Big Idea 16 : Heredity and Reproduction

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14 Δεκ 2012 (πριν από 4 χρόνια και 11 μήνες)

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Big Idea 16: Heredity and
Reproduction

Description



A. Reproduction is characteristic of living things and
is essential for the survival of species.

B. Genetic information is passed from generation to
generation by DNA; DNA controls the traits of an
organism.

C. Changes in the DNA of an organism can cause
changes in traits, and manipulation of DNA in
organisms has led to genetically modified organisms.


Benchmark Number

&
Descriptor



SC.7.L.16.1


Understand and explain that every organism requires a set of
instructions that specifies its traits, that this hereditary information
(DNA) contains genes located in the chromosomes of each cell, and
that heredity is the passage of these instructions from one generation
to another.


SC.7.L.16.2


Determine the probabilities for genotype and phenotype
combinations using Punnett Squares and pedigrees.


SC.7.L.16.3


Compare and contrast the general processes of sexual reproduction
requiring meiosis and asexual reproduction requiring mitosis.


SC.7.L.16.4


Recognize and explore the impact of biotechnology (cloning, genetic
engineering, artificial selection) on the individual, society and the
environment.


WHO ARE YOU?

DNA


DNA =
Deoxyribonucleic Acid


Traits which are
passed from parents
to offspring are carried
in DNA.


DNA is a blueprint for
the cells in an
organism.


Without DNA, an
organisms traits would
never form.




DIRECTIONS

GENES


Pieces of DNA


Carry traits


Characteristics


Help pass traits from parent
to offspring


You inherit your genes.


Offspring receive only some
genes from parents.


Genes combine differently,
so you look different.

CHROMOSOMES


Genes are located on
chromosomes.


Thousands of genes can be
found on a single
chromosome.


Chromosomes are found in
the nucleus of the cells.


Each type of organism
contains a set number of
chromosomes.


Humans = 23 Pairs

PUTTING IT
ALL
TOGETHER

KNOWLEDGE CHECK


1.
What does DNA stand for?


2.
Where is DNA located?


3.
Why is DNA important?




KNOWLEDGE CHECK

1.
What does DNA stand for?
Deoxyribonucleic Acid



2.
Where is DNA located?

DNA is
located on genes which are carried by
chromosomes.


3.
Why is DNA important?
It’s the
blueprint for how organisms are
made.




WHY DON’T WE
LOOK ALIKE?

What
is
Heredity
?


Heredity

is the
passing on
of characteristics (traits)
from parents to
offspring.


Genetics

is the study of
heredity.

Gregor Mendel



WHO:


Austrian monk



WHAT:


Worked with pea

plants and discovered how traits get
passed from generation to generation



WHEN:


Around 1856

PASSING OF TRAITS


Each gene contains 2 ALLELES


1 allele from mom


1 allele from dad


Individual alleles are represented by an upper or
lowercase letter.


Some alleles are dominant, and others are
recessive.


BLUE = allele

RED = allele


together =
gene

TRAITS

TYPES OF TRAITS



The trait that is observed in
the offspring is the


DOMINANT TRAIT


(uppercase).


It only takes one dominant allele for
that trait to be shown.



The trait that disappears in
the offspring is the


RECESSIVE TRAIT


(lowercase).


It takes 2 recessive alleles for that
trait to be shown.


LETTER COMBINATIONS



Heterozygous

-

if the
two alleles for a trait
are different (Aa)


Also referred to as a
hybrid combination



Homozygous

-

if the two
alleles for a trait are
the same (AA or aa)


Also referred to as a
purebred combination


TRAITS

GENOTYPE


Refers to the letter (allele)
combination


TT, Tt. tt


If a capital letter is present in
the letter pair, the dominant
trait will be expressed in that
organism.


If 2 lower case letters are
paired, the recessive trait will
be expressed in that organism.



PHENOTYPE


Refers to the physical
characteristic being
expressed


Uses words/phrases to
describe not letters


Examples:


tall, short


white, black

PUNNETT SQUARES




Tool used to determine
characteristics of offspring


Each box represents the
probability of an offspring
receiving a trait.


Example:


Top outside (Tt) is a
gene passed on by the
father


Left outside (tt) is a
gene passed on by the
mother.


4 middle boxes are
possible gene
combinations an
offspring may receive.


T

t

T

t

Tt

Tt

Tt

Tt

T = Tall

t = Short

All offsprings will be tall (all
boxes contain the dominant
trait for tallness).

PUNNETT SQUARES


Short hair (L) is
dominant to long
hair (l) in mice.
What is the
genotype and
phenotype ratio of a
heterozygous short
-
haired mouse
crossed with a long
-
haired mouse?




