Download Genetics

Genetics
&
Heredity
Chp. 10:1
Who was Gregor Mendel?
• “Father of Genetics”
Who was Gregor Mendel?
• Austrian monk who studied
mathematics and science
• As a boy he could predict the
possible types of flowers and
fruits that would result from
crossbreeding two plants in his
father’s garden
Who was Gregor Mendel?
• Curiosity about the connection
between the color of a pea flower and
the type of seed that same plant
produced inspired him to begin
experimenting with garden peas in
1856.
• Made careful use of scientific
methods, which resulted in the first
recorded study of how traits pass
from one generation to the next.
What is GENETICS?
The study heredity of how
traits (characteristics) are
inherited through the
interactions of genes.
What is a GENE?
• The material that controls
which traits are expressed
in an organism
• Genes come in pairs and
offspring inherit one copy
of each gene from each
parent
Define HEREDITY
The passing of traits from
parent to offspring
Define ALLELE
• Either member of a pair of
genes that determine a
trait.
• The different forms of a
trait that a gene may have
• One form of a gene
Define TRAIT
• Ways of looking, thinking,
or being
• Traits that are genetic
are passed down through
the genes from parents to
offspring
Describe RECESSIVE
(weak)
• A trait that is covered over,
or dominated, by another
form of that trait and seems
to disappear
• Hidden when the other copy
of the gene contains the
dominant allele.
• A recessive allele shows up
only when there is no
dominant allele present
• Shown with a lower-case
letter
Describe DOMINANT
(strong)
• A trait that covers over,
or dominates, another
form of that trait
• Trait that always shows
up, even when only one of
the two alleles is in the
dominant form
• Shown by a capital letter
Define GENOTYPE
• An organism's genetic makeup
• The allele combination an organism
contains
Think ... (I am looking for the letters)
Ex. TT, Tt, tt, RR, rr, Rr
Define PHENOTYPE
• Outward physical appearance
and behavior of an organism
• Is the result of both genotype
and the environment
think…”what does it look like”
Ex. green, round, tall …
HOMOZYGOUS or Pure
(same)
• Both alleles [forms of the gene]
are the same ex. BB, bb, TT, tt
• When offspring inherit two
dominant genes, (one dominant gene
from each parent) they are said to
be homozygous dominant
• When offspring inherit two
recessive genes, (one recessive
gene from each parent) they are
said to be homozygous recessive
HETEROZYGOUS or Hybrid
(different)
• When alleles occur in different
forms ex. Tt, Bb, Rr
• When offspring inherit one
dominant gene and one recessive
gene, they are said to be
heterozygous
• Since the dominant gene will be
expressed, they are said to be
heterozygous dominant
3 Principles of Heredity
• Principle of Dominance and Recessive
(one trait is masked or covered up by
another trait)
• Principle of Segregation
[two alleles (pair of genes) for a trait
separate during gamete formations]
• Principle of Independent Assortment
( each trait is independently
inherited)
What is a PUNNETT SQUARE?
• A tool to predict the probability of
certain traits in offspring that shows
the different ways alleles can
combine
• A way to show phenotype & genotype
• A chart that shows all the possible
combinations of alleles that can
result when genes are crossed
What is a PUNNETT SQUARE?
• Letters stand for dominant and
recessive alleles
• An uppercase letter stands for a
dominant allele
• Lowercase letters stand for
recessive alleles
• The dominant trait determines
which letter to use
Punnett Square
• P1
(Parents)
• F1 (First Generation)
Show your parents
• (X) shows mating
• The dominate trait should be
displayed 1st in the square
ex: P1
TT X TT
Punnett Square
• Shows the probability of the traits
of offspring. ex: P1 TT X TT
Parent 1
Genotype
Parent 2
Genotype
INCOMPLETE DOMINANCE
p. 316 snap dragons
•
A blend of 2 traits,
resulting in a cross
•
of homozygous.
•
P1 RR x WW
No dominance or recessive,
all offspring are pink
Describe CO-DOMINANCE
• Alleles result in expression of
both traits
• When an organism has two
different alleles for a gene that
does not follow the
dominant/recessive pattern
• Ex. AB blood type
Describe CO-DOMINANCE
P. 317 (checkered chicken)
For example:
P1 BB x WW
Both traits are displayed
All the offspring are black and white
MULTIPLE ALLELES
• traits controlled by more than
two alleles
• Traits controlled by multiple
alleles produce more than
three phenotypes of that trait
What is meant by MULTIPLE
ALLELES?
For Example: Blood Types
4 types
Genotype
phenotype
A
AA, AO, IAIA, IAi
B
BB, BO, IBIB, IBi
AB
AB, IAIB
OO
OO, ii
Universal
Recipient
Universal
Donor
What is POLYGENIC
INHERITANCE?
• Occurs when a group of gene
pairs acts together to produce a
trait
• The effects of many alleles
produces a wide variety of
phenotypes
• Ex. hair color, skin color, eye
color