notes kuliah1 aqu2203 sem_i 201213d

AQU2203

Teknik Pembiakbakaan Ikan

Lecture 1

Introduction to Genetics

© Dr. Shahreza, FPAI, UMT

1

Lecture 1


Objective :

1) To expose students to the basic concepts of

genetic and its relation to fish breeding.

2) To develop understanding about genetic

approach in fish production.


AQU2203 Teknik Pembiakbakaan Ikan 2

Lecture 1


Lecture Content :

Basic concepts of genetics.

Gene

Phenotype and Genotype.

Gene Interaction


AQU2203 Teknik Pembiakbakaan Ikan 3

Lecture 1

Concepts of Genetics

Learning Outcome :

At the end of lecture, students should be able to :

Explain how certain traits are produced and

inherited in fish

Characterize the types of phenotypes

Differentiate the gene interaction

AQU2203 Teknik Pembiakbakaan Ikan


4


Zygote

Fertilization Sperm

Egg

Fish like all living organisms, reproduce and

inherit their traits from one generation to the

other

It involve several processes which

ensures that their genetic information

are maintained and passed on to the

next generation.


5

These information are found in

the DNA which is located in the

cell.

Cell

DNA contains all the biological information of an organism

(e.g. type of body colour, scale, pattern, fin, shape)



6

Organisms are made up of billions of cells

These cells carry all the information about the biological functions of an organism

Genetic information is located in the double helix structure called DNA (Deoxyribonucleic Acid)

DNA is a chemical structure that forms Chromosome

Consist of sequence of bases and nucleotides : (Adenine (A), Guanine (G), Thymine (T) dan Cytosine (C)) in a double helix structure.

Genetic information is coded in the different arrangements of these 4 nucleotides.

Contains various sequence that can be identified through various methods in the study of DNA.

All living things are made up of DNA

7 AQU2203 Teknik Pembiakbakaan Ikan


A field of science about hereditary and variation

Studies the inheritance scientifically

A science about gene



GENE

Body colour

Body shape

Flesh Quality

Growth

Disease resistance

Controls various biological function in

organism



What is a Gene ?

Basic unit of hereditary information that can be inherited from

one generation to the other.

It is made of DNA :

- Consist of DNA sequence (nucleotides that codes for a

certain function)

Exist in a chemical structure of a DNA molecule

Sequence of DNA that codes for a certain

function (protein, biochemical process,

physical characteristics) in an organism



11

In an organism, genes are

carried on a chromosome that

is found in the nucleus of

each cell

Location of a gene on a

chromosome is called locus



A gene or set of genes contains the blueprints or chemical instructions

for the production of a protein.

Proteins – forms or helps produce various phenotypes (body colour,

shape, sex, number of rays, body length)



Protein

DNA RNA Trancription

Translation



How a Characteristics of an Organism is

Expressed

Genotype

Gene that controls a

particular phenotype of an

organism

Acts together with

environmental factors to form

a certain phenotype

Phenotype

The physical characteristics that is

expressed by a particular gene or a

group of genes

Can be divided into :

- Qualitative Phenotype

- Quantitave Phenotype



Qualitative Phenotype

Phenotypes that can be described – colour, sex,

scale and colour pattern

Usually controlled by one or two genes

An alternative form of a phenotype is produced

by an alternative form of a gene (allele)



Different body colouration are due to

different allele of colour genes



Qualitative Phenotype – Autosomal

Phenotype that is controlled by genes located on an autosome

They are not related with sex

Autosomal genes are inherited and expressed equally in male and female



Qualitative Phenotype – Autosomal



Body colouration and pattern in some fishes

are not controlled by sex and are expressed

equally in males and females

Qualitative Phenotype – Sex-Linked

Phenotype that is controlled by genes located on a chromosome that controls sex

Sex-linked genes are inherited and expressed differently in male and female

Mostly identified in ornamental fish.

e.g. body colour, fin shape



Qualitative Phenotype – Sex-Linked

Swordtail

Guppy

Body colouration and fin shape in

some fishes are controlled by sex

and are expressed differently in

males and females



Quantitative Phenotype

Phenotypes that are measured – length, weight, feed

conversion

Usually controlled by many genes (up to hundreds of genes)

