Download Genetics Notes - Biloxi Public Schools

Term 3---Genetics Notes
term
definition or information
diagram or examples
Gregor Mendel
experiments with pea plants laid the
foundations for the science of
genetics

Thomas Hunt
Morgan

known for his experimental
research with the fruit fly
(Drosophila) by which he
established the chromosome
theory of heredity
discovered that fruit fly eye
color is sex-linked
Rosalind
Franklin
created images of DNA molecules
through X-ray diffraction which
suggested that DNA has a spiral
shape
Francis Crick


& James Watson
developed the double-helix
model of the structure of DNA
(deoxyribonucleic acid)
The DNA molecule resembles
a twisted ladder or zipper and
the DNA sequence forms a
code.
1
2
Term 3---Genetics Notes
term
trait
definition or information
 any characteristic of an
organism such as body shape
or what it eats
 All traits are inherited.
 passed from parent to
offspring
heredity
passing of traits from one
generation to another during
reproduction
reproduction---process by which organisms
make more organisms of the
same kind
--sexual reproduction
--asexual reproduction
*** some organisms can
reproduce both sexually and
asexually
diagram or examples
Term 3---Genetics Notes
DNA
 determines what traits are
(deoxyribonucleic
passed from one generation to
acid)
the next—blueprint of an
organism
 Before a cell divides, it makes
a copy of its DNA. This
ensures that both new cells
have all the genetic
information they need.
 A genome is the complete
sequence of an organism’s
DNA.
chromosomes
gene
allele
A molecule of DNA can be very
long. To fit inside the nucleus,
the DNA wraps around proteins
and coils tightly. These tightly
coiled structures that contain the
genetic information
***genetic mutations---the
permanent change in the DNA
sequence that makes up a gene
---may be inherited from
parents or acquired during a
person’s lifetime
---acquired mutations are not
passed to offspring
small section of DNA on a
chromosome that carries
information about a trait
Hundreds of genes are located
on each chromosome
each gene of a gene pair
(different forms of a gene)
3
Term 3---Genetics Notes
Punnett square
used to predict the possible
genes and traits of offspring,
based on the genes of their
parents
--monohybrid cross (1 trait)
--dihybrid cross (2 traits)
phenotype
physical characteristics of an
organism or what is
expressed/shows (tall, short, eye
color, flower color)
genotype
 all the genes that are passed
on to an offspring or the
genetic makeup of an
organism—the letters on the
Punnett square (tt, Tt, TT)
The genotype of an organism
determines its phenotype.
4
5
Term 3---Genetics Notes
dominant
 one allele covers over or
masks another allele of that
trait (visible or seen)
 A dominant allele is
expressed in the phenotype of
an organism. If the organism
has that allele, it will show
that trait.
recessive
 alleles are seen only when a
trait is recessive pure (two
recessive traits---tt)
 If offspring has one dominant
allele and one recessive allele
for a trait, the recessive trait is
not expressed
purebred
 organism is one that has two
matching alleles for a trait
(example: TT or tt)
 homozygous (homozygotes)- organisms that have two
identical alleles for a
particular trait (BB or bb)
hybrids
incomplete
dominance
codominance
 organisms that inherit two
different alleles for a trait (Tt)
 heterozygous
(heterozygotes)-- organisms
that have two different alleles
for a particular trait (Bb)
 heterozygous alleles are both
expressed, resulting in a
combined phenotype
 For example, in crosspollination experiments
between red and white
snapdragon plants the
resulting offspring are pink.
alleles of a gene pair in a
heterozygote are fully expressed
resulting in offspring with a
phenotype that is neither
dominant nor recessive
R = allele for red flowers
W = allele for white
flowers
red x white  pink
RR x WW  100% RW
R = allele for red flowers
W = allele for white
flowers
red x white  red &
white spotted
RR x WW  100% RW
Term 3---Genetics Notes
pedigree
 genetic family tree
 The parental generation is
