SBI3U Biology Notes: Chromosomes
Word
NAME:
Karyotype
Definition
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.
Having only one copy of each chromosome (or half of a full, diploid set). Identified
as ‘n’ Sex cells are haploid cells
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.
Chromosomes that determine non-sexual traits. In humans these are the first 22
homologous chromosome pairs.
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.
When there is one extra chromosome in a person/embryo (three copies of a
chromosome)
When there is one too few chromosomes in a person/embryo (one copy of a
chromosome)
A picture of an embryo or fetus’s chromosomes. They are used to determine
gender and if there are any chromosomal abnormalities
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.
Diploid
Haploid
Homologous
chromosomes
Autosomes
Sex chromosomes
Trisomy
Monosomy
Karyogram
Prokaryotes have one
chromosome consisting of a
circular DNA molecule.
How many copies of each gene do prokaryotes have?
Why is prokaryotic DNA considered ‘naked?’
Some prokaryotes also have
plasmids but eukaryotes do
not.
Cairn’s technique for
measuring the length of
DNA molecules by
autoradiography.
Eukaryotic chromosomes
are linear DNA molecules
associated with histone
proteins.
In a eukaryotic species
there are different
chromosomes that carry
different genes.
Homologous chromosomes
carry the same sequence of
genes but not necessarily
the same alleles of those
genes.
Comparison of genome size
in T2 phage, Escherichia
coli, Drosophila
melanogaster, Homo
sapiens, and Paris
japonica.
Organism
Genome size
(million base pairs)
T2 Phage
Escherichia coli
Drosophila melanogaster
Homo sapiens
Paris japonica
Use of online databases to
identify locus of a human
gene and its protein
product.
Gene Name
CFTR
HBB
F8
TDF
Description
Description
Haploid nuclei have one
chromosome of each pair.
How many chromosomes in a haploid human cell?
What types of cells have diploid nuclei?
Diploid nuclei have pairs of
homologous chromosomes.
How many chromosomes in a diploid human cell?
The number of
chromosomes is a
characteristic feature of
members of a species.
Comparison of diploid
chromosome numbers of
Homo sapiens, Pan
troglodytes, Canis
familiaris, Oryza sativa,
and Parascaris equorum.
Scientific Name
Parascaris equorum
Oryza sativa
Homo sapiens
Pan troglodytes
Canis familiaris
Common Name
Diploid Chromosome Number
Sex is determined by sex
chromosomes and
autosomes are
chromosomes that do not
determine sex.
A karyogram (karyotype)
shows the chromosomes of
an organism in homologous
pairs of decreasing length.
Use of karyotypes to
deduce sex and diagnose
Down syndrome in
humans.
What types of cells have
haploid nuclei?
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: