Peas, Genes, and Inheritance

Question 1

Allele

Answer 1

Variant form of a given gene. Different alleles can result in different observable phenotypic traits.

Question 2

Blending inheritance

Answer 2

Inheritance of traits from 2 parents (black and blond hair) produces offspring with characteristics that are intermediate / a mixture between those of the parents (brown hair)

Question 3

Single-gene characteristic

Answer 3

any characteristic where allelic variation in a single gene accounts for differences in the phenotype

Question 4

Polygenic trait

Answer 4

Traits are polygenic when there is wide variation in them and each (dominant) allele “adds up” to the expression of the trait (i.e., if you have many alleles that code for height they add up and contribute to the overall big height)

Question 5

Co-dominance

Answer 5

heterozygotes fully express the phenotype of both their homozygous parents (i.e., blood groups like AB)

Question 6

Incomplete dominance

Answer 6

phenotype of the heterozygote is intermediate in form between those of the two homozygotes (i.e., red homozygote + white homozygote = pink flower), the third phenotype is a combination of the phenotypes of both alleles.

Question 7

Linkage

Answer 7

Tendency of DNA sequences that are close together on a chromosome to be inherited together during meiosis. The closer together on a chromosome, the less the chance of recombination between them.

Question 8

Law of segregration

Answer 8

Allele pairs randomly separate/segregate during gamete formation and randomly unite at fertilization, each gamete carries only one allele for each gene.

Question 9

Law of dominance

Answer 9

Recessive alleles will always be masked by dominant ones, therefore only the dominant phenotype will be expressed, while still having a heterozygote genotype.

Question 10

Law of independent assortment

Answer 10

When 2 or more characteristics are inherited, individual hereditary factors assort independently during gamete production, giving different traits and equal opportunity of occurring together (wrinkles or smooth and yellow or green).

Question 11

Hardy-Weinberg equilibrium

Answer 11

Model of change in expected frequencies of alleles over generations, states that allele and genotype frequencies in a (perfect) population will remain constant from generation to generation in the absence of other evolutionary influences.
p + q = 1 and p^2 + 2pq + q^2 =1

Question 12

Polygenic inheritance

Answer 12

a sum of genes can be inherited differently but the single alleles that contribute follow the mendelian laws

Question 13

Quantitative genetics

Answer 13

Branch of population genetics that deals with continuously varying phenotypes as opposed to discretely identifiable phenotypes and gene products (predicting phenotypes which are not either/or)

Question 14

Genetic drift

Answer 14

Variation in the relative frequency of different genotypes in a small population, due to the chance of disappearance of genes as individuals die or don’t reproduce

Question 15

Heritability

Answer 15

Estimation of the degree of variation in a phenotypic trait in a population that is due to genetic variation between individuals in that population.

Question 16

Coefficient of relatedness

Answer 16

Probability that 2 individuals share an allele due to common ancestry, expressed by symbol r, ranges from 0 (unrelated) to 1 (clones)

Question 17

Behavior genetics

Answer 17

Research that uses genetic methods to investigate the nature and origins of individual differences in behavior

Question 18

Shared environmental influences

Answer 18

Factors that will influence both twins regardless of MZ or DZ like parental social class, parental behavior, diet available, the school attended, or the house grown up in.

Question 19

Non-shared environmental influences

Answer 19

Influences that are neither shared by MZ nor by DZ twins such as childhood diseases or accidents that affected one twin and not the other like a disease or an accident

Question 20

Falconer’s estimate of heritability

Answer 20

Formula used to determine the genetic heritability of a trait based on the differences between twin correlations (correlation of MZ twins being higher than the one of DZ twins)
2*(r(monozygotic twins) - r(dizygotic twins)) = estimated heritability

Question 21

ACE models

Answer 21

Epidemiological model that states that individual differences in a phenotype are accounted by A (additive genetic factors), C (common environmental factors), and E (specific environmental factors)

Question 22

Epistatic effects

Answer 22

A gene is epistatic when its presence suppresses the effect of a gene at another locus. Also called inhibitory gene.

Question 23

Narrow-sense heritabilities

Answer 23

Heritability estimates (variance) based on additive genetic effects (A) (study designs include only A,C, and E) = h^2

Question 24

broad-sense heritabilites

Answer 24

Estimates of variance that include epistatic effects (all genetic factors) = H^2

Question 25

Coefficient of additive genetic variance

Answer 25

estimate of the amount of genetic variation in a population relevant to a particular trait, independent of the amount of environmental variation.

Question 26

Complex traits

Answer 26

Trait that does not follow Mendelian inheritance patterns, likely derived from multiple genes and exhibits a large variety of phenotypes.

Question 27

Liability thresholds

Answer 27

When a certain threshold is reached you develop a disease, because you have too many genes coding for that disease

Question 28

Genetic amplification

Answer 28

Increase in the number of copies of a gene without an increase in other genes.

Question 29

Mendelian diseases and deleterious recessives

Answer 29

a disease state associated with allelic variation in a single gene; only one gene is involved -> follow the Mendelian laws of inheritance

Question 30

Schizophrenia

Answer 30

The risk of developing schizophrenia increases systematically with the degree of genetic similarity that an individual has to another who is affected (1st degree relative: 9%, 2nd degree relative: 4%)

Question 31

General cognitive ability

Answer 31

Runs in family and depend to a great deal on the nurture and the environment. Parents with high intelligence test scores tend to have children with higher than average scores.

Question 32

Liability Threshold

Answer 32

When a certain threshold is reached, you develop a disease, because you have too many genes coding for that disease but a certain threshold of the coding of the genes has to be reached.

Question 33

GWAS (genome-wide association studies)

Answer 33

studying heritable traits like height, diabetes, obesity, autism, schizophrenia, and promising to find the genes associated to these characteristics.