Mechanisms of Hereditary

Question 1

what are monohybrid crosses?

Answer 1

parents differ in only one trait (phenotype)

Question 2

what are the 5 properties of peas that made it very useful for studying genetics?

Answer 2

1. binary traits (2 possible phenotypes)
2. short generation time
3. easy to grow
4. produces lots of offspring
5. self-fertilise

Question 3

what are true breeding parents?

Answer 3

crosses that results in all offspring having the same phenotype as parents

Question 4

how did mendel know that parents contribute equally to offspring?

Answer 4

reciprocal crosses gave identical results

Question 5

what is the principle of segregation?

Answer 5

two alleles for each trait segregate during gamete formation and then unite randomly at fertilisation

Question 6

when do we use the product rule of probability?

Answer 6

gamete formation

Question 7

when do we use the sum rule of probability?

Answer 7

after gametes fuse

Question 8

what does it mean if the p value is greater than 0.05?

Answer 8

the null hypothesis cannot be rejected, thus there is no significant difference in expected vs observed values

Question 9

what does it mean if the p value is less than 0.05?

Answer 9

the null hypothesis is rejected, and there is a significant difference between the predicted and observed ratios

Question 10

what are the 5 non mendelian types of inheritance?

Answer 10

• domanince is incomplete
• lethality
• phenotype determined by multiple genes and interaction between them
• sex-linkage
• linkage

Question 11

what is complete dominance

Answer 11

when you only see the dominant phenotype in 1st generation

Question 12

what is co dominance?

Answer 12

when the offspring show two traits (e.g. blood types)

Question 13

what is incomplete dominance?

Answer 13

when a new phenotype occurs that doesnt look like either of the parents

Question 14

what is lethality (non mendelian inheritance)

Answer 14

an allele or specific genotype leads to death or non-viablity of organism

Question 15

what are complementation tests?

Answer 15

way to determine whether 2 mutants (with the same phenotype) are defective in the same gene or in different genes

Question 16

what does it mean if you cross two mutants together and see a mutant phenotype in the F1 generation?

Answer 16

mutants are defective in the same gene

Question 17

what does it mean if you cross two mutants together and see a wild type phenotype in the F1 generation?

Answer 17

mutants are defective in different genes

Question 18

what is a complementation group?

Answer 18

a group of mutations that are all defective in the same gene, the groups dont complement one another

Question 19

what do complementation groups tell you about the number of genes the mutants are defective in

Answer 19

nr of comp groups = nr of different genes mutants are defective in

Question 20

what is recessive epistasis?

Answer 20

homozygosity for a recessive allele at one locus masks genotype at a second locus (e.g. recessive allele determines whether pigment is deposited or not)

Question 21

what is dominant epistasis?

Answer 21

having a dominant allele mask the phenotype coded by the second allele

Question 22

what is the expected phenotypic ratio of recessive epistasis?

Answer 22

9:3:4

A-B- : aaB- : A-bb + aabb

Question 23

what is the expected phenotypic ratio of dominant epistasis?

Answer 23

12:3:1

A-B- + aaB- : A-bb : aabb

Question 24

what is penetrance?

Answer 24

% of individuals with phenotype

Question 25

what is the difference between mitosis and meiosis

Answer 25

in mitosis there is one round of nuclear division
but in meiosis there are two rounds of nuclear division

Question 26

what is a barr body?

Answer 26

an inactivated X chromosome that ensures dosage compensation between males & females

Question 27

what makes humans bad for experiments?

Answer 27

• long lifespan
• small nr of offspring (chance plays larger role)
• ethics
• can’t self fertilise
• most of our traits are multi genic

Question 28

what clues should we look for on a pedigree to determine if the disease is x-linked recessive?

Answer 28

• M&raquo_space; F
• skips a generation

Question 29

what clues should we look for on a pedigree to determine if the disease is x-linked dominant?

Answer 29

• F&raquo_space; M
• is found in all generations

Question 30

what clues should we look for on a pedigree to determine if the disease is autosomal dominant ?

Answer 30

• equally in males and females
• in every generation

Question 31

what clues should we look for on a pedigree to determine if the disease is autosomal recessive?

Answer 31

• equally in males & femaes
• skips a generation

Question 32

what is sry

Answer 32

sex determining region of y - drives male development and kicks off signalling cascades to lead to production of male sex hormones