Human Heredity:Human Heredity:Karyotypes and PedigreesKaryotypes and Pedigrees

Mrs. KooimanMrs. Kooiman

LSHS LSHS

09-1009-10

VocabularyVocabulary

karyotype karyotype

sex chromosome sex chromosome

autosome autosome

pedigree pedigree

Human ChromosomesHuman Chromosomes By taking a look at the nucleus, we will see By taking a look at the nucleus, we will see

chromosomes of a human cell.chromosomes of a human cell. To analyze chromosomes, cell biologists To analyze chromosomes, cell biologists

photograph cells in mitosis, when the photograph cells in mitosis, when the chromosomes are fully condensed and easy to chromosomes are fully condensed and easy to see. see.

The biologists then cut out the chromosomes The biologists then cut out the chromosomes from the photographs and group them together from the photographs and group them together in pairs. in pairs.

A picture of chromosomes arranged in this way A picture of chromosomes arranged in this way is known as a is known as a karyotypekaryotype (KAR-ee-uh-typ).(KAR-ee-uh-typ).

Karyotype Karyotype 

These human These human chromosomes have chromosomes have been cut out of a been cut out of a photograph and photograph and arranged to form a arranged to form a karyotype.karyotype.

There are There are 46 46 chromosomes in chromosomes in this karyotype of this karyotype of somatic cellssomatic cells

There are There are 23 pairs23 pairs of somatic cellsof somatic cells

The first 22 pairs The first 22 pairs are called are called autosomesautosomes

The last pair are The last pair are called called sex sex chromosomeschromosomes

XX XX == Female Female XY XY = = MaleMale What is the gender What is the gender

of this karyotype?of this karyotype?

Males and females are born in a roughly 50 : 50 Males and females are born in a roughly 50 : 50 ratio because of the way in which sex ratio because of the way in which sex chromosomes segregate during meiosis. chromosomes segregate during meiosis.    

All human All human egg cells egg cells carry a single carry a single X X chromosome.chromosome.

However, half However, half of all sperm of all sperm cells carry an cells carry an X X chromosome chromosome and half carry and half carry a Y a Y chromosome.chromosome.

This ensures This ensures that just that just about half, 2 about half, 2 out of 4, of out of 4, of the zygotes the zygotes will be XX will be XX

This ensures This ensures that just about that just about half, 2 out of 4, half, 2 out of 4, of the zygotes of the zygotes will be XYwill be XY

Pedigree Charts Pedigree Charts

Human genes are inherited according to Human genes are inherited according to the same principles that Gregor Mendel the same principles that Gregor Mendel discovered in his work with garden peas. discovered in his work with garden peas.

However, in order to apply Mendelian However, in order to apply Mendelian genetics to humans, biologists must genetics to humans, biologists must identify an inherited trait controlled by a identify an inherited trait controlled by a single gene to ensure that the trait is single gene to ensure that the trait is actually inherited and not the result of actually inherited and not the result of environmental influences. environmental influences.

A A pedigreepedigree chart shows chart shows the the relationships relationships within a within a family family

A CIRCLE A CIRCLE represents a represents a Female, Female,

A SQUARE A SQUARE represents a represents a Male, Male, ■■

A A HORIZONTAL HORIZONTAL line represents line represents a marriagea marriage

A VERTICAL A VERTICAL line and a line and a BRACKET BRACKET connect the connect the parents to their parents to their childrenchildren

Generation 1 Generation 1 had 5 childrenhad 5 children

How many How many sons?sons?

How many How many daughters?daughters?

The children The children are listed from are listed from LEFT to LEFT to RIGHTRIGHT

The OLDEST The OLDEST child is firstchild is first

The The YOUNGEST YOUNGEST child is lastchild is last

A SHADED circle A SHADED circle or square means or square means the person the person expresses the expresses the trait.trait.

An OPEN circle An OPEN circle or square means or square means the person does the person does not express the not express the trait.trait.