Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Genetics > Chapter 19 (M2) > Flashcards

Chapter 19 (M2) Flashcards

(48 cards)

Start Studying
1
Q

Discontinuous variation

A
  • traits sharply defined and easy to categorize

ex. mendel’s peas, drosophila mutant phenos

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Continuous variation

A
  • pheno variation exists on a large numerical scale
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Multifactorial trait

A

Genetic and non genetic variation affect trait

ex. developmental and environmental factors like nutrition

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Genetic potential

A

transmitted by parents

may or may not be met

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Polygenetic traits

A

determined by multiple genes

genes may contribute differently to the phenotype

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Human eye colour (polygenetic)

major vs minor (modifier) genes

A
  • OCA2 and HERC2 are two genes with strong influence (major genes)
  • Other genes have minor effects on eye colour and are called modifier genes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Additive gene effects

A
  • Multiple genes contribute an incremental amount of phenotypic influence
  • Alleles of each additive gene can be assigned a value of contribution
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

5 questions of quantitative genetics

A
  1. How much is the phenotypic variation contributed by genetic
    factors?
  2. How many genes influence the specific phenotypic trait?
  3. How much does each of the genes contribute to the phenotypic
    variation?
  4. How do genes interact with each other to influence phenotypic
    variation?
  5. How do genes interact with environmental factors to influence phenotypic variation?
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Multiple-Gene Hypothesis

think additive

A

The idea that alleles of multiple genes segregate and assort independently and impart additive effects on phenotype

first done by Hermann Nilsson-Ehle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Model for additive genes

(wheat plant kernel colour)

A

two genes (A, B)
two alleles (1, 2)

A1A1B1B1
- darkest colour

A2A2B2B2
- lightest colour

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Phenotype Distributions with Additive Genes

Number of pheno categories and frequency of extremes

A
  • Number of phenotypic
    categories calculated as
    2n + 1 where n = number of genes
  • Frequency of most
    extreme phenotypes =
    1/4^n
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Pascal’s triangle

A

Number of events = # of alleles

ex. 3 genes x 2 alleles = 6 alleles

on pascal 7 phenotypes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Frequency of most extreme phenotypes

A

most rare

when they ask frequency of most extreme pheno, do frequency of one

ex. 1/64

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Edward East length of corolla in tobacco plants

observations

A

Tall and short pure-breeding parents

Intermediate height F1

More variant F2

Continued selective breeding = eventually tall and short again

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Edward East experiment results

A
  • Trait is based on segregation of alleles from multiple genes
  • Phenotypic variance seen in each generation due to environmental factors
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Gene-by-Environment Factors on Phenotypic Variation

A

more gene-environment interaction
= wider distribution but same mean

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Threshold traits

A

continuous distribution but two observed phenotypes

once you reach the threshold of genetic liability, you will be affected

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Genetic liability for a disorder

A

refers to alleles that push phenotypes towards threshold (affected end of spectrum)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Mean, median, mode

A

used to analyze distribution of continuous traits

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Variance (s^2)

Study These Flashcards
A

a measure of the spread of distribution around the mean

s^2 = sum (xi - xbar)^2 / df

Sum of square difference between each value and the mean divided by degrees of freedom
(number independent variables)

21
Q

Standard deviation (s)

Study These Flashcards
A

s = √ s^2

s = √ variance

22
Q

Formula for phenotypic variance

Study These Flashcards
A

Phenotypic variance (VP)
= genetic variance (VG) + environmental
variance (VE)

