Guided notes covering material from Topic 3.2 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: Chromosomes (3.2) NAME:
Word Definition
Diploid Having two copies of each chromosome. One is the maternal copy and one is the
paternal copy. Identified as ‘2n’ (n = number of chromosomes). Body cells are
diploid cells.
Haploid Having only one copy of each chromosome (or half of a full, diploid set). Identified
as ‘n’ Sex cells are haploid cells
Homologous
chromosomes
Pairs of chromosomes that are the same size, shape, banding pattern and have the
same genes in the same order but may have different alleles.
Autosomes Chromosomes that determine non-sexual traits. In humans these are the first 22
homologous chromosome pairs.
Sex chromosomes Chromosomes that determine sex. In humans these are the 23rd pair of
chromosomes. XX is a female and XY is a male. This pair is not homologous.
Trisomy When there is one extra chromosome in a person/embryo (three copies of a
chromosome)
Monosomy When there is one too few chromosomes in a person/embryo (one copy of a
chromosome)
Karyogram A picture of an embryo or fetus’s chromosomes. They are used to determine gender
and if there are any chromosomal abnormalities
Karyotype Property of a cell that refers to the number and types of chromosomes it contains
Plasmid Small, circular loops of DNA found in prokaryotes that carry extra genetic material
Autoradiography A method for visualizing DNA and measuring its length by labeling the DNA with a
radioactive isotope of Hydrogen.

2. 3.2.1 Prokaryotes have one
chromosome consisting of a
circular DNA molecule.
3.2.2 Some prokaryotes
also have plasmids but
eukaryotes do not.
3.2.11 Cairn’s technique for
measuring the length of
DNA molecules by
autoradiography.
3.2.3 Eukaryotic
chromosomes are linear
DNA molecules associated
with histone proteins.
3.2.4 In a eukaryotic
species there are different
chromosomes that carry
different genes.
3.2.5 Homologous
chromosomes carry the
same sequence ofgenes but
not necessarily the same
alleles of those genes.
3.2.12 Comparison of
genome size in T2 phage,
Escherichia coli,
Drosophila melanogaster,
Homo sapiens, and Paris
japonica.
3.2.15 Use of online
databases to identify locus
of a human gene and its
protein product.
How many copies of each gene do prokaryotes have?
Why is prokaryotic DNA considered ‘naked?’
Organism Genome size
(million base pairs)
Description
T2 Phage
Escherichia coli
Drosophila melanogaster
Homo sapiens
Paris japonica
Gene Name Description
CFTR
HBB
F8
TDF

3. 3.2.7 Haploid nuclei have
one chromosome of each
pair.
3.2.6 Diploid nuclei have
pairs of homologous
chromosomes.
3.2.8 The number of
chromosomes is a
characteristic feature of
members of a species.
3.2.13 Comparison of
diploid chromosome
numbers of Homo sapiens,
Pan troglodytes,Canis
familiaris, Oryza sativa,
and Parascarisequorum.
3.2.10 Sex is determined by
sex chromosomes and
autosomes are
chromosomes that do not
determine sex.
3.2.9 A karyogram
(karyotype) shows the
chromosomes of an
organism in homologous
pairs of decreasing length.
3.2.14 Use of karyotypes to
deduce sex and diagnose
Down syndrome in
humans.
What types of cells have haploid nuclei?
How many chromosomes in a haploid human cell?
What types of cells have diploid nuclei?
How many chromosomes in a diploid human cell?
Scientific Name Common Name Diploid Chromosome Number
Parascaris equorum
Oryza sativa
Homo sapiens
Pan troglodytes
Canisfamiliaris
What features are used to distinguish chromosomes when assembling a karyotype?
State the sex of each karyotype and whether or not there is a chromosomal abnormality. Circle the
karyotype that shows a Down Syndrome fetus: