Genetics: Genotype and Phenotype Overview

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Questions and Answers

What will be the phenotype of all offspring from the cross of two homozygous recessive parents (pp * pp)?

  • Heterozygous recessive
  • Homozygous dominant
  • Heterozygous dominant
  • Homozygous recessive (correct)

What principle did Mendel discover that explains how alleles segregate during gamete formation?

  • The principle of segregation (correct)
  • The principle of dominance
  • The principle of independent assortment
  • The principle of genetic linkage

What is a complete set of chromosomes in a cell called?

  • Chromatid
  • Chromosome set
  • Genome
  • Karyotype (correct)

What is the cause of Down's syndrome (trisomy 21)?

<p>Failure of homologous chromosomes to separate during meiosis (B)</p> Signup and view all the answers

What is shown by heterozygous chickens that have both black and white speckled feathers?

<p>Codominance (C)</p> Signup and view all the answers

What does the term gametogenesis refer to?

<p>Production of sex cells (D)</p> Signup and view all the answers

How do harmful mutations affect organisms?

<p>They make the organism less able to survive (D)</p> Signup and view all the answers

What is the difference between outcrossing and cross breeding?

<p>Outcrossing is within a breed, while cross breeding involves different breeds. (D)</p> Signup and view all the answers

What effect does polyploidy have on chromosomes?

<p>It results in chromosomes that are multiples of the haploid number. (B)</p> Signup and view all the answers

Which statement about phenotypes and genotypes is correct?

<p>Phenotype can be influenced by the environment. (A)</p> Signup and view all the answers

What chromosomal condition is characterized by the gain of a single chromosome?

<p>Trisomy (A)</p> Signup and view all the answers

What information can be obtained from a karyotype?

<p>Number and structure of chromosomes (B)</p> Signup and view all the answers

What is grading up in animal breeding?

<p>Mating sires to commercial grade females to improve livestock (A)</p> Signup and view all the answers

Flashcards

Phenotype Prediction

The observable trait of offspring based on parent's genotype.

Principle of Segregation

Mendel's principle stating allele pairs separate during gamete formation.

Karyotype

A complete set of chromosomes in an organism.

Trisomy 21

A condition caused by a failure in chromosome separation, leading to Down's syndrome.

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Codominance in Chickens

A situation where both black and white feather traits are expressed equally.

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Condominance

A genetic scenario where both alleles in a heterozygote contribute to the phenotype.

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Gametogenesis

The process of producing gametes or sex cells in an organism.

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Harmful mutation

A genetic mutation that reduces an organism's ability to survive.

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Genotype vs Phenotype

Genotype is the genetic makeup; phenotype is the physical expression.

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Karyotype function

The karyotype reveals the number and structure of chromosomes in an organism.

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Polyploidy

A condition where an organism has extra sets of chromosomes (3n or 4n).

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Outcrossing

Mating individuals within the same breed to increase genetic variation.

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Domestication prerequisites

Characteristics necessary for turning wild animals into domestic ones.

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Study Notes

Genotype and Phenotype

  • Genotype predicts phenotype in offspring (pp x pp = pp offspring)
  • Homozygous recessive offspring have a homozygous recessive genotype.

Mendel's Discoveries

  • Discovered the principle of dominance
  • Discovered the principle of segregation
  • Discovered the principle of independent assortment
  • Birds and mammals have different sex chromosomes (false)
  • Animal genotypes can be manipulated by breeding (true)

Karyotype and Chromosome Number

  • A complete set of chromosomes is a karyotype.
  • All body cells (except gametes) have a diploid chromosome number.
  • Down syndrome (trisomy 21) results from homologous chromosomes failing to separate during meiosis.
  • Genotypes of parents can predict offspring phenotypes.

Predicting Offspring Genotypes

  • Offspring genotypes can be predicted by crossing heterozygous parents (Yy x Yy = YY, Yy, yY, yy)

Codominance Example

  • Heterozygous chickens with black and white speckled feathers exemplify codominance.

Phenotype Factors

  • Many factors (genes, environment) influence phenotype (true).

Gametogenesis

  • Gametogenesis is the term for the production of sex cells (true).

Genetic Disorders

  • Only changes in chromosome structure can cause genetic disorders (false).
  • Embryos have a haploid number of chromosomes (false).

Mutations and Survival

  • Mutations can make organisms less likely to survive (harmful).

Chromosomal Characteristics

  • Cells contain half the chromosome number (1N) in gametes (e.g., spermatozoa).
  • Genotype is the actual genetic makeup and phenotype is physical appearance.
  • Examples of phenotypes: eye color, hair color, height, tail length.
  • Examples of genotypes: genes responsible for hair, height, diseases.
  • Genome is called diploid, total number of chromosomes is called diploid number.
  • Karyotype provides information about chromosome number, sex, and structural abnormalities.
  • Autosomes control somatic characters, sex chromosomes control sexual characters.
  • Phenotype is a result of genotype and environment

Polyploidy and Aneuploidy

  • Polyploidy has a chromosome number that's a multiple of the normal haploid number (3n or 4n).
  • Aneuploidy involves gaining or losing a single chromosome (monosomy or trisomy).

Chromosome Structure Variations

  • Chromosome structure variations include deletions, duplications, translocations, and inversions.

Mating Systems

  • Inbreeding increases homozygosity.
  • Outbreeding increases heterozygosity (e.g., species cross; crossbreeding).

Crossbreeding Reasons

  • Crossing breeds brings good genes and increases productivity.

Domestication Prerequisites

  • Domesticated animals adapt to various feed types and can survive and reproduce with humans.

Breeding Effects - Broilers and Laying Hens

  • Broiler chickens have metabolic health problems due to rapid growth.
  • Laying hens have increased bone fractures and reduced fertility due to lower calcium intake.
  • Dairy cows may have reduced fertility and difficult births.

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