lecture 2

Question 1

what is blending theory

Answer 1

hypothesis
traits of parents get mixed like fluid in the offspring = results in new traits that resembles parents

Question 2

what is the prediction of blending theory

Answer 2

if blended like fluid = parents traits are lost in offspring and cannot be recovered
mendel tested blending theory

Question 3

describe mendels method

Answer 3

purple petals = take pollen and cross with other - white petal
fertilize stigma - where took of anthers = controls genotype
prevented self pollination
controlled the crosses between different purebred pea plants - control trait from one generation to next - important for farmers

Question 4

describe plants - mendels method

Answer 4

plants are hermaphrodites = have stigma and anther
can self fertilize but cutting anthers prevents self fertilization

Question 5

what is mendels first experiment and result

Answer 5

white cross purple = purple 100% F1 = maybe they do not blend
how to test this = see if blending theory works = mendels experiment 2

Question 6

what is mendels second experiment and result

Answer 6

F1 purple petals = self cross of F1 - monohybrid cross
expectations = should be all purple
result = recovered fraction of white flowers from purple F1 mono cross

Question 7

what did mendels 2nd experiment prove

Answer 7

argues against blending theory
white flowers = means parental traits do not get lost
suggests element responsible for flower colour (trait/phenotype) works like particles and not fluid - can be maintained from one gen to next and separated

Question 8

what else did mendel do - after the 2 experiments

Answer 8

many diff experiments with 7 diff traits
F1 = looked like dominant trait, hid recessive
F2 ratio = approx 3:1, certain way traits are mediated

Question 9

what 2 things did mendels further experiments prove

Answer 9

there is a dominant trait that hides the recessive trait
element producing traits are transmitted to next gen in predictable pattern

Question 10

when was mendels hypothesis/model

Answer 10

1866

Question 11

what is mendels model

Answer 11

there are 2 copies of the element that are inherited from parents - diploid organism - only one of the 2 is visible - dominant/recessive
only one of the 2 is transmitted to next gen

Question 12

describe what happens in monohybrid cross in mendel’s model

Answer 12

each of 2 parental elements have an equal chance of being transmitted to the next generation
3 out of 4 possible element combos in the offspring contain at least one dominant trait = 3:1 ratio of dominant and recessive traits, equal chance of how dom and recessive traits transmit

Question 13

describe punnet square

Answer 13

all alleles
equal chances - no bias from one trait to other
3:1 ratio - monohybrid cross

Question 14

name the 3 reasons why mendels experiments worked

Answer 14

traits affected by only one gene - many traits, like height, are affected by multiple genes
pure genetic background and ability to cross or self pollinate = must be able to control cross or mating
ability to obtain a large number of progeny - tested large number of F2s

Question 15

Why is the ability to obtain a large number of progeny important?

Answer 15

low probability events can happen at any time during the data collection
large sample size helps to determine precise data
large sample size reduces variability between experiments

Question 16

what is the element

Answer 16

the gene

Question 17

describe drosophila - element

Answer 17

few chromosomes
weird morphological differences compare to wild type - identified mutants before genes - knew phenotype before identifying gene responsible
traits determined by a single gene

Question 18

what is the base of mendels law

Answer 18

Meiosis in the GERM CELL is the cellular/molecular base of Mendel’s law

Question 19

describe what happens during meiosis

Answer 19

a A/a cell produces 4 gamete = 2 x A and 2 x a
meiosis produces the same ratio of A to a, giving an equal chance of transmitting between A or a
maternal and paternal have equal chances of being passed on to offspring

Question 20

define monohybrid

Answer 20

heterozygote of a gene

Question 21

describe monohybrid cross

Answer 21

self pollination
only 1 of 4 gametes (from meiosis) is transmitted to the next generation, one egg and one sperm (pollen)
fertilization is a random event, need large number of test products
phenotypically = 3 purple, 1 white

Question 22

define testcross

Answer 22

the cross of an individual to a
fully recessive individual

Question 23

what is test cross useful for

Answer 23

determining genotype of a testee = whats being tested
way to see if 2 or 1 copy of dominant element

Question 24

describe test cross experiment

Answer 24

1 = purple (P/P) + fully recessive (w/w) = 100% purple, heterozygous

#2 = purple (P/w) + fully recessive (w/w) = 50/50 purple and white
phenotypes of progeny depends on genotype of testee

Question 25

what is loss of function mutation

Answer 25

molecular term lose function of gene product mutation kills kinase activity = function of protein

Question 26

what is recessive

Answer 26

phenotype

Question 27

what is haplosufficient

Answer 27

even if one functional copy = sufficient to carry out function of gene

Question 28

describe loss of function mutations

Answer 28

often recessive since a single wild type copy of the gene can often provide necessary functions for the organism most genes (wild type) are haplosufficient

Question 29

describe genetic disorders and cousin marriage

Answer 29

in family = cousins could have same mutation and then offspring would have 2 copies of mutated genes

Question 30

what is cystic fibrosis

Answer 30

view as a mendelian disorder affects cells that produce mucus, sweat and digestive juices such as the lung, affects tissue and cells that produce mucus

Question 31

describe prevalence of cystic fibrosis and why

Answer 31

in canada = around 1/3600 and around 1/30 is a carrier

Question 32

what is cystic fibrosis caused by

Answer 32

mutation in the cystic fibrosis transmembrane receptor = CFTR gene needed for good functioning exports chloride gene identified by researchers at hospital for sick children - toronto

Question 33

what are chances of having a child with CF

Answer 33

2 carrier parents have 1 in 4 chances of having a child with cf bc cf is a haplosufficient gene

Question 34

what does allele mean

Answer 34

diff forms of single gene

Question 35

name and describe the classes of CFTR mutations

Answer 35

normal = exports chloride, 100% class I, II, III = no pump chloride, complete elimination of protein function, 0% class IV, V = not as efficient but some function to export chloride, better off than other mutant cases, 10%

Question 36

describe CF as a haplosufficient gene

Answer 36

missing half = results in cellular defect. loss of function mutation, but dominant cf develops if homozygous for it if carry one mutant with one functional copy = sufficient, no cf cases = loss of function mutation, phenotypically dominant trait