Genetics Flashcards
Genetic material is passed from parents through reproductive cells, _____ and _____, to offspring creating a link from generation to generation
Sperm and ova
Study of heredity and variation
Genetics
The occurrence of differences among individuals of the same species
Variation
Nuclear structures that carry the genes containing genetic material
Chromosomes
_____ are found at a fixed location on the chromosome
Genes
The basic unit of inheritance
Gene
A gene is a defined unit of ____ composed of a certain _______ _______
DNA
nucleotide sequence
Double stranded molecule composed of nucleotides
DNA
Nucleotides are composed of what 3 things?
Pentose sugar
Phosphate group
Nitrogen containing base
Bases can be classified as a _____ or a _____
Purine or pyrimidine
Two purines
Adenine and guinine
Two pyrimidines
Thymine and cytosine
Adenine bonds to______
Cytosine bonds to______
Thymine
Guinine
______ are double ringed and ______ are single ringed
Purines
Pyrimidines
Double helix structure founded by who?
Watson and Crick
Process where mRNA is formed from DNA
Transcription
Process where mRNA is converted to a protein
Translation
3 base sequence provided for a specific protein after _____ attaches to ribosome
Codon
mRNA
____ attaches to a specific amino acid based in a 3 base sequence called an ____ ____
tRNA
anti codon
Occur in pairs in mammalian cells and the number is constant for a species
Somatic cells
All cells have a full set of ______ (2n:____) except for reproductive cells which one have n (____)
Chromosomes
Diploid
Haploi
For each pair of chromosomes in an individual, one came from the ____ and one came from the _____
Male
Female
Chromosome numbers Man Cattle Swine Horse Sheep All are haploid or diploid?
46 (23 pairs) 60 (30 pairs) 38 (19 pairs) 64 (32 pairs) 54 (27 pairs) Diploid (2n)
What determines the sex of the animal?
XY=_____
XX=_____
Sex chromosomes
Male
Female
Process of cell division where two identical daughter cells are formed with the same compliment of chromosome pairs
Haploid or diploid?
Mitosis
Diploid
Process of cell division where daughter cells (sperm or ova) contain one half the number of chromosomes
Haploid or diploid?
Meiosis
Haploid
The production of gametes
Gametogenesis
Steps of spermatogenesis
Primordial germ cell Primary spermatocyte Secondary spermatocyte Spermatid Mature sperm
The primordial germ cell is also called ____ and ____ during gamete formation
Spermatogonia and oogonia
Steps of oogenesis
Primordial germ cell Primary oocyte Secondary oocyte Ootid Ovum
____ mature sperm are produced from spermatogenesis and ___ mature ova are produced from oogenesis
4
1
1 cell in oogenesis becomes ____ ____ and does not continue through maturation process
Polar body
The specific location of a gene on a chromosome
Gene locus
______ chromosomes are right across from each other
Homologous
Forms the coding system that directs the production of enzymes and proteins and thus controls the development of all traits
Gene locus
Different forms of a gene that can occur at the same locus
Ex?
Allele
Coat color in cattle
Alleles at homologous gene sites are identical
Homozygous
Alleles at homologous gene sites are not identical
Heterozygous
Genetic material of an individual as determined by it’s genes
Genotype
Physical expression of an individual’s genotype
Result of _____ _____ and _____
Phenotype
Gene content and environment
Phenotype=_____+_____
Genotype
Environment
Who is the father of genetics?
______ monk
First to understand ______
Found two major _____
Gregor Mendel
Austrian
Inheritance
Principles
Two principles founded by Gregor Mendel
Principle of segregation
Principle of independent assortment
Paired genes are separated from each other and distributed in different sex cells
Principle of segregation
Alleles are separated into sex cells
Each allele has an equal chance of being included in a gamete
Principle of independent assortment
What are the two types of inherited traits?
Qualitative and quantitative
Traits controlled by one or two genes
Examples
Qualitative traits
Coat color, horns, inverted nipple, cryptorchidism
One testicle doesn’t descent from body
Cryptorchidism
Traits affected by man genes and contain a continuous variation
Examples
Quantitative
Rate of gain, feed efficiency, milk production, carcass quality, fertility
Hornlike tissue attached to skin of polled cattle
Dominant or recessive trait?