Strongly influenced by environmental variables (size, age,

stocking density and water condition)



Quantitative Phenotype – Sex-Linked

Tilapia

Grouper

Body size in some fishes are

controlled by sex and are expressed

differently in males and females

Example :

Male Tilapia and grouper are bigger

compared to female



2N Spermatogonium

N N Secondary Spermatocyte

(haploid)

First Meiotic Division

Second Meiotic

Division N N N N Spermatid (haploid)

2N Primary Spermatocyte

Mitosis

2N

SPERMATOGENESIS

N N N N Sperm (haploid)



2N Oogonium

N N Secondary Oocyte and

First Polar Body

First Meiotic Division

Primary Oocyte 2N 2N

N N

Ovum dan Second

Polar Body

N N

Second Meiotic

Division

OOGENESIS

Mitosis



Zygote (2n)

Fertilization Gamete (n)

Female

Gamete (n)

Male



Cell Replication Formation of Gametes

Involves Mitosis and Meiosis

•Affect gene interaction and inheritance

•Can be manipulated



Expression of a phenotype is caused by reaction of 1 or a pair of

allele in the genome of an organism

2N

Occurs due to reaction of a gene or a group of genes that is

responsible towards a specific phenotypic characteristics

2N



Interaction of a

pair of allele

Interaction of a

group of alleles

Gene can be expressed in an additive or non-additive manner

2N

Equally

Expressed

2N

> or

<

Each allele contributes equally

to the production of the

phenotype

One allele (dominant allele) is

expressed more strongly than

the other allele (recessive

allele)



Gene action will give variation in the phenotypic expression of an organism

Phenotypic expression can be divided into 2 major catogories :

Qualitative Phenotype and Quantitative Phenotype

The result of gene action can be analyzed and determined

Example :

Colours, sex, scale pattern

Example :

Length, weight



Most qualitative phenotypes are controlled by single autosomal genes

with 2 alleles per locus

Qualitative phenotypes can also be controlled by 2 autosomal genes

(example : scale pattern of common carp; body colour of fighting fish)

2N

Single autosomal gene

with 2 alleles per locus

2N

2 autosomal gene with

2 alleles per locus



Different genotype will produce clearly define different phenotype

The genetic of qualitative phenotypes is simple and is often called

”Mendelian Genetics”.

Complete

Dominant Incomplete

Dominant

Additive



Occurs when a strong dominant allele produces phenotype regardless of

the genotype.

Recessive allele only produced its phenotypic characteristics when no

dominant allele is present.

Phenotype Genotype

Dominant

Dominant

Recessive

Homozygous Dominant

Heterozygous

Homozygous Recessive

2N

Locus which has 2 dominant alleles will produce only 1 phenotype.

Dominant gene action can produce 3 genotypes and 2 phenotypes



X

A a

AA Aa

aa

A : dominant allele

a : recessive allele

2 Phenotype

3 Genotype



AA AA AA AA

X A A a a

Aa Aa Aa Aa

X A A A A

AA Aa AA Aa

X A A A a

Genotype :

100% AA

Phenotype :

100% Dominant

Genotype:

100% Aa

Phenotype :

100% dominant

Genotype :

50% AA : 50% Aa

Phenotype :

100% dominant



AA Aa Aa

X A a a a

Aa Aa

X A a A a

aa aa aa

aa aa

X a a a a

aa aa

Genotype :

25% AA : 50% Aa : 25% aa

Phenotype :

75% Dominant : 25% recessive

Genotype :

50% Aa : 50% aa

Phenotype :

50% Dominant : 50% recessive

Genotype :

100% aa

Phenotype :

100% recessive



Occurs when the dominant allele expresses itself more strongly than the

recessive allele but not strong enough to suppress the recessive allele in

the heterozygous genotype.

