Download Genetics

Genetics
OB1: Explain how characteristics of living things are
passed on from generation to generation.
Characteristics of
living things are
passed on from
generation to
generation by an
organism’s genes.
Every species has its own characteristic DNA sequence.
Of all of the cats in the world, Cinnamon The genetic complement (or genome) of
was chosen to be the definitive genetic
the pig is comprised of 18 pairs of
model for all cats in a project called the
chromosomes plus the X and Y (sex)
feline genome project.
chromosomes.
OB5: Students will explain and describe dominant and recessive traits,
DNA (genetic material), gene pair, gene combination, and gene sorting.
Students will describe how genetic material is passed from parent to
young during sexual and asexual reproduction.
*Since chromosomes come in pairs (GENE PAIR), there
exist two open slots for each gene. (One from each parent)
*Sometimes there are two or more forms of the gene, called
alleles, for a particular trait. Often there is a dominant and
a recessive gene like the tall (TT or Tt) and short (tt) pea
plants Mendel studied. (Tt or TT or tt are all GENE
COMBINATIONS)
*A DOMINANT gene masks or cancels out the effects of
a recessive gene, even if the recessive gene is present.
*A RECESSIVE gene is only expressed when present
with another recessive gene
A Punnett square is often used to show how alleles
segregate (sort) from an individual when their gametes
(sperm & eggs or pollen grains and ova) form.
Gametes only
have one of the
two possible
alleles. It is
totally random
which ones the
gamete gets.
*The above cross shows the possible combinations by crossing two
parents that are HETEROZYGOUS for a particular trait.
Note that three of the offspring will show the dominant trait, while
only one will show the recessive one.
*A co-dominant trait is one where both alleles are
expressed on the same organism at the same time.
-Human blood type is a co-dominant trait
-Speckled feathers in chickens is another
-”Rainbow” coloration in boas is another
*A polygenic trait is one where more than one gene
determines its expression.
-Most human traits are polygenic, like skin, hair and
eye color, and body height. These traits show a
continuous gradation in their expression.
*A sex-linked trait is one where the gene is on one of the
sex chromosomes, usually the X chromosome.
In humans, since males are XY and females are XX, males
have only one chance at each of the genes that happen to
be on the X chromosome.
The Y is not homologous; it does not have the same genes
that the X does. If a male gets a bad gene (from his
mother), then he’s stuck with it. He doesn’t have a
backup like females do.
Homologous chromosomes are a pair of
chromosomes, one inherited from each parent, that
have corresponding gene sequences and that pair
during meiosis.
OB2: Explain the structure and function of the DNA molecule.
DNA is the material that stores and
transmits the genetic information from one
generation of an organism to the next.
*DNA forms a double helix…Its two strands
spiral around each other. It resembles a
twisted ladder. Sugar-phosphate backbones
form the sides of the ladder, and the
nitrogenous bases form the rungs.
(see figure 12-7)
The nitrogenous bases on each strand pair up exactly
opposite with each other: BASE PAIRING:
*Hydrogen bonds form, holding the strands
together
*Adenine pairs only with thymine
*Cytosine pairs only with guanine
A-T
T-A
C-G
G-C
OB7: Students will explain and describe DNA replication.
*Before a cell can divide, it
must duplicate its DNA
*Enzymes do the work
*The original strand unzips
*Base pairs separate at the
hydrogen bonds
*Each original strand becomes a
template
*Each complementary strand
forms along the template by base
pairing
*Two identical DNA molecules
are the result
OB3: Outline and explain the central dogma of genetics.
*DNA stays in the nucleus, but protein is made out in the
cytoplasm by the ribosomes…
*Messenger RNA is made in the nucleus using a section
of DNA as a template. This is called TRANSCRIPTION.
*The segment of DNA that codes for a needed protein
unzips, revealing open bases. Complementary bases of
mRNA form on the DNA strand, then are moved off by
an enzyme RNA polymerase.
*RNA is single stranded, but it obeys the same base
pairing rules as DNA (substitute Uracil in place of
Thymine)
*mRNA goes to the ribosome and acts as a template
for protein synthesis.
*TRANSFER RNA brings specific amino acids to
the ribosome to be hooked on. Every three letters of
the mRNA is a code for one of about twenty different
amino acids and is therefore called a CODON.
*The “feet” of the tRNA that match the CODON are
called the ANTI-CODON sequence. Each anticodon carries its own specific amino acid. This
process is called TRANSLATION.
*There are start and stop sequences built in too.
*The new protein then may travel to the Golgi body
for further modification and packaging.
*Characteristics of living things are called
TRAITS.
*Since the body is put together with and works
chemically by proteins, the action of one or
more proteins determines traits in living
things.
*A GENE is a sequence of DNA that eventually
codes for a protein that determines or helps
determine a trait.
