Transcript Genetics

Genetics
The Science of Heredity
Unit Vocabulary
Heredity
Traits
Genes
Alleles
Passing of traits from parent to
offspring.
Different physical
characteristics
Factors that control
traits.
Different forms of a gene.
Always two for each trait. One
from each parent.
Alleles
Dominant
Allele
The trait that is always
exhibited or “shows up.”
(Tt) Heterozygous two
different alleles for a trait
(hybrid)
(TT)Homozygous two
identical alleles for a
trait (purebred)
Recessive
Allele
The trait that is masked or
covered up when
a dominant allele is present.
A recessive allele will show up
only if there are two recessive
alleles (tt) (ss)
Homozygous 2 identical
recessive alleles (tt) (ss)
Monohybrid
A hybrid produced by
crossing parents that are
homozygous for two alleles.
(TT) (tt)
Dihybrid
A dihybrid is produced by crossing
parents that are heterozygous for two
alleles, so that each gene is
represented by two different forms of
alleles. (Tt)
Phenotype – The physical appearance or visible traits (green
eyes, brown hair, shape of face)
Genotype – The genetic makeup or allele combinations (Tt,
TT, tt)
Symbolic representation
Co dominance - a cross between organisms with two different
phenotypes produces offspring with a third phenotype in which
both of the parental traits appear together. (chicken with white
and black feathers)
Incomplete Dominance - a cross between organisms with two
different phenotypes produces offspring with a third phenotype
that is a blending of the parental traits. (flower - white and red=
pink)
Punnett Square - is a chart that is used to show possible
combinations of a genetic cross, and to determine the
probability of a particular outcome.
***created by geneticist named Reginald Punnett
Mendelian Genetics
Gregor Mendel (1822 – 1884) was an
Austrian monk whose studies of the
inheritance of traits in pea plants
helped to lay the foundation for the
later development of the field of
genetics. He is often called the
"father of genetics." His studies
showed that there was particulate
inheritance of traits according to
basic laws of inheritance. The
significance of Mendel's work was
not recognized until the turn of the
twentieth century.
Living as a monk, he raised and
monitored more than 20,000 pea
plants inside the walls of his
monastery.
Particulate inheritance - traits that
insures a species survival.
Mendel’s Pea Plant Experiments
Mendel’s 1st Experiments
 Mendel used purebred
plants PP, pp
 PP for all purple flowers
and tt for white flowers
 He called the offspring
from each cross First/F1
Generation plants
 Each of the offspring had
purple flowers with an
heterozygous allele
combination Pp
Mendel’s 2nd Experiment
 Mendel allowed the first
generation to self-pollinate
 The white flower
reappeared.
 3:1 Ratio
Probability
 Probability - (or
likelihood) is a
measure or
estimation of how
likely it is that
something will
happen.
 Probability is often
written as a fraction
or a percentage.
 If you flip a coin the
probability of
flipping heads is
50% or ½.
Meiosis
Meiosis 1
• At the end of Meiosis 1 there
are two daughter cells with
a full set of chromosomes
that are identical to the
parent cell.
• The two cells are called
daughter cells.
• During meiosis II the
chromosomes are not copied
• Four (sex cells) called
gametes are produced. Egg
cells for females and sperm
cell for males.
• Each gamete has half the
number of chromosomes than
the original cell.
Mitosis Vs. Meiosis
• One large cell makes two
smaller cells with same
number of chromosomes;
allows organisms to grow,
develop and repair.
•
Cell division for reproduction
•
One large cell will produce four
smaller cells called gametes.
Each cell will have half the
normal number of
chromosomes.
• Before Mitosis begins the
chromosomes copy
themselves.
•
DNA does not duplicate during
meiosis 2.
•
Cells produced will fuse
together during sexual
reproduction.
•
The egg cell and sperm cell will
combine (fertilization) to form
zygote (new organism) with a
complete set of chromosomes.
• The two new cells are called
daughter cells.
• Both new daughter cell have a
full set of chromosomes.
 DNA - DEOXYRIBONUCLEIC
ACID
 The double helix model was
discovered by a group of
scientists named Watson,
Crick and Franklin
 The steps of the double helix
is made of nucleotides.
