BICH107/GENE105 9-18-2007

Features of a chromosome

What is the function of a telomere?

What is the function of a centromere?

From Figure 13.6, pg. 245, Human Genetics 6th edition by R. Lewis

Human chromosomes 1-22 are AUTOSOMES. We inherit one set from Mom and one set from Dad.

The X and Y chromosomes are SEX CHROMOSOMES. We also inherit these from our parents. Male offspring inherit one X and one Y. Female offspring inherit two X chromosomes.

Mitosis - (pronounced my-toe-sis) a process that divides duplicated genetic material in the nucleus plus cytokinesis (division of the cell) to produce two identical daughter cells

Here is a link to the Biology Project at the University of Arizona with a figure and animation depicting a cell undergoing mitosishttp://www.biology.arizona.edu/cell_bio/tutorials/cell_cycle/cells3.html

Meiosis - (pronounced my-o-sis) a process to convert a diploid cell to a haploid gamete, and cause a change in the genetic information to increase diversity in the offspring

Here is a link to the Biology Project at the University of Arizona and a tutorial on meiosis:http://www.biology.arizona.edu/cell_bio/tutorials/meiosis/main.html

Vertical transmission of genetic informationMost higher eukaryotes propagate through sexual reproduction that forms a new individual from two haploid sex cells (gametes).

Horizontal transmission of genetic information - will cover in detail next week

XX XY

Possible gametes: All are X 1/2 are X and 1/2 are Y

Genotype of sexchromosomes:

Gametes fromthe female

X

X

Gametes from the male

X YPunnett Square

XX

XX

XY

XY

Inheritance of sex chromosomes from parents to offspring

Gregor Mendel studied the inheritance of stable traits with two easily distinguishable forms, like plant height (tall and short) in

pea plantstrue tall true short

Tall phenotype is dominant over short

Hybrid tall true short

T

T

t t

Tt Tt

Tt Tt

The short phenotype reappears in crosses with hybrid tall parent

T

t

t t

Tt Tt

tt ttExpect all hybrid tallplants

Expect two hybrid tallplants and two short plants

From http://www.hhmi.org/genetictrail/

Inheritance of Recessive Disorders: One Chance in Four

BICH107/GENE105 9-18-2007

N

d

N d

NN

Nd

Nd

dd

Inheritance of Dominant Disorders: A Fifty-Fifty Chance

From http://www.hhmi.org/genetictrail/

BICH107/GENE105 9-18-2007

n

n

D n

Dn

Dn

nn

nn

From http://www.hhmi.org/genetictrail/

Inheritance of X-Linked Disorders: Males are at Risk

BICH107/GENE105 9-18-2007

X

X

X Y

XX

XX

XY

XY

Human traits that determined by inheritance of alleles that have simple dominant and recessive characteristics

ability to roll the tongue is dominant (R)non-rolling is recessive (r)

ear lobes hang free is the dominant (E) attached earlobe is recessive (e)

left thumb is on top is dominant (C)the right thumb is recessive (c)

A straight thumb is dominant (S)a bent thumb is recessive (s)

Widow’s peak is dominant (W)a straight hairline is recessive (w)

mid-digital hair is dominant (H) lack of mid-digital hair is recessive (h)

little fingers bend away is dominant (B)straight little fingers are recessive (b)