Alleles
Different versions of a gene
Dominant allele
Always expressed even if only one copy is present
Recessive allele
Only expressed if 2 copies are present
Homozygous
2 of the same alleles of a particular gene eg BB or bb
Heterozygous
2 different ales of a particular gene eg Bb
Genotype
The genes and the alleles of these genes that an organism has
Phenotype
Observable characteristics of an organism
Nucleus
The part of the cell which contains the chromosomes
Genome
The entire genetic material of an organism
Chromosomes
A large section of DNA, they carry many genes, human body cells have 46 In total (23 pairs)
Gene
A small section of DNA on a chromosome that codes for a specific protein and controls a characteristic
DNA
A chemical molecule that holds the genetic information
Protein
A chemical molecule made from many amino acids joined together
Polymer
A large molecule made of many small repeating units called monomers
Nucleotides
Monomer of DNA, each one consists of a sugar, phosphate and one of 4 different bases ( A T G or C)
What are the 3 ways for fossils to be formed
-from gradual replacement by minerals (works on bones, teeth and shells ext)
-from casts and impressions (eg footprints or plant roots in clay that hardens)
-from preservation in places where no decay can happen (eg in amber because there is no oxygen or moisture fir decay microbes to survive and peat bogs bc they are too acidic)
What are the three branches from the universal ancestor
-bacteria
-archaea(primitive bacteria found in extreme environments)
-eukaryotes
binomial name =
Universal Way of naming species by using their genus and their species (G S) eg homosapiens
How to remember Linnaean Classification System
Katy - kingdom
Perry - phylum
Came -class
Over -order
For -family
Great -genus
Soup - species
How were species originally classified
To understand how this has happened we put them into groups based
on their characteristics and structure – Carl Linnaeus (1700s)
What else do we use to classify species today
The three domain system made by Carl woese in the 1990’s
Why can we classify better today
Beaches we have electron microscopes that allow us to examine better and gives us
evidence of internal structures.
• Improvement in understanding and
comparison of biochemical
processes e.g. DNA.
Why can’t be certain about how life began on
Earth
• Many early life forms were soft-bodied (no shell /
skeleton) – left few traces (decay completely)
• What traces there were have been mainly destroyed
by geological activity e.g. volcanoes
• Most don’t become fossils (conditions needs for
fossilisation absent)
• Lots of fossils still to be found
When did life on earth first form
Roughly 3.8 billion years ago
