case Study – ABO Blood group alleles
The ABO blood group gene codes for a type of protein which determines an individuals blood type.
The gene is approximately base pairs (bp) long and is found on chromosome 9.
There are three allelic variations to the ABO gene
The A allele develops the A marker on red blood cells
The B allele develops the B marker on red blood cells
The O allele results in a non-functional gene and develops no marker on red blood cells
Let’s compare the nucleotide sequence of the three alleles

9. Case study – ABO Blood group alleles
How many changes need to occur to change the allele?
What proportion of the total gene is this?

10. Genome
A genome is an organism’s complete set of DNA, including all of its genes.
Each genome contains all of the information needed to build and maintain that organism.
In Eukaryotes, a copy of the entire genome— more than 3 billion DNA base pairs—is found in all cells that have a nucleus.
All of the genomic information of an organism is contained in one haploid set of chromosomes.
With the exception of the sex chromosomes

11. Comparing Genomes
The below table compares the genomes of various organisms
What organism has the biggest genome?
What organism has the most chromosomes?
What organism has the most genes?
Organism
Base pairs
Chromosome number (Haploid number)
Number of genes
Human
3 Billion
46 (23)
21 000
Mouse
2.5 Billion
40 (20)
23 000
Fruit Fly
150 Million
8 (4)
17 000
Arabidopsis (weed)
157 Million
10 (5)
25 000
Roundworm
97 Million
12 (6)
19 000
Yeast
13 Million
32 (16)
6 000
E. Coli (bacteria)
4.6 Million 1
3 200