Bell Work Of the following which would represent

Bell Work • Of the following which would represent that dominant allele? • A or a • In a second generation of hybrids (heterozygous), where pink is dominant and white is recessive, you have 24 pink flowers. How many white flowers should you expect to see? 1

Bell Work • Of the following which would represent that dominant allele? • A or a • In a second generation of hybrids (heterozygous), where pink is dominant and white is recessive, you have 24 pink flowers. How many white flowers should you expect to see? – 3: 1; so 24/3 = 8 white flowers 2

Incomplete & Codominance

Codominance • Defined: when a single gene has more than one dominant allele • Ex: Cattle Coat Red cow x White cow = – Myth: Colors blend

Codominance • Defined: when a single gene has more than one dominant allele • Ex: Cattle Coat Red cow x White cow = – Myth: Colors blend – Reality: Both colors are equally seen

A A A B B A A B B B Codominance • Defined: when a single gene has more than one dominant allele • Ex: Cattle Coat Red cow x White cow = – Myth: Colors blend – Reality: Both colors are equally seen • Ex: Human Blood types Type A x Type B = Type AB

Blood Types • Human blood type has 3 alleles – Dominant A allele – Dominant B allele – Recessive O allele • Type A & Type B are dominant to type O • Type A and Type B are codominant to each other Dad will pass 1 of these 3 Mom will pass 1 of these 3 Type AB Type A Child genotypes Type B Type AB Type A Type B Type O

Incomplete Dominance PP pp pp Purple must be dominant to white.

Incomplete Dominance RED • • PINK WHITE Defined: Neither allele is completely dominant Heterozygous = blended appearance More than 2 different phenotypes can occur Ex: Many flower colors

Which is which? Which flower shows incomplete dominance? Which flower shows codominance? Codominance Incomplete dominance

• SEX-LINKED GENES

Sex Determination - Review • Thomas Hunt Morgan – studied fruit flies in the early 1900’s; Columbia University. • Proved meiosis works in animals.

Sex Determination - Review • Observed that one pair of chromosomes was different between males and females – Large one named “X” chromosome – Smaller one named “Y” chromosome – XX = female; XY = male

Sex Chromosomes In many organisms, the Y chromosome is greatly reduced or inactive. genes on the X chromosome are present in only 1 copy in males (XY) sex-linked traits: controlled by genes present on the X chromosome Sex-linked traits show inheritance patterns 14

Sex Linkage • Sex Linkage: the presence of a gene on a sex chromosome (X or Y) • X-linked genes: genes found on the X chromosome – X chromosome carries more genes • Y-linked genes: genes found on the Y chromosome

Hemophilia • 1 in 5000 male births. 1/3 of the births happen to families with no history. • Sex-linked = X linked • This is a bleeding disorder, where the affected people cannot clot the blood. • Treatment is that patients are given injections of the clotting factors

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In humans colorblindness (b) is an example of a sex-linked recessive trait. A male with colorblindness marries a female who isn’t colorblind and does not carry the allele. What is the chance they will have a child that is colorblind?

Sex Chromosomes and Barr Bodies • Barr Body: Two X Chromosomes are found in every cell of a mammalian females. • One will become inactive in each cell of the body. Either from The male or female parent. • The inactivation of X chromosome is random in each embryonic cell. (Father or Mother lineage. ) Giving a mosaic of traits. Each cell will divide through mitosis. • Ex. Patchy coloration in female tortoise shelled collored 19 cats, and females with patchy sweat glands.

Review Videos • Co/Incomplete: https: //www. youtube. com/watch? v=VG 0 Kt dpj 7 Rg • Sex-Linked Traits: https: //www. youtube. com/watch? v=q. YHJq 47 i. ZPE • **Punnett squares will be covered in the next class

Class Work / Home Work • Read Pages 468 – 481 • AFTER READING, complete the forms assignment (link on the website)