Inheritance

Question 1

homozygote

Answer 1

gene with two identical alleles (PP, pp)

Question 2

heterozygote

Answer 2

gene with two different alleles ( one of them is dominant -> visible and the other recessive (Pp)

Question 3

First Mendelian Law :

Law of Segregation

Answer 3

The two alleles for the heritable characteristic segregate during gamete formation (meiosis) and end up in different gametes

-> If two hetereozygote individuals are crossed with one another ( F1 genertaion)

Question 4

allele

Answer 4

alternative form of gene that accounts for variations in inherited characters
example
gene : hair colour
allele1 blond; allele2 brown

Question 5

Punnet Square

Answer 5

predicts allele composition

Question 6

true-breeding

Answer 6

p generation are both homozygote (PP and pp)

Question 7

ratio in f1 and f2 generation after true breeding

Answer 7

f1 : Pp Pp Pp Pp (4:0)

f2. PP Pp Pp pp (3:1)

Question 8

Law of Independent Assortment

Answer 8

• Each pair of alleles segregats independently of each other pair during gamete formation
• each gene has an independent biologically effect

Question 9

Law of Dominance

Answer 9

recessive allele will be always masked by dominant allele

Question 10

Mendelian Disease -> lethal recessives

Answer 10

Lethal recessives - recessive allele that causes death of an organism that carries it

• an individual carrying a aingle recessive deleterious allele will be healthy and can easily pass the deleterious allele into next generation as long as population is large as then -> rarely expressed

REASON TO AVOID INBREEDING

Question 11

co-dominant genes

Answer 11

fully express the phenotype of both of homozygous parents

Question 12

Complete dominance

Answer 12

dominant allele completely masks the recessive one

- one copy of the dominant allele is enough to produce some enzyme

Question 13

Incomplete dominance

Answer 13

heterozygous phenotype intermediate between the two homozygous phenotypes

Question 14

Co-dominance

Answer 14

two allels each affect the phenotype in seperate, distinguishable way , both phenotypes are fully expressed
eg blood group

Question 15

Pleiotropy

Answer 15

one gene affects multiple phenotypic characteristics

-> causes multiple disesase eg albinism

Question 16

Epistasis

Answer 16

the phenotypic expression of a gene at one locus alters the that of a gene at another locus

• > the gene that affects another is ‘epistatic’ to that other gene
• > modyfies 9:3:3:1 ratio

Question 17

Quantitative characters

Answer 17

classification is impossible as they vary along a continuum ( eg skin colour)

Question 18

Polygenic Inheritance

Answer 18

additive effect of multiple genes on a single phenotypic character
Eg AABBCC -> darkest
AaBbCc -> middle
aabbcc-> lightest ( majority of the population is in the middle)

Question 19

Norm of reaction for a genotype

Answer 19

genotype is generally not associated with one definite phenotype but rather with a range of phenotypic possibilities ( broadest for polygenic characteristics)

Question 20

Multifactorial characters

Answer 20

refers to both genetic and environmental factors ; collectively influence phenotype

Question 21

Linkage

Answer 21

when two genes lie on the same chromosome

closer together -> greater linkage

Question 22

Variation

Answer 22

• provides raw material for natural selection
• interplay between environment and genotype will determine which genetic combinations persist over time
• if new arised traits better suit for a given environment , organisms possessing those will thrive and leave more offspring -> next generation: generation again shuffled

Question 23

Hardy Weinberg - conditions

Answer 23

1 no mutation in gene pool 
2 random mating
3 extremely large population size 
4 no gene flow ( from and to other populations) -> no migration 
5 no selection

Question 24

Hardy Weinberg Principle

Answer 24

the frequencies of alleles and genotypes in a population will remain constant from generation to generation provided that only Mendelian segregation adn recombination of alleles are at work -> equilibrium

Question 25

HW - theorem

Answer 25

p = frequency of one allele q= frequency of the other allele p+q=1 p*2+2pq+q*2=1

Question 26

HW and natural selection

Answer 26

NS occurs when the frquencies change a

Question 27

Equilibrium

Answer 27

- if expected frequencies are same as actual frequencies | - some genes can be in equilibrium while other at same time arent

Question 28

Genetic Drift

Answer 28

- the smaller a population the more frequencies will fluctuate - new mutations can fluctuate all the way till point where everyone has it -> muations becomes fixed - the number of new mutation arising is greater the greater the population

Question 29

Neutral Theory of Molecular Evolution

Answer 29

amount of divergence between the dna sequences of two populations reflects their time since their common ancestor -> molecular clock - accounts for much of the functionless molecular change not phenotype

Question 30

Heritability (h2)

Answer 30

proportion of the observed phenotypic variation between individuals that can be accounted for by genetic variation -> soil example demonstrates this

Question 31

misunderstanding of heritable

Answer 31

Heritable does not mean ''genetically'' determined

Question 32

Environmental variation

Answer 32

Environmental variation changes the heritability -> as environmental variation becomes higher heritability goes down NECESSARY for evolutionary change

Question 33

Schizophrenia

Answer 33

risk of developing schizophrenia increases systematically as a function of the degree of genetic similarity -> pattern of affected individuals does not conform to Mendelian proportions

Question 34

genes with additive gene effect ( neither dominant nor recessive)

Answer 34

leads to normal distribution in population

Question 35

phenotypic variation

Answer 35

genetic variation + environmental variation

Question 36

Coefficient of relatedness (r)

Answer 36

probability that any particular allele in individual A is identical by descent ( derived from same immediate source) as the allele in individual B ``` r = 0 -> unrelated r = 1 -> identical twins ```

Question 37

coefficient of relatedness between siblings

Answer 37

humans are diploid organisms ( receive one 1/2 maternal and one 1/2 paternal gene) siblings could share no alleles ( in case they got in both case the opposite of the half gene) ; all allels ( both siblings got same set of genes from parents) or anywhere inbetween , thus average 0.5

Question 38

Monozygotic Twins

Answer 38

identical r = 1

Question 39

Dizygotic Twins

Answer 39

no more related than normal siblings r=0.5

Question 40

Non-shared environmental influences

Answer 40

any phenotypic difference bw Monozygotic Twins that must be due to NSE eg accident, disease -> thus estimate of impact = 1-rmz

Question 41

Shared environmental influences

Answer 41

eg parental social class, behavior, scool, household estimate of its effect = rmz-heritability of the trait

Question 42

Falconers Estimate of Heritability

Answer 42

equiation to estimate the heritability of traits ( mainly used in twin studies) h*2 = 2 x rmz -rdz

Question 43

ACE model components

Answer 43

A - heritability C - effect of shared environment E - effect of non-shared environment -> C tends to be much less important than E but it is often underestimated

Question 44

ACE Model

Answer 44

it relies on assumption that genetic effects accumulate in an additive manner -> r =1 is twice the effect of r = 0.5

Question 45

Adaptation studies

Answer 45

helps distangle genetic and environmentalsources - kids get genetic contribution from one set of parents and the shared environment from another - > test correlation between kids and their biological parents and adopted parents ; or biological siblings adopted into different families

Question 46

selection vs evolution

Answer 46

selection : individuals that are well adapted on average survive longer evolution : over time selected characteristics will increase in frequency in the population

Question 47

mechanisms of evolution and HW

Answer 47

correspond to violations of different Hardy-Weinberg assumptions. They are: mutation, non-random mating, gene flow, finite population size (genetic drift), and natural selection.

Question 48

genetic hitchhiking

Answer 48

when an allele changes frequency not because it itself is under natural selection, but because it is near another gene that is undergoing selective pressure ( in linkage with that gene)