Genetics Study Guide

Questions and Answers

What is the difference between dominant and recessive traits?

Dominant traits appear when the dominant alleles are present. Recessive traits appear only when dominant traits are not present.

What is a genotype? What is a phenotype?

Genotype: the actual alleles that represent a trait on a chromosome. Phenotype: the physical appearance.

What is the difference between homozygous and heterozygous?

Heterozygous genotypes have two different alleles for a trait (e.g., Tt), whereas homozygous genotypes have two of the same alleles (e.g., TT, tt).

What is the relationship between a chromosome, nucleus, and gene?

Genes are found on chromosomes, which are located in the nucleus. Signup and view all the answers

What is a Punnett Square? Do they help predict probability?

Punnett squares are tools used to predict the probability of genetic crosses. Signup and view all the answers

What is a gene? What is an allele?

Genes are segments of DNA that code for specific traits. Alleles are different forms of a gene (e.g., T or t). Signup and view all the answers

What is incomplete dominance? Is it common in nature?

Incomplete dominance is when the phenotype of a heterozygous individual is a blend of the phenotypes of the homozygous dominant and homozygous recessive individuals. Signup and view all the answers

What is codominance?

Codominance is when the phenotype shows both traits of the homozygous dominant and homozygous recessive parents. Signup and view all the answers

What are sex-linked traits?

Traits that are linked to either of the sex chromosomes. Signup and view all the answers

What does the law of segregation say?

The way chromosomes separate is random and independent of one another. Signup and view all the answers

What does the law of independent assortment say?

You may be dominant for one trait but recessive for another. Signup and view all the answers

What is probability?

The likelihood that something would happen. Signup and view all the answers

What do you use a test cross for?

A test cross is used to determine the genotype of an individual by crossing it with a homozygous recessive individual. Signup and view all the answers

Can you see genotypes?

False Signup and view all the answers

Can you see phenotypes?

True Signup and view all the answers

What is the structure of DNA?

Double-helix Signup and view all the answers

What are purebreds? What are hybrids?

Purebreds are homozygous individuals; hybrids are heterozygous individuals. Signup and view all the answers

What is self-pollination? Cross pollination?

Self-pollination: Flowers fertilizing flowers on the same plant; Cross-pollination: flowers fertilizing flowers on a different plant. Signup and view all the answers

What allows different tissues that have the same DNA to function differently?

Different genes are being expressed on the DNA. Signup and view all the answers

What are multiple alleles?

Traits that are coded by more than one different type of allele. Signup and view all the answers

What phenotypic ratio do you get when you cross two heterozygous organisms?

3:1 Signup and view all the answers

What is the probability that the child of a heterozygous man and a homozygous recessive woman will develop Huntington's disease?

50% probability (Tt) Signup and view all the answers

What is the probability that the puppies would have wire-hair when a homozygous wire-haired male is mated to a smooth-haired female?

100% Signup and view all the answers

What is the probability that the puppies would have smooth hair when a homozygous wire-haired male is mated to a smooth-haired female?

0% Signup and view all the answers

Study Notes

Genetics Basics

Dominant vs. Recessive Traits: Dominant traits manifest with one dominant allele, while recessive traits require both alleles to be recessive.
Genotype vs. Phenotype: Genotype refers to the genetic makeup, while phenotype is the observable physical expression of traits.

Alleles and Genotypes

Homozygous vs. Heterozygous: Homozygous has two identical alleles (e.g., TT, tt); heterozygous has two different alleles (e.g., Tt).
Alleles: Variants of a gene that represent different expressions of a trait, such as T and t.

Chromosomes and Genes

Relationship: Genes are located on chromosomes, which reside in the nucleus of the cell.

Predictive Genetics Tools

Punnett Square: A diagram used to predict the probability of genetic outcomes from crosses.

Genetic Expressions

Incomplete Dominance: A genetic condition where the heterozygous phenotype is an intermediate between the two homozygous phenotypes (e.g., red and white flowers producing pink).
Codominance: A situation where both traits from homozygous parents are fully expressed in the offspring (e.g., black and white chickens producing black and white offspring).

Special Trait Considerations

Sex-linked Traits: Traits associated with genes located on sex chromosomes, such as color blindness linked to the X chromosome.

Mendelian Laws

Law of Segregation: Chromosomes segregate independently and randomly during gamete formation.
Law of Independent Assortment: The inheritance of one trait does not affect the inheritance of another.

Probabilities in Genetics

Probability: The mathematical likelihood of a specific genetic outcome.
Test Cross: A method to determine an unknown genotype by crossing it with a homozygous recessive individual.

Visibility of Genotypes and Phenotypes

Genotype Visibility: Genotypes cannot be directly observed as they exist within DNA; phenotypes can be directly observed as physical traits.

DNA Structure and Genetic Diversity

DNA Structure: Comprises a double-helix formation.
Purebreds vs. Hybrids: Purebreds are homozygous, whereas hybrids are heterozygous individuals.

Pollination Types

Self-Pollination: Occurs when flowers fertilize themselves on the same plant.
Cross-Pollination: Involves fertilization between flowers from different plants.

Tissue Functionality

Gene Expression: Different genes in the same DNA can lead to varied tissue functions due to selective gene expression.

Multiple Alleles

Multiple Alleles: Genes that can be represented by more than two alleles, contributing to trait diversity.

Punnett Square Outcomes

Heterozygous Cross Ratio: Crossing two heterozygous organisms typically yields a phenotypic ratio of 3:1.

Example Scenarios

Huntington's Disease: A person with a dominant allele has a 50% chance of passing it to offspring if partnered with a homozygous recessive individual.
Dog Coat Types: Crossing a homozygous wire-haired dog with a smooth-haired dog results in all offspring having wire-haired fur (100% probability) and none with smooth fur (0% probability).

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Description

This quiz explores key concepts in genetics, including the distinctions between dominant and recessive traits, as well as the definitions of genotype and phenotype. Perfect for students preparing for exams or to enhance their understanding of genetic principles.