Genetics: Allele Dominance and Sex Determination

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Questions and Answers

What genotype combination represents a homozygous dominant plant for seed color?

AA (correct)

Which of the following genotypes would produce green seeds in the F2 generation?

aa (correct)

In Mendelian genetics, how are traits produced in the F2 generation from the F1 progeny?

The traits assort independently and can be a mix of dominant and recessive. (correct)

The F2 generation has only one genotype.

F2 generation exhibits the same phenotype as F1.

Only dominant traits are expressed.

What is meant by the term 'linkage' in genetics?

Genes that are physically close together on the same chromosome. Signup and view all the answers

What is the resulting phenotype when the F1 generation (AaBb) is crossed?

Yellow rough seeds and green smooth seeds appear. Signup and view all the answers

How many types of gametes are produced in males during segregation?

Two types of haploid sperm cells. Signup and view all the answers

Which sex-determining system is most common in fish species and humans?

XX/XY system Signup and view all the answers

What are polar bodies in the context of female gamete formation?

Non-functional cells produced during meiosis that do not develop further. Signup and view all the answers

What does the variable P represent in the relationship P = G + E + GE?

Phenotypic value for an expressed phenotype Signup and view all the answers

Which component is NOT part of the genetic value (G) breakdown?

Genomic design (Gd) Signup and view all the answers

What does GE refer to in the equation P = G + E + GE?

The combined effects of environment on genotype Signup and view all the answers

How can different individuals within the same environment respond?

Their responses can vary based on genetic differences. Signup and view all the answers

What is the significance of genetic variance in breeding programs?

It plays a key role in exploiting desirable traits. Signup and view all the answers

Which term is associated with interaction effects in genetic value?

Epistatic effects (I) Signup and view all the answers

In the equation P = G + E + GE, which factor represents the environmental influences?

E Signup and view all the answers

Which of the following statements about phenotype is true?

Phenotype can vary significantly based on environmental factors. Signup and view all the answers

What is the initial phase of cell division in fish after fertilization called?

Cleavage phase Signup and view all the answers

Which sex-determining system designates homoga- metic fish as males?

WZ system Signup and view all the answers

Which statement about blue tilapia is correct?

Females contain the WZ sex chromosomes. Signup and view all the answers

What happens during the cleavage phase?

Blastomeres undergo rapid division. Signup and view all the answers

In the ZO sex-determining system, what does the female phenotype represent?

Heterogametic sex Signup and view all the answers

How does the W chromosome function in sex determination?

It serves as the sex-determining chromosome for females. Signup and view all the answers

Which species is identified to have the ZO sex-determining system?

Dwarf gourami fish Signup and view all the answers

What initiates the formation of germ layers in embryonic development?

Event of gastrulation Signup and view all the answers

What is the equation that describes the relationship between total phenotypic variance and its components?

VP = VG + VE + VGE Signup and view all the answers

What does a heritability value of 0 imply about a phenotype?

The phenotype cannot be inherited predictably. Signup and view all the answers

For a selection program to be effective, which of the following should be determined?

The amount of additive variance. Signup and view all the answers

What does a heritability value greater than 0.2 suggest?

The trait may be reliably exploited in a selection program. Signup and view all the answers

Which component contributes to the genetic variance for a trait?

Additive genetic variance (VA) Signup and view all the answers

What type of hybridization involves breeding different species?

Interspecific hybridization Signup and view all the answers

The interaction between genetic variance and environmental variance is denoted as which component?

VGE Signup and view all the answers

Which heritability value indicates a phenotype resulting entirely from additive genetic variance?

1 Signup and view all the answers

What is a significant advantage of using a homozygous DNA template in whole genome sequencing?

It reduces the complexities from DNA sequence variations. Signup and view all the answers

How are androgens produced using irradiated eggs?

By fertilizing with regular sperm and shocking the zygote post-replication. Signup and view all the answers

What result is achieved by fertilizing an irradiated egg with normal sperm?

A haploid zygote that is shocked to prevent cell division. Signup and view all the answers

What is the name given to fish created using the genetic method mentioned, which are commercially available in the United States?

GloFishTM. Signup and view all the answers

What does the use of an inducible promoter achieve in transgenic fish?

It enables expression of a marker gene when exposed to contaminants. Signup and view all the answers

What is a characteristic feature of androgens in the context of genetic studies?

They are completely homozygous. Signup and view all the answers

What is a significant concern regarding the application of genetic engineering in aquaculture?

The safety of genetically modified foods and ecological balance. Signup and view all the answers

What is the process used to create diploid zygotes that only contain male chromosomal material?

Doubling haploid nuclei after fertilization of an egg. Signup and view all the answers

Study Notes

Allele Dominance and Segregation

Dominant Allele: Yellow seed color (A)
Recessive Allele: Green seed color (a)
Parental Cross: Homozygous dominant (AA) x Homozygous recessive (aa)
F1 Generation: All heterozygous dominant (Aa) and yellow seeds
F2 Generation: Three genotypes (AA, Aa, aa) and two phenotypes (yellow or green seeds)

Independent Assortment of Genes

Independent assortment of genes may not hold true for all combinations of alleles (e.g., linked genes)

Sex Determination

XY Diploid System: Most common system in mammals and fish (e.g., humans, channel catfish)
WZ System: Opposite of XY system (e.g., blue tilapia); female is heterogametic, male is homogametic
ZO System: Female is heterogametic, male is homogametic (e.g., dwarf gourami fish, sole fish)

Phenotype and Genetic Variance

Phenotype (P) is a combination of genotype (G), environment (E), and genotype-environment interaction (GE): P = G + E + GE
Genetic Variance (VG): Additive genetic variance (VA), dominance genetic variance (VD), and epistatic or interaction variance (I): G = VA + VD + I
Phenotypic Variance (VP): VG + VE + VGE

Breeding Programs and Genetic Variance

Genetic variance: Key component in breeding programs to exploit desired traits
Heritability (h2): Proportion of additive genetic variance contributing to a phenotype
Heritability values (h2): Range from 0 to 1, with values greater than 0.2 suggesting a trait can be exploited for selection

Genetic Engineering in Aquaculture

Transgenic fish: Genetically modified fish
Advantages: Increased growth rates, disease resistance, and environmental monitoring
Disadvantages: Concerns about food and ecological safety, limited economic impact
GloFishTM: A commercially available glowing zebrafish, an example of transgenic fish

Androgens

Androgens: Fish with chromosomes only from the father
Creation: Fertilizing irradiated eggs with regular sperm, followed by genome duplication
Characteristics: Completely homozygous, useful for genetic studies due to reduced genetic complexity

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Description

Test your understanding of allele dominance, segregation, and independent assortment in genetics. This quiz covers key concepts such as phenotypes, sex determination systems, and genetic variance. Ideal for students exploring the fundamentals of genetic inheritance.