Punnett Square:



L l



l


l



Genotype ratio: ½ Ll:
½ ll


Phenotype ratio: ½
short hair: ½ long hair


Ll

ll

Ll

ll

PEDIGREE


A chart used to trace
traits throughout a
family


Parts of the chart


Circle = females


Squares = males


Half
-
filled in/Dotted =
carrier


Have the gene but do
not show signs of it


Filled
-
in = affected


Have both the gene
and symptoms of that
trait


KNOWLEDGE CHECK


1.
What do we call the
trait that is
observed?

2.
What case (upper or
lower) is it written
in?

3.
What about the one
that disappears?

4.
What case is it
written in?



Trait Tall = Aa


Trait short = aa


Aa x aa

5. Complete the
Punnett


Square.



____

____

____

____

KNOWLEDGE CHECK

1.
What do we call the
trait that is
observed?

Dominant

2.
What case (
upper

or
lower) is it written
in?
Upper

3.
What about the one
that disappears?
Recessive

4.
What case is it
written in?

Lower



Trait Tall = Aa


Trait short = aa


Aa x aa

5. Complete the
Punnett

Square.



__A_

__a_

_a__

Aa

aa

_a__

Aa

aa

HOW DO WE GET
ALL THIS STUFF?

REPRODUCTION

SEXUAL


Primary method of
reproduction for the vast
majority of visible organisms,
including almost all animals
and plants



Characterized by two
processes:


meiosis, halving of the
number of chromosomes


fertilization, combination of
two gametes and the
restoration of the original
number of chromosomes


Results in increasing genetic
diversity of the offspring.


ASEXUAL


A form of reproduction
which does not involve
meiosis or fertilization


Asexual reproduction = one
parent.


The primary form of
reproduction for single
-
celled organisms such as
archaea, bacteria, and
protists


Mitosis is the main way of
reproduction.


REPRODUCTION

ASEXUAL


MITOSIS


All forms of asexual
reproduction utilize the
process of mitosis.


Begins with one

replication
(copying of the chromosome
material) and one division of
the chromosome material




This results is 2 daughter cells
being produced with the same
number of and identical
chromosomes as in the parent
cell.

Asexual reproduction in
liverworts: a caducuous
phylloid germinating

Mitosis


Interphase


Normal functions


Upon trigger,
chromosomes &
centrioles

duplicate.


Prophase


Early: nuclear envelope
degrades;
chromosomes
start to
condense.


Late: chromosomes
thicken;
spindle forms
between centrioles


Metaphase


Spindle fibers attach to
kinetochores
.


Chromosomes line up at
cell
equator.



sdst.org
/
shs
/
apbio
/
...

/
mitosis

powerpoint
.ppt

Mitosis


Anaphase


Chromatids separate at
centromeres


Chromosomes move to
poles.


Telophase


Nuclear envelope
reforms in each of two
daughter
cells.


Cytokinesis separates
two new
cells.


Interphase


Daughter cells are
genetically identical to
each other and the
parent
cell
but
smaller.


sdst.org
/
shs
/
apbio
/
...

/
mitosis

powerpoint
.ppt

REPRODUCTION

SEXUAL


MEIOSIS


Process produces the sex
cells


Contain ½ the chromosomes
as the parent



Since ½ male chromosomes
and ½ female chromosomes
combine = genetic variety


Hoverflies mating in midair
flight.

MEIOSIS


Prophase I
: the chromosomes
condense and homologous
chromosomes pair up to form
tetrads.


Metaphase I
: the tetrads are
all arranged at the metaphase
plate.


Anaphase I
: the homologous

chromosomes separate and

are pulled toward opposite
poles.


Telophase I
: movement of
homologous chromosomes
continues until there is a
haploid set at each pole.


Cytokinesis

: by the same

mechanisms as mitosis

usually occurs simultaneously



Prophase 2
: spindle reforms
and chromosomes move
toward the metaphase plate.


Metaphase 2
: sister
chromatids lined up on the


metaphase plate.


Anaphase 2
: sister chromatids
are separated and pulled
toward opposite poles of the
cell.


Telophase 2 and
Cytokinesis
: nuclei form at


either pole, and each cell is
finally divided into two identical
daughter cells.


MEIOSIS


Mitosis vs. Meiosis

REPRODUCTION

SEXUAL


EXAMPLES:


Sexual Reproduction


DNA from 2 individuals merge
to form one.


Animals, plants



Fertilization


Pollen is delivered to female
part of plant.


Flowering plants



ASEXUAL


EXAMPLES:


Fragmentation/Regeneration


Body of parent breaks and
produces offspring.


Fungi, moss, sea stars,
planarian



Budding


Offspring grows out of parent.


