Chapter 12

Question 1

character

Answer 1

an observable feature of an organism ex) eye color

Question 2

trait

Answer 2

different versions of a character

ex) brown eye color

Question 3

there are genes and alleles for

Answer 3

genes: characters
alleles: traits

Question 4

2 basic conditions in diploid organisms

Answer 4

homozygous: identical alleles for a character are present
heterozygous: different alleles for a character are present
each allele is on one of the homologous chromosome
there terms dont apply to haploid cells

Question 5

genotype

Answer 5

the genetic makeup of an organism

Question 6

phenotype

Answer 6

the traits in an organism

Question 7

wild type

Answer 7

the most common trait or phenotype found in a population

Question 8

genotype influence phenotype but

Answer 8

individuals with different genotype can have the same phenotype
(because in some cases only one of the pair of alleles is expressed)

Question 9

rules of heredity

Answer 9

discovered by gregor mendel in the 1860’s but ignored until 1900’s
his results relied probabilities
mechanisms of meiosis were not understood

Question 10

he used pea plants which can be

Answer 10

a) can bred in a controlled fashion
b) have true breeding lines
c) have large number of varieties
d) have character that are discrete
e) have a short generation
f) the character have the same traits regardless of the environmental conditional

Question 11

in many organisms the phenotype

Answer 11

is a result of the genotype and environment conditions

Question 12

mendel found:

Answer 12

1. when peas with different traits are crossed, all the offspring (hybrids) show only one trait
2. the offspring of self fertilization hybrids show both traits in a 3:1 ratio

Question 13

mendels hypotheses

Answer 13

1. inheritance of genetic material is particulate, not blending
2. there are alternative forms of genes (alleles)
3. organisms receive genes from both egg and sperm cells
4. organisms contain 2 copies of a gene, gametes only have one copy
5. when gametes form, the 2 copies of a gene are separated
6. if both dominant and recessive alleles are present in an organism, only the dominant allele is expressed

Question 14

explanation of mendels results

Answer 14

true breeding plants are homozygous (all gametes have the same allele)
crosses between homozygous plants that have different alleles produce heterozygous individuals
self pollination in heterzygous indivdials produce offspring that are either:
-homozygous with the dominant allele
-heterzygous
-homozygous with the recessive allele
homozygous dominant individual look the same as hetro people

Question 15

determining offspring genetypes from parent genotypes

Answer 15

1. each gamete has equal probability of containing either allele present in the parent
2. each egg has an equal probability of being fertilized by each sperm

Question 16

determining genotypes from phenotypes

Answer 16

1. organisms expressing a recessive trait
   a) are homozygous recessive
   b) have parents who each have at least one recessive allele
2. organisms that express a dominant trait are either:
   homozygous dominant
   or heterozgous