Transcript 14-1, 2 - greinerudsd

What do you see?
Colorblindness is an example of a sex-linked disorder
Human
Genetics
Chapter 14-1, 14-2
Human Heredity
The Human Genome
ATGGGTCGCGTATCGTAGCTGATGGGGGTAGTATTT
TATATGCTGGTAGACAAAACGGTGTACTGCCGTC
GTCGTAGTGATGTGCGGCGCCAAAAATTATACTG
TGACTGATCGTAGTGTAAAAAAAAAAGTCGTGCT
GCTTTTTTCGATCGCGCGTAGTAGCTACGCCGCG
GTTCGCGCGTAAGAGACTGATGCGACTGATATATA
TACGCGCTAGCATATATCTCTCGATCTGATCGTAGA
TGCTTAAGTTACTAGCTGTCGTATACGTAGTTAGT
CGGGTGATGATGCTGTATATATCGCGCTCTATATGC
TAGCTAGTGTTGTAGCTAGCTGATTCCCTCGAAGT
CTCGTGAATAATCGCGCTTTCGGGGGCTCTCTATA
Human Genome
• 3 billion base pairs
– 6 billion individual bases
• “4 million pages”
• Bases (letters) spell out
genes (words) that result
in the phenotype (the
story)
• Some spell out bad
stories (diseases)
Gene count source: Wellcome Trust. Unveiling your genome. Wellcome News Supplement Q1:13-23(2001).
Chromosome
Chromosome 1
Chromosome 2
Chromosome 3
Chromosome 4
Chromosome 5
Chromosome 6
Chromosome 7
Chromosome 8
Chromosome 9
Chromosome 10
Chromosome 11
Chromosome 12
Chromosome 13
Chromosome 14
Chromosome 15
Chromosome 16
Chromosome 17
Chromosome 18
Chromosome 19
Chromosome 20
Chromosome 21
Chromosome 22
Chromosome X
Chromosome Y
# Genes
2968
2288
2032
1297
1643
1963
1443
1127
1299
1440
2093
1652
748
1098
1122
1098
1576
766
1454
927
303
288
1184
231
# of Bases
279 million bases
251 million bases
221 million bases
197 million bases
198 million bases
176 million bases
163 million bases
148 million bases
140 million bases
143 million bases
148 million bases
142 million bases
118 million bases
107 million bases
100 million bases
104 million bases
88 million bases
86 million bases
72 million bases
66 million bases
45 million bases
48 million bases
163 million bases
51 million bases
Humans have 22 pairs of AUTOSOMES
Why is the 23rd pair different? What is it called?
What is this picture called? When was this cell photographed?
Is this a man or a woman? How do you know?
Answers…
2. The “23rd” pair are the sex chromosomes
3. This picture is a karyotype
4. It was taken during mitosis (likely metaphase)
5. It is a man
• He has one X chromosome (larger) and one Y
chromosome (smaller)
What do you see?
Colorblindness is an example of a sex-linked disorder
• h = hemophilia, a sex-linked disorder
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•
•
•
For each, can you answer…
Is the dad affected?
Is the mom affected?
How many children have the
disease?
• How many children are carriers?
• How many children are healthy?
(careful!)
PEDIGREES  another way to study
inheritance
• What do you think the F1
generation (line II) # 2
and #5 offspring
represent?
• Can you draw the
Punnett Square for the
Parent generation? (I)
How to read a pedigree…
Carrier female
Carrier male
Pedigrees
• Show how traits are passed down through
many generations
• Based mostly on phenotypes
• Show the actual offspring
– Punnett squares show the possible offspring
• Really only works well for single traits
– Not polygenic traits
• Only works for inherited traits
– Environmental factors play a large role in who we are
Inheriting Diseases
• Just like physical traits, some diseases can be
inherited on our chromosomes.
• And, just like physical traits, some are X-linked,
some are recessive, some are dominant or
codominant.
Genetic Disorder Project topics
Fragile x syndrome
Gaucher disease
Duschene Muscular Dystrophy
Marfan syndrome
Color blindness
Hurler syndrome
Tay-Sachs
Albinism
Cystic Fibrosis
Sickle cell anemia
PKU
Lou Gehrig’s disease
Cri du Chat syndrome
Huntington Disease
Turner’s syndrome
Klinefelter syndrome
Down syndrome
Fanconi anemia
Other Chromosomal Actions
• X-Inactivation  if men only need one X
chromosome, do women need both X’s?
– If not, which one “works”?
• Non-disjunction  how gametes can end up
with the wrong # of chromosomes in meiosis
X-Chromosome Inactivation
• Men are XY: One X chromosome is enough
• Women are XX: The “extra” copy is not needed.
It condenses into a “Barr body.”
• Remember, you have trillions of cells. Which X
chromosome that “switches off” can vary in
each cell!
Mosaicism
Nondisjunction
• “Not coming apart”
• Homologous
chromosomes fail to
separate in meiosis
• Result in Trisomy or
Monosomy
• Examples:
– Klinefelter syndrome (trisomy X)
– Down syndrome (trisomy 21)
– Turners syndrome (X_
monosomy)
Video 2
Nondisjunction
• Click the image to play the video segment.