Transcript Chromosomes-and-Inherited-Traits (PowerPoint)

Genetics and
Genomics
Why Do I Look Like
I Do?
Dr. Ron McNeel
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We’re the Same
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
The human species has
similar characteristics

Name a few

Characteristics are called
TRAITS
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But We are also Different
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
Humans can have different
forms of the same trait

Name some different
forms of the same trait
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
These different forms of
traits are called
Variations
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But Wait!! Families are Similar
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Sometimes Identical
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Start in the Cell Nucleus

Nucleus Coordinates the Cell Processes

Contains the Genetic Information that
makes you
 Your genome
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Part of the Genome
is Divided into chromosomes
Short arm
Centromere
Long
arm
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Chromosomes have similarities and differences

Similarities
 Only found in the nucleus



Normally, humans have 46 chromosomes
All packaged the same way
Differences
 44 chromosomes NOT involved in determining sex
of individual
 Called Autosomes
 What do you think the other two chromosomes are
called?
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Differences

Sex Chromosomes
 X & Y Chromosomes

Determines Sex
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Other Differences

Chromosomes have Different
 Lengths

Physical Appearance
Centromeres
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Autosome Surprise

Each autosome has a
“partner”

How many autosomes are
there?
 44

How many partner pairs
are there?
 22 pairs

See them?
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Finding the Autosomal “Partners”

Difficult to find them easy
like this

Putting numbers on them
doesn’t help much

Any ideas to help find the
“partners”?
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Sorting Out the Autosomes
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
What if we arrange the
“partners” based on their
lengths?

What is this called?
 karyotype
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Where does each partner come from?
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Where does each partner come from?

One from your mother

One from your father
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What About the Sex Chromosomes (X and Y)?

One from your mother

One from your father
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Which Sex Chromosome
can the Mother Contribute?

X Chromosome ONLY!
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
X or Y Chromosome

Who determines the sex of
the offspring?
 MALE
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Review

What percentage of your
chromosomes comes from
each parent?
 50%

How many autosomes
from each parent?


22
How many sex
chromosomes from each
parent?
 1
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Hey, wait a second!


How many total
chromosomes in human
female cell nucleus?
How many chromosomes
in human male cell
nucleus?

Then matting would
produce…

Why does this not
happen?
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46
46
92 chromosomes in
offspring
92
92
184 chromosomes in
offspring
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ANSWER: Special Cells - Gametes

Female
 Egg

Male
 Sperm
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Gametes Formed by a
Special Type of Cell Division

Meiosis (reduction division)
 found only in reproductive cells (gametes)
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We Must Divide to Multiply

Meiosis – reduction division

Gametes have half the number of chromosomes

Female 46 

Male 46

23 in egg
23 in sperm
46 in offspring
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During Fertilization

23 chromosomes from your mother

23 chromosomes from your father

46 chromosomes in offspring

Life is good again!
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Closer Look at Chromosomes

Chromosomes are long molecules of
deoxyribonucleic acid (DNA)
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Closer Look at Chromosomes
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DNA Packaging

Your genomes has 3 billion base pairs (every cell)

Typist 360 letters/minute for 8 hours a day copy your
genome in 50 years

If recited the genome at 1 letter per second 24/7 it
would take 100 years to finish
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DNA Packaging

If the DNA from ONE cell was stretched out:
 It’d be from 6-9 feet in length

If stretched the DNA from every cell and placed end to
end
 It would reach to the sun and back over 600 times
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DNA Contains Genes

Gene = DNA segment that
contains the code to make
a particular protein

Proteins determine your
characteristics or traits
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DNA → Protein → Trait

Trait = Physical appearance or Phenotype

Red hair

Brown eyes

Sickle cell

Albinism
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Summing it Up

Chromosomes → DNA

DNA → Genes

Genes → Proteins

Proteins → Make you, YOU

Francis Crick  “DNA makes protein, and protein makes us”
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