Lecture 10 Part B

Intermediate phenotypes

With incomplete dominance, heterozygotes exhibit ______ (Rr will be pink)

1:2:1

A cross between two plants with pink flowers yields ______ genotypic and phenotypic ratios

Hypercholesterolemia & hair type (straight, curly, or wavy)

Human example of incomplete dominance: ______ & ______

Codominance

______ - heterozygotes exhibit both phenotypes (Rr will show both colors)

Dominant

Co-dominant

Many genes have more than just two possible alleles

• blood type is determined by three alleles (I^A, I^B, and i)

  • I^A and I^B are both ______ to i

  • I^A and I^B are ______

Pleiotrophy

______ - one single gene affects more than 1 trait

Ie: Sickle cell disease

• blood flow sniffing oxygen transport are impaired

• Confers an advantage against malaria

Polygenic inheritance

______ - two or more genes affect one single trait

• produces a distribution with continuous phenotypic variation

• Skin color is determined by 100+ genes

  • Aa, Bb, and Cc are examples

Linked genes

Independent assortment

_____ are genes located on the same chromosome

• are inherited together

• Do not follow Mendel’s law of _______

same chromosome

genes that are inherited together are linked on the ____________

crossing over

recombinant

Gene linkage might not result in parental phenotypes since ______ produces _______ phenotypes

farther apart on a chromosome

closer

more recombinant phenotypes will be produced between genes that are __________

(_______ = less likely for crossing over to occur)

linkage maps

gene loci

_______ - use recombination data to determine the location of genes on chromosomes (_____)

xx

xy

human somatic cells have 44 autosomes and 2 sex chromosomes

• _____ = female

• _____ = male

single X chromosome

single X or Y chromosome

Fertilization unites egg + sperm

• An egg has 22 autosomes and a(n) ______

• A sperm has 22 autosomes and a(n) ______

homologous

much smaller

the two X chromosomes of females are _______, but the X and Y chromosomes of males are not

• (Y chromosome is ________ than the X chromosome)

sex-linked genes

x-linked genes

______ - genes on the sex chromosomes that code for traits other than sex

• (all are ______ since Y chromosomes code only for sex)

  • males receive all ______ traits from mom

males

females

sex-linked disorders are more common in ______ than in ______ (recessive alleles are always expressed in ______)

• the Y chromosome does not have an allele for the trait to “offset” the disorder Ie: muscular dystrophy, hemophilia, red/green color blindness

female with normal color vision

XᴺXᴺ

carrier female with normal color vision

XᴺXⁿ

colorblind female

XⁿXⁿ

male with normal color vision

XᴺY

colorblind male

XⁿY