Genetics - Science4Warriors

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