Biology Chapter 9

Question 1

Explain how human experiences breeding dog and food crops can provide insights into principles of genetics.

Answer 1

Dogs and food have been bred for certain traits over thousands of years, so we now have an incredible variety of different kinds of dogs and food. We can see how different combinations of sperm and eggs produce different traits.

Question 2

self-fertilization

Answer 2

When an organism can produce the necessary sperm and eggs to reproduce by itself

Question 3

Cross-fertilization

Answer 3

When the sperm from one organism is used to fertlize the eggs of another

Question 4

purebred organism

Answer 4

An organism which consistently passes down the same traits to offspring

Question 5

Hybrids

Answer 5

The offspring of two different purebred varieties

Question 6

P generation

Answer 6

Parent generation (2 different purebred organisms)

Question 7

F₁ Generation

Answer 7

Hybrid of the P generation

Question 8

F₂ Generation

Answer 8

A cross of the F₁ organisms

Question 9

heterozygous vs. homozygous

Answer 9

homozygous: organism with 2 identical alleles for a certain trait

heterozygous: organism with 2 different alleles for a certain trait.

Question 10

Dominante Allele vs. Recessive Allele

Answer 10

Dominant Allele: Determines the organism’s appearance

Recessive Allele: Has no noticeable affect on organism’s appearance

Question 11

Allele

Answer 11

Alternative versions of genes

Question 12

Genotype vs. Phenotype

Answer 12

Genotype: Organism’s genetic makeup

Phenotype: Organism’s physical appearance

Question 13

Phenotypic Ratio vs. Genotypic Ratio

Answer 13

Phenotypic Ratio: Ratio of physical appearance

Genotypic Ratio: Ratio of genetic makeup

Question 14

Law of Segregation

Answer 14

Gametes carry only one allele for each inherited character.
The two alleles for a character segregate (separate) from each other during the production of gametes.

Question 15

Define Mendel’s law of independent assortment and explain how it applies to a dihybrid cross.

Answer 15

Each pair of alleles segregates independently of the other pairs during gamete formation. Thus, the inheritance of one character has no effect on the inheritance of another.

Question 16

Explain how a testcross can be performed to determine an organism’s genotype.

Answer 16

A testcross is a mating between an individual of dominant phenotype (but unknown genotype) and a homozygous recessive individual.

Question 17

Rule of Multiplication

Answer 17

The probability of a compound event is the product of the separate probabilities of the independent events.

Question 18

Explain how a pedigree is used to determine how a particular human trait is inherited.

Answer 18

A pedigree is a a history of a certain trait in a family

Question 19

Define a carrier and explain how carriers are revealed in human pedigrees.

Answer 19

Organisms that carry a recessive allele but do not exhibit the trait physically

Question 20

Incomplete dominance

Answer 20

F1 hybrids have an appearance between the phenotypes of the two parents. (A dominant red flower and a recessive white flower might have a heterozygous offspring with a pink flower)

Question 21

Complete dominance

Answer 21

The dominant gene covers up the recessive gene (a dominant red flower and a recessive white flower have offpsring where the heterozygotes all had red flowers).

Question 22

Codominance

Answer 22

Both genotypes express themselves at the same time (a dominant red flower and a recessive white flower would have offspring where the heterozygote had both red and white–stripes or dots or something–but not mixed to form pink)

Question 23

Define and distinguish between pleiotropy and polygenic inheritance. Describe examples of each.

Answer 23

Pleiotropy: One gene influences several traits

Polygenic inheritance: The additive effects of two or more genes on a single phenotype.

Question 24

Define the chromosome theory of inheritance and explain how linked genes are inherited differently from nonlinked genes.

Answer 24

genes are located at specific positions (loci) on chromosomes and the behavior of chromosomes during meiosis and fertilization accounts for inheritance patterns.

Question 25

Explain how the environment influences the expression of traits.

Answer 25

Many human characters result from a combination of the environment and inherited genes

Question 26

Explain why researchers used fruit flies and how they created linkage maps.

Answer 26

Researchers used fruit flies because they have very short life cycles which allows researchers to study many generations in a short time. Linkage maps were created by studying each generation and seeing which traits tended to be inherited together.

Question 27

Explain how chromosomes determine the sex of a human.

Answer 27

Humans have a set of chromosomes called X and Y. Females inherit two X chromosomes. Males inherit an X and a Y chromosome.

Question 28

escribe the general characters of the following sex-linked disorders in humans: red-green colorblindness and hemophilia.

Answer 28

Red-green colorblindness: malfunction of light-sensitive cells in eyes.

Hemophilia: causes excessive (dangerous) bleeding even after small cuts

Question 29

Describe the relationships between the many breeds of dogs.

Answer 29

All dogs were descended from a common ancestor, but they were bred in areas where they became distinct.