Download Genetics - westmiddle6b

Genetics
Investigation 9-2
Quick Review
• The traits in a population of
walkingsticks change over the course of
several generations.
• Green
• Brown
• Green-brown
• How can that kind of change happen?
Inheritance
Passing genetic information from one
generation to the next
(why offspring grow up pretty much looking like their parents)
• You inherited alleles from your parents,
larkeys inherit alleles from their parents, and
the same is true of every other living thing on
Earth.
Gregor Mendel
• The pioneer on inheritance
• He spent years growing thousands of plants
and animals, observing closely to see how
similar they were to their parents.
Gregor Mendel (cont.)
• His most important work was done with pea plants
• All of his pea plants had flowers, but there was
variation in the feature of color.
• Some had the trait of purple flowers, some had the
trait of white flowers.
• When both parent pea plants had purple flowers,
the offspring has purple flowers. (same with white)
• With one purple & one white parent, some offspring
had purple flowers and some had white flowers
• He reasoned the offspring must inherit something
from each parent to determine color, but didn’t live
to find out the answer.
CELLS
• Inheritance unfolds inside
the cell
• Everything is made of cells
and that’s where the
information describing
how to make you resides
• Cells have smaller
structures inside that
perform functions essential
to life.
• One of interest is the
nucleus.
Nucleus
• Inside the nucleus is the
inheritance messenger,
DNA.
• DNA molecules are
coiled again and again
into structures called
chromosomes.
• Chromosomes carry the
message of inheritance.
CHROMOSOMES
• Nucleus of a cell from the
larkey.
• There are 8 chromosomes,
looking a little like bent
hot dogs of different
lengths.
• Chromosomes always
come in pairs.
• Our larkey has 4 pairs of
chromosomes, rather than
eight different ones.
ALLELES
• Look at these 2 dark
areas. Both
chromosomes in a pair
have dark areas in the
exact same location.
• The dark areas are
called alleles .
(alleles aren’t really dark-its used to
represent the location of the alleles
on the chromosomes)
• The 2 alleles on the paired
chromosomes work together.
• Together they constitute a gene.
• A gene (2 alleles working
together) controls a trait.
• This gene could be the one that
determines the larkey’s eye color,
or perhaps the pattern of its fur.
RECAP
• Nuclei contain chromosomes
• Chromosomes come in almost identical pairs
• Chromosomes have specific active locations
called alleles.
• The two alleles in identical locations on paired
chromosomes constitute a gene.
• Each larkey feature
is controlled by one
gene.
• Each of the four
genes is on a
different
chromosome.
• The gene for
appendages (legs)
is the 2 (A) alleles.
• Eye color (E)
• Fur pattern (F)
• Tail (T)
• Both uppercase and
lowercase letter Es are
alleles for eye color
• The alleles are the
code that determines
the traits of the larkey
• This chart is the larkey
genetics code
• The alleles for legs are
aa (so on)
GENOTYPE
• The combination of alleles in an organism’s
chromosomes is the organism’s genotype.
• The genotype lists the paired alleles that are
particular to that organism.
• The previous chart is the genotype of one of
the larkeys in the yammer
• Alleles don’t all have equal influence in
determining traits.
• Some alleles have more influence.
• Dominant allele—more-influential alleles and
are represented by an uppercase letter
• Recessive alleles—less-influential and are
represented by a lowercase letter
Identify the two alleles for
each feature as dominant
or recessive
Leg length –
Eye Color—
Fur pattern—
Tail–
• The left column has the 4
alleles this larkey got from its
mother.
• The right column has the 4
alleles it got from its father.
• Use the transparency 6 to fill
in the Genotype box.
• The middle column shows all
the possible combinations of
alleles in the genes for each
of the 4 features and the
traits that results from each
combination.
• What alleles make up our
larkey’s gene for leg
length?
• What trait does that
produce in our larkey?
(draw the legs on the larkey)
• Do the other features,
adding the traits to the
torso.
PHENOTYPE
• This is what the larkey with this genotype
looks like.
• PHENOTYPE—the way it looks
Genetics Vocabulary
The offspring of organisms often grow up to look like one or both
of their parents. This is because offspring inherit information
from their parents that directs their development.
The inherited information is located in the _____________ of every
cell in the organism. The information is coded in the huge
______________ molecule. The huge molecules are coiled into
compact hot dog–shaped structures called ______________.
________________ are always present in almost identical pairs.
Locations on chromosomes that affect features of organisms are
called ______________. A gene is composed of _____________.
An organism’s unique combination of genes is its . The traits produced
by an organism’s genes is its _____________. Alleles that have more
influence in
determining traits are _____________alleles. Alleles that have less
influence in determining
traits are ______________alleles.
chromosome