Transcript Genetics Terminology

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 = T
2. 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.
2.
Can roll tongue =
Dominant = T
Cannot roll tongue. =
Recessive = t
Each 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
•
•
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
•
Look at the offspring of the test cross
to determine if it is heter or
homozygous.
9,10,11
• 10.
–B½
– 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= Cocaptains 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
Sperm
1/
4 BC
1/

4 bC
BbCc
1/
4 Bc
1/
4 bc
Eggs
1/
1/
1/
1/
4BC
BBCC
BbCC
BBCc
BbCc
BbCC
bbCC
BbCc
bbCc
BBCc
BbCc
BBcc
Bbcc
BbCc
bbCc
Bbcc
bbcc
4 bC
4 Bc
4 bc
9
: 3
: 4
Non-Dominant Inheritance

• Polygenic InheritanceMany alleles develop a
trait. Example: Skin
Color
• Role of the environment
AaBbCcAaBbCc
Sperm
1/
1/
8
1/
8
1/
8
1/
8
Eggs1
8
1/
8
1/
8
1/ 1/ 1/ 1/ 1/
8 8 8 8 8
/8
1/
8
1/
1/
8
8
Phenotypes:1/64 6/64 15/64 20/64 15/64 6/64 1/64
Number of
0 1 2 3 4 5 6
dark-skin alleles:
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.
44 +
XY
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 +
XX
Parents
22 +
22 +
or Y
X
Sperm
+
44 +
XX
or
22 +
X
Egg
44 +
XY
Zygotes (offspring)
(a) The X-Y system
22 +
XX
22 +
X
76 +
ZW
76 +
ZZ
32
(Diploid)
16
(Haploid)
(b) The X-0 system
(c) The Z-W system
(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.
XNXN
Sperm Xn

Xn Y
(a)
Sperm XN
Y
Eggs XN XNXn XNY
XN
XNXn

XNY
Xn
(b)
Sperm Xn
Y
Eggs XN XNXN XNY
XNXn XNY
XNXn

Xn Y
Y
Eggs XN XNXn XNY
Xn XN Xn Y
Xn
(c)
Xn Xn Xn Y
Fig. 15-15
(a)
(b)
(c)
(d)
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 D E
F G H
Deletion
Duplication
A B C E
F G H
A B C B C D E
Inversion
A D C B E
R
F G H
M N O C D E
Reciprocal
translocation
M N O P Q
F G H
A B P Q
R
F G H
Quiz on Wednesday:chapter 16
•
•
•
•
•
A, T, C, G bonds
Purines vs. Pyrimidine
5’-3’ order
Replication, Transcription, Translation
Helicase, Leading and Lagging strand,