Chapter 4

Question 1

Selective Breeding

Answer 1

A practice where animals or plant breeders choose which individual animals or plants will be allowed to mate in order to pass on desired traits in future generations

Question 2

What else can selective breeding do?

Answer 2

Can influence the frequency of desirable traits in mammals

Question 3

hybrid

Answer 3

the offspring of parents who differ from each other with regard to certain traits or aspects of genetic makeup

Question 4

Segregation

Answer 4

Genes (alleles) occur in pairs because chromosomes occur in pairs. During gamete formation, the members of each pair of alleles separate, so that each gamete contains one member of each pair. (the first principle of inheritance

Question 5

Recessive

Answer 5

• describing a trait that isn’t expressed in heterozygotes; also refers to the allele that governs the trait, for a recessive allele to be expressed, an individual must have two copies of it

Question 6

a trait governed by an allele that’s expressed in the presence of another allele

Answer 6

Dominant

Question 7

prevent the expression of recessive alleles in heterozygotes.

Answer 7

Dominant alleles

Question 8

having the same allele at the same locus on both members of a pair of chromosomes

Answer 8

homozygous

Question 9

having different alleles at the same locus on members of a pair of chromosomes

Answer 9

heterozygous

Question 10

Genotype

Answer 10

the genetic makeup of an individual

Question 11

the observable or detectable physical characteristics of an organisms; the detectable expressions of genotypes, frequently influenced by environmental factors

Answer 11

Phenotype

Question 12

the distribution of one pair of alleles into gametes does not influence the distribution of another pair. The genes controlling different traits are inherited independently of one another.

Answer 12

Principle of Independent Assortment-

Question 13

the chance distribution of chromosomes to daughter cells during meiosis

Answer 13

random assortment

Question 14

• characteristics that are influenced by alleles at only one genetic locus. Examples include many blood types, genetic disorders, etc.

Answer 14

Mendelian traits

Question 15

discrete

Answer 15

do not overlap in expression

Question 16

Antigens

Answer 16

large molecules found on the surface of cells, several different loci govern various antigens on red and white blood cells.

Question 17

Codominance

Answer 17

the expression of two alleles in heterozygotes, both influence the phenotype.

Question 18

Recessive Alleles have an influence on phenotype

Answer 18

Example- Tay-Sachs disease. Inability to produce an enzyme. Carriers don’t have the disease.

Question 19

Pedigree chart

Answer 19

a diagram showing family relationships. It is used to trace a hereditary pattern of particular genetic traits.

Question 20

Autosomal Dominant Traits

Answer 20

traits which are governed by dominant alleles located on autosomes. (ex- achondroplasia-dwarfism)

Question 21

Autosomal Recessive Traits

Answer 21

influenced by loci on autosomes but show a different pattern of inheritance

Question 22

Sex-linked traits

Answer 22

Sex-linked traits- controlled by genes located on the X and Y chromosomes.
Example- Hemophilia caused by a recessive allele on the X chromosome.

Question 23

Polygenic

Answer 23

referring to traits that are influenced by genes at two or more loci (examples include height, skin color, eye color, and hair color, may be influenced by environmental factors)

Question 24

Mitochrondria

Answer 24

contain around 40 genes that direct the conversion of energy within the cell

Question 25

Pleiotropy

Answer 25

A situation where a single gene influences more than one characteristics (or phenotypic expressions)
Example- autosomal recessive disorder phenylketonuria- can lead to mental problems.

Question 26

Mendelian traits are less likely to be influenced by

Answer 26

environmental factors

Question 27

1920’s and 1930’s- biologists realized that mutation and natural selection were not opposing processes, they contributed to evolution. They decided evolution is a two stage process:

Answer 27

The production and redistribution of variation

Natural selection acted upon variation

Question 28

Current Evolution Principle States What?

Answer 28

Evolution s a change in allele frequency from one generation to then next

Question 29

Microevolution

Answer 29

small changes occurring within species such as changes in allele frequencies

Question 30

Macroevolution

Answer 30

the long term effects through time of these small changes

Question 31

Mutation

Answer 31

Point mutations- substitutions of one DNA to another
Must occur in sex cells if they are to have any evolutionary differences
Rare for evolution to take place solely because of mutation

Question 32

Tandem repeats

Answer 32

short adjacent segments of DNA within a gene that are repeated several times

Question 33

why are tandem repeats important?

Answer 33

Important because they have much higher mutation rates than single alleles do and therefore could have significant influence on the rate of evolution.

Question 34

Gene Flow

Answer 34

The exchange of genes between populations
Only happens when migrants interbreed
Changes in allele frequencies can be influenced by long term patterns of mate selection

Question 35

Genetic drift

Answer 35

Genetic drift- the random factor in evolution, a function of population size. It is evolutionary changes in allele frequencies that are produced by random factors in small populations.

Question 36

Founder Effect

Answer 36

a type of genetic drift in which allele frequencies are altered in small populations that are taken from or are remnants of a larger population, results in a loss of genetic diversity

Question 37

Recombination

Answer 37

When paired chromosomes exchange DNA genes sometimes find themselves in different genetic environments. This can influence the functions of some genes because of the closeness of alleles.

Question 38

If the environment changes, then the selection pressures also change, such a shift is known as what?

Answer 38

adaptation