Transcript Whose got Genes?

www.sciencequeen.net
Whose got Genes?
Genes, Heredity, & DNA
Baker 2003/2004
What is GENETICS?
The study of how traits are
inherited through the
interactions of genes.
Baker 2003/2004
What are genes?
Genes are a segment of DNA
on a chromosome that
controls a particular trait.
Genes are located on the
chromosomes in the nuclei. Each
organims has a fixed number of
chromosomes.
Humans have 23 pairs (46)
chromosomes.
Genetics is the study of how
traits are passed on from one
generation to another
Baker 2003/2004
Define TRAIT
Ways of looking,
thinking, or being
Traits that are genetic
are passed down through
the genes from parents
to offspring
Baker 2003/2004
Describe RECESSIVE
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 Baker 2003/2004
Describe DOMINANT
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
Baker 2003/2004
Define GENOTYPE
An organism's genetic
makeup
Baker 2003/2004
Define PHENOTYPE
Outward physical appearance
and behavior of an organism
Baker 2003/2004
What is a PUNNETT
SQUARE?
Used to determine the likely
hood that the offspring
receives a certain trait.
An uppercase letter stands for
a dominant allele
Lowercase letters stand for
recessive alleles
Baker 2003/2004
Punnett Squares
Sample Problem 1. In roses, red
flowers are dominant over white flowers.
What are the possible offspring when a
homozygous red rose is crossed with a
homozygous white rose.
Baker 2003/2004
Generation 1 (I Do)
R
r
R
R r
R r
Red rose = RR
white rose = rr
Genotype
r
R
r
R
r
4 Rr
Phenotype
100% Red Rose
Baker 2003/2004
Generation 2 (We do)
R
r
R r
r
r r
Red rose = Rr
white rose = rr
Genotype
r
R r
r r
2 Rr 2 rr
Phenotype
50% Red 50% White
Baker 2003/2004
Generation 3 (You do)
R
R
r
R R
R
r
Red rose = Rr
Red rose = Rr
Genotype
r
R r
r
r
1 RR 2Rr 1 rr
Phenotype
Baker 2003/2004
75% Red 25%
Whose got Genes? Part 2
Genes, Heredity, & DNA
Baker 2003/2004
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
Picture taken from biography.com
Baker 2003/2004
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.
Baker 2003/2004
Define HEREDITY
The passing of traits
from parent to
offspring
Baker 2003/2004
Define ALLELE
The different forms of a
trait that a gene may
have
One form of a gene
Baker 2003/2004
What is HOMOZYGOUS?
AA
aa
Both alleles [forms of the gene]
are the same
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
Baker 2003/2004
What is
HETEROZYGOUS?
Aa
When alleles occur in
different forms
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
Baker 2003/2004
Generation 1
B
B
b
b
B Brown Eyes are
Dominant to b Blue Eyes
b
b b
Heterozygous
Homozygous
recessive
Genotype
b
B b
2 Bb 2bb
b b
Phenotype
50% Brown
50% Blue
Baker 2003/2004
Generation 2
B Brown Eyes are
Dominant to b Blue Eyes
B
b
B
B b
B
b
Homozygous
Dominant
Homozygous
Recessive
Genotype
b
B
b
B
b
4 Bb
Phenotype
100% Brown Eyes
Baker 2003/2004
Generation 3
B Brown Eyes are Dominant
to b Blue Eyes
B
B
B B
B
B B
Homozygous
Dominant
Heterozygous
Genotype
b
B b
B b
2 BB 2 Bb
Phenotype
Baker 2003/2004
100% Brown
Eyes
References
Slideshow adapted from
http://www.scienceclass.net/PowerPoints/Genetics.htm
Baker 2003/2004