23
Q

Genetic variance

Study These Flashcards
A

genotypic contribution to phenotype

24
Q

Environmental variance

Study These Flashcards
A

environmental contribution to
phenotype

25
Parents, F1, and F2 calculations
* Parental pure-breeding lines: VP = VE (VG= 0) * Genetically uniform F1: VP = VE (VG= 0) * Genetically diverse F2: VP = VE + VG or VG = VP - VE
26
2 things that make a wider variance of phenotypic values
1. stronger environmental effects 2. more diverse populations
27
Why are model organisms useful for studying in the laboratory | think genetic variation
* Use of inbred populations: VG = 0 (for each population) * Control environment in experiments: VE approaches 0 * Therefore, phenotypic differences between populations (strains) are genetic
28
Formula for genetic variance
VG = VA + VD + VI
29
Additive variance (VA)
Added effects of all alleles contributing to trait
30
Dominance variance (VD)
contributions due to heterozygous individuals not having intermediate phenotype between two homozygous states
31
Interactive variance (VI)
epistatic interactions between alleles of different genes
32
Heritability
The measure of the degree to which genetic differences contribute to phenotypic variation of a trait is called heritability It's important to note that heritability does not mean a trait is solely determined by genes, but rather how much genetic differences account for variations in that trait within a population
33
2 types of heritability and their formulas significance of 0 to 1
* Broad sense heritability (H^2) = VG/VP * Narrow sense heritability (h^2) = VA/VP both expressed as a proportion that ranges from 0 to 1 * 1 = phenotypic variance very strongly explained by genetic variance * 0 = little or no genetic variance contributes to phenotypic variance
34
4 caveats with heritability | 4. High heritability does not preclude ...
1. Does not indicate mechanism by which genes control a trait, nor does it indicate how much of a trait is produced by gene action (just does general genetic differences contribution) 2. Heritability values are accurate only for the environment and population in which they are measured (can't be generalized) 3. Heritability for a given trait in a population can change 4. High heritability does not preclude environmental factors
35
Broad sense heritability - twin studies (mono vs di)
Identical twins (monozygotic, MZ) share all the same alleles * Therefore VP = VE Fraternal or dizygotic twins (DZ) are related like any other sibling and share on average 50% of their alleles in common * Therefore VP = VE + ½VG
36
Twin study H^2 caveats (3)
1. Stronger maternal effects in MZ 2. Parents treat MZ more similar than DZ 3. More similarity in gene-environment interactions for MZ
37
Narrow sense heritability (h^2) | high h^2 = high or low degree of response to selection
the proportion of phenotypic variation due to additive genetic variation high h^2 correlates with a greater degree to response of selection
38
Selection differential (S)
is the difference between the mean of the whole population and the breeding population S = x1 - x0
39
Response to selection (R)
depends on the extent to which the difference between the population mean and the mean of mating individuals can be passed on to progeny x2 - x0
40
Response to selection formulas
R = S(h^2) h^2 = R/S Selection is strongest when h^2 = 1
41
Variables they use for response to selection
S = Ms – M R = M’ – M h^2 = R/S
42
Quantitative Trait Loci (QTLs)
genes/DNA regions that contribute to phenotypic variation in quantitative traits QTL analysis, a statistical method, links phenotypic data (continuous trait measurements) with genotypic data (molecular markers) to understand the genetic basis of these variations.
43
QTL mapping - what is it
mapping QTLs to chromosome regions/linkage groups Chromosomal regions are identified through the co-occurrence of a genetic marker (e.g. SNP) with a particular phenotype
44
QTL mapping - how to do it
* Construct genetic crosses between parental strains with different phenotypes * Cross parentals to gather F1 * Cross either F1 together or backcross F1 to parentals * Obtain a phenotype and genotype of all progeny * Identify associations between phenotype and genotype at individual loci * Develop DNA markers (eg SNPs) that differ between parental strains (that might be responsible)
45
Identifying QTL genes using introgression lines (ILs)
* Introgression lines are derived from backcross progeny by selectively breeding inbred lines together * Carefully planned selective breeding can enable introgression lines to have a similar genetic background * Most of their genome is similar; differences are at key locations of interest * Introgression lines are basically recombinants and QTL mapping uses genetic markers to locate where crossovers occurred to map a gene * Analyze DNA sequence, SNPs, etc to determine if phenotypic variation correlates with differences in markers
46
Smallest interval on SNP map that correlates with phenotype
Look at two QTLs with variation in recombination between introgression lines Relative trait difference between introgression line and domesticated species (parental) See map and pheno correlate
47
Degrees of kevin bacon gene
regulates an ordered social network Social network tools were developed in 2012 to study how social interactions are organized in Drosophila * Two strains studied – Canton-S (CS) and Oregon-R (OR) * CS and OR consistently differed in a phenotype called betweenness centrality (BC) * BC is a social network measure that captures hubs in networks * Higher BC = more individuals in the centre of network; * BC, scored in social networks of other animals, including humans, widely reported to be heritable
48
QTL Mapping Betweenness Centrality
* Years were spent generating introgression lines by crossing the CS and OR strains together * SNPs used to track “CS-like” genomic regions and “OR-like” genomic regions * Social behaviour measured for all recombinants, compared to CS and OR flies in order to map the gene contributing to phenotypic differences dokb gene in narrowest interval that correlates with behavioural data

Genetics (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions