BIO 101 Chapter 9 Study Guide

Questions and Answers

Who was Gregor Mendel?

Father of Genetics. Found the principles of genetics by breeding garden peas.

What plant did Gregor Mendel study and why?

Garden Peas. They grow quickly.

What is the difference between a character and a trait?

A character is a heritable feature that varies among individuals, while a trait is each variant for a character.

What is the difference between self-fertilization and cross-fertilization?

Self-fertilization is when a flower fertilizes itself, while cross-fertilization involves fertilization by another flower. Signup and view all the answers

What is a true-breeding variety?

When a self-fertilized plant produces offspring that are all identical to the parent. Signup and view all the answers

How did Mendel ensure that each variety of garden peas was true-breeding for a particular trait?

Self-fertilized the plant with that particular trait. Signup and view all the answers

Define: Hybrid.

An offspring of parents of two different species or varieties. Signup and view all the answers

Define: Cross.

A mating of two sexually reproducing individuals. Signup and view all the answers

What is a monohybrid cross?

A cross between two individuals differing in a single character. Signup and view all the answers

Define: Alleles.

An alternative version of a gene. Signup and view all the answers

Explain the terms homozygous and heterozygous.

Homozygous has identical alleles; heterozygous has two different alleles. Signup and view all the answers

Define Dominant.

The allele that determines the phenotype when heterozygous. Signup and view all the answers

Define Recessive.

An allele with no noticeable effect when heterozygous. Signup and view all the answers

How are dominant and recessive alleles represented?

Dominant alleles are represented by a capital letter; recessive by a lowercase letter. Signup and view all the answers

Briefly explain Mendel's four hypotheses.

<ol> <li>Alleles are alternative versions of genes. 2. An organism inherits two alleles for each characteristic. 3. Dominant alleles determine appearance; recessive alleles do not. 4. Sperm or egg carries one allele due to segregation.</li> </ol> Signup and view all the answers

What is the difference between a genotype and a phenotype?

Genotype is the genetic makeup; phenotype is the appearance or expression of a trait. Signup and view all the answers

What is a Punnett square?

A diagram used to show the results of random fertilization. Signup and view all the answers

Explain the difference between a monohybrid cross and a dihybrid cross.

Monohybrid involves one character; dihybrid involves two characters. Signup and view all the answers

In a dihybrid cross, what approximate ratio of plants expressing contrasting traits did Mendel calculate in his F2 generation of garden peas?

Approximately 9:3:3:1. Signup and view all the answers

Explain the law of independent assortment.

The law states that alleles of different genes assort independently of one another during gamete formation. Signup and view all the answers

Explain a test cross.

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

What is the purpose of a family pedigree?

To track inheritance patterns of traits and genetic disorders within a family. Signup and view all the answers

Explain the differences between recessive and dominant disorders. (Know examples of each and their symptoms)

Recessive disorders require two copies of the allele; dominant disorders require only one. Examples: Cystic fibrosis (recessive) and Huntington's disease (dominant). Signup and view all the answers

When considering genetic disease, what is a carrier?

A carrier is an individual who has one copy of a recessive allele but does not show symptoms. Signup and view all the answers

Define: Inbreeding.

Mating between close blood relatives. Signup and view all the answers

Study Notes

Gregor Mendel and Genetics

Gregor Mendel is known as the Father of Genetics.
He discovered genetic principles through his work with garden peas.

Study Organism

Garden peas were chosen for study due to their rapid growth.

Characters and Traits

A character is a heritable feature that varies among individuals.
A trait is a specific variant of a character.

Fertilization Methods

Self-fertilization results in offspring genetically identical to the parent.
Cross-fertilization involves gametes from two different individuals.

True-Breeding

A true-breeding variety consistently produces offspring identical to itself through self-fertilization.

Ensuring True-Breeding

Mendel achieved true-breeding by self-fertilizing plants with specific traits.

Hybrid Definition

A hybrid is the offspring of parents from two different species or varieties, and it is usually heterozygous.

Genetic Cross

A cross refers to the mating of two sexually reproducing individuals for genetic experimentation.

Monohybrid Cross

A monohybrid cross examines the inheritance of a single character.

Alleles

Alleles are alternative versions of a gene responsible for variations in traits.

Genotypes

Homozygous genotype: identical alleles (AA or aa).
Heterozygous genotype: different alleles (Aa).

Dominant and Recessive Alleles

Dominant allele: determines appearance in heterozygous pairs.
Recessive allele: has no observable effect in heterozygous pairs.
Dominant alleles are represented by capital letters; recessive alleles by lowercase letters.

Mendel's Hypotheses

Alternative alleles lead to trait variation.
Organisms inherit two alleles, one from each parent.
Dominant alleles mask recessive alleles.
Allele pairs segregate during gamete formation (Law of Segregation).

Genotype vs. Phenotype

Genotype: genetic composition of a trait.
Phenotype: observable characteristics of a trait.

Punnett Square

A Punnett square is a diagram used to predict genetic variation from fertilization.

Crossing Types

A monohybrid cross involves one character; a dihybrid cross involves two characters.

Dihybrid Cross Ratios

Mendel calculated specific ratios of contrasting traits in the F2 generation of a dihybrid cross.

Law of Independent Assortment

This law states that the segregation of alleles for one character occurs independently of the alleles for another character.

Test Cross

A test cross is used to determine the genotype of an individual by crossing with a homozygous recessive.

Purpose of Family Pedigree

A family pedigree charts the inheritance of traits across generations.

Disorders: Recessive vs. Dominant

Recessive disorders require two copies of the mutated gene; dominant disorders need only one.
Symptoms and examples vary between disorder types.

Genetic Disease Carrier

A carrier has one copy of a recessive allele but does not exhibit symptoms of the disorder.

Inbreeding

Inbreeding is the mating of closely related individuals, increasing genetic similarity in offspring.

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Description

This quiz covers key concepts from Chapter 9 of BIO 101, focusing on genetics and the foundational work of Gregor Mendel. You'll explore the distinction between characters and traits as well as the significance of garden peas in Mendel's experiments. Perfect for reinforcing your understanding of genetic principles.