Chapter 8 – Chromosomes and Cell
Division
Genes – A segment of DNA that
transmits information from parents
to offspring
One molecule of DNA contains thousands of
genes,
Examples of thing coded for in genes:
-Hair color, Eye color, Number of Toes, Baldness
Chromosome – A rod shaped
structure formed from DNA and
proteins prior to Mitosis.
-Form from chromatin (DNA/Protein)
-Approximately 40% DNA, 60% Protein
Histone - A protein which serves as a spool for
DNA to wrap around. Helps organize DNA.
Homologous Pairs – two copies of
DNA that carry the same genes.
-Humans have 23 unique chromosomes
-Each chromosome has two copies for a
total of 46 chromosomes (23 pairs) in
each human cell.
Diploid vs.Haploid
Diploid Cells (2n) – Cells possessing
two copies of each chromosome.
-All adult human cells are diploid.
Haploid (n) – Cells possessing one copy
of each chromosome.
-All reproductive cells are haploid
(Sperm and Egg)
Chromosomes
-The number of chromosomes is
specific for a species.
-Each species has a set number of
chromosomes
Humans – 2n=46
Penicillium Fungus – n=1-4
Dog – 2n=78
Tongue Fern - 2n=1262
Somatic Cells – diploid cells
performing everyday tasks
ie. Liver, Muscle, Nerve cells
Sex Cells – Haploid cells used for
reproduction
-Sperm cells – found in males
-Males produce sperm throughout entire lifetime
-Egg Cells – found in females
-Females are born with their entire set of
immature egg cells.
Autosomes – Chromosomes that
are the same in both sexes
-22 of the 23 Chromosomes found in each cell
-Numbered #1-22
-Each autosome contains different genes
-Each autosome is of different lengths
Sex Chromosomes – Chromosomes
that are different in males and
females
-X Chromosome – Found in a pair in females,
and as a single in males.
-Carries genes necessary for life
-Y Chromosome – Found as a single only in
males.
-Carries genes associated with male gender.
Sex Chromosomes
In Humans:
XX = Female
XY = Male
X and Y
chromosomes in
people (note the
shape of the single
chromosome)
Not all species determine sex in the
same way!
Birds – XY = Female
XX = Male
Bees – XX = Female
XY = Male
X = Worker Bee
(Androgenous)
Karyotype – A process of staining
and viewing chromosomes.
-Each chromosome has its own unique
size, shape, and banding pattern (based
on genes)
-Chromosomes can be prepared,
viewed under a microscope, and lined
up in their pairs from #1-22 and XX or
XY.
Karyotype
-Allows us to determine sex
-Allows us to look for genetic
abnormalities (Diseases)
-ie. Down Syndrome – Caused by an
extra Chromosome #21 (Trisomy 21)
Is this person normal?
Are they male or female?
Is this person normal?
Are they male or female?