Ch. 14 and 15 Review

Question 1

What is the blending model of inheritance?

Answer 1

Genetic material mixes from paternal and maternal genes. Like mixing paint.

Question 2

Why did Mendel use peas?

Answer 2

-are eukaryotes
-multicellular
-reproduce sexually and asexually (cross and self pollination)
-cheap, easy to handle
-short generation time
-obvious characteristics and varieties

Question 3

True breeding produces offspring _____ the parent

Answer 3

like

Question 4

What was Mendel’s first experiment?

Answer 4

Mixing true breeding pea parents via cross pollination, then allowing the F1 generation to self pollinate

Question 5

What conclusions did Mendel draw from his first experiment (5)

Answer 5

1. characters are produced by “heritable factors” (genes) that are discrete (unchanging)
2. An organism had two genes for each character, one from each parent
3. Alleles have alternate versions
4. When different alleles are together:
   dominant allele- affects appearance
   recessive allele- has no effect on appearance
5. Alleles separate during gamete production LAW OF SEGREGATION

Question 6

What happens first when making offspring?

Answer 6

The law of segregation
parent must give one allele only

Question 7

Define phenotype and genotype

Answer 7

Phenotype- physicial appearance of an organism
Genotype- genetic makeup

Question 8

Define homozygous and heterozygous

Answer 8

Homozygous- having identical alleles for a gene pair
Heterozygous- having different alleles for a gene pair

Question 9

Define monohybrid and dihybrid crosses

Answer 9

Monohybrid- parents differ in one character (gene)
Dihybrid-parents differ in two characters (genes)

Question 10

What were Mendel’s 2nd experiment conclusions

Answer 10

Law of independent assortment
a pair of alleles may sort to gametes independently of other pairs of alleles

meiosis sorts homologous chromosomes randomly during meiosis 1

ONLY true for genes on DIFFERENT chromosomes

Question 11

What are some examples of dominance?

Answer 11

Complete dominance- flower color in pea plants

Incomplete dominance- flower color in snap dragons

Codominance- AB blood type

Question 12

How many distinct alleles can one person have?

Answer 12

Only 2 different alleles

Question 13

Do dominant alleles mean most common?

Answer 13

NO, an example would be pea color, dominant color is yellow

Question 14

Why do some traits have many alleles?

Answer 14

Some phenotypes result from more than one gene, polygenetic inheritance

ex. skin color

Question 15

Phenotype is the result of the genotype and the ________

Answer 15

environment

Question 16

Mendel observed _________ not chromosomes. Who observed chromosomes?

Answer 16

characters, Thomas Hunt Morgan

Question 17

What did Morgan study in fruit flies?

Answer 17

Eye color, body color, wing shape

Question 18

Wild type vs mutant type

Answer 18

wild type- typically found in nature (normal)
mutant type- occurs when mutation produces a new allele

Question 19

What was Morgans experiment 1, what were the conclusions?

Answer 19

Crossing between red and white eyed flies

conclusions- red allele is dominant to white, eye color is linked to sex (X linked)

Question 20

In Morgans first experiment, which parents allele determined eye color?

Answer 20

Females

Question 21

For X linked genes, who usually shows this gene?

Answer 21

males

Question 22

Explain Morgan’s second experiment

Answer 22

Morgan crossed true breeding wild type and mutant type flies in a dihybrid cross

body color- gray (b+), black (b)
wing shape- normal (vg+), vestigial (vg)

Question 23

Explain Morgan’s second experiment conclusions?

Answer 23

The genes for body color and wing shape appear to be linked

independent assortment does not apply

however, linked genes can be unlinked by crossing over

Question 24

What differed on Morgan’s dihybrid cross from Mendel’s?

Answer 24

Morgan crossed the F1 generation with a true breeding black vestigial

Mendel self pollinated

Question 25

Why did Morgan deviate from Mendels experiment in his dihybrid cross?

Answer 25

To avoid a 4x4 punnett square

Question 26

What is a test cross?

Answer 26

Crossing true breeding for homozygous dominant and recessive respectively parents

wild type parent determines phenotype