Transcript Genetics - Cloudfront.net

What is Genetics?
• Genetics: Study of heredity
• Heredity: passing of traits
from parent to child
• Patterns of relatedness can
help predict offspring
characteristics
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Autosomal recessive
Autosomal dominance
Sex-Linked
Incomplete dominance
Codominance
When parents get
together…they
exchange their genes
The genes
combine to
create a baby
• “Father of Genetics”
• Famous for pea plant
studies
• Mendel studied seven
pea plant traits
– Color, shape, texture,
height, etc…
• Results shaped our
understanding of genetics
Mendel’s 7
traits studied
P Generation
Mendel crossed a
purple and a
white flower
The flowers
exchanged their
genes to make
babies
F1 Generation
Mendel was shocked! Even though 1 parent was white in color, every flower that
was produced was purple!
Was white gone forever?
F1 Generation
Mendel then took two of the
newly created purple flowers
and let them reproduce
F2 Generation
WOW! White returned! Even
though both parents were
purple!
Mendel found a 3:1
ratio for flower
color. But what
about the other
traits he examined?
Each trait had a 3:1
ratio. No way that
can be a
coincidence!
• 1 form of a gene may
prevent the
expression of the
other
– Dominant gene hides
recessive gene
• Organisms inherit 2
copies of each gene
– One from each parent
Dominant + Dominant Allele
Homozygous Dominant
Recessive + Recessive Allele
Homozygous Recessive
Recessive + Dominant Allele
Heterozygous
Dominant + Recessive Allele
Heterozygous
• Genes are located on
chromosomes
• Traits are determined by genes
from mom and dad
– Allele: Alternative forms of a
gene
• Letters used to abbreviate
alleles
– Dominant Allele = Capital
letter
– Recessive Allele =
Lowercase letter
• Phenotype: Actual appearance of a gene
Ex: Purple flowers
• Genotype: Genetic makeup of an organism
Ex: 2 dominant alleles (PP)
• Genotype determines phenotype
Cross a homozygous dominant yellow (YY) plant with
a homozygous recessive green (yy) plant
Key
Y = yellow
y = green
100%
Probability of growing a yellow plant? _____________
0%
Probability of growing a homozygous recessive plant? ____________
0%
Probability of growing a homozygous dominant plant? ____________
Cross a heterozygous dominant yellow (Yy) plant with a
heterozygous dominant yellow (Yy) plant
Key
Y = Yellow
y = green
50%
Probability of growing a heterozygous plant? ________
25%
Probability of growing a green plant? ________
25%
Probability of growing pure yellow? _________
Maria is a heterozygous healthy (Hh) female and Jeff
suffers from recessive cystic fibrosis (??).
Key
H = healthy
h = cystic
fibrosis
Probability of having a healthy
50%
child? _________
Probability of having a homozygous
0%
dominant child? ________
Kobe Kuiz
1) How are dominant alleles expressed? Recessive?
2) Which of the following are genotypes? Phenotypes?
TT Green yY Pp Purple gg Smooth
3) Which of the following are heterozygous genotypes?
TT Green yY Pp Purple gg Smooth
4) Genes may often be found in two forms (dominant and recessive). What are
these alternate forms of a gene called?
5) Genes are segments of DNA found on _______________.
6) If item A is found in a 2:1 ratio compared to item B, what percentage is item A?
7) If item A is found in a 4:1 ratio compared to item B, what percentage is item A?
8) George & Martha are planning a family. Each has a family history of autosomal
recessive disorder and they agree to have their blood tested. George is found to
be heterozygous healthy and Martha is found to be homozygous dominant
healthy. What are the chances they have a healthy child? Homozygous
dominant child? Heterozygous child? Homozygous recessive child?