lecture 7

Question 1

does all genetics fall under mendelian theory

Answer 1

uhmm nooooooo

Question 1

describe what protein function does - for gene inheritance

Answer 1

affects how it inherits, ratio and how they inherit changes
does not fit mendels law

Question 2

what is pleiotropy

Answer 2

the property of a single gene product affecting two or more seemingly unrelated traits

Question 3

describe mutations in haplosufficient genes

Answer 3

RECESSIVE
most loss of function is recessive
must be homozygous to see mutation

Question 4

what are dominant mutations

Answer 4

having a single copy of the mutation produces a phenotype - disease - despite having a wild type copy of gene

Question 5

describe oncogenes

Answer 5

many are activated by dominant mutations

Question 6

can loss of function mutations be dominant

Answer 6

YEEEE

Question 7

describe gain of function mutation

Answer 7

activating mutation
dont see it since helps protein gain function

Question 8

name dominant mutation models

Answer 8

haploinsufficiency and dominant negative

Question 9

Describe haploinsufficient genes

Answer 9

need 2 full copies of wild type to cause phenotype

Question 10

describe haploinsufficiency model

Answer 10

2 doses = wild type
0 doses = mutant
1 dose = mutant, since inadequate

Question 11

describe dominant negative model

Answer 11

protein dimerizes, 2 functional = wild type
2 mutants = mutant
1 mutant and 1 functional = mutant affects wild type, can still dimerize and will interfere with wildtype, since they physically interact

Question 12

describe mutations in genes coding ribosomal subunits in drosophila

Answer 12

often dominant, haploinsufficient
Mutation on single copy of gene makes ribosomes = morphological defects = tend to be shorter and thicker
loss of function mutation
cells need full load ribosomes to do what they need to do

Question 13

describe p53 mutant allels in cancer

Answer 13

function as dominant negative
mutation in the dna binding domain in one of 2 alleles = even if mutated still makes tetramer but wont bind dna, no activation of canonical p54 target genes

Question 14

what is p53

Answer 14

transcription factor that binds dna as a homotetramer - tetramerizes = 4 proteins come together

Question 15

describe incomplete or partial dominance (dose determinant)

Answer 15

flower colour = mutation of gene that produces pigments = both copies of enzyme needed for red pure breed
if one functional copy = not sufficient amounts of red so will be pink
red not completely dominant = looks like blending theory kinda

Question 16

what is codominance

Answer 16

both alleles expressed or detected

Question 17

describe how blood type determined

Answer 17

2 alles = A, B, i
gene responsible for blood type encodes a glycosyltransferase = puts sugar molecule on another chain

Question 18

describe what each blood allele does

Answer 18

i = no sugars added
A = will be acetyl galactosamine at end of sugar chain - present on surface of rbc
B = puts simple galactose

Question 19

describe how codominance is discovered in blood types

Answer 19

AB = will have both sugars
uses antibody that recognizes specific structure
depends on assay

Question 20

describe A vs B vs O - codominance

Answer 20

A and B are dominant over O
but A and B are codominant with each other in conventional assay
coagulates = see clear phenotype of both = why they are co dominant, both expressed
could also be incomplete dominance if have sensitive assay = quantify number of sugar molecules = end up with number between A and B

Question 21

how we classify codominance is determined by what

Answer 21

Determined by phenotype we characterize - methods of detection or observation

Question 22

what is Hb gene

Answer 22

encodes beta globin = subunit of hemoglobin

Question 23

describe phenotype anemia example

Answer 23

if HbA/HbA = no anemia
if HbS/HbS = anemia
if HbA/HbS = no anemia
as long as one not affected = fine
so sickle cell= recessive
HbA = dominant to HbS

Question 24

describe phenotype blood cell shape example

Answer 24

if HbA/HbA = normal shape
if HbS/HbS = sickle cell shape
if HbA/HbS = slight sickle cell shape
HbS = incomplete dominance to HbA
aa sequence affected so protein oligomerizes = polymerizes = back = causes shape

Question 25

describe protein level analysis of blood

Answer 25

could consider sickle cell as codominant = if only looking at presence protein
phenotype = presence of HbA and HbS at protein level
proteins migrate at diff rates = see both phenotypes separately (HbA and HbS = codominant bc both alleles can be clearly discerned at protein level)
if has band in middle =would be incomplete dominance
depends on assay and phenotype

Question 26

describe recessive lethal

Answer 26

if 2 copies = cannot have organism = will die
often heterozygous for recessive lethal appear normal - since most genes are haplosufficient

Question 27

can humans carry recessive lethal mutations

Answer 27

yesss
we heterozygous thooo
we healthy since have one healthy copy

Question 28

describe recessive lethal mutations in diploids vs haploids

Answer 28

in diploids = recessive lethal mutations maintained as heterozygous
in haploids = not possible since only one copy of gene

Question 29

describe homozygous mutations causing lethality in animals - mice

Answer 29

either recessive or dominant mutations
normal mice = dark, yellow mice = lighter coats
yellow x normal = 1:1, since yellow dom, but 2 copies of dom allele = lethal so we never get it
yellow x yellow = 2:1 (yellow to normal), never get YY = since lethal
gene is dominant when it comes to pigmentation phenotype but recessive for viability bc animal with 2 copies of dom will die

Question 30

describe conditional alleles

Answer 30

alleles depend on condition = expression of certain features or traits depends on external factors

Question 31

describe conditional alleles - temp sensitive mutations

Answer 31

at lower temps = gene functions like wild type
at higher temps = gene is nonfunctional and lethal
Depends on conditions

Question 32

describe conditional alleles - auxotrophs

Answer 32

if on minimal media and arginine = functions like wild type
if on minimal media only = non functional - lethal

Question 33

what are auxotrophs

Answer 33

organisms that lost the ability to synthesize certain substances required for their growth

Question 34

describe conditional alleles temp controlled phenotypes - rabbits

Answer 34

black pigmentation at extremities = depends on temp, must lower
tyrosine kinase = active at a lower temp = important for producing pigmentation
wont show colour in middle of rabbit since can control body temp, at extremities = harder to control

Question 35

what is variable penetrance

Answer 35

percentage of individuals with a given allele who exhibit the phenotype of that allele
can be obvious in one person but not other since factors can contribute

Question 36

give ex of variable penetrance

Answer 36

BRCA2 mutations predispose to breast, ovarian and pancreatic cancers
why = environment, interacting genes, subtlety of mutant phenotype - difficult to diagnose (psychiatric disorder) = other factors contribute

Question 37

describe incomplete penetrance and pedigrees

Answer 37

dom mutation
gen 2 = carriers but exception to mendelian rule
not penetrant so not shown but carrier, phenotype not detected or manifested in generation
gen 3 = recovers it

Question 38

describe variable expressivity

Answer 38

degree to which a given allele is expresses at the phenotypic level = the intensity of the phenotype

Question 39

describe ex of variance penetrance and expressivity

Answer 39

neurofibromatosis type 1 = single gene mutation
all affected in diff ways
(diff levels of phenotype, expressivity and penetrance) = same factor affecting penetrance may be affecting expressivity among diff individuals
based on assay

Question 40

what could sick cell be also classified as

Answer 40

snp = yes since caused by single nt chain and prevalent in certain ethnic background