Download Slide 1 - Brookwood High School

Human Genetics &
Genetic Engineering
Notes
CP BIOLOGY
MS. MORRISON
Human Chromosomes

Karyotypes =
picture of
chromosomes lined
up by size and
grouped in pairs
(use cells in mitosis
since this is only
time can see
individual
chromosomes)
Human Chromosomes
46 chromosomes = 23 pairs
 Pairs 1-22 = autosomes
 Pair 23 = sex chromosomes,
determine individual’s gender
 XX = female, XY = male
 50%/50% chances of female/male
zygotes
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Human Chromosomes
X
X
X
XX
XX
Y
XY
XY
Pedigree Charts
Shows the relationship within a family
 Used to study how a trait is passed
from one generation to the next
 Often used to track diseases or
genetic disorders in a family
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Pedigree Charts
Pedigree Charts
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Males shown as squares
Females shown as circles
Individuals with trait of interest are shaded
Heterozygous individuals have only half of
square or circle shaded
Horizontal lines connect mating couples
Vertical lines connect to their offspring
Oldest generation is the top level
Types of Genetic Disorders
Recessive – must have both
recessive genes to have disorder, ex.
PKU, Tay Sachs, cystic fibrosis
 Dominant – only need one dominant
allele, ex. dwarfism, Huntington’s
 Codominant – both alleles expressed,
ex. Sickle-cell

Sex-Linked Traits/Disorders
Sex-linked genes = genes located on
the sex chromosomes
 Y chromosome much smaller than X
so many genes only found on X
 Males express all X-linked alleles
since they have only one X
chromosome – even recessives
 Ex. Color blindness, hemophilia

Chromosomal Disorders
Result when chromosomes do not
separate correctly during meiosis
 Most common error = nondisjunction –
chromosomes do not separately
properly and results in abnormal
number of chromosomes in gametes
 Ex. Down syndrome = Trisomy 21,
have 3 copies of chromosome 21
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Genetic Engineering
Earliest types – selective breeding –
allowing only certain plants or animals
to breed in order to pass on desired
traits
 Today – involves recombinant DNA
technology which means altering
genes in a living organism to produce
organisms with new genotypes

Types of Genetic
Engineering Techniques
DNA extraction – opening cell to
separate DNA from rest of cell parts
 Restriction enzymes – used to cut
DNA at specific points to make small
fragments
 Gel electrophoresis – used to
separate DNA fragments on the basis
of their length

Benefits of Gel
Electrophoresis
Compare genomes of different
organisms
 Compare genes of different individuals
(forensics and paternity)
 Locate and identify particular gene

PCR (Polymerase Chain
Reaction)
Process used to amplify or clone very small
samples of DNA so enough of DNA to study
DNA Sequencing
Read base sequence of a DNA
fragment
 Once know sequence – then amino
acid sequence is known for protein it
codes for
 Known DNA sequences can be
compared among individuals of same
species and of different species

Recombinant DNA
Used to transform the DNA of a cell (often a
bacterium) so that it takes in a piece of DNA from
outside the cell and incorporates it into its DNA
Reasons for using Genetic
Engineering
Genetically modify bacteria to produce
chemicals for medical or industrial
applications, ex. Human insulin,
growth hormone
 Alter the characteristics of organisms,
ex. Long-life tomatoes, diseaseresistant crops
 Gene therapy – insert gene to replace
missing or defective gene
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