Genetics - Science4Warriors

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14 Δεκ 2012 (πριν από 4 χρόνια και 10 μήνες)

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Genetics

Chapters 9 and 12

Introduction to Genetics


Genetics

is the science
of heredity and
variation in living
organisms.


Every living thing has
inherited

a set of
characteristics from its
parent or parents.


Traits



genetically
determined variant of a
characteristic


Francis Crick's first sketch of
the deoxyribonucleic acid
double
-
helix



At its most fundamental
level,
inheritance in
organisms occurs by
means of discrete traits
,
called “
genes
”.


This property was first
observed by


Gregor Mendel

Introduction to Genetics

http://en.wikipedia.org/wiki/Genetics

Chapter 12: Day One

Introduction to Genetics

The molecular basis for genes is:
deoxyribonucleic acid.

http://en.wikipedia.org/wiki/Genetics

Chapter 12: Day One

DNA

Good thing to know.

Gregor Mendel


Called the father of
genetics for his study of
the inheritance of traits
in pea plants.

Chapter 11: Day Five Start Here

http://en.wikipedia.org/wiki/Gregor_Mendel

Gregor Mendel


Used garden peas and
studied 7 specific traits


These different varieties
of peas are called
true
-
breeding
because
they
always pass on their
traits to their offspring

Chapter 11: Day Five

http://en.wikipedia.org/wiki/Gregor_Mendel

Gregor Mendel


Normally the flowers of
pea plants
self
-
pollinate:
the
pollen

(
male sex cells
)
and the
ovum

(
female sex
cells
) come from the
same flower

Chapter 11: Day Five

Gregor Mendel


He studied 7 specific
traits


Each trait had 2 possible
forms (
alleles
)


Allele
-

one of a number
of different forms of a
gene

P generation Cross

P generation

Original true
-
breeding
plants

F1 generation

Hybrid

plants
-

offspring that
have inherited 1 trait from
each parent

Chapter 11: Day Five

r

r

r

r

r

r

P generation Cross


Mendel concluded that
each P1 parent had
2
identical genes for each
trait
AND

that 1 allele
must be
DOMINANT

and the other

RECESSIVE

Chapter 11: Day Five

Why are the F2 hybrids
all red?

r

r

r

r

r

r


Genotype
-

the letter combinations showing
possible alleles


Identical alleles are
homozygous



Opposite alleles are
heterozygous



Phenotype

is the form of the trait that shows
up in what the organism looks like

rr = homozygous white

Rr = heterozygous red

RR = homozygous red

white

red

or

Chapter 11: Day Five

F1 generation

F2 generation

Chapter 11: Day Five

3:1 ratio

r

r

r

r

r

r

RR

rr

Rr

Rr

3:1 ratio, why is that?

When each F1 plant flowers and produces
gametes, the 2 alleles segregate from each
other so that each gamete carries only a
single copy of each gene.


Therefore, each F1 plant produces 2 types of
gametes
-

those with the allele for redness
and those with the allele for whiteness.

Mendel’s Results

& Conclusions


Law of Segregation


a pair of factors is
segregated, or separated, during the formation
of gametes



Law of Independent Assortment
-

factors
separate independently of one another during
the formation of gametes


Gregor Mendel Review


The inheritance of biological characteristics is
determined by individual units known as genes.
Genes are passed from parents to their offspring.


The principle of dominance states
-
some alleles
are dominant and some others are recessive.


During gamete formation, alleles segregate from
each other so that each gamete carries only a
single copy of each gene.


Principle of independent assortment

alleles
segregate independently

Inheritance Pattern

and Human Genetics

Chapter 12

Chromosomes


Sex chromosomes


Contain genes that determine the sex of an
individual


Autosomes


All the other chromosomes

This is old news.

Sex Determination

Sex
-
Linked Trait


A trait that is coded for an allele on a sex
chromosome

Most X
-
linked alleles have no counterpart on the Y chromosome.

Bigger, has
more
information

r

Is
something
missing
here?

Linked Genes


Pairs of genes that tend to be inherited
together, found on same chromosome

Dude, I
ain’t
going
nowher
e!!

Don’t
leave
me,
man!!

Chromosome Map


A diagram that shows the linear order of
genes on a chromosome.

Mutations


A change in the nucleotide
-
base sequence.


Involve an entire chromosome or a single
nucleotide.

Germ cell:

Occurs in the
organism’s
gametes.
Passed onto
offspring.

Somatic
-
cell:

Take place in
organism’s own
body cell

Lethal:

Cause death.

Chromosome Mutations


Deletion


Loss of a piece of chromosome


Inversion


Segment breaks off, flips, and reattaches


Translocation


Piece breaks off and reattaches to different chromosome


Nondisjunction


Chromosome fails to separate from its homologous
partner during meiosis

Gene Mutations


Point mutations


Change that occurs within a single gene or other DNA
segment


Substitution


One nucleotide replaces another


Frameshift mutation


Loss of nucleotides cause incorrect grouping of codons


Insertion mutation


One or more nucleotides are added to a gene, which can
also result in a frameshift mutation

See page 240

Pedigree


A diagram that shows how a trait is inherited
over several generations.

Genetic Traits and Disorders


Genetic disorders


Diseases or disabling conditions that have a
genetic basis



Complex characters


Characters that are influenced strongly by the
enviroment and by genes

Beyond Gregor Mendel


Some alleles are neither dominant nor
recessive, and many traits are controlled by
multiple alleles or multiple genes.


Incomplete dominance


Codominance


Multiple alleles


Polygenic traits

Polygenic


Characteristics are influenced by several genes

Multiple Alleles


Genes with 3 or more alleles

Codominance


Both alleles are expressed

Incomplete Dominance


A trait that is blended

Genetic Engineering


Genetic engineering, recombinant DNA
technology, genetic modification/manipulation
(GM) and gene splicing are terms that are
applied to the direct manipulation of an
organism's genes.

Chapter 13: Day Seven

http://en.wikipedia.org/wiki/Genetic_engineering

http://www.foxnews.com/images/330367/0_61_121207_cat.jpg

Cloned glow in the dark cats.

Genetic Engineering


There are a number of ways through which genetic
engineering is accomplished. Essentially, the process
has four main steps.



1) Isolation of the gene of interest



2) Insertion of the gene into a vector



3) Transformation of cells of organism to be modified



4) Tests to isolate genetically modified organism (GMO)



Chapter 13: Day Seven

http://en.wikipedia.org/wiki/Genetic_engineering

Lab Assignment


In your team, begin discussion on what you
think genetic engineering is and your position
on stem cell research.

Chapter 13: Day Seven Stop Here

AFP / Getty Images