Phenotype Genotype

Dominant

Heterozygous

Recessive

Homozygous Dominant

Heterozygous


2N

Dominant phenotype can be produced only when individual has 2 copies

of the dominant allele (Homozygous dominant, example : AA)

Heterozygous individuals will produced a phenotype that resembles but

not identical to the dominant phenotype

Each set of genotype produces its own phenotype :

3 Genotypes dan 3 Phenotypes

>



AA Aa aa

X

A a

A : dominant allele

a : recessive allele

3 Phenotype

3 Genotype



AA AA AA AA

X A A a a

X A A A A

X A A A a

AA AA Aa Aa

Aa Aa Aa Aa

Genotype :

100% AA

Phenotype :

100% Dominant

Genotype :

100% Aa

Phenotype :

100% Semi-Dominant

Genotype

50% AA : 50% Aa

Phenotype :

50% Dominant : 50% Semi-Dominant



X A a a a

AA aa Aa Aa aa aa Aa Aa

Genotype :

25% AA : 50% Aa : 25% aa

Phenotype :

25% Dominant : 50% Semi-Dominant : 25% recessive

Genotype :

50% Aa : 50% aa

Phenotype :

50% Semi-Dominant : 50% recessive

X a a a a

aa aa aa aa

Genotype :

100% aa

Phenotype :

100% recessive

X A a A a



Occurs when no allele is dominant over the other allele.

Both alleles contribute equally to the production of the phenotypes.

Phenotype Genotype

Dominant

Heterozygous

Recessive

Homozygous Dominant

Heterozygous


2N

Heterozygous genotype (A a) produces a phenotype that is intermediate

between the 2 homozygous genotypes (A A or a a).

In additive gene action, 3 types of genotypes will produce 3 types of

phenotypes.



CC CC’ C’C’

X

C C’

3 Phenotype

3 Genotype



AA AA AA AA

X A A a a

X A A A A

Aa Aa Aa Aa

AA Aa AA Aa

X A A A a

Genotype :

100 AA

Phenotype :

100% Dominant

Genotype:

100% Aa

Phenotype :

100% Co-Dominant

Genotype :

50% AA : 50% Aa

Phenotype :

50% Dominant : 50% Co-Dominant



X a a a a

aa aa aa aa

X A a A a

AA Aa Aa aa

X A a a a

Aa Aa aa aa

Genotype :

25% AA : 50% Aa : 25% aa

Phenotype :

25% Dominant : 50% Co-Dominant : 25% recessive

Genotype :

50% Aa : 50% aa

Phenotype :

50% Co-Dominant : 50% recessive

Genotype :

100% aa

Phenotype :

100% recessive



X A a

AA Aa aa

AA Aa aa

CC CC’ C’C’

X

C C’

X A a



Traits that can be measured

It is complex because it involves interaction of more than 2 genes.

Influenced by environmental factors.

2N

Interaction of

several genes

Can be determined based on MEASUREMENT and DIMENSION



Growth Rate

FCR (Feed Conversion Efficiency)

Tolerance to temperature, salinity

or low dissolve oxygen

Fecundity

Dressout percentage



In a population, variation of a trait forms a continuum rather than discrete

phenotypic classes.

Individual Length Weight

1 20.5 210.4

2 21.0 200.0

3 22.0 205.5

4 20.0 212.4

5 20.2 207.8

6 19.6 203.3

7 21.4 209.6



Example of a continuous data

(VP) = VG + VE

Where :

VP = Phenotypic variance

VG = Genetic Variance

VE = Environmental variance

Phenotypic Variance



A component that breeders try to manipulate in a breeding

programme

Genetic variance is the sum of 3 components

Genetic Variance (VG)

GENETIC VARIANCE

ADDITIVE GENETIC VARIANCE

DOMINANCE

GENETIC VARIANCE

EPISTATIC

GENETIC VARIANCE

Superior

genetic traits



Genetic Variance

Contribution of alleles

towards the phenotypic

production of a fish

Interaction between

pairs of alleles

Interaction Among Loci

Interaction Between Loci

ADDITIVE

GENETIC VARIANCE (VA)

DOMINANCE

GENETIC VARIANCE

(VD)

EPISTATIC

GENETIC VARIANCE

(VI)

VG = VA + VD+ VI



X

Parent

Contribution of alleles towards the

phenotypic production of a fish

Interaction between

pairs of alleles

ADDITIVE

GENETIC VARIANCE (VA)

DOMINANCE

GENETIC VARIANCE (VD)

Male Female

Progeny



notes kuliah1 aqu2203 sem_i 201213d

Documents

gene phenotype

sequence of dna

gene allele

gene interaction

dna sequence nucleotides

dna deoxyribonucleic

dna molecule

particular gene