 Four nitrogen bases: Adenine
always pairs with Thymine
(AT) and Guanine always
pairs with Cytosine (GC)
 Alternating bands of sugar
and phosphates make up the
sides of the double helix.
DNA Continued
 DNA stores all the genetic
information for an
organism, and it can
replicate itself and be
transmitted to all the
organism's offspring.
 DNA is located in the nuclei
of cells, which make up the
body.
 DNA can be considered one
of the building blocks of the
body.
 Genes are hereditary
material that lies within the
cell nucleus. Genes, which
are made up of DNA, act as
instructions to make
molecules called proteins.
Humans sex cells normally have 23
pairs of chromosomes, for a total of
46 after the egg cell and sperm cell
combine. Twenty-two of these pairs,
called autosomes, look the same in
both males and females.
The 23rd pair is called the sex
chromosomes and differs between
males and females. Females have
two copies of the X chromosome or
XX, while males have one X and one
Y chromosome.
DNA lies within the nucleus of all
cells in humans and other living
organisms. Most of the DNA is
placed within the nucleus and is
called nuclear DNA. However, a
small portion of DNA can also be
found in the mitochondria and is
called mitochondrial DNA or
mtDNA.
The DNA can make copies of itself. Both the strands of the
DNA open up and make a copy of each and become two DNA
stands.
DNA consists of 2 strands in a twisted ladder structure called
the Double Helix.
Karyotype – A picture of all the
chromosomes in a cell lined in
pairs.
Female
Male
Pedigrees
 Pedigrees are one tool
that geneticists use to
trace the inheritance of
traits in humans.
 A pedigree chart or
“family tree” that
tracks which members
of a family have a
particular trait.
 The trait recorded in a
pedigree can be for an
ordinary trait such as a
widows peak, or it
could be a sex link
traits such as color
blindness or
hemophilia.
Hemophilia
Hemophilia is the name of a genetic disorder which
means the body's inability to control bleeding. It is
called a sex linked disorder because it is carried on the x
chromosome.
Color Blindness
The charts below show the most common types of color
blindness. If a certain pigment is missing in your eyes, you may
have trouble seeing blue-yellow colors. People with blue-yellow
color blindness usually have problems identifying reds and
greens, too.
Mutations
A genetic disorder is an
abnormal condition that a
person inherits through genes
or chromosomes.
Some occur in sex cells during
meiosis, and are passed down
from the parent’s cells.
These abnormal conditions
are called mutations. There
are three types of mutations.
Deletion – a base pair is left
out.
Insertion –an extra base is
added
Substitution - the wrong
base is used. (most
common)
Genetic Disorders
This adorable child has a
genetic disorder called down
syndrome.
A person with down syndrome
has an extra copy of
chromosome 21. The extra
chromosome is the result of
an error made during meiosis.
People with down syndrome
have a distinctive physical
appearance and some degree
of mental or cognitive
problems. Heart defects are
also common but can be
treated.
 Klinefelter syndrome is a
disorder that affects only
males. Males normally
have an X chromosome
and a Y chromosome (XY).
But males who have
Klinefelter syndrome have
an extra X chromosome
(XXY), This called an
insertian giving them a
total of 47 instead of the
normal 46 chromosomes.
 People with this disorder
develop as males with
subtle characteristics that
become apparent during
puberty. They are often
tall and usually don't
develop secondary sex
characteristics, such as
facial hair or underarm.
The extra X chromosome
primarily affects the
testes, which produce
sperm cells and the male
hormone testosterone.
Genetic Disorders
cont.
Turner Syndrome
• Normally, females inherit one X
chromosome from their mother
and one X chromosome from
their father. But females who
have Turner syndrome are
missing one of their X
chromosomes. (omission)
• Women with Turner syndrome
are usually sterile and cannot
have children.
Other Genetic Disorders
 Albinism is a congenital disorder in which there is little or
completely no production of melanin in hair, skin and iris of
the eyes. Hence people suffering from albinism have lightcolored skin, hair and eyes.
 Color Blindness - refers to the inability to differentiate
among certain colors. Color blindness is most commonly
the result of mutations in the X chromosome. However,
research has shown that mutation in 19 different
chromosomes can cause color blindness.
