Mendel's Laws of Inheritance

Question 1

What is the mlcr unit of heredity?

Answer 1

gene

means the thing that is actually passed from parent to offspring

Question 2

What are gene variants called? What is another description for gene variant?

Answer 2

alleles; different forms of a gene

Question 3

each trait has at least ____ alleles for a given ____

Answer 3

• 2
• gene

Question 4

some genes have more than 2 what? what is an example?

Answer 4

alleles

• ie. ABO blood type

Question 5

one trait is always coded by one gene. T or F?

Answer 5

false. sometimes more than one gene can code for one trait

Question 6

what is a locus?

Answer 6

the location of the alleles for a gene for a trait on a chromosome

Question 7

What does homozygous dominant mean?

Answer 7

you have 2 of the same alleles that are both dominant for the trait from both parents

ie. AA

Question 8

What does heterozygous mean?

Answer 8

you have one dominant and one recessive allele for the trait

ie. Aa

Question 9

What does homozygous recessive mean?

Answer 9

you have 2 of the same alleles that are both recessive for the trait from both parents

ie. aa

Question 10

What is phenotype?

Answer 10

the physical appearance/ expression from the alleles for the gene that you have

Question 11

What is genotype?

Answer 11

the actual set of alleles you have

Question 12

What are the 3 Mendel’s laws of heredity?

Answer 12

• Law of dominance
• Law of segregation
• Law of independent assortment

Question 13

Explain the law of dominance

Answer 13

a heterozygous individual with a dominant allele and recessive allele for a trait will show the dominant trait bc the dominant allele masks the recessive allele.

a mendelian law

Question 14

Explain the law of segregation

Answer 14

each gamete only contains ONE gene copy aka ALLELE of a single trait.
* this is randomly selected during gamete formation
* one gamete is randomly chosen for fertilization

a mendelian law

Question 15

Explain the law of independent assortment

Answer 15

a pair of traits will segregate INDEPENDENTLY from each other during gamete formation; traits DO NOT influence each other
* exception: linked traits

think about a dihybrid cross

Question 16

What are 2 examples of non-mendelian inheritance?

Answer 16

• incomplete dominance
• co-dominance

Question 17

Explain incomplete dominance. Give an example.

Answer 17

• no dominant or recessive allele aka both are expressed and there is a mixed/ intermediate phenotype in the heterozygote
• example: flower color (RR= red; WW= white; RW= pink)

Question 18

Explain co-dominance. Give an example

Answer 18

• both alleles are expressed, but there is NO mixing like incomplete dominance / when 2 dominant alleles are present, both are expressed
• example: ABO blood type (A and B are co-dominant and O is recessive)
  -AB blood. the RBC’s have BOTH A and B antigens on the surface

Question 19

How can you distinguish mendelian from NON-mendelian inheritance?

Answer 19

if there are two HETEROZYGOUS PARENTS,
* if dealing with one trait, then look for the 3:1 phenotypic ratio of dominant to recessive trait in the F2 generation
* OR
* if dealing with two traits, then look for the 9:3:3:1 phenotypic ratio of 2 dominant traits: one dominant and one recessive trait: 2 recessive traits in the F2 generation.

if the ratios ARE MET = MENDELIAN inheritance IS present

Question 20

how many traits are involved in a monohydrid cross? What is a typical heterozygous cross phenotypic and genotypic ratio?

Answer 20

• 1 trait
• 2 heterozygous parents phenotypic ratio: 3: 1 [dominant: recessive]
• 2 heterozygous parents genotypic ratio: 1: 2: 1 [ homozygous dominant: heterozygous: homozygous recessive]

Question 21

how many traits are involved in a dihybrid cross? What is the typical phenotypic ratio for 2 heterozygous parents?

Answer 21

• 2 traits
• 2 heterzygous parents phenotypic ratio: 9:3:3:1 [ 2 dominant traits: one dominant and one recessive trait: 2 recessive traits]

Question 22

What is the general definition of non-mendelian inheritance?

Answer 22

there are factors OTHER than dominant and recessive traits