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