 Cystic Fibrosis - is an inherited disease of the glands that
secrete mucus and sweat. Cystic fibrosis causes the mucus
to become thick, sticky. The mucus clogs various organs of
the body, that results in other complications. It mostly
affects lungs, liver, pancreas, sinuses, intestines and sex
organs. At present, there is no cure for cystic fibrosis.
Hemophilia is the name of a genetic disorders which mean the
body's inability to control bleeding. The bleeding might be
exterior, if the skin is broken by a cut, scrape, or abrasion, or it
can be interior, into joints, muscles, or organs which are hollow.
The result can be visible on the skin or subtle (e.g., brain
bleeding).
Muscular Dystrophy is a genetically inherited disorders of
progressive degeneration of skeletal muscles. It also causes
defects in muscle proteins and death of muscle cells and tissues.
These disorders vary in severity and the extent and distribution
of muscle weakness. Although the skeletal muscles are primarily
affected, muscular dystrophy may impair functions of other
systems of the body as well.
Sickle cell disease or sickle cell anemia is a blood disorder. A
mutation causes sickling of the red blood cells that may lead to a
number of complications.
Genetic Counseling
If a couple has a family
history or concern about a
genetic disorder they may
seek help from a genetic
counselor. Genetic
counselors help couples
understand their chances
of having a child with a
particular genetic
disorder. They use tools
such as karyotyping,
pedigree charts and
Punnett squares to help
them in their work.
Genetic Engineering
In the last few
decades geneticists
have developed a
powerful technique
for producing
organisms with
desired traits. This
process is called
genetic engineering.
In genetic
engineering genetic
information is
transferred from one
organism to another
organism.
Genetic engineering is
sometimes called
“gene splicing”
because a DNA
molecule is cut open
and a gene from
another organism is
spliced into it. Genetic
engineering can
improve medicines,
improve food crops,
and may cure many
human genetic
disorders.
Genetic Engineering in Bacteria
Researchers had their
first success with
genetic engineering
when they inserted
DNA from another
organism into bacteria.
Once the DNA is
spliced into the
bacteria, for example,
insulin all of that
bacteria's offspring
will contain this
human gene. In this
case the human code
for insulin.
Why are bacteria used for gene
splicing?
Because bacteria reproduce
quickly, and large amounts of
insulin can be produced in a
short amount of time. Then the
insulin can be collected and
used to treat people with
diabetes.
Gene Therapy
This process involves inserting
working copies of a gene directly
into the cells of a person with a
genetic disorder.
For example, people with cystic
fibrosis do not produce a protein
that is needed for proper lung
function. With gene therapy
scientists can insert copies of the
gene into the harmless virus. The
engineered virus can then be
sprayed into the lungs of patients
with cystic fibrosis.
Selective Breeding
Their are two types of selective breeding
called inbreeding and hybridization
Inbreeding
Inbreeding involves
cross breeding two
individuals that have
identical or similar sets
of alleles. As a result
organisms have
offspring that are very
similar to those of their
parents. For example,
breeders produce pure
breed dogs such as
golden retrievers and
other dog breeds.
Unfortunately, because
of inbreeding the
offspring have a greater
chance of inheriting
alleles that lead to
genetic disorders such
as hip problems,
cataracts and certain
types of cancers.
Hybridization
Hybridization – breeders cross two genetically different
individuals. The hybrid organism that results is bred to have the
best traits from both parents. For example, a farmer might cross
corn that produces many kernels with corn that is resistant to
disease. The result is corn plants with both of the desired traits.
Today, most crops grown on farms and in gardens were produced
by hybridization.
Cloning
A clone is an
organism that is
identical to the
organism from
which it was
produced. This
means that a clone
has exactly the
same genes as the
organism from
which it was
produced.
Cloning Plants – A cutting is
one way to clone a plant. A
small stem or leaf is cut from
a plant and an entire new
plant will grow. The new
plant will be identical to the
plant is was cut from.
Cloning Animals – Dolly was
the first clone of an adult
mammal ever produced. To
create Dolly scientists followed
these steps:
• First – researcher removed
an egg cell from one sheep.
• Second – the cell’s nucleus
was replaced with the
nucleus from a six year old
sheep.
• Third – the egg was then
implanted into the uterus of
a third sheep.