Scurs
Dominant trait
Inheritance
Each _____ will have a different affect on _____
Allele
Phenotype
Allele expresses itself or limits the expression of other alleles
Dominant allele
The allele whose expression is limited
Recessive allele
The polled traitor cattle is dominant or recessive
Dominant
Neither allele completely covers the other, this the phenotype is a mixture or blending
Example
Codominance Coat color in shorthorn - RR: red - WW : white - RW : roam
A gene or gene pair masks (or controls) the expression of another non-allergic gene pair
Example
Epistasis
Albinoism in cats
The heterozygote is superior to either of the homozygotes
Overdominance
Performance of offspring is superior to average of the parents
Example
Heterosis
Milk production, growth traits, reproduction
Two methods for genetic improvement
Selection
Mating or breeding systems
Choosing which animals in a generation will be allowed to become parents in the next generation and thus be the source of genetic material for the population
Selection
Selection changes the _____ _____ of a gene in the population
Allelic frequency
Methods of selection (4)
Single trait selection
Tandem selection
Independent culling level
Selection index
Select for a trait until some desired level is reached then select for another trait
Tandem selection
Set minimum standards for a trait and cull animals that fail
Downside?
Independent culling level
Animal could be superior in other traits as well
Combines traits into one value based on their economic importance and level of genetic variation
Most fundamentally sound method!
Selection index
Selection tools (6)
Appearance Pedigree Family selection Individual performance records Progeny testing Genotyping
Portion of phenotypic variation that is due to genetic causes and can be passed onto offspring
Heritability
Selection tools:
Eliminate physical abnormalities
Select for certain conformation
Structural soundness
Appearance
Selection tools:
Record of ancestry
Identifies lines that excel in traits
Pedigree
Selection tools:
Selection based on performance of the entire family
Poor performing families are culled
Family selection
Selection tools:
Information on the individual
Trait has to be moderately to highly heritable
Individual performance records
Selection tools:
Evaluation of an individual based on its offspring
Progeny testing
Selection tools:
Absence/presence of markers
Look for favorable traits
Genotyping
The objective of using selection tools is to develop _______ _______
Breeding values
A measure do the genetic value of an animal
Breeding value
The amount an individual can contribute to its offspring
Formula?
Transmitting ability
Breeding value/2
Two main forms of transmitting abilities use in the livestock industry
Expected progeny difference
Predicted transmitting ability
EPDs and PTAs are based on records from what 3 things?
Individual
Pedigree
Progeny
Requirements to make genetic progress (2)
Trait must be heritable
Must be variation in population
Genetic progress formula
H^2 x selection differential
Difference between the average of the individuals selected for mating and the population
Selection differential
3 types of mating systems
Random
Inbreeding
Outbreeding
Mating with no selection
Random mating
Mating of animals that are more closely related than the average of the population
Inbreeding
Concentrate the genotype of one superior animal
_____ _____ mated to __________
_____ _____ mated to __________
Consequence?
Line breeding
Male parent to granddaughter
Female parent to grandson
All begin to look alike
Reduction of genetic variability and thus reduced vigor and fertility
In breeding depression
Mating of animals that are less closely related than the average of the population (but same breed)
Outbreeding
genetics of one of crossbred parents that would maintain superiority in crossbreeds
Complimentarity
Performance of crossbred offspring that exceeds average of the parents
Formula?
Heterosis
To get heterosis: _______-_______
Percent heterosis: (_____-_____)/____ x100
(Average of population)-(average of parents aka expected value)
(Actual-expected)/expected x100
Carcass has a ______ heritability and a ____ heterosis
High
Low
Growth has a _____ heritability and a ______ heterosis
Medium
Medium
Reproduction had a ______ heritability and a _____ heterosis
Low
High
mating systems (4)
Two breed terminal cross
Two breed rotational cross
Three breed rotational cross
Three breed rota terminal cross
Advantages of two breed terminal cross (2)
Simple Maximized heterosis (100%)
Disadvantages of two breed terminal cross (2)
Have to maintain purebred herds
No heterosis in females
Advantages of two breed rotational cross
Simple
Produce females
Heterosis in dam
Heterosis in dam means added _______ and ______
Reproduction and fertility
Disadvantages or two breed rotational cross
67% heterosis
Two pastures needed
Advantages of 3 breed rotational cross
86% heterosis
Produce females
Heterosis in dam
Disadvantages of 3 breed rotational cross
Large numbers needed
Multiple pastures
Labor intensive
Advantages of two breed rota-terminal cross
Produce replacement females
Heterosis in female
Maxi mum heterosis in terminal cross calves
Can utilize complimentarity in terminal cross calves
Disadvantages of two breed rota terminal cross
Only 67% heterosis in females and rotational calves
Requires greater number of animals to implement
Requires greater management input
