Download Mendel and Heredity

Awesome website
for images!!!!
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Mendel and Heredity
The Origins of Genetics
Mendel’s the Man!
Connection:
(see cell cycle on board and
image of meiosis)
A gene is a segment of DNA capable of producing a specific
protein.
A gene is found on a section of DNA
↓
This section causes a trait
↓
A trait is a physical / chemical
appearances (could be trait for hair or
insulin production)
Hundreds or thousands of genes on one chromosome.
Characteristics of a gene
1.
2.
3.
4.
5.
6.
7.
Identical throughout cells of a body
Same number in same species
Chemical units can function individually
Responsible for biosynthesis
Reproduce themselves (S phase)
Pass to next generation (meiosis)
In the nucleus
Gregor Mendel – Father of Genetics
(read blurp)
The man studied peas.
Why?
- 2 clear different forms of a trait
- reproduction easy to control
- small, grows easily & quickly, and
there are many offspring
Mendel Continued
Pea plants can self pollinate and cross pollinate
♂ + ♀ (P1 = parents)
male
female
↓
F1 = First filial generation
F1 x F1
↓
F2 = Second filial generation
Terminology
Show cell cycle and how organisms has two letters
• Genotype – genetic makeup, description
of genes: ex. AA, Aa, aa
– Homozygous:
• AA, aa
– Heterozygous:
• Aa
• Phenotype – physical expression, what it
looks like:
– ex. white, black, spotted
Organism’s characteristics (traits) are caused by genes.
There are multiple types of traits:
1. Dominant
hides recessive trait
identifies with upper case letter
B = brown eyes
Ex. Brown eyes (shows up more often)
2. Recessive
Identified with lower case letter
b- blue eyes
Ex. Blue eyes (shows up less often)
(Show cell cycle and how organisms has two letters)
Law of Segregation – during meiosis genes separate
so that there is only 1 gene for each characteristic
in each gamete.
Law of Independent Assortment – alleles of different
genes (traits) separate independently of one
another during gamete formation
Test Cross - mating of a known genotype with
unknown to help identify the unknown genotype
Types of Chromosomal Mutation
These occur in metaphase I, why?
Name of Mutation
Description
Deletion
A piece of a chromosome
breaks off; a piece is
missing
Duplication
A chromosome fragment
breaks off and attaches to
its homologous chromosome; now it carries 2
copies of same gene
Inversion
The chromosome piece breaks
off reattaches to the
original chromosome in a
reverse manner
Translocation
The piece reattaches to a
nonhomologous
chromosome
Great Website
Sketch
Notice I do not have a REAL picture of
meiosis.
Causes of variation in gametes (good,
normal)
- crossing over
- random assortment of chromosomes
Types of Chromosomes and Sex determination
• Autosomes – chromosomes not involved in
determining if an organism (you) are
going to be a male or female
• Sex Chromosomes – one chromosome of
our 23 ( or 2 of our 46)
– Female is XX (X from mom and X from dad)
– Male XY – (x from mom and Y from dad)
Only chromosome not “identical” to its pair (see Figure 6.5 in
text)
• Male gamete determines sex of fertilized egg
A
B
C
D
E
F

deletion
A
B
C
A
B
C
D
E
F
D
E
F
A
B
C

Inversion
F
E
D
A
B
A
B
C
A
B
C
D
E
F
D
E
F

duplication
A
B
C
A
B
C
D
E
F
D
E
F
A
B
C
D
E
F
A
B
C
X 
translocation
Z
D
E
F
A
B
X
Z
Abnormalities in Chromosome Number
• Karyotype – a photo of the chromosomes in a
dividing cell (See p.329)
• Abnormalities in Chromosome Number, happen
in anaphase I, as a result of non-disjunction
– Trisomy – an extra chromosome, 3 instead of two in
a pair, 47 instead of 46 in a human karyotype
• Down syndrome – Trisomy 21, an extra 21st chromosome
• Klinefelter’s syndrome – Male with XXY
– Monosomy – missing a chromosome, havine 1
instead of 2 in a pair, 45 instead of 46 in a human
karyotype
• Turner’s syndrome – Female with only 1 sex chromosome,
or missing part of one (XO)
Traits Caused by Mutations
(Mutated alleles can be passed on)
• Sickle Cell Anemia
– Poor blood circulation
– 1:500 African Americans
• Tay-Sachs disease
– Deterioration of central nervous system
– 1:3,500 Ashkenazi Jews
– Affected die at early childhood
http://www.sfn.org/SiteObjects/published/0000BDF20016F63800FD712C3158BA55/0000BDF2000006250110C68C45857663/file/bb_feb2007_la rge.jpg
http://adultstemcellawareness.files.wordpress.com/2007/10/sickle-cell.jpg
Traits Caused by Mutations
(Mutated alleles can be passed on)
• Cystic fibrosis
– Mucus clogs many organs
– 1:2,500
– Usually do not survive to adult hood
• Hemophilia
– Failure of blood to clot
– 1:10,000 (white males)
• Huntington’s disease
http://images.google.com/imgres?imgurl=http://
www.freeinfosociety.com/images/science/physio
logy/cysticfibrosis2.jpg&imgrefurl=http://www.fre
einfosociety.com/site.php%3Fpostnum%3D435
&h=374&w=336&sz=31&hl=en&start=6&um=1&
tbnid=3BEZHLcR5GIjM:&tbnh=122&tbnw=110&prev=/images%3
Fq%3DCystic%2BFibrosis%26svnum%3D10%2
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– Dominant trait
– Gradual deterioration of brain tissue, middle age
– 1:10,000