Genetics Terminology

• Trait-characteristic or quality– EX: Tongue rolling.

• The gene codes for the trait. There are 2 versions of the gene called Alleles. 1.Can roll tongue = Dominant = T2.Cannot roll tongue. = Recessive = t

Each trait receives two alleles, one from the mother, one from the father.

• Homozygous: all of the same alleles.– TT or tt

• Heterozygous: Different alleles– Tt

• Genotype: Phenotype• TT : Rolls Tongue• Tt : Rolls Tongue• tt : cannot roll

• Phenotype: Physical/feel• Genotype: Genes

• Trait-characteristic or quality– EX: Tongue rolling.

• The gene codes for the trait. There are 2 versions of the gene called Alleles. 1. Can roll tongue =

Dominant = T2. Cannot roll tongue. =

Recessive = tEach trait receives two

alleles, one from the mother, one from the father.

Genetic Crosses• Monohybrid: one trait• Dihybrid: two traits

• Working backwards with you-grandparents: P generation

- parents : F1 Generation-You: F2 generation

Test Cross: used to determine if a phenotypically dominant individual is homozygous or heterozygous

True-breeding: homozygous for a trait.

• Homozygous: all of the same alleles.– TT or tt

• Heterozygous: Different alleles– Tt

• Genotype: Phenotype• TT : Rolls Tongue• Tt : Rolls Tongue• tt : cannot roll

• Phenotype: Physical• Genotype: Genes

Test Cross• Unknown dominant x known

recessive

• See example on the board

• Look at the offspring of the test cross to determine if it is heter or homozygous.

• Monohybrid: one trait• Dihybrid: two traits

• Working backwards with you-grandparents: P generation

- parents : F1 Generation-You: F2 generation

Test Cross: used to determine if a phenotypically dominant individual is homozygous or heterozygous

9,10,11

• 10. – B ½– C. ¼

• 11. – A. 1/8– B. 1/32– C. 1/32– D 1/32

Complete Dominance

• “Normal” dominance• The dominant allele is

completely expressed over the recessive allele.

Incomplete Dominance

• Incomplete = IN between

• The heterozygous genotypes have a phenotype that is IN between the two homozygous genotypes

• Red-Pink-White• RR – Rr - rr

Codominance and Multiple Alleles

• Co dominant= Co-captains of equal strenth on a team.

• The heterozygous alleles are equally expressed

• Multiple alleles. An additional allele can represent the recessive.

More non-Dominant Inheritance

• Pleiotropy-one gene has many effects

• Epistatis-one gene affects the expression of another gene

BbCc BbCc

Sperm

EggsBC bC Bc bc

BC

bC

Bc

bc

BBCC

1/41/4

1/41/4

1/4

1/4

1/4

1/4

BbCC BBCc BbCc

BbCC bbCC BbCc bbCc

BBCc BbCc

BbCc bbCc

BBcc Bbcc

Bbcc bbcc

9 : 3 : 4

Non-Dominant Inheritance

• Polygenic Inheritance-Many alleles develop a trait. Example: Skin Color

• Role of the environment Eggs

Sperm

Phenotypes:Number ofdark-skin alleles:0 1 2 3 4 5 6

1/646/64

15/6420/64

15/646/64

1/64

1/8

1/8

1/8

1/8

1/8

1/8

1/8

1/8

1/81/8

1/81/8

1/81/8

1/81/8

AaBbCcAaBbCc

Ch 15-mostly review

• Law of Segregation

• Law of Independent Assortment

• The 2 alleles that each parent has for a trait separate to make sex cells

• The alleles will be random in the sperm and egg.

Not all like humans

• Grasshoppers = two x is female, one x is male

• Z-W system is opposite humans, females determine

• Bees-diploid are females, haploid are males.

44 + XY

Parents 44 + XX

22 + X

22 +X

22 + Yor +

44 + XX or

Sperm Egg

44 + XY

Zygotes (offspring)

(a) The X-Y system

22 + XX

22 + X

(b) The X-0 system

76 + ZW

76 + ZZ

(c) The Z-W system

32(Diploid)

16(Haploid)

(d) The haplo-diploid system

• W+ is wild type, usually dominant always homozygous.

• Only male flies can have white eyes if they receive their only x from the mutant x.

Colorblindness: males are more affected than females. Gene is located

on X chromosome, heterozygous females are carriers.

(a) (b) (c)

XNXN XnY XNXn XNY XNXn XnY

YXnSpermYXNSpermYXnSperm

XNXnEggs XN

XN XNXn

XNY

XNY

Eggs XN

Xn

XNXN

XnXN

XNY

XnY

Eggs XN

Xn

XNXn

XnXn

XNY

XnY

Fig. 15-15

DeletionA B C D E F G H A B C E F G H(a)

(b)

(c)

(d)

Duplication

Inversion

Reciprocaltranslocation

A B C D E F G H

A B C D E F G H

A B C D E F G H

A B C B C D E F G H

A D C B E F G H

M N O C D E F G H

M N O P Q R A B P Q R

Quiz on Wednesday:chapter 16

• A, T, C, G bonds• Purines vs. Pyrimidine• 5’-3’ order• Replication, Transcription, Translation• Helicase, Leading and Lagging strand,