*This process is virtually the same in all living
things.
OB4: List and give examples of the main types of human proteins.
Basic Types of Proteins:
1. Proteins that are structural:
-keratins of fingernails, skin, hair
-collagens of connective tissue
-lipoproteins of cell membrane systems
2. Proteins that are hormones, such as insulin
3. Proteins that transport oxygen (hemoglobin)
4. Proteins that make up chromosomes, such as histones
5. Proteins that are organic catalysts or ENZYMES
*Since there are an estimated 22,000+ proteins in the
human body alone, it can be said that the functions of
proteins are at the very center of life itself!
PROTEINS
Protein complex from a dinoflagellate…it
makes light! (Bioluminescence)
*Asexual reproduction involves a cell splitting in
half by mitosis (previous chapter).
*Other forms of growth can also be considered
asexual, like a strawberry plant sending out
runners to start new plants, or a starfish or a
worm breaking apart to become several new
individuals (each genetically identical to the
original).
*Asexual reproduction results in identical
offspring genetically--the only changes come from
mutations
OB6: Students will explain and describe the purpose of
meiosis. Students will explain and describe genetic variation,
and the results of new gene combinations.
*Meiosis is the special type of cell division that produces
gametes (sex cells)
*Meiosis takes the maternal and paternal alleles of the
individual and gives them a random shuffle.
*This means an organism’s gametes are actually a new,
totally unique combination of that individual’s own
parents!
*Chromosomes come in pairs-here parts of each pair are seen
swapping pieces during meiosis--this is called CROSSING OVER
Here is a
diagram of all
the possible
combinations of
gamete
chromosomes
from crossing
over during
meiosis with
only three
chromosomes…
With 23
chromosomes in
humans, there
would be well
over 8 million
possibilities...
OB8: Students will explain and describe the
structure and function of chromosomes and how
they are duplicated through mitosis.
*Coil DNA up around
protein (histones) before
cell division and you’ve got
chromosomes
*As you recall,
chromosomes are
important in cell division
Organisms grow
not by making
their cells bigger,
but by making
more cells.
This process is
called cell
division, or
mitosis.
You must know
the four phases.
Through
mitosis cells
can specialize.
Genetic
controls tell
stem cells to
specialize
into different
tissues.
Family members who have adopted frozen embryo babies applaud
President Bush as he makes remarks on embryonic stem cell research in
the East Room of the White House in Washington, on 19 July 2006.
(Image: AP Photo/Ron Edmonds)
And then….
Still going……….
And going…………..
OB9: Students will explain how new traits may
arise in individuals through changes in genetic
material (DNA) through mutation.
*A mutation is a mistake in duplicating genetic
information and/or in transmitting it to the next
generation.
*Mutations may occur in any cell.
*Mutations in reproductive cells (“germ cells”) are GERM
MUTATIONS. These may be inherited even if the new
trait is not expressed in the parent.
*Mutations in all other body cells are called SOMATIC
MUTATIONS. Since body cells produce only more body
cells, the mutation is not inheritable.
Many cancers are caused by somatic mutations.
*Mutations can be INSERTIONS or DELETIONS,
where a DNA base is inserted into or taken away from a
DNA strand. This causes a “frameshift mutation”.
Try to read the following:
THF ATC ATA TET HER AT
Now try it with the missing base put back in:
THE FAT CAT ATE THE RAT
Since DNA is read three letters at a time, the result of
inserting or deleting a base are seen all down the line.
A mutation may also be a SUBSTITUTION where one
base is accidentally replaced with a different one.
This may or may not cause harm to the organism. If the
mutation changes the amino acid sequence, it may make
the resulting protein inactive and useless.
Sickle Cell Anemia is caused by a point mutation in one
of the genes that codes for part of the blood protein
hemoglobin.
OB10: Students will explain and describe natural
and human produced sources of mutation.
*Mutations may occur naturally and completely at random.
*Mutations may also be caused by radiation or by
chemical agents.
*Mutations are a major source of variation in all speciesthe trick is getting one that is beneficial and not deadly.
*Scientists actually try to induce mutations in a variety of
plants, animals, and bacteria to obtain, at random, desired
traits.
*Increasing mutations by any means increases the risk of
cancer developing.
OB11: Students will explain and describe products
of genetic engineering.
*Genetic engineering involves cutting useful genes out of
one species, and splicing them into the genes of another
species.
Usually involving bacteria, viruses, and plants, the
possibilities of genetic engineering (both good and
disastrous) are unlimited.
*Disease & drought resistant plants & faster growing
*Medicines for animals & humans
*Faster growing salmon for fish farms (inserted flounder genes)
*Roundup resistant soybeans (produced by Monsanto)
*Longer lasting tomatoes & other fruits & veggies
*Medical advances using cloning & stem cells