DNA (Deoxyribo Nucleic acid) - Molecules that carry genetic ...

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23 Οκτ 2013 (πριν από 3 χρόνια και 5 μήνες)

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The Living Environment

Unit 3
Genetic Continuity


HEREDITY


The passing of genetic information to offspring through reproduction
.



*
GENES



Genetic instructions passed onto offspring that determines traits and characteristics
.

ALL living
things pass their genetic characteristics to their offspring.


GENES
contain the instructions to make different types of proteins, which are the building

blocks of all cells and organisms.

*
Allele



different types of a specific gene.
(ex) Blue eyes al
lele vs. Brown eyes allele.


*
DNA
(Deoxyribo Nucleic acid)
-

Molecules that carry genetic information.


CHROMOSOMES



Pairs of tightly wound packets of DNA located in the nucleus of
every cell
.


(Ex) Humans
-

46 chromosomes (23 pairs)






Fly
-

6 chromosomes (3 pairs)






Carp Fish


104 chromosomes (52 pairs)


METHODS OF REPRODUCTION


Asexual Reproduction



ONE parent produces an identical offspring (
Clone
).


* An
exact genetic copy of itself
. (ex) Bacteria


Sexual Reproduction



TWO parents produce sex cells that carry genetic information of each parent


to create an offspring.



Genetic Recombination


When sperm & egg co
mbine to form a unique organism.

(ex) In Humans
-

Sperm


23 chromosomes Egg


23 chromosomes = Offspring 46 chromosomes















Between two parents, there is a possibility of 16,777,216 variations of offspring (

2
23
)


THE GENETIC CODE

The G
enetic code of all organisms is chemically held in its DNA.


THE STRUCTURE OF DNA



Pg 41 fig 3
-
2

Double Helix



Twisted ladder shape
.




Rails

or sides are a
Sugar / Phosphate



Rungs

or steps are
Bases A
-

T

(Adenine


Thymine)





C
-

G

( Cytosine


Guanine

)


Pg 42 fig 3
-
3


Subunits



Consists of a Sugar, a Phosphate and a base Pair


Base Sequences



are coded messages for a specific gene trait
. (ex) A T

Code for an entire Humans can have 3 billion bases !


G C

PAIRING RULES

-

A always goes with T C G


G always goes with C T A

May determine Eye Color








DNA REPLICATION

pg. 42 fig 3
-
4


Involves the production of identical copies of
DNA to pass genetic information to offspring
.


1)

The bases of DNA are held together by weak chemical bonds

2)

Special enzymes break these bonds (unzipping them apart) into 2 strands

3)

Both strands pair up with free
-
floating bases following A
-
T & C
-
G pairing rules
.

4)

Two identical DNA sequence copies are formed.







PROTEINS and CELL FUNCTIONING

Proteins


are formed by 20 kinds of amino acids in a
specific sequence
.

* The sequence of amino acids determines its
shape, which

then determines the protein’s
function.


(ex) Proteins can be hormones, enzymes, antibodies or different types of organs
.


PROTEINS DO MOST OF THE WORK IN CELLS



PROTEIN SYNTHESIS (Creation)

Ribosomes



Cell organelles that make different types of proteins using instructions from DNA.


1)

Specia
l enzyme molecules read DNA instructions in cell nucleus.

2)

Special enzymes create a “messenger molecule”,
RNA
, to carry
instructions

to Ribosome.

3)

The
RNA

carries the
instructions

through the cytoplasm to the Ribosome.

4)

Transfer molecules

gather up
amino acid
s
in cytoplasm and
deliver them

to Ribosome.

5)

Ribosome
assembles the protein

molecule using
delivered A Acids

and following
RNA instructions
.


Mutations



Any change in the DNA sequence which changes the genetic instructions, thereby causing



incorrect protein assembly.


*
Substitution


Changing the base *
Deletion



removing a base


*
Addition



adding a base

*
Inversion



Reversing a base sequence


Mutated cells that don’t die can cause disease or deformities.

Only muta
tions found in sex cells can be passed onto offspring.


DNA & INDIVIDUALITY
-

Every cell of an organism has a COMPLETE set of genetic instructions to


make an ENTIRE & EXACT organism. (Clone)


* Cells are different because only SOME of th
e entire genetic instructions become activated.


Genetic Activation can be Hormonal (ex) Puberty or Environmental (ex) Temperature change (Pg 46 fig 3
-
8

Genetic Expression
-

When

a genetic trait or characteristic

is

revealed

by hormones or environmental
conditions


Genetic Engineering



deliberately altering the genetic instructions in an organism.


Biotechnology



Applying technology to biological sciences (ex) Bread / Cheese


Adding microbes like yeast.


Selective Breeding



choosing to breed certain

plants and animals for desired traits (ex) Chicken / Cattle for less fat







Plants


naturally resistant to disease


GENE MANIPULATION


using genetic engineering to produce better plants and animals


(ex) Plants containing gen
es that make chemicals harmful to insects but are harmless to humans.


Organisms like Bacteria that eat oil spills or that make insulin for diabetics.


How Genes are manipulated



Special enzymes are used to cut and splice specific
DNA gene segments to be attached to


a new organism.
Pg 47 Fig 3
-
9



Transplanted genes direct organism to make specific desired proteins that were made by original donor organism.


APPLICATIONS OF BIOTECHNOLOGY




By decoding the genes th
at cause disease, we can alter the sequence mutation and cure the disease.


Medicines can be made more effective.


Creating purer forms of missing chemicals is cheaper and safer than extracting chemicals from other organisms