Yeast, hydras


KNOWLEDGE CHECK

1.
Label each of the following as either Asexual or
Sexual reproduction:


Spores budding


Nearly all organisms reproduce this way


Mitosis


Meiosis


Starfish is cut in half; both halves grow into a
whole starfish.


One parent needed


Not identical to parents


Two parents needed


Identical to parent


Sperm and eggs


KNOWLEDGE CHECK

ASEXUAL


SEXUAL


Spores budding


Mitosis


Starfish is cut in half; both
halves grow into a whole
starfish.


Identical to parent


One parent needed



Not identical to parents


Two parents needed


Sperm and eggs


Meiosis


Nearly all organisms
reproduce this way.

SHOULD WE MESS
WITH MOTHER
NATURE?

MAKING IT JUST RIGHT

SELECTIVE
BREEDING


The process of using
specific plants or animals
with specific traits to
reproduce offspring with
those traits


These
breeded

plants/animals can be:


Larger in size


Provide more food


Resistant to disease

HYBRIDIZATION


The process of crossing to
plants/animals with different
variations of the same trait


The resulting offspring is
created to have the best
traits of the parents.


Examples:


Corn: farmers each year try to
grow corn that are disease
free and higher quality.


Animals: if 2 different species
are bred, a stronger but sterile
species may be produced

MAKING IT JUST
RIGHT




Involves using two plants/animals that have the same or
similar genes.


The offspring produced will be purebred.


If purebreds are created, specific genes can be passed along.


Inbreeding, though, can cause a population to die.


Since they are genetically similar, if one animal/plant
comes down with a disease, the entire population may
have it.


INBREEDING

BREEDING EXAMPLES

Due to inbreeding, all
cheetahs are closely
related.

Miniature Horse
was specifically
bred small to work
in mines.

Disease
resistance,
greater
nutritional value

Mule combines the
best traits of a horse
and a donkey.

GENETIC ENGINEERING


Processes in which genes with specific DNA
strands are removed and transferred into another
organism.


This process is much faster then altering organisms
through breeding techniques.



Genetic engineering is used in biotechnology,
medicine, and cloning.

GENETIC ENGINEERING

BIOTECHNOLOGY


Involves growing cells for
industrial purposes


Agriculture:


Many plants and crops are
susceptible to disease.


Scientists have been able to
isolate fighting genes and
insert them into plants/crops
for better survival rates.

GENETIC MODIFICATION


Genetic engineering produces
a lot of strong feelings among
people.


PROS:


Crops and farm animals may be
produced to better tolerate
drought, disease, and infestations,
therefore increasing the food
production around the world.


CONS:


Many people are concerned
about mixing genetic material with
different species.


Once in the wild, the effects of
changes are out of the scientists
hands.

GENETIC ENGINEERING

MEDICINES


Insulin has been able to be
created through Genetic
engineering.


Insulin was once made from
animals, but people were allergic
to it. Now it is created from
bacteria with no allergies and is
less expensive.


Vaccines have been able to be
produced through Genetic
engineering.


Vaccines such as Hepatitis B are
now less expensive to produce
and can be made in mass
production.



CLONING


Clones are living things that
have exactly the same
genes.


Agriculture has done this
forever:


Taking clippings of plants and
replanting them


The cuttings grow into new
and identical plants.


Humans and animals,
however, become more
controversial:


Is it ok to clone spare body
parts?


GENETIC ENGINEERING

GENE THERAPY


Faulty genes inside a
human bodies can be
replaced with normal,
healthy ones


Unfortunately, most cells in
our body only live for a short
period of time.


The new cells with the new
genes can function for a short
period of time.


WHAT WOULD YOU
DO?


The more we know about DNA
and genes, the more we may
be able to predict our future.


People today can be screened
for certain genetic conditions.


For example


If a person is found to be a
carrier of a specific gene
defect, he/she will need to
make a choice if he/she are to
have kids.


Perhaps you carry a gene for
cancer which may or may not
turn on. What would you do?

KNOWLEDGE CHECK

1.
Name three types of breeding and a
reason why they are used.


2.
What is Genetic engineering?


3.
Why is Genetic engineering supported
by some yet forbidden by others?

KNOWLEDGE CHECK

1.
Name three types of breeding and a reason why they are
used.
Selective breeding, hybridization, inbreeding. All 3 can
be used to make specific higher yielding crops. Crops less
vulnerable to disease and animals for specified jobs


2.
What is Genetic engineering?
Processes in which genes with
specific DNA strands are removed and transferred into
another organism.


3.
Why is Genetic engineering supported by some yet forbidden
by others?
Supported = create medicines and cells for
people to survive




Forbidden = Messing with mother nature. Do not
have control if changes were to get into the wild