1-Modes of Inheritance: Non-mendelian Inheritance and Genetic Crosses

Question 1

patterns for X-linked traits?

Answer 1

it depends on whether the dominant allele is on the X-chromosome of the mother or father

Question 2

Female inheritance of X-linked traits

Answer 2

• female inherits an X-chromosomes from both mother and father
• if father carries the dominant allele on his X-chromosome, the female offspring must also have the dominant phenotype because she will inherit this dominant allele
• female can only have the recessive phenotype if she inherits the recessive allele from both parents

Question 3

male inheritance of X-linked traits

Answer 3

• the male parent never donates his X chromosome to male offspring, only his y chromosome
• the female parent genotype determines the phenotype of her male offspring
• male offspring only need one recessive allele to have a recessive phenotype

Question 4

how to see if is x-linked inheritance?

Answer 4

look for sex bias in the phenotypes of the progeny (i.e. males and females differ)

Question 5

what happens if neither allele is dominant?

Answer 5

can produce 3 different phenotypes
DO NOT USE UPPER AND LOWERCASE LETTERS!!

Question 6

patterns regarding non-dominant inheritance

Answer 6

• if you cross 2 homozygous parents, the offspring will have a different 3rd phenotype
• if you cross 2 heterozygotes, it will create 3 phenotypes with a 1:2:1 phenotypic ratio

Question 7

Steps to determine most likely mode of inheritance for a trait

Answer 7

1. carefully read the scenario and scan the data
2. after scanning data, should have a hunch/starting hypothesis for mode of inheritance
3. define genes/alleles/genotypes based on this hypothesis
4. use punnett square to make PREDICTIONS about the EXPECTED genotype/phenotype frequencies for the F1 and F2 generation, if that hypothesis is true
5. compare PREDICTED frequencies with OBSERVED frequencies
   
   2. QUANTIFY!!!
   3. Important: genotypes specified, phenotypes quantified (if possible) for both generations, and an explicit comparison of expected (predicted) and observed results was included.
6. conclusion: explicitly state whether your results support your hypothesis about the mode of inheritance for the trait