Human Genomics 1- Karyotypes and Mutations

1. GENOMICS:
Karyotypes &
Mutations
Seamon

2. Karyotype-
• an organized profile
of chromosomes
• arranged and
numbered by size
from largest to
smallest

3. HUMAN KARYOTYPE
• 23 PAIRS of
chromosomes
called
homologous
chromosomes
• 1 chromosome
from each parent
• That makes 46 total
chromosomes

4. HUMAN KARYOTYPE
• autosomes-
chromosomes 1-22
• sex chromosomes
• chromosome 23
• X = female
• Y = male

5. Karyotypes show us…
• sex of the individual
• genetic disorders caused by too few or too
many of a chromosome

6. Nondisjuction
too many or too few chromosomes are caused
by a mistake in meiosis

7. Trisomy-21
• three of #21
• likelihood of
Downs Syndrome
increases with
mother’s age
DOWNS SYNDROME

8. • delayed physical
and mental
development
• flattened face &
eyes slanted
upward

9. Female with a
single X
• ovaries do not
develop
• do not mature
sexually
TURNER SYNDROME

10. Male with an extra X
• less facial hair and
muscles
• no sperm
KLINFELTER SYNDROME

11. Mutations-
• a change in the DNA
• causes changes in genetic code
• can be…
• an entire chromosome
• in any cell
• harmless, beneficial or harmful
• lead to genetic variation
• EXAMPLE: PTC tasters/non-tasters

12. PTC tasters & non-
tasters
• some people can
taste this bitter
chemical while
others cannot
• it’s genetic
• tasters & non-tasters
have slightly different
receptors (proteins)
on taste buds for
bitter taste

13. CCG and CCG
GTA and CCG
GTA and GTA
Tasters
Medium Tasters
Non-Tasters
A change in DNA causes
• change in the protein
• which causes a change in function

14. Gene Mutations
• may involve large areas of DNA or a single
nucleotide
• Point Mutation (of a single nucleotide)
• substitution
• duplication
• deletion
• mutation can code for the wrong amino acid,
leading to difference in function

15. What is the mRNA codon that would pair with a
DNA sequence of CTC?
The paired mRNA codon is GAG
What is the amino acid that it receives?
glutamic acid
THIS IS WHAT HAPPENS IN A NORMAL CELL
SICKLE CELL ANEMIA
TAKE OUT YOUR CODON CHART

16. In sickle Cell anemia, in CTC the T gets substituted
with an A resulting in CAC
What is the mutated mRNA codon?
The paired mRNA codon is GUG
What is the mutated amino acid that it receives?
For a mutated (substituted) DNA sequence, the
paired mRNA codon is Valine WRONG AMINO ACID
makes the wrong protein
SICKLE CELL ANEMIA

18. Frame shift mutation
• point mutation
• a nucleotide is deleted or inserted
• all codons after that are affected… the frame
shifts
• subsequent reading gives a nonsense
sequence of amino acids

19. ACTIVITY
• THE OLD RED DOG WAS TOO BIG FOR HIS BED
• Deletion that would delete the D in OLD…
• THE OLR EDD OGW AST OOB IGF ORH ISB ED
• Inversion of the word DOG...
• THE OLD RED GOD WAS TOO BIG FOR HIS BED
19
FRAME SHIFT- confuses the
whole message: bad mutation
less of a problem

20. Chromosome Mutations
MEIOSIS-
• crossing over- pieces of chromosomes are
exchanged
• another source of genetic variation
• new combinations of genes

21. Translocation
• chromosome
mutation
• fragments trade
with the wrong
chromosome
• not always a
problem

22. Deletion
• fragment is lost
(often in
translocation)
• Cri du Chat-
deletion in
chromosome 5;
infants have the
‘cry’ of a cat

23. Inversion
• fragment is lost
flips around
• not always a
problem

24. Duplication
• sometimes a
piece is repeated
• chromosome #4
has CAG repeated
10 to 30 times

25. • Gene has too
many repeats of
CAG
• Forms a protein
that clumps in
the brain and
kills nerve cells
• protein formed
does not work
properly
HUNTINGTON’S DISEASE (40 or more repeats)

26. Huntington’s Disease (HD)
• Early symptoms are forgetfulness and
irritability in 30’s or 40’s
• Progressive deterioration of the nervous
system
• Leads to loss of muscle control and eventually
death
• Because of late onset, it is passed on
unknowingly.

27. • traits found on the sex chromosomes (X & Y)
• carrier- “carries” the gene but does not have
the disease (often on X chromosome)
X-linked: genes on the X chromosome.
Y-linked: genes on the Y chromosome.
Most are recessive traits
Sex-Linked Traits

28. EXAMPLES
• baldness
• hemophilia
• muscular dystrophy
• red-green color
blindness
Sex-Linked Traits
red-green color blindness

29. Color-blindness is recessive.
B = normal
b = colorblind
Father is colorblind. His wife is not.
Father’s genotype is _____
Mother’s genotype is _____
What is the likelihood of them having a
colorblind son? Colorblind daughter?
XbY
XBXB

30. • X-Linked Trait
• blood does not clot
properly
• Any one of several
mutations on
genes for clotting
factors
• Treatment involves
replacing defective
clotting factor
HEMOPHILIA