3.1 Genes Flashcards
Gene Definition
a gene is a heritable factor that consists of a length of DNA and influences a specific characteristic
it is a length of DNA that codes to make a protein
Locus (loci)
is a position on a chromosome where a gene for a particular trait is located
Alleles
are various specific forms of a gene
they differ from one another by one or only a few bases
Mutations Effects
neutral - they have no observable effects on the organism
harmful - evident because they may alter the survival capacity of the organism
beneficial - mutations form the basis of evolution. Any mutation that improves the survival of an organism will be passed on.
Mutation Definition
they are alterations in the DNA of chromosomes that is not immediately and properly repairs
Causes of Mutations
- Spontaneous Mutations: arise from errors in DNA replication
- Induced Mutations: can be induced by mutagens e.g. radiation, alcohol etc.
Locations of Mutations
somatic cells - most occur here, and are not inherited
gametes - may be inherited
Gene Mutations
change the sequence of bases in DNA for a single gene. They may produce a new allele for that gene
Point Mutations
are gene mutations involving a single nucleotide base
Sickle Cell Anemia
is caused by an autosomal recessive mutation on chromosome 11
this results in the substitution of a single nucleotide base in the gene coding for beta chain of haemoglobin
mutates GAG to GUG
changing the amino acid produced in translation from glutamic acid to valine
they are less efficient at carrying oxygen
Genome
is the whole of the genetic information of an organism
Comparing Genome Sizes
Virus T2 phage - 5 kb
Escherichia coli (bacteria) - 4.6 Mb
Drosophila melanogaster (fruit fly) - 130 Mb
Homo Sapiens - 3.2 Gb
Paris japonica - 150 Gb
Protopterus aetheopicus (lungfish) 130 Gb
