Guided notes covering material from Topic 3.1 of the updated IB Biology syllabus for 2016 exams. Notes sequence and prompts are based on the Oxford IB Biology textbook by Allott and Mindorff.

1. IB Biology Chapter 3 Notes: Genes (3.1) NAME:
Word Definition
Gene A heritable factor that controls specific characteristic. It is also a section of DNA
that codes for a polypeptide.
Allele Different forms or variants of a specific gene.
Genome The whole of the genetic information of an organism.
Gene mutation When the nucleotide base letter sequence of the DNA is changed.
Base substitution
mutation (point
mutation)
When a single letter in the DNA sequence is replaced with a different letter.
Frameshift mutation When a single letter in the DNA sequence is added or deleted.
Gene Locus A specific position of a gene on a chromosome.
Human Genome
Project
An international research project that led to the mapping/sequencing of the entire
genetic material of a human being.

2. 3.1.1 A gene is a heritable
factor that consists ofa
length of DNA and
influences a specific
characteristic.
3.1.9 Comparison of the
number of genes in humans
with other species.
3.1.2 A gene occupies a
specific position (locus) on
one type of chromosome.
3.1.3 The various specific
forms of a gene are alleles.
3.1.4 Alleles differ from
each other by one or a few
bases only.
3.1.10 Use of a database to
determine differences in the
base sequence of a gene in
two species.
3.1.5 New alleles are
formed by mutation.
3.1.8 The causes of sickle
cell anemia, including a
base substitution mutation,
a change to the base
sequence of mRNA
transcribed from it, and a
change to the sequence of a
polypeptide in hemoglobin.
3.1.6 The genome is the
whole of the genetic
information of an organism.
3.1.7 The entire base
sequence of human genes
was sequenced in the
Human Genome Project.
Which types of organisms have the fewest genes?
Identify two organisms with more genes than humans:
What is the ‘locus’ of a gene?
What is an allele?
What does it mean to have ‘multiple alleles’ for a trait?
How do scientists determine sequence differences in two species for a gene and why is this done?
What is a base substitution mutation?
What gene is mutated in Sickle Cell Anemia?
What base change occurs in the DNA?
What amino acid change occurs in the polypeptide?
Describe the effects of Sickle Cell Anemia:
Describe the Human Genome Project (HGP) and its outcomes: