genetics terminology
DESCRIPTION
Genetics Terminology. Trait -characteristic or quality EX: Tongue rolling. The gene codes for the trait. There are 2 versions of the gene called Alleles. Can roll tongue = Dominant = T Cannot roll tongue. = Recessive = t - PowerPoint PPT PresentationTRANSCRIPT
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
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