Five months later Dolly was
born. Dolly was genetically
identical to the six year old
sheep that supplied the
nucleus.
Since Dolly, scientist have cloned
pigs and calves. Scientists hope
that cloning animals will help
humans live healthier lives. For
example, pigs that are being
cloned have genes the will make
their organs suitable for organ
transplant into humans.
Biotechnology
Biotechnology is the use of biological processes,
organisms, or systems to manufacture products intended
to improve the quality of human life.
A few examples of modern biotechnology are tissue
cultures, genetic engineering, recombinant DNA
techniques, mutagenesis, drugs, antibiotics, antibodies,
pesticide free crops, breeding , hybridization, and
cloning.
Bioethics
Bioethics is a group of principles that help people determine
what is right and what is wrong in biological and medical
investigations. When scientist conduct investigations they
follow these guidelines:
In the laboratory they must follow all safety instructions and
wear safety equipment.
In the field they must respect all living organisms, their
habitats and their environment.
During any testing with humans or animals, subjects should
not be harmed unnecessarily. Human test subjects should be
informed of possible consequences of the test before they
agree to take part. Lastly, all subjects should be treated
humanly.
Sexual and Asexual Reproduction
Sexual Reproduction - Reproduction that
involves two parents.
Asexual Reproduction – Reproduction that
involves one parent.
Reproduction of Bacteria
Bacteria – When bacteria are
living in the suitable conditions
(lots of food, stable
temperature) they can
reproduce every 20 minutes.
Binary Fission – (asexual) a type
of reproduction in which one cell
divides into two identical cells.
Conjugation – (sexual) one
bacterium transfers some of its
genetic material into another
bacterial cell through a thin,
thread-like bridge that joins the
two cells.
Conjugation results in bacteria
with a new combination of
genetic material.
Reproduction in Protist
 Protist also
reproduce through
binary fission
(asexual) and
multiple fission to
make more than
two offsprings
from one parent
 Conjugation
(sexual)are in
single cell
organisms.
Reproduction in Fungus
Sexual or Asexual
 Asexual Reproduction– 2
ways
1. The hyphae break apart and
each new piece becomes a
new fungus.
2. Production of spores - spores
are small reproductive cells
that are protected by a thick
cell wall. Spores are light
and can spread by the wind.
When conditions are right
the spore will grow into a
fungus.
 Sexual Reproduction –
happen when special
structures form to make sex
cells. The sex cells join to
produce sexual spores that
grow into new cells.
Hyphae are threadlike
filaments made of cells that
have openings that allow
cytoplasm to move freely
between cells.
Reproduction in Plants
Stamens the male
reproductive parts where
pollen is produced .
Pistils the female
reproductive parts . The
base of the pistil contains
ovary which has one or more
ovules.
First pollen falls on a stigma.
Next the sperm cell and the
egg cell join together in the
flower ovule. The zygote
develops into the embryo
part of the seed.
Reproduction in Animals
Invertebrates
Fragmentation - In this type of
reproduction, the body of the
parent breaks into distinct
pieces, each of which can
produce an offspring.
Planarians exhibit this type of
reproduction.
Regeneration - In regeneration,
if a piece of a parent is
detached, it can grow and
develop into a completely new
individual. Echinoderms exhibit
this type of reproduction.
(starfish, worms)
Budding – when part of an
organism breaks off and forms a
new organism (hydra, sponge)
Vertebrates
• Sexual Reproduction – Two
parents.
• Internal Reproduction – Egg
cell and sperm cell fertilize
inside the organism. ex,
humans, cats, dogs and
manatees.
• External Reproduction – Egg
cell and sperm fertilize
outside of the organism –
ex. amphibians and fish.
Advantages of Asexual and Sexual
Reproduction
Asexual
• Asexual reproduction does
not require any meeting of
two gametes which means
that it can reproduce many
individuals very quickly.
•
But with this it means that
there will be very little
variations in the offspring.
• Asexual reproduction
contain the identical
genetic information from
their parents as they are
essentially a clone.
• Less energy required for
reproduction.
Sexual
 With sexual reproduction
there are lots of variations
because they have a
different cell from each
parent.
 Sexual reproduction is very
slow.
 Purges the species of
mutations. Since most
mutations.
 Less population growth
 Requires long-term energy
use