Download DNA PPT

All about your DNA
Structure of DNA
 Every DNA molecule is made in a twisted ladder
shape called a “double helix”.
 The sides of the ladder are called the backbone of
the DNA molecule.
 The backbone is made up of alternating sugar
(ribose) and phosphate molecules.
 The rungs or steps of the DNA ladder are made
up of “nitrogen base pairs”
 Each rung is actually 2 individual molecules
connected in the middle.
 There are 4 possible nitrogen base molecules
that make the rungs of the ladder:
 Thymine
 Adenine
 Cytosine
 Guanine
 Thymine ALWAYS and ONLY bonds with
Adenine.
 Cytosine ALWAYS and ONLY bonds with
Guanine.
Nucleotides
 Nucleotides link together and form DNA.
 Nucleotide = One ribose (sugar), one
Phosphate, and one nitrogen base.
The DNA Hand Trick
 Palm = Sugar (Ribose)
 Thumb = (Phosphate)
 Fingers = Nitrogen Bases (A,T,C,G)
Genes
 90% of your DNA is never used for anything
that we know of.
 “Genes” are sections of the DNA code that
are actually used by the cell to create
proteins.
 Genes can be anywhere from 100’s to 1000’s of
base pairs long.
Chromosomes
 “Chromo” =
DNA
 “Some” = Body
 Chromosomes are coils of DNA that are
wound super tight and are X-shaped.
 Every human has 23 pairs of chromosomes46 in total. 23 from mom, 23 from dad.
Boys vs. Girls
 The only genetic difference between males and
females occurs on the 23rd chromosome pair.
 In boys, the 23rd pair do not match. One
chromosome- the “Y” chromosome- is much shorter
than the other. This “XY” combination makes the
person male.
 Females do not have the “Y”- they have two “regular”
shaped chromosomes (XX).
Boy
Girl
Making Boys and Girls
 Women have XX, so they can only give an X to
their offspring.
 Men have XY. They have an equal chance of
giving either an X or Y to their child.
 If a male gives an X, that would create XX (girl)
when combined with the mother’s X. If the
male donates Y, that means XY (boy).
Chromosome’s Jobs
 Chromosomes are giant clumps of DNA, so they
carry the critical instructions for life.
 Genes are located on chromosomes.
 Chromosomes are the way information is passed
from one generation to the next.
 Chromosomes are found in pairs- one from
mom, one from dad.
Other Organism Chromosome Totals
Fruit Fly: 8 Chromosomes
Pea Plant: 14 Chromosomes
Kangaroo: 12 Chromosomes
Algae: 148 Chromosomes
Dog: 78 Chromosomes
 1260 Chromosomes
(Highest for Plants)
 Wooly Mammoth (extinct): 58 Chromosomes
 Retrieved from frozen remains
Protein Synthesis
 Protein Synthesis = creating a protein by
reading DNA code
 This is how DNA code comes to life.
Unzipping?!
 The bonds in the middle of the “steps” of the
double helix can come apart.
 This is called “unzipping” and must happen for the
DNA code to be read.
Step 1
 The DNA never leaves the nucleus. Why?
 The DNA is very safe in the nucleus. Even very small
changes in the DNA molecule can be catastrophic.
 Step 1: DNA “unwinds” and “unzips” itself at a specific
gene.
Step 2
 A molecule called “RNA Polymerase”
attaches to the unzipped DNA and reads the
A, T, G, C code.
Step 3
 “Transcription- mRNA is created- a copy of
the DNA code that replaces Thymine with
Uracilto and can leave the nucleus.
 RNA is a single strand that
looks like a single twisted
ribbon
(a single; helix).
 RNA, for some reason, does
not use Thymine.
 Every place Thymine would be
used, RNA uses a similar
molecule called “Uracil”
instead.
Step 4
 mRNA Travels out of the nucleus and hooks
onto a ribosome.
Step 5
 Translation- The Ribosome reads the RNA and
creates the protein.
Step 6
 Amino acids are added to the Protein and is used by
the cell for a body process or to create a new
structure.
Protein Synthesis Flow Chart p. 28
On your
paper,
write the
title and
explain
how the
cell reads
the DNA
to make
protein.
DNA “unwinds” and “unzips” itself at a specific
gene
RNA attaches to the “unzipped” DNA
mRNA makes a transcription of the DNA code
replacing Thymine with Uracil
mRNA travels out of the nucleus and hooks onto
a Ribosome
tRNA takes the mRNA to the ribosome. The
Ribosome reads the RNA code through
translation and creates a protein
Amino Acids are added to the protein. The
protein is used by the cell for a body process
Protein Synthesis p. 28
Determining Sex
 The gender of a person is determined by the passing down of the
“sex chromosomes” from parents to offspring.
• Since females
have two X’s, they
can ONLY pass
down an X to their
offspring.
• Males have an X
and Y chromosome,
so they can pass
either X or Y to their
offspring.
Sex-Linked Traits
 The X and Y chromosomes have genes on them, just like
all the other chromosomes.
 The traits controlled by genes on these X or Y sex
chromosomes are called sex-linked.
 Some diseases are sex linked, such as hemophilia.
 Ex: All the physical and chemical differences that make
someone a male are sex-linked traits because they are passed
down on the Y chromosome. .
 hemophilacs
Mutations
 Any abnormal change in an organisms’ DNA.
Examples
 If the nitrogen bases aren’t kept exactly the same, large problems or changes
occur.
 If a letter simply disappears, this mutation is called a “deletion”. This is very
bad.
 If one letter accidentally switches to a different letter, it is called
“substitution”.
 If extra letters are added to the code, it is called an “addition” mutation.
 All mutations on active genes can cause changes/problems in the organism.
i.e.. Blue eye mutation, 6 fingers, 3 nipples, etc.