Upload
raymond-carter
View
216
Download
2
Tags:
Embed Size (px)
Citation preview
A human diploid cell contains more than 6 billion base pairs of DNA
All DNA is packed into 46 chromosomes.
Human Genes and ChromosomesChromosomes 21 and 22 are the smallest human autosomes.
• Chromosome 21 contains 225 genes• Contains associated amyotrophic lateral sclerosis (ALS) Lou Gehrig’s disease.• Many regions have no genes at all.
• Chromosome 22 contains as many as 545 different genes• Disorders can cause leukemia and neurofibromatosis• Long stretches of repetitive DNA are unstable sites.
RememberGenes located close together on the same chromosome are linked, meaning that they tend to be inherited. It is true for many genes but they might be divided by crossing over.
Sex- Linked GenesThere is a special patter of
inheritance for genes located on the X chromosome or the Y chromosome because they determine the sex.
Many sex-linked genes are found on the X- chromosome
SEX CHROMOSOMES CAN CARRY OTHER GENES TOO= ___________________SEX LINKED TRAITS
These traits show up in different _______________ in males and females because they move with the sex chromosomes
percentages
Y-LINKED GENES: Genes ______________ chromosome
EXAMPLE:Hairy pinna
________genes _____ show up _______Y linked in males
carried on Y
ONLY
____________ GENES: are carried on the X chromosome
X-linked recessive disorders show up _____________in ______ than femalesbecause males only have______ X chromosome.
MALES
X-LINKED
ONE
MORE frequently
Males ONLY HAVE ONE X
They eitherhave the disorder
DEFECTIVE NORMAL
They are normal
Or
FEMALES HAVE TWO X CHROMOSOMES
Females have one normalgene that works.
NORMAL DEFECTIVEDEFECTIVE
Females __________defective recessivealleles to show the disorder
need 2
The X chromosome in males . . . flies WITHOUT a copilot!
. . . there’s NO BACK UP X to help them!
Examples of ____________________
DISORDERS:
____________________
____________________
____________________
HEMOPHILIA
COLORBLINDNESS
DUCHENNE MUSCULAR DYSTROPHY
X-LINKED RECESSIVE
COLORBLINDNESS CAUSE:
Mutation in one of three genes for _______________ carried on X chromosome
Persons with this disorder have trouble distinguishing colors.
_________________ colorblindness is most common
Seen in 1 in 10 males 1 in 100 females
Red-green
Color vision
http://gizmodo.com/gadgets/peripherals/samsung-develops-lcd-for-colorblind-036306.php
http://www.beavton.k12.or.us/sunset/academics/genetics.htm
HEMOPHILIA CAUSE:
Mutation in genes for __________________ carried ______ chromosome
Blood clotting proteins are missing so person with this disorder can’t stop bleeding when injured; can ________________ from minor cuts or suffer internal bleedingfrom bruises or bumps.
bleed to death
Blood clotting proteins
on X
HEMOPHILIA Treatment:
Need ____________ of normal clotting proteins to stop bleeding
_____________ in ______ because it is X-linked, but females with ______ recessive hemophilia alleles will also show the trait.
1 in 10,000 males has hemophilia
injections
malesTWO
More common
http://www.ikm.jmu.edu/Buttsjl/ISAT493/Hemophilia/hemophiliaeurope.html
Duchenne Muscular DystrophyCAUSE: deletion in genethat codes for a_______________
Results in ____________________and loss of
___________________
muscle protein
progressive weakeningskeletal muscle
Duchenne Muscular Dystrophy (DMD)
SYMPTOMS: 1 in 3000 male births Appears before age 5 Progressive muscle weakening
Most in wheelchair by age 13
Eventually lethal
What’s the pattern: ________ traits show up _______ in _______
__________________ traits:________________________ than females. ________________ can be ________.
_______________________ traits:BOTH ______ & _________ can be ________
Y-linked ONLY males
X-linked recessivemore common in males
AUTOSOMAL RECESSIVE
ONLY FEMALES _______ carriers
MALES FEMALES carriers
In some female cells the X with the allele for orange spots is switched off and in some cells the X with the allele for black spots is switched off, so cat has different colored spots.
CAT COLORIn cats, a gene thatcontrols the _____________
is carried on the ____________________X chromosome
SPOT COLOR
See a video
_________ cats have only one X chromosome, so they can only have ____________ of spots!
CAT COLOR
Male
one color
THINK ABOUT IT?
How many colors of spots could a male cat withKlinefelter syndrome have?
________________ Abnormalities• 1 infant in 200 newborns has a chromosomal abnormality • 28% of first trimester miscarriages have a chromosomal abnormality
• Abnormalities in larger chromosomes don’t usually survive
CHROMOSOMAL
____________________________:Change in the ______________ or ____________ of chromosomes
CHROMOSOMAL MUTATIONS
structurenumber
Homologous chromosomes ________________ during MEIOSIS
= _________________________
One cell gets 2 copies of the chromosome the other cell gets none.
NONDISJUNCTION
fail to separate
Normal Meiosis Nondisjunction
http://www.tokyo-med.ac.jp/genet/anm/domov.gif
http://web.udl.es/usuaris/e4650869/docencia/gen_etica/meioferti2.html
Nondisjunction
NondisjunctionSince it happens to asperm or egg, the newbaby can end upwith _____________ of achromosome= __________________OR only ___________ of achromosome= ___________________
TRISOMY
MONOSOMY
3 copies
one copy
Human Abnormalities caused by Non-Disjunction______________________________________________________
Down syndrome
Klinefelter syndrome
Turner syndrome
Down syndrome (= ____________)TRISOMY 21
Down syndrome (Trisomy 21)1 in 800 births
Similar facial features
Slanted eyes
Protruding tongue
Down syndrome (Trisomy 21)Simian line on palm
Down syndrome (Trisomy 21)Most common
chromosomal abnormality
50% have heart defects that need surgery to repair
Mild to severe mental retardation
Increases susceptibility to many diseases
Risk of having a child with Down syndrome increases with age of mom
Sex Chromosome Disorders
Turner syndrome
Turner syndrome ____ 1 in 5000 birthsFemales have only one X
chromosome (45,X)Small sizeSlightly decreased intelligence35% have heart abnormalitiesHearing loss commonBroad chestReproductive organs don’t develop
at pubertyCan’t have children
XO
Klinefelter syndrome XXy
Klinefelter syndrome1 in 1000 birthsMales have extra X chromosomes(Can be XXy, XXXy, or XXXXy) (46,XXY)
Average to slight decrease in intelligenceSmall testes/can’t have childrenUsually not discovered until puberty when don’t mature like peers
Karyotype (need cells from baby)
Can tell __________________ chromosomes__________Some _____________________Can’t see _______________ mutations
MISSING/EXTRAGENDER
DELETIONS/INSERTIONS
single gene
If having extra chromosomes causes genetic problems, how come having two X chromosomes in females and one X in males is not a problem?
X-chromosome Inactivation
In female cells ______ chromosome is randomly ________________
It condenses and forms a dense region in the nucleus called a
_____________BARR BODY
ONE XSWITCHED
OFF