7.1 Inheritance

Question 1

What are the 5 different types of inheritance?

Answer 1

codominant
multiple alleles
sex-linkage
autosomal linkage
epistasis

Question 2

What is a genotype?

Answer 2

the genetic constitition of an organism = the alleles it has for 1 gene

Question 3

What is a phenotype?

Answer 3

the expression of genes and its interaction with the environment

Question 4

What does homozygous mean?

Answer 4

a pair of homologous chromosones carrying the same alleles for a single gene

Question 5

What does heterozygous mean?

Answer 5

a pair of homologous chromosome carrying two different alleles for a single gene

Question 6

What is codominant inheritance?

Answer 6

both alleles are equally dominant and expressed in the phenotype

Question 7

What does multiple alleles mean?

Answer 7

more than 2 alleles for a single gene

Question 8

What does sex-linkage mean?

Answer 8

a gene whose locus is on the X chromosome

Question 9

What does autosomal linkage mean?

Answer 9

genes that are located on the same non-sex chromosome

Question 10

What is epistasis?

Answer 10

when 1 gene modifies or masks the expression of a different gene at a different locus

Question 11

What is monohybrid inheritance?

Answer 11

cross of characteristics determined by 1 gene

Question 12

What is dihybrid inheritance?

Answer 12

cross of characteristics determined by 2 genes

Question 13

What is chi-squared?

Answer 13

statistial comparison between observed and expected results

Question 14

How can you tell something was by chance due to deviation from the expected (chi-squared)?

Answer 14

deviation from what was expected is small

Question 15

How can you tell something was by bias due to deviation from the expected (chi-squared)?

Answer 15

deviation from what was expected is large

Question 16

What is the chi-squared equation?

Answer 16

sum of (O-E)^2 / E
E = expected value
O = observed value

Question 17

How do you calculate the expected value E?

Answer 17

sum of observed x phenotype ratio / sum of ratios

Question 18

How do you calculate the degrees of freedom?

Answer 18

number of categories (phenotypes) - 1

Question 19

What can you conclude if the x2 value is less than the crititcal value @ P = 0.05?

Answer 19

the difference between observed and expected is NOT significant = due to chance
accept H0

Question 20

What can you conclude if the x2 value is greater than the critical value @ P=0.05?

Answer 20

the difference between observed and expected IS significant = not due to chance
reject H0

Question 21

what is a dihybrid cross?

Answer 21

a genetic cross where the inheritance of 2 genes is considered at the same time

Question 22

How did Mendel discover dihybrid inheritance?

Answer 22

found different characteristics in pea plants:
round or wrinkled
green or yellow
purple or white flower

these characteristics are coded by 2 different genes

Question 23

What does F0 represent?

Answer 23

parental phenotypes = homozygous

Question 24

What does F1 represent?

Answer 24

first generation after x2 homozygous parents combine = heterozygotes 100%

Question 25

What must you include in a genetic cross?

Answer 25

parental phenotype and genotype possible gametes offspring genotype and phenotype phenotype ratio

Question 26

What is the F2 phenotype ratio of monohybrid inheritance?

Answer 26

3:1

Question 27

What is the F2 phenotype ratio of co-dominant inheritance?

Answer 27

1:2:1

Question 28

What is the F2 phenotype ratio of dihybrid inheritance?

Answer 28

9:3:3:1

Question 29

What is the result of crossing over in meiosis?

Answer 29

new combinations of alleles in the gametes

Question 30

What is the F2 phenotype ratio of autosomal linkage?

Answer 30

3:1

Question 31

How can you tell if crossing over has occured in autosomal linkage?

Answer 31

other phenotypes that were not expected in the 3:1 ratio are produed = recombinant offspring

Question 32

What are recombinant offspring?

Answer 32

offspring that have a different combination of characteristics than their parents

Question 33

Why are homozygous dominant and homozygous recessive offspring most common in autosomal linkage?

Answer 33

their gametes are not as a result of crossing over

Question 34

What happens when genes become further apart on a chomosome?

Answer 34

the genes are less linked = increase chance of crossing over = increased chance of recombinant offspring

Question 35

Are females homogametic or heterogametic?

Answer 35

homogametic = XX

Question 36

Where are the sex-linked genes located on the X chromosome?

Answer 36

in the non-homologous region = Y chromosomes do not have this because they are shorter

Question 37

Who is more likely to suffere from a sex-linked disorder caused by a recessive allele?

Answer 37

males = they only have 1 X chromosome so it is easier to obtain a recessive allele

Question 38

What is evidence from a pedigree diagram that a disorder is recessive?

Answer 38

2 non-affected parents produce an affected child

Question 39

What evidence from a pedigree diagram shows a disorder is NOT sex-linked?

Answer 39

an affected daughter is produced from a non-affected father = the father does not have the recessive allele on his X chromosome

Question 40

How can you tell from a pedrigree diagram that a disorder IS sex-linked?

Answer 40

only males have the disorder