denoted as the P1 generation.
The offspring of the P1
generation are the F1
generation (first filial). The
self-fertilizing F1 generation
produced the F2 generation
(second filial).
 An autosome or autosomal
is a chromosome that is not a
sex chromosome.
6
Term 3---Genetics Notes
Biotechnology--Term
Definition or information
biotechnology
 manipulation of living
things to make useful
products
 causes changes in
organisms
selective
breeding
(artificial
selection)
 intentional mating of
organisms to produce
offspring with specific
traits
 breeding of animals or
plants having desirable
characteristics
 domesticated animals is
the process of developing
a cultivated breed over
time
 weeding-out of undesired
characteristics and the
fixation of desired traits
 Cross-pollination--crosses two different
varieties of vegetable but
has traits of both parents
7
Diagrams or examples
Term 3---Genetics Notes
genetic
 changes the genetic
engineering
material of a living
organism
 make medicines and treat
disease
 improve crops
 produce organisms in
scientific research
 Gene splicing ---a gene
from one organism is
inserted into the DNA of
another organism
Examples----- produce human insulin
--- make medicine
---prevent inherited disorders
 disease resistance---make
corn that is resistant to
some herbicides (product
that kills weeds)
 make food better tasting
and last longer
 Gene therapy involves
replacing the nonworking
cells with cells that have
been genetically altered.
---may negatively affect
other genes.
Benefits of Biotechnology
make crops that are resistant to
disease, herbicides, and frost
crops taste better and more nutritious
Stoneville Pedigreed Seed Company-to improve cotton
Stoneville Pedigreed Seed Company 1st to sell genetically altered cotton
plants
Bacteria to help clean oil spills
Risks of Biotechnology
Genes bred into some crop plants may cross over into wild
populations
GE foods must be tested for safety; may cause allergic reactions
may cause a new disease that could not be treated with available
drugs
harmful new organisms could escape into the environment
How human gene information could be used--Ex.--an insurance company might refuse to cover a person who
carries a gene for a specific disease
GE crops may be too successful--If one kind of rice is more nourishing than any other, all the farmers
in an area might plant that kind of rice. In the short term, everyone
would benefit from the modified rice. However, the new rice might
be vulnerable to disease or it might not produce a crop in a
particularly wet or hot weather. If people have planted only one
kind of rice, they could lose the entire crop. If farmers grow many
different breeds of rice, they will not lose the whole harvest.
8
9
Term 3---Genetics Notes
Disorder
Symptom
Cystic
fibrosis
Mucus clogs lungs, liver, and
pancreas; victims usually don’t
survive to adulthood
Impaired blood circulation,
organ damage
---Some scientists think that
people with one mutated sickle
cell gene are not affected by
sickle cell anemia and have
some protection against malaria
Deterioration of central nervous
system in infancy; death occurs
in early childhood
Failure of blood to clot
Sickle cell
anemia
Tay-Sachs
disease
Hemophili
a
Muscular
dystrophy
Down
syndrome
Color
blindness
Wasting away of muscles;
shortened life expectancy
mild to moderate learning
disabilities, developmental
delays, characteristic facial
features, and low muscle tone in
early infancy
person's ability to ascertain
specific colors, and in some
instances all colors
Genetic Disorders
Defect
Failure of chloride ion
transport mechanism
Pattern of
Inheritance
Autosomal
recessive
Frequency among
human births
1/2,080 (whites)
Abnormal hemoglobin
molecules
Autosomal
recessive
1/500 (African
Americans)
Defective form of enzyme
hexosaminidase A
Autosomal
recessive
1/1,600 (Jews of
European descent)
Defective form of bloodclotting factor
Muscle fibers degenerate
X-linked
recessive
X-linked
recessive
1/7,000
Genes on an extra copy of
chromosome 21
malfunctions of the retina,
the inner eye lining
1/10,000
1/800
X-linked
recessive
1/33,000 in U.S.