CHAPTER 14HUMAN
HEREDITY
BIG IDEA: How can we use
genetics to study human
inheritance?
14.1 HUMAN CHROMOSOMES
The study of any genome begins w/ chromosomesfound in nucleus of eukaryotes
o Karyotype shows the complete diploid set of
chromosomes grouped in pairs, from largest 
smallest in size
Human karyotype contains (46
individual) / 23 pairs of
chromosomes
The last pair of chromosomes (pair 23)
are the sex chromosomes, which
determine if you’re male or female
Female= XX (contributes X always)
Male= XY (50:50 chance of contributing
X or Y)
Autosomes are the remaining 44
chromosomes in the human karyotype
Many human traits follow simple patterns of
dominance
The alleles for many human genes display
codominant inheritance
Sex-linked genes are genes located on
either the X or Y chromosomes.
Sex-liked genes on:
Y: directly father  son
X: given to daughter or son, but recessive
diseases MUCH more common in males!!!
-Males don’t have another X chromosome to
mask diseases located on X chromosome
Ex: color blindness, hemophilia, Duchnne
muscular dystrophy
Females undergo “X-inactivation” =,
where random genes in either
chromosome are switched off (so it’s on
in the other X)
- Causes spots in calico cats
A pedigree shows the presence or
absence of a trait according to the
relationships between parents, siblings,
and offspring
14.2 HUMAN GENETIC DISORDERS
Changes in a gene’s DNA sequence can change
proteins by altering their amino acid sequences,
which can directly affect phenotype
Disorders caused by Individual genes:
o Sickle cell anemia: defect in beta-globin
(carries oxygen), causing red blood cells to
clump together
o Cystic fibrosis: deletion of 3 bases, causing
protein to missfold, problems w/ breathing
and digestion
o Huntington’s disease: “CAG” repeat x40,
causing mental and physical deterioration
Genetic Advantage:
1/12 people w/ African descendent carry sickle
cell.
In Africa the heterozygous form of sickle cell
makes them resistant to malaria, yet no
symptoms of disease
Errors in meiosis
Nondisjunction: failure of chromosomes to
separate
If nondisjunction occurs gametes w/ an
abnormal # of chromosomes may result
Down syndrome: trisomy 21 (mental
retardation)
Turner syndrome: female w/ 1 X (sterile)
Klinfelter: XXY male (usually sterile)
14.3 STUDYING THE HUMAN GENOME
By using tools that cut, separate, and then
replicate DNA base by base, scientists can
now read the base sequences in DNA from
any cell
Most DNA is too large to be analyzed, so it
must be cut into smaller pieces by restriction
enzymes.
After DNA is cut, gel electrophoresis is used
to separate and analyze differently sized
fragments.
- Mix of DNA is put in well @ top, voltage is
applied, DNA is (-) charged, smaller DNA
fragments move quickly to (+) end.
Reading DNA: Dye-labeled nucleotides and
DNA polymerase are inserted to produce a
color banded complementary strand
Human Genome Project:
The Human Genome Project was a 13-year
international effort w/ the goal of
sequencing all 3 billion base pairs of human
DNA and identifying all human genes
Sequencing and identifying genes: “shotgun
sequencing”=rapid method cutting DNA into
fragments and determining the sequence of those
fragments. Linked together by overlapping frag.s
and id-ing promoters
About 99.9% of genes in humans are the same, but
bases that don’t match = single nucleotide
polymorphism (SNPs)
Human Genome Project was completed in 2003, copies
of certain human and other organisms genomes are in
databases on the internet.
Development from project: bioinformatics, which
combines molecular biology w/ information science.
Putting together human genome would’ve been
impossible w/out computer databases
Genomics- study of whole genomes, including genes
and functions
Human Genome Project pinpointed genes
and assocaited particular sequences w/
numerous diseases and disorders. Also ided 3 million diff. locations where singlebase DNA differences occur in humans.
-May help us understand, and eventually
develop cure for certain diseases.
One day your genetic info. may be public to
health insurance companies, doctors,
employers, etc. Right now “Genetic
Information Nondiscrimination Act” (2008)
prohibits discrimination based off of
genetic tests.