Human Heredity Chapter 14

Human Chromosomes Chromosomes are only visible during cell division (mitosis/meiosis). To analyze chromosomes, biologist photograph cells during mitosis and align the chromosomes in homologous pairs. This picture is known as a karyotype

Types of Chromosomes On a human karyotype: Chromosome pairs 1-22 are known as autosomes. – They code for traits that are not related to sex. – Both males and females have the same type Chromosome pair 23 contains the sex chromosomes. – Males have XY and females have XX.

Boy or Girl?

Did you know??? Sex is determined by the father of a child. You have a 50% chance of having a boy or a girl ?

Who decides? Mom can give X Dad can give X or y SO ____ determines sex of the baby. If dad gives X with mom’s X = girl If dad give y with mom’s X = boy X X X y X X y Dad

GENETIC DISORDERS Human

____________________________: Change in the ______________ or ____________ of chromosomes CHROMOSOMAL MUTATIONS structure number

Homologous chromosomes ________________ during MEIOSIS = _________________________ One cell gets 2 copies of the chromosome the other cell gets none. NONDISJUNCTION fail to separate

Down syndrome = TRISOMY 21

Down syndrome (Trisomy 21) Most common chromosomal abnormality Mild to severe mental retardation Risk of having a child with Down syndrome increases with age of mom

GENETIC DISORDERS Sex Linked

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 in males Y linked carried on Y ONLY

____________ GENES: are carried on the X chromosome X-linked recessive disorders show up _____________ in ______ than females because males only have ______ X chromosome. MALES X-LINKED ONE MORE frequently

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 bleeding from bruises or bumps. bleed to death Blood clotting proteins on X

Muscular Dystrophy CAUSE: deletion in gene that codes for a _______________ On X Chromosome Results in ____________________ and loss of ___________________ muscle protein weakening skeletal muscle 1 out of 3000 males in US

COLORBLINDNESS CAUSE: Mutation in one of three genes for _______________ carried on X chromosome Persons with this disorder have trouble distinguishing colors. Seen in 1 in 10 males 1 in 100 females Color vision

When Harry Met Sally… Harry and Sally are two normal vision adults who have a color blind son. – B – normal vision b – color blind – What are the genotypes of Harry and Sally? X B Y, X B X b Show the cross between Harry and Sally /2/istockphoto_ _cute_cartoon_couple_drinki ng_vector.jpg

When Harry Met Sally… Give all of the possible genotypes and phenotypes of their offspring. _________ – normal vision daughter ________ – normal vision daughter (carrier) ________ – normal vision son ________– color blind son Sally’s dad has normal vision. Is Sally’s Mom colorblind? She could be colorblind, or she could be a carrier for the colorblindness trait /2/istockphoto_ _cute_cartoon_couple_drinki ng_vector.jpg

PEDIGREE CHARTS Show the relationships within a family to study one particular observable trait/phenotype. Refer to page 342 in text. Circle=female Square=male Horizontal line=marriage Vertical line and bracket=children Shaded=person expresses trait Unshaded=person does not express trait.

Pedigree Chart for Color Blindness