Transcript DNA - Trinity Regional School

Everything there is to know
about DNA
Mitosis
Meiosis
RNA synthesis
Genetic engineering
Mendelian genetics
Mitosis = cell cycle
a. Process through which a body
cell replicates itself.
b. Process produces two NEW body
cells.
c. Cells must be identical to each
other.
d. Process takes place continuously,
at the rate of once every 24 hours
Mitosis is controlled by the codes
found on DNA. DNA is found on
chromosomes.
There are many interchangeable
terms that are used to talk about
genetic codes.
DNA = DEOXYRIBOSE NUCLEIC ACID
CHROMOSOMES = GENERIC TERM TO MEAN
THE CODES FOUND ON DNA.
Prokaryotes-circular Eukaryotes-linear
CHROMATIN =TWO STRANDS OF A
CHROMOSOME
CHROMATID
CENTROMERE
CHROMATIN= A PAIR OF CHROMATID
MITOSIS involves 6 steps.
1. Interphase – longest phase
“resting” phase
cell matures
organelles develop
process begins:
nuclear membrane breaks
down
DNA duplicates
organelles replicate
DNA DUPLICATION
DNA is composed of: phosphate groups –PO3
ribose group
nitrogen bases:
thiamine
adenine
guanine
cytosine
thiamine always bonds with adenine
guanine always bonds with cytosine
PHOSPHATE
TA
nucleotide
AT
GC
RIBOSE
CG
polypeptide
CG
AT
TA
T A
A T
G C
C G
C G
A T
T A
T A
T A
AT
GC
AT
GC
C G
C G
C G
C G
A T
A T
T A
T A
2. Prophase – chromatin become visible
centrioles appear
spindle fibers appear
chromatid begin to move
3. Metaphase – chromatid line up along
equator of cell
prepare to separate
4. Anaphase – chromatid pair separates
I
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P
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M
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E
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A
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A
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T
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K
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There are now two new
cells that are identical
to each other.
They contain the ribosomes
and mitochondria made
during interphase.
The cells will now begin the
process of producing the
organelles that are not yet
present in the cell, like …
When all the organelles are
present, the cell will enter
interphase and the process
will begin all over again.
I
N
T
E
R
P
H
A
S
E
Meiosis
Reduction Division
Meiosis is the process by which gametes are
coded with inheritable traits.
Remember: for every genetic trait, an organism
must inherit 2 alleles - one from the father and
one from the mother.
In sexual reproduction, an offspring is the result
of the union of two cells - an egg and a sperm.
These two cells are called gametes. Each gamete
contains one allele for each inheritable trait.
Mitosis: production of body cells
one duplication of DNA
one cell division
resulting cell contains all the DNA
of the parent cell - diploid
resulting cell contains both
alleles for each trait
human cell: 46 chromosomes
23 pairs = 2 alleles for each
trait
diploid number
Meiosis: production of gametes
one duplication of DNA
two cell divisions
resulting cell contains half the
DNA of the parent – haploid
resulting cell contains one allele
for each trait.
Gamete = sperm/egg 23 chromosomes
1 allele for each trait
haploid number
23
Egg
Haploid #
One allele
23
46
sperm
haploid #
one allele
offspring
diploid #
two alleles
46
92
46
46
23
23
23
23
4 gametes each with the haploid number
Egg - haploid
Sperm - haploid
b
Diploid
W
d
Eye color Bb heterozygoous
Hair color RR homozygous dominant
Dimples dd homozygous recessive
Widow’s peak Ww heterozygous
Offspring
B
B
B
BB
BB
b
Bb
Bb
R
R
r
Rr
Rr
r
Rr
Rr
RNA and PROTEIN
SYNTHESIS
There are two types of nucleic acids:
1. DNA
2. RNA
Let’s review a few terms:
Protein:
structure: long chain of C,H, O, N, and S
Amino acid: building blocks of proteins
structure: made up of 3 nitrogen bases
function: necessary for cellular growth and repair
large covalent molecules
produced in the ribosomes
enzymes-speed up chemical reactions.
Enzymes-specific for compounds they digest.
Without these enzymes, the matching
compounds will not be digested or broken down.
Because these enzymes are specific there must
be a code for their production.
Lactase - lactose.
Amylase - simple starches
Pepsin - food proteins
RNA will provide the code for protein
synthesis. Each protein performs a specific
function and therefore requires a specific
code.
This code will come from DNA.
DNA:
A
T
C
G
G
C
A
T
T
A
G
C
DNA code is found in the …..
Proteins are made in the ……
DNA:
A
T
C
G
G
C
A
T
T
A
G
C
DNA:
mRNA
A
A
T
C
C
G
G
G
C
A
A
T
T
U
A
G
G
C
DNA:
mRNA
A
C
G
A
T
G
tRNA
U
G
C
U
A
C
DNA:
mRNA
A
C
G
A
T
G
tRNA
U
G
C
U
A
C
Ribosomal RNA or rRNA now has the
Code it needs to make specific
Proteins needed by the organism.
The code for this rRNA is ACGAUG. Each
Letter stands for a nitrogen base. The
Ribosome will ‘read’ the nitrogen bases
In groups of three. Every three nitrogen
Bases = an amino acid. Several amino
Acids grouped together = a protein.
ACG = amino acid = threonine
AUG = amino acid = methionine
Mendellian genetics
Gregor Mendel
The father of genetics
Monk
Gardener
Heredity - process through which traits are passed on from
one generation to another.
Trait – any visible or invisible characteristic, function, or
process that is a necessary part of an organism.
Gene –structure that contains the code for every trait.
DNA
Allele – particular form of a trait. There are at least two
alleles for every trait:
one dominant
one recessive
Dominant – the allele for a trait that is ALWAYS seen
in the organism.
Recessive – the allele for a trait that can be masked by
the dominant trait.
Every chromosome (2 chromatids) will be composed
Of two alleles!
Allele 1 and allele 2
are carrying the
codes for the same
trait. One allele
comes from the
mother, the other
from the father.
Allele 1
Allele 2
chromatid
Dominant – the allele for a trait that is ALWAYS seen
in the organism.
Recessive – the allele for a trait that can be masked by
the dominant trait.
Every chromosome (2 chromatids) will be composed
Of two alleles!
Allele 1 and allele 2
are carrying the
codes for the same
trait. One allele
comes from the
mother, the other
from the father.
Allele 1
Allele 2
chromatid
Combinations of alleles result in what an offspring
inherits. And what an offspring inherits determines
what the offspring looks like and how that offspring
functions.
POSSIBLE COMBINATIONS:
B
B
b
b
B
b
HOMOZYGOUS
HETEROZYGOUS
COMBINATIONS OF ALLELES WILL DETERMINE
WHAT THE OFFSPRING LOOKS LIKE =
PHENOTYPE.
COMBINATIONS OF ALLELES WILL DETERMINE THE
WAY AN OFFSPRING FUNCTIONS, I.E. ITS CODE=
GENOTYPE.
THERE ARE THREE TYPES OF GENOTYPE:
HOMOZYGOUS DOMINANT
HOMOZYGOUS RECESSIVE
HETEROZYGOUS
Homozygous dominant
Gene carries two dominant alleles
for any trait
Phenotype: red flower
Genotype: RR (purebred)
Homozygous recessive
Gene carries two recessive alleles
for any trait.
Phenotype: white flower
Genotype: rr (purebred)
Heterozygous
Gene carries one recessive
allele and one dominant
allele
Phenotype: red flower
Genotype: Rr
(hybrid)
Heredity and genetics are processes that
involve chance=probability-the chance
of something happening.
Traits are inherited by the passing on of
two alleles-either dominant or recessive
or both.
This inheritance and chance are
predicted by using punnett squares.
Punnet square--used to predict possible
genotype of an offspring when the
genotype of the parents is known. Once
genotype is known, the phenotype will
father
be decided.
25%
Chance of
an offspring
25%
Chance of
an offspring
25%
Chance of
an offspring
25%
Chance of
an offspring
mother
Mother :
Phenotype white
Genotype homozygous recessive
r
mother
r
Father:
Phenotype red
Genotype homozygous dominant
R
R
Rr
Rr
25%
25%
Rr
Rr
25%
25%
father
Offspring: 100% heterozygous - genotype
100% red - phenotype
Mother:
Phenotype: short
Genotype: homozygous recessive
T
t
t
Father:
Phenotype: tall
Genotype: heterozygous
t
Tt
25%
tt
25%
Tt
25%
tt
25%
Offspring: 50% tall 50% short - phenotype
50% heterozygous
- genotype
50% homozygous recessive - genotype
Red sweet pea
Homozygous
Dominant
White sweet pea
Homozygous
recessive
Pink sweet